perissodus microlepis is a species of cichlid endemic to lake tanganyika .

this species reaches a length of 11 centimetres ( 4.3 in ) tl .

this species can also be found in the aquarium trade .

it is a scale-eating ' parasite ' on other fish species .

it occurs in two distinct morphological forms .

one morph has mouth parts twisted to the left , enabling it to eat scales off its victim ’s right flank .

in contrast , the other morph , whose mouth is twisted to the right , eats scales off its victim ’s left flank .

the relative abundance of the two morphs in populations is regulated by frequency-dependent selection .

perissodus microlepis

un jeune perissodus microlepis attaque un jeune lepidiolamprologus elongatus , pour lui prélever quelques écailles .
one parent was experimentally removed from brooding pairs of perissodus microlepis in the field . the removal elicited drastic behavioural changes in the remaining parent and young . the remaining parent sometimes showed a sequence of peculiar behaviours which were not observed when guarding the young with its mate . some left the brooding site with young in their mouths and then put the young under the care of another pair of brooding parents .
fifty - four breeding pairs of perissodus microlepis were collected in april 2010 by diving with hand nets at toby veal ' s lodge ( s08°37 . 4′ e031°12′ ) near mpulungu ( zambia ) on the southern tip of lake tanganyika to assess the mating pattern ( kusche , lee , meyer , in revision ) . twenty - one out of these 54 pairs were used for foraging experiments on adult p . microlepis under semi - natural conditions . mouth laterality of each of the pairs was judged by eye in the field by two independent researchers ( h . k . and a . m . ) ( see figure 1 ) .
unknown , but large schools of thousands of juvenile p . microlepis are often seen at sites not far from brooding pairs . this species is very common throughout its habitat , but is never abundant .
thirteen outdoor pools ( 1000 l ) at the shore of lake tanganyika were stocked with one breeding pair of p . microlepis each ( 7 rl , 5 rr and 1 ll pairs ) . also two large community tanks of 4000 l volume ( with 6 l - morphs and 10 r - morphs of p . microlepis , respectively ) were used in these foraging experiments . the cichlid species tropheus moorii ( pair tanks : n = 3–6 ; community tanks : n = 18 and 25 ) was used as prey since it is a preferred natural prey species of p . microlepis [ 22 ] . after 72 hours , all t . moorii were removed from the pools and presence / absence of scars and missing scales and the numbers of bites on both flanks of the prey fish were recorded .
the handedness of the foraging behavior and the associated asymmetry in mouth / head morphology have made the scale - eating cichlid fish , perissodus microlepis , a textbook example [ 16 ] of both , the astonishing degree of ecological specialization and negative frequency - dependent selection [ 8 ] . however , how and when lateralized foraging behavior manifests itself during ontogeny , and whether its association with mouth asymmetry is already apparent in juvenile individual fish had remained untested . here , we report on the strength and individual variation of lateralized foraging behavior as well as its relationship with mouth asymmetry in p . microlepis during its juvenile as well as adult life stages . we find that handed foraging behavior is already prominent at an early age ( e . g . at two - months ) , although the initial morphological asymmetry is less evident , which hints that handed behavior might play a role in bringing about pronounced morphological laterality , considering the potential influences of phenotypic plasticity on mouth asymmetry [ 18 ] .
in this study , we examine the strength and individual variation of lateralized behavior and its interaction with mouth laterality in perissodus microlepis . in semi - natural conditions , we conducted feeding experiments on adult wild - caught scale - eaters with their natural prey to test whether pronounced morphological laterality predicts foraging preferences . we further tested whether laboratory - reared juvenile scale - eaters , which had never encountered prey fish before , displayed lateralized scale - feeding behavior in reference to mouth asymmetry . here we demonstrate relatively strong handedness in foraging behavior in juvenile fish that showed much less mouth asymmetry ( compared to wild - caught adult fish ) and we then discuss the potential role of lateralized foraging behavior in shaping the head asymmetry of this species .
maréchal , c . and m . poll , 1991 . perissodus . p . 367 - 368 . in j . daget , j . - p . gosse , g . g . teugels and d . f . e . thys van den audenaerde ( eds . ) check - list of the freshwater fishes of africa ( cloffa ) . isnb , brussels ; mrac , tervuren ; and orstom , paris . vol . 4 . ( ref . 5678 )
scale - eating cichlid fish , perissodus microlepis , from lake tanganyika display handed ( lateralized ) foraging behavior , where an asymmetric ‘left’ mouth morph preferentially feeds on the scales of the right side of its victim fish and a ‘right’ morph bites the scales of the left side . this species has therefore become a textbook example of the astonishing degree of ecological specialization and negative frequency - dependent selection . we investigated the strength of handedness of foraging behavior as well as its interaction with morphological mouth laterality in p . microlepis . in wild - caught adult fish we found that mouth laterality is , as expected , a strong predictor of their preferred attack orientation . also laboratory - reared juvenile fish exhibited a strong laterality in behavioral preference to feed on scales , even at an early age , although the initial level of mouth asymmetry appeared to be small . this suggests that pronounced mouth asymmetry is not a prerequisite for handed foraging behavior in juvenile scale - eating cichlid fish and might suggest that behavioral preference to attack a particular side of the prey plays a role in facilitating morphological asymmetry of this species .
the frequency of l and r morphs in natural populations of p . microlepis is suggested to be maintained by negative frequency - dependent selection [ 8 ] . over time , the proportion of l and r morphs within populations oscillates around a 50∶50 ratio [ 8 ] , [ 17 ] . the resulting lateralized foraging behavior of p . microlepis is expected to make prey fish more alert to being attacked from the preferred side of the more abundant morph . thus , increased prey vigilance would reduce the predation success of the more abundant morph , and negative frequency - dependent selection would thereby favor the rarer morph in each generation . consequently , the frequency of both morphs is maintained in approximately equal abundances [ 8 ] .
sixty - one more juveniles from three different broods ( 3 young of rl , 6 of ll and 52 of rr parental - pairs ) were obtained by breeding wild - caught fish in the laboratory . lab - reared p . microlepis fish reached sexual maturity at about six to nine months of age . these 61 juveniles , the f 1 fish of wild - caught stock , were used for foraging experiments that examined behavioral handedness and its interaction with mouth asymmetry .
nonetheless , the observed lack of correlation between mouth asymmetry and lateralized foraging behavior in juvenile p . microlepis might also result from the measurement technique used for the quantification of mouth asymmetry ( i . e . mouth bending angle ) not fully capturing the existing true laterality ( i . e . asymmetric skeletal features ) in the mouth / head apparatus of this fish . further tests with cleared and double - stained juvenile fish samples of known behavioral laterality are required to check this possibility .
to statistically analyze if juvenile p . microlepis fish show a bimodal or unimodal distribution in their foraging behavior ( e . g . foraging score , behavioral foraging preference ) , the dip statistic [ 23 ] and a mixture analysis with a parametric bootstrap test ( 1000 iterations ) using the mixtools package [ 24 ] were performed in r [ 25 ] . an anscombe - glynn test [ 26 ] for platykurtosis was further performed for the seven - month old fish only ( see below ) .
mouth asymmetry ( mouth bending angle ) is not significantly correlated with foraging handedness in juvenile p . microlepis . ( a ) two month ( r = 0 . 148 ; p = 0 . 255 ) ; ( b ) three month ( r = −0 . 229 ; p = 0 . 154 ) ; ( c ) seven month old fish ( r = 0 . 069 ; p = 0 . 749 ) . note that 11 fish were tested at two different ontogenetic stages ( i . e . at three and seven months of age ) .
several important questions about this fish , including the bases of its behavioral and morphological laterality remain unanswered [ 20 ] . mouth laterality of p . microlepis has been suggested to be genetically determined by a single mendelian locus with two alleles : the ‘r’ - allele was suggested to be dominant over the ‘l’ - allele and ‘r’ was suggested to be homozygous lethal [ 8 ] , [ 14 ] , [ 21 ] . but a recent review [ 20 ] noted that the data reported so far ( of mouth - morph ratios in the offspring of parents of known laterality ) actually are inconsistent with a single locus mendelian model . this model was further questioned because the distribution of mouth asymmetry was found to be unimodal rather than bimodal [ 18 ] , [ 21 ] ( kusche , lee , meyer , in revision ) . phenotypic plasticity may therefore play a role in shaping mouth asymmetry [ 18 ] and hence , head asymmetry may be governed by both genetic and environmental factors [ 18 ] ( lee et al . , unpublished data ) . the genetic and / or environmental basis of behavioral handedness in p . microlepis , however , remains largely unexplored .
this species belongs to the deep benthic community . it feed upon the scales of a variety of benthic species , chiefly cichlids . they are probably solitary except during periodsof reproduction . young p . microlepis have been only been seen close to the shore . its diet shifts from a variety of micro - organisms and algae when young to an adult diet of mainly fish scales . little is known about its reproduction although it is known to reproduce inshore among rocks and is remarkable for showing features both of mouth - brooding and substrate - guarding , the two major patterns of parental shown in cichlids
the foraging experiments with juvenile fish in the laboratory show that mouth asymmetry does not predict handedness in foraging behavior , possibly due to the small degree of mouth asymmetry . surprisingly , young and still quite small scale - eaters preyed on scales of prey fish and exhibited pronounced handed behavior ( figure 3 ) . even the two - month old fish readily fed on scales of similar - or even slightly larger - sized goldfish . however , the degree of mouth asymmetry in juvenile scale - eaters was rather small [ on average only 2 . 67° ( for two - month : sd = 1 . 92° ) , 2 . 01° ( three - month : sd = 1 . 73° ) and 2 . 12° ( seven - month : sd = 1 . 61° ) ] and the relationship between behavioral bias and morphological asymmetry was always non - significant ( figure 5 ) . note that the degree of mouth asymmetry in those laboratory - reared scale - eaters is indeed substantially lower than in wild - caught adult p . microlepis ( the average = 5 . 07° ; n = 238 ; sd = 3 . 51° ; kusche , lee , meyer , in revision ) . this too supports the hypothesis that handed behavior might play a significant role in shaping the asymmetry of mouths in p . microlepis .
furthermore , whether foraging handedness is expressed earlier during development and induces and thereby facilitates mouth asymmetry via phenotypic plasticity [ 15 ] , [ 18 ] or the reverse – remains unclear . hori [ 8 ] originally suggested that mouth laterality in p . microlepis is a functional ‘prerequisite’ for efficient lepidophagy . he further proposed that mouth asymmetry ( controlled by a single mendelian locus ) precedes and invokes and directs lateralized foraging behavior through natural selection . but , several lepidophagous cichlid species in lake tanganyika lack a pronounced laterality in their heads [ 21 ] and behavioral preferences have not been tested in these species . moreover , handed foraging behavior might actually precede , and even induce mouth asymmetry , given the purported role of phenotypic plasticity in mouth laterality [ 18 ] .
the same clear pattern was found in the 13 pools with one pair of p . microlepis each as predators ( figure 2 c , d ) : seven rl pairs fed from both flanks with similar frequencies ( ratio of attacked left flanks : 40–60 % ; average : 52 % ; median : 50 % ) and produced similar amount of damage onto both flanks ( range of foraging scores on left flanks : 25–67 % ; average : 48 % ; median : 50 % ) . five rr pairs strongly preferred to feed from the left flank ( range : 67–100 % ; average : 88 % ; median : 100 % ) , which caused more bites on that flank ( range : 83–100 % ; average : 94 % ; median : 100 % ) . a single ll pair exclusively fed from the right flanks of their prey fish . differences in foraging patterns such as foraging preference and foraging score among morph pair combinations were both highly statistically significant ( wilcoxon - rank - sum - test with continuity correction : proportion of left flanks affected : w = 35 , p < 0 . 01 ; proportion of foraging scores at the left flank : w = 35 , p < 0 . 01 ) .
juvenile p . microlepis of about two [ n = 61 ; mean standard length ( sl ) = 3 . 2 cm ; sd = 0 . 28 cm ] , three [ n = 47 ; total length ( tl ) = 3–4 cm ] and seven [ n = 24 ; mean total length ( tl ) = 7 . 7 cm ; sd = 0 . 58 cm ] months of age , that had not had an opportunity to eat scales from prey fish before , were tested for lateralized foraging behavior . the older test cohorts ( that were tested at three and seven months ) were caught as 1 - 2 week old fry in the field , whereas the fish tested at two months were bred in the laboratory ( the f 1 fish of the older cohorts ; see above ) . eleven of the three - month old fish were re - tested at seven months , but those individuals could not be traced due to logistical reasons . the scale - eaters were placed individually with a single prey fish ( platy fish , xiphophorus maculatus , for three - month old fish and goldfish , carassius auratus auratus , for two - and seven - month old fish ) in the trial tanks .
neither of the juvenile cohorts showed a significant correlation between mouth asymmetry and lateralized foraging behavior ( two - month old fish : r = 0 . 148 ; p = 0 . 255 ; three - month : r = −0 . 229 ; p = 0 . 154 ; seven - month : r = 0 . 069 ; p = 0 . 749 ; figure 5 ) . unexpectedly , some fish that were morphologically scored as ( slightly ) r - morphs ( with negative values of mouth bending angle of α l − β r ) occasionally even attacked the right side more frequently than the left side , and vice versa ( figure 5 ) . this lack of correspondence suggests that mouth laterality is not a prerequisite for handed foraging behavior for juvenile p . microlepis . also , the level of mouth asymmetry ( i . e . absolute values of mouth bending angles ) of the laboratory - reared juvenile fish did not significantly increase with body size in either two - ( n = 61 , y = 0 . 831 x + 0 . 04 , r 2 = 0 . 015 , p = 0 . 35 ) or seven - ( n = 24 , y = −0 . 496 x + 5 . 394 , r 2 = 0 . 032 , p = 0 . 4 ) month old fish .
through phenotypic effects of “use and disuse” , handed behavior has been shown to drive morphological laterality in different animal groups ( e . g . lobsters [ 37 ] ; snakes [ 4 ] , [ 5 ] ; humans [ 38 ] ) ( reviewed in [ 15 ] ) . lobsters provide a clear example of how claw asymmetry is shaped during development as a function of handed behavior [ 37 ] . laboratory experiments demonstrated that differential use of claws during early juvenile stage induces and facilitates development of a crusher claw [ 37 ] . as such , in p . microlepis lateralized behavior might conceivably lead to an asymmetric remodeling of the structural elements ( e . g . bones ) involved in defining mouth shape [ 39 ] , given that lateralized behavior in fish sometimes has a strong additive genetic component [ 40 ] , [ 41 ] , e . g . , the estimated heritability of laterality of eye preference in the poeciliid fish , girardinus falcatus is 0 . 5 to 0 . 6 ) [ 40 ] . although we are uncertain whether handed scale - eating behavior is genetically programmed ( innate ) , rather than environmentally plastic ( learning ) or both [ 42 ] , the bimodal trait distribution in very young fish ( figure 3 ) speaks for a major genetic locus determining handedness in scale - eating behavior ( [ 18 ] ) .
to more precisely quantify ‘behavioral’ foraging preference in juvenile p . microlepis , a second series of experiments for the seven - and later two - month old scale - eaters was carried out . for each seven - month old individual , its foraging behavior was monitored ( in 3–4 replicates during 1–2 weeks ) by counting the number of attacks to the left and / or right flanks on a single goldfish , until a total of maximally 20 attacks per individual within up to 30 minutes were reached . the scale - eaters showed reported natural foraging behavior , i . e . , they attacked prey from behind [ 8 ] . in only a few cases they attacked from the front , but those attacks were not counted . behavioral foraging preference ( i . e . probability of left attack ) was again found to be consistent among the 3–4 trials ( repeated - measure anova ; f 3 , 45 = 0 . 363 , p = 0 . 78 ) as observed in the three - month old fish . therefore , the handedness scores ( e . g . number of left and right attacks ) were pooled over the trials to calculate behavioral foraging preference for each scale - eater . the total number of attacks observed per fish ranged from 39 to 80 ( mean = 64 ) . for the two - month old scale - eaters , we employed the same procedure as for the seven - month old fish , except that we conducted only one experimental trial per individual . the average number of attacks observed per fish in this test cohort was 19 .
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citation : lee hj , kusche h , meyer a ( 2012 ) handed foraging behavior in scale - eating cichlid fish : its potential role in shaping morphological asymmetry . plos one 7 ( 9 ) : e44670 . urltoken
copyright : © lee et al . this is an open - access article distributed under the terms of the creative commons attribution license , which permits unrestricted use , distribution , and reproduction in any medium , provided the original author and source are credited .
funding : financial support was provided through a travel grant from the international max planck research school ( imprs ) for organismal biology to hk , through the zukunftskolleg postdoctoral fellowship to hl , through grants of the deutsche forschungsgemeinschaft ( dfg ) to hl ( le2848 / 1 - 1 ) and am , the young scholar fund ( ysf ) to hl ( fp 411 / 12 ) and the university of konstanz to am . the funders had no role in study design , data collection and analysis , decision to publish , or preparation of the manuscript .
competing interests : axel meyer is a plos one academic editor . this does not alter the authors ' adherence to all the plos one policies on sharing data and materials .
handed behavior has also been frequently reported in fish , e . g . , with respect to eye usage preference ( i . e . visual lateralization ) in a poeciliid fish [ 9 ] , [ 10 ] , swimming - turns in zebra - and goldfish [ 11 ] and foraging in a freshwater goby [ 12 ] and in some african cichlid fishes [ 13 ] , [ 14 ] . lateralized behavior in fish is often correlated with morphological asymmetries . in the herbivorous cichlid telmatochromis temporalis , for example , the right mouth morph uses the right side of the jaw more frequently and the left morph the left side [ 13 ] . a significant correlation between lateralization in swimming and the anatomical bias of the prevalence of different muscle types was found in zebrafish [ 11 ] . however , relatively little effort has been directed towards the exploration of the potential role of handed behavior in facilitating morphological laterality [ 15 ] .
five broods from different parents of determined mouth - laterality ( 3 rl and 2 rr pairs ) were transported to the animal care facility at the university of konstanz . in total , 65 young were raised brood - wise in separate 40 l and later 200 l aquaria with artemia nauplii and flake food . these fish were used for laboratory feeding experiments on juveniles as well as for quantitative measures of mouth asymmetry ( kusche , lee , meyer , in revision ) .
field research was conducted under the study permit ( g . r . no : 2077761 ) granted by the government of the republic of zambia ( immigration department , ministry of home affairs , republic of zambia ) according to their immigration and deportation act . cap123 , section 16 . animal care of the fish and all foraging experiments in the laboratory were approved by the regional board of animal welfare in germany ( regierungspräsidium freiburg , abteilung landwirtschaft , ländlicher raum , veterinär - und lebensmittelwesen ) ( permit number : 35 / 9185 . 81 / g - 10 / 96 ) .
percentages of pooled attacked left ( and right ) flanks of prey fish were calculated for each tank . we considered these estimates as foraging preference for a particular side , given that the scale - eaters had in principle an equal opportunity to attack both flanks . foraging preference was further assessed by taking into account foraging scores reflecting different levels of injury ( i . e . the amount of damage done by the scale - eaters ; 0 bites = 0 scores ; 1–3 bites = 1 score ; 4–6 bites = 2 scores ; > 6 bites = 3 scores ) . the proportion of these scores for the prey fishes ' pooled left ( and right ) flanks was calculated for each tank .
two - tailed fisher ' s exact probability tests were performed to examine whether in both community tanks the left or right side of the prey fish were preferentially attacked and whether the morphs differed in their foraging scores . a mann - whitney - test was performed to test for differences in ratios of affected left flanks of the prey as well as in the amount of foraging scores between rl and rr pairs .
two different methods were used to analyze foraging behavior . for the three - month old fish , one prey fish was added to a 40 l aquarium and after 12 hours , the prey fish was examined for scars and missing scales by two different researchers ( h . l . and h . k . ) . this procedure was replicated ( 2–5 times ) for each individual scale - eater to investigate whether its foraging behavior was consistent across a series of 2–5 experimental trials during a period of 1–2 weeks . because it was impossible to enumerate number of scars and missing scales on the prey fish ( x . maculatus ) , foraging preference was assessed for each scale - eater based on observed presence / absence of scars and missing scales . a foraging score of + 1 was given for fish that attacked only the right side of prey fish in a particular trial , a score of 0 meant that both sides were attacked , and a score of −1 was given for fish that attacked only the left side . the trials where no scars and no missing scales were observed on the prey fish , or where the prey fish died during the experiments were excluded from the analysis . since the estimated foraging score of each individual was found to be constant over the trials ( e . g . 2 trials : wilcoxon - signed - ranks - test , n = 17 , z = −0 . 333 , p = 1 . 0 ; 3 trials : friedman - test , n = 12 , chi - square statistic = 4 . 333 , p = 0 . 189 ) , the mean foraging score was calculated and used in further analyses . note that the foraging score of 34 scale - eaters was calculated from the 2–5 trials , while that of 10 individuals was obtained from a single trial only . only three of the 47 scale - eaters ( 6 % ) tested at three months never fed on scales .
to investigate whether behavioral foraging preference is translated into foraging score ( e . g . number of scales bitten by the scale - eaters ) , surface areas of attacked left and right flanks of prey ( i . e . surface areas of scars and missing scales ) were calculated for a sub - sample ( n = 15 ) of the two - month old fish . because individual fish that exclusively attacked one side of the prey only left scars / missing scales at that flank ( 100 % ) , the 15 fish were selected from individuals that did not forage exclusively from one side ( e . g . 0 . 1 < probability of left attack < 0 . 9 ) . the attacked areas of the prey fish were estimated in imagej 1 . 45r ( urltoken ) from standardized photographs in a lateral view with an implemented scale . a ratio of the attacked areas ( left to right flanks ) on the prey fish was calculated for each scale - eater and linear regression analysis was then conducted using probability of left attack as an independent variable ( predictor ) and the estimated ratio as a dependent ( response ) variable .
the mouth bending angle , ‘α l − β r’ in ° following [ 14 ] was measured to test for a relationship between mouth / head asymmetry and handed foraging behavior in juvenile fish . for this test , each live test fish was photographed from a dorsal view in a standardized upright position using a zeiss axiophot digital microscope ( zeiss , germany ) . the mouth bending angles were then measured in imagej 1 . 45r : on each image , a triangle connecting the most anterior points of the eye sockets and the tip of the snout was drawn to estimate angles ( ° ) , α l ( angle of the vertex by the left eye ) and β r ( angle of the vertex by the right eye ) ( kusche , lee , meyer , in revision ) .
to evaluate the accuracy of the measurements , repeatability of α l − β r was estimated from repeated and blind measurements that were done from two replicate photographs of the same individuals from sub - samples ( n = 20 , 15 and 15 for the two - , three - and seven - month old fish , respectively ) . repeatability , referred to as the proportion of the total variation that is due to variation among individuals , was calculated from one - way anova ( individual = factor ) following [ 27 ] .
correlation analyses were performed between mouth bending angles and foraging score ( for our test cohort of the three - month old fish ) and behavioral foraging preference ( probability of left attack for the two - and seven - month old fish ) to test for the significant relationship between mouth asymmetry and behavioral handedness . linear regression analyses were also carried out to test whether mouth asymmetry amplifies as body size increases in the two - and seven - month old fish . for those analyses , sl ( standard length ) and tl ( total length ) were used as size measures for the two - and seven - month old fish , respectively .
mouth laterality strongly predicted the preferred attack side as well as foraging scores on either side of the prey fish ( figure 2 ; table s1 ) . both l - and r - mouth morphs from the community tanks clearly exhibited opposed foraging preferences ( fisher ' s exact probability test : n = 41 ; p < 0 . 001 ) and yielded more scars / missing scales in foraging from their preferred flanks ( fisher ' s exact probability test : n = 63 ; p < 0 . 0001 ) ( figure 2 a , b ) . r - morphs preferentially attacked left flanks of the prey fish ( 80 % of affected flanks ; 82 % of foraging scores ) . l - morphs preferred to feed from right flanks ( 75 % of affected flanks ; 80 % of foraging scores ) .
mouth asymmetry strongly predicts foraging preferences and foraging scores in community tanks ( a and b ) and pair tanks ( c and d ) of different laterality combinations .
feeding experiments with laboratory - raised juveniles showed that nearly all test fish preyed immediately on scales . scale - eating behavior is already expressed at an early ontogenetic stage ( two - month old : 100 % ; three - month old : 94 % ; seven - month old : 100 % ) . most individuals showed a clear bias to attack only a particular side of their prey and the frequency distribution of the foraging score and behavioral foraging preference clearly exhibited a bimodal distribution ( except in the seven - month old fish ) ( figure 3 ) . foraging behavior of the younger test cohorts ( of two and three months of age ) showed a significant departure from a unimodal distribution ( two - month old : dip statistic = 0 . 114 , p < 0 . 001 ; three - month old : dip statistic = 0 . 136 , p < 0 . 001 ) , whereas the oldest cohort of seven months of age did not ( dip statistic = 0 . 057 , p > 0 . 5 ) . the mixture analyses with the parametric bootstrap tests further showed that two - component normal distributions best fitted foraging behavior data of the two - ( p < 0 . 001 ) and three - month old fish ( p < 0 . 001 ) , while one - component normal distribution statistically best fitted the data of the seven - month old fish with marginal significance ( p = 0 . 057 ) . however , the graphical inspection of the mixture analysis ( figure 3 c ) and a marginal significance of platykurtosis ( p = 0 . 092 ) rather support a weak bimodal distribution [ 28 ] .
frequency distribution of behavioral foraging preference ( for two - and seven - month old fish ) and foraging score ( for three - month old fish ) shows a bimodal distribution . ( a ) two month ; ( b ) three month ; ( c ) seven month old fish . in ( c ) , the graphical inspection of the mixture analysis ( fitting two single - component normal distributions to the data ) is shown , indicating that the distribution better fits to bimodality than to unimodality , despite a marginal statistical significance of one single - component normal distribution ( p = 0 . 057 ) .
there was considerable ‘inter - individual’ variation in the intensity ( strength ) of lateralized foraging behavior ( figure 3 ) . many fish strongly preferred or even exclusively attacked the left or the right sides [ e . g . 7 of 61 ( 12 % ) and 15 of 61 ( 25 % ) of the two - month old fish foraged exclusively from the left and the right sides , respectively ] , while other fish displayed a less pronounced bias in foraging behavior ( figure 3 ) .
as predicted , a highly significant positive correlation was found between behavioral foraging preference and foraging score in the subset ( n = 15 ) of the two - month old juveniles ( y = 1 . 787 x + 0 . 176 , r 2 = 0 . 759 , p < 0 . 001 ; figure 4 ) , suggesting that foraging score is an outcome of behavioral attack preference . this result further indicates that our field data on foraging preference and foraging score of wild - caught adult fish could indeed reflect ‘behavioral’ foraging preference .
lateralized foraging behavior and foraging score ( e . g . number of scales eaten by the scale - eaters ) are highly significantly correlated ( in a sub - sample [ n = 15 ] of the two - month old fish [ y = 1 . 787 x + 0 . 176 , r 2 = 0 . 759 , p < 0 . 001 ] ) .
our measurements of mouth bending angles appeared to be fairly repeatable : estimated repeatability of the mouth bending angles was 0 . 80 , 0 . 77 and 0 . 87 for the two - , three - and seven - month old fish , respectively . those estimates of the repeatability imply that 77 to 87 % of the total observed variation is attributed to underlying ‘true’ variation in the mouth bending angles among individuals and the remaining 13 to 23 % variation is due to measurement error .
the observed strong lateralization in foraging behavior in young scale - eaters ( e . g . bimodal distribution ) that was not accompanied by notable morphological asymmetry ( see also kusche , lee , meyer , in revision ) and the obvious correspondence between mouth orientation and foraging behavior in adult fish might suggest that handed behavior is probably expressed earlier during development . and , it may actually induce and facilitate morphological asymmetry [ 18 ] , if phenotypic plasticity plays a relatively larger role than the genetic determination of this trait ( lee et al . , unpublished data ) . an alternative hypothesis is that both handed behavior and morphological laterality are genetically governed , but expressed at different ontogenetic stages . however , this hypothesis would seem to be rather unlikely given our observation that laboratory - reared fish of now about two - year of age still have a relatively symmetrical mouth ( hl , personal observation ) .
however , we observed a rather more pronounced laterality in foraging behavior among the younger juvenile fish ( e . g . at two and three months ) , compared to the fish at seven months . the observed dwindling laterality in foraging behavior in the older fish might imply that feeding preference is expressed at an early age ( e . g . at two months ) , but the initial level of laterality would diminish over time ( under laboratory conditions ) unless the fish were constantly to feed on scales . yet , whether this trend means the strength of handed behavior truly decreases with age awaits future experiments on “tracked” individuals over a series of ontogenetic stages during their life time .
we here argue that the hypothesis – ‘handed behavior preceding and driving mouth asymmetry’ [ 15 ] , [ 18 ] – seems more strongly supported by evidence than the original hypothesis [ 8 ] that mouth asymmetry precedes and directs lateralized foraging behavior through natural selection acting on a single gene . different lines of evidence support this hypothesis . in a parallel study , we observed a large amount of variation in mouth asymmetry in 238 wild - caught adult specimens and found a continuous and unimodal ( and not bimodal ) trait distribution ( kusche , lee , meyer , in revision ) . if plasticity rather than genetics plays a comparatively larger role ( lee et al . , unpublished data ) , then this unimodal distribution of laterality might simply be the outcome of different levels of lateralization in foraging behavior . this hypothesis is supported by the findings from the foraging experiments of juvenile fish : juvenile fish did not show complete lateralization of foraging preference and even some individuals attacked equally often at both flanks . whether symmetrically attacking fish might have a potential selective advantage over left or right preferentially attacking fish needs to be tested .
a significant role of phenotypic plasticity in the evolutionary origin of novel morphologies has been suggested repeatedly during the last several decades [ 15 ] , [ 29 ] – [ 32 ] . phenotypic plasticity clearly contributes to shaping the morphology of the jaw and the mouth apparatus in teleost fishes , particularly in cichlids [ 33 ] , [ 34 ] . even different food types or diet hardness can induce changes in the external shape of the head during the ontogeny of some cichlids [ 33 ] , [ 35 ] . the teleost skeleton can quickly adapt to changing external factors , so called ‘mechanical adaptation’ , and skeletal phenotypic plasticity in teleosts seems to be rather pronounced and taxonomically widespread [ 36 ] .
we thank christian sturmbauer for support in the field . thanks to frederico henning for statistical advice and julia c . jones , tom j . m . van dooren and richard a . palmer for helpful comments on an earlier version of the manuscript . we thank mr . zyambo , mr . chiti , mr . chansa , mr . musosa and particularly gabriele legant for their superb technical assistance in the field .
conceived and designed the experiments : hl hk am . performed the experiments : hl hk am . analyzed the data : hl hk . contributed reagents / materials / analysis tools : hl hk am . wrote the paper : hl hk am .
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science 09 apr 1993 : vol . 260 , issue 5105 , pp . 216 - 219 doi : 10 . 1126 / science . 260 . 5105 . 216
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greek , perissos = uneven + greek , odous = teeth ( ref . 45335 )
maturity : l m ? range ? - ? cm max length : 11 . 0 cm tl male / unsexed ; ( ref . 5678 )
scale - eating . prefers fish that feed from the algal layer or fish which are inattentive , the usual prey being tropheus and pseudosimochromis ( ref . 7343 ) .
phylogenetic diversity index ( ref . 82805 ) : pd 50 = 0 . 7500 [ uniqueness , from 0 . 5 = low to 2 . 0 = high ] .
bayesian length - weight : a = 0 . 01514 ( 0 . 00700 - 0 . 03275 ) , b = 2 . 97 ( 2 . 80 - 3 . 14 ) , in cm total length , based on lwr estimates for this ( sub ) family - body shape ( ref . 93245 ) .
trophic level ( ref . 69278 ) : 4 . 2 ±0 . 86 se ; based on food items .
resilience ( ref . 69278 ) : high , minimum population doubling time less than 15 months ( preliminary k or fecundity . ) .
vulnerability ( ref . 59153 ) : low vulnerability ( 13 of 100 ) .
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disclaimer : itis taxonomy is based on the latest scientific consensus available , and is provided as a general reference source for interested parties . however , it is not a legal authority for statutory or regulatory purposes . while every effort has been made to provide the most reliable and up - to - date information available , ultimate legal requirements with respect to species are contained in provisions of treaties to which the united states is a party , wildlife statutes , regulations , and any applicable notices that have been published in the federal register . for further information on u . s . legal requirements with respect to protected taxa , please contact the u . s . fish and wildlife service .
pronunciation : refer to our pronunciation key for an explanation of the phonetic symbols .
habitat : this is the primary location where the cichlid is found and is a generalization . this does not mean a fish cannot be found in other habitats .
diet : many cichlids specialize in eating one type of food ; notwithstanding , some of these specialized feeders are flexible and can be opportunistic feeders .
temperament : this describes the overall demeanor of a cichlid toward other tankmates that are of a different species . consider that there is variability in temperament due to various factors , including aquarium size , tankmates of similar appearance , stocking levels , and order of introduction . there may even be some variability among individual specimens .
conspecific temperament : this describes the overall demeanor of a cichlid toward other tank - mates of the same species . consider that there is variability in temperament due to such factors as aquarium size , stocking levels and order of introduction . there may even be some variability among individual specimens .
maximum size : this is in regards to total length ( including the tail ) of typical aquarium specimens . wild specimens may not attain this size , or may in fact grow larger than aquarium raised individuals due to various factors . also consider that this is the typical maximum size and there are exceptional individuals that will exceed it .
difficulty : this measure is a relative value , comparing a single species against all other cichlids . this only accounts for maintanence in the aquarium and not breeding considerations . 1 = easy and forgiving , 5 = extremely challenging .
many people know organisms only by the common names , or
vernacular
names . unlike scientific names , common names are almost always different for speakers of different languages . they may also vary regionally within a language . this tab shows all the common names provided to eol for this organism from a variety of providers , including eol curators . currently we can only set one preferred common name per language on a given eol page , but all the names should be searchable .
eol content is automatically assembled from many different content providers . as a result , from time to time you may find pages on eol that are confusing .
to request an improvement , please leave a comment on the page . thank you !
baerends , g . p . & j . m . baerends - van roon . 1950 . an introduction to the study of the ethology of cichlid fishes . behaviour suppl . 1 : 1–242 .
barlow , g . w . 1974 . contrasts in social behavior between central american cichlid fishes and coral - reef surgeon fishes . amer . zool . 14 : 9–34 .
brichard , p . 1978 . fishes of lake tanganyika . t . f . h . publications , neptune city . 448 pp .
davies , n . b . 1978 . ecological questions about territorial behaviour . pp . 317–350 .
j . r . krebs & n . b . davies ( ed . ) behavioural ecology , and evolutionary approach , blackwell , oxford .
fryer , g . & t . d . iles . 1972 . the cichlid fishes of the great lakes of africa . oliver and boyd , edinburgh . 641 pp .
keenleyside m . h . a . 1978 . parental care behavior in fishes and birds . pp . 3–29 .
e . s . reese & f . j . lighter ( ed . ) contrasts in bahavior , wiley and sons , new york .
keenleyside , m . h . a . 1979 . diversity and adaptation in fish behaviour . springer - verlag , new york . 208 pp .
krebs , j . r . & n . b . davies . 1981 . an introduction to behavioural ecology . blackwell , oxford . 292 pp .
lewis , d . s . c . 1980 . mixed species broods in lake malawi cichlids : an alternative to the cuckoo theory . copeia 1980 : 874–875 .
liem , k . f . & d . j . stewart . 1976 . evolution of the scale - eating cichlid fishes of lake tanganyika : a generic revision with a description of a new species . bull . mus . comp . zool . 147 : 319–350 .


the secretarybird or secretary bird ( sagittarius serpentarius ) is a very large , mostly terrestrial bird of prey .

endemic to africa , it is usually found in the open grasslands and savannah of the sub-saharan region .

although a member of the order accipitriformes , which also includes many other diurnal raptors such as kites , hawks , vultures , and harriers , it is given its own family , sagittariidae .

it appears on the coats of arms of sudan and south africa .

secretarybird

fuertes’ secretarybird by louis agassiz fuertes is licensed under public domain mark 1 . 0 .
global raptor information network . species account : secretarybird sagittarius serpentarius ( july , 2010 ) urltoken
secretarybird by ian white is licensed under cc by - nc - sa 2 . 0 .
museum specimens indicate historical distributions . the map below shows locations from which museum specimens of secretarybird were collected . you can see more information on the individual museum specimens of secretarybird here .
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secretarybird with a tasty treat by jean & nathalie is licensed under cc by 2 . 0 .
sabap comparison map for the secretarybird , extracted 19 april 2013 . colour coding of qdgcs as per
secretarybird can reach 4 to 5 feet in height and 5 to 9 ½ pounds of weight .
researchers used to believe that name
secretarybird
originates from 19th century when male secretaries wore quills in their wigs ( similar in appearance with crest of secretarybird ) . more likely , name
secretarybird
originates from arabic word
saqu ettair
which means
hunter - bird
.
southern african bird atlas project ( sabap ) comparison map for the secretarybird , extracted 19 april 2013 .
the secretarybird has always been admired by the african people due to its striking appearance and great ally against pests such as snakes and rodents . the secretarybird is also known as the devil horse by many african cultures .
the secretarybird is the national emblem of sudan and is also on the south african coat of arms , representing vigilance and military might . the secretarybird also appears on many postage stamps in over 30 countries in africa .
a third fossil bird from 10 million year - old nebraska rocks has been called the
false secretarybird
since its similarity to the modern secretarybird is believed to be due to convergence rather than a close genetic relationship .
the secretarybird is a nomadic species and will often travel far and wide in search of food and other resources .
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the secretarybird was supposedly named because it resembles an old - fashioned secretary carrying quill - pens tucked behind her ears .
habitat : secretarybird lives in open grass plains and steppes , also in savannahs with scarce bushes and open spaces between trees .
monster hunter on twitter :
# nationalbirdday fun fact : seregios was inspired by the secretarybird and its stomping attack . urltoken urltoken
a large bird of prey , the secretarybird feeds mainly on large insects and small mammals , which it often stamps on before swallowing whole .
the secretarybird is endemic to sub - saharan africa . it ranges from senegal and somalia all the way to the tip of south africa .
embed this arkive thumbnail link (
portlet
) by copying and pasting the code below . < a href =
urltoken
title =
arkive species - secretarybird ( sagittarius serpentarius )
> < img src =
urltoken
alt =
arkive species - secretarybird ( sagittarius serpentarius )
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arkive species - secretarybird ( sagittarius serpentarius )
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baker n , brouwer j , baker l , sinclair a , harebottle d , et al . . ( 2010 ) the status of the secretarybird
diet : secretarybird feeds mainly on insects ( grasshoppers ) , lizards , small birds and eggs , young hares , rodents , small amphibians and snakes .
although it can fly , the secretarybird prefers to move around on foot and can cover 30 km a day , earning it the title ‘africa’s marching eagle’ .
the secretarybird is classified as vulnerable ( vu ) on the iucn red list ( 1 ) , and listed on appendix ii of cites ( 3 ) .
the secretary bird or secretarybird is a bird of prey found widely across africa , belonging to the same order as hawks , vultures , kites and harriers .
unlike many other birds of prey , the secretarybird often catches it prey with its bill . but like many owl species , secretarybirds swallow most of their prey whole .
protection / threats / status : secretarybird is officially protected because it kills poisonous snakes , but decline of this species continues , and they don’t breed successfully in captivity .
the secretarybird is the odd man out amongst the raptors . it ' s a grey and black terrestrial eagle , 1 . 3m tall , with a distinctive red face .
kemp , a . c . 1995 . aspects of the breeding and behaviour of the secretarybird sagittarius serpentarius near pretoria , south africa . ostrich , 66 : 61 - 68 .
secretarybird has wingspan of 7 feet . these birds rarely fly even though they are proficient in the air . they fly with the help of warm air currents to preserve energy .
the secretarybird is a charismatic and familiar species , and uses a variety of habitats across its range in sub - saharan africa . it occurs in all nine provinces in south africa .
the secretarybird is easy to identify ; it has long legs , grey - black plumage , crest feathers and orange facial skin . in flight its long elongated central tail feathers are characteristic .
the common name secretarybird is said to derive from the bird’s crest of long feathers which look like the long quill pens that the olden day secretaries had tucked behind their ears or in their wigs .
citation : hofmeyr sd , symes ct , underhill lg ( 2014 ) secretarybird sagittarius serpentarius population trends and ecology : insights from south african citizen science data . plos one 9 ( 5 ) : e96772 . urltoken
it is regularly told in south africa that the common name of the secretarybird is due to the dark quill like feathers , resembling a quill pen behind the ear ( apparently common practice for an 18th century secretary ) .
the secretarybird has a widespread distribution throughout much of sub - saharan africa , from senegal and the gambia in the west across to ethiopia in the east , and extending southwards through the eastern african countries into south africa . a fairly nomadic species , the secretarybird will often travel widely in search of food , or in response to rainfall , fires and other changes in environmental conditions ( 2 ) ( 4 ) ( 5 ) ( 7 ) .
secretarybird is large bird of prey that lives in the sub - saharan africa . secretarybird usually inhabits savannas and open grasslands which enable fast identification of the potential prey . other than that , secretarybirds can be found in semi - deserts , forests and farmlands . secretarybirds are threatened by habitat loss due to increased agriculture and urban development . luckily , number of secretarybirds in the wild is large and they are not on the list of endangered species .
dean wrj , simmons re ( 2005 ) secretarybird . in : hockey par , dean wrj , ryan pg , editors . roberts birds of southern africa . trustees of the john voelcker bird book fund : cape town . pp . 542–543 .
behaviour : secretarybird is largely terrestrial , but it is a very good flier . they hunt for preys in grass , walking or running very fast . secretarybird feeds on snakes , and has a method to catch them . it stamps the snake with its long legs and its short but hard rear talon . it is quite equipped to tackle them . it may kill them by grabbing the victim , and beating it to death on the ground . prey may also be tossed into the air several times to stunt it . secretarybird is not immune to the snake poison , and it has to be sure that its prey is dead before to eat . secretarybirds often hunt in small groups or in pair , and keep contact by hooting .
the secretarybird breeds year - round , but with a distinct peak during the spring and summer months further south . two to three broods are often reared in productive years after good rainfall ( 7 ) . the secretarybird makes a nest out of sticks , creating a large platform on a flat - topped acacia tree or other thorny bush , and lining it with dry grass and other materials . it may also nest in non - thorny or exotic tree species if preferred nesting sites are not available .
a more recent theory on the naming of the secretarybird , is that it is a corruption of the arabic saqu ettair meaning
hunter - bird
, which passed , incorrectly , into french as secrétaire & was subsequently translated into english as secretary .
voice : sounds by xeno - canto secretarybird is a silent bird . but when it is displaying , it utters a hoarse croaking sound , very deep and rapid . it may also make a kind of mewing noise during the night , on the roost - site .
kemp ac ( 1994 ) family sagittariidae ( secretarybird ) . in : del hoyo j , elliott a , sargatal j , editors . handbook of the birds of the world . vol 2 . new world vultures to guineafowl . lynx edicions : barcelona . pp . 206–215 .
below are links to dedicated pages for each secretarybird which has been fitted with a tracking device . basic information about each bird as well as a map indicating the movement of the bird can be found on each page . the pages will be updated on a regular basis .
although usually found in grassland and open savanna scattered with small thorny trees , the secretarybird also inhabits farmland , particularly where cereals are grown , as well as semi - desert habitats and grassy , open clearings in forests and woodlands ( 2 ) ( 4 ) ( 5 ) .
we develop a method for inferring changes in abundance from atlas reporting rates , with a measure of statistical significance attached . while the count data provided by the car project are not useful for a species such as the secretarybird , because of its low general abundance and nomadic / wide - ranging behaviour [ 3 ] , the habitat use data provide information about the species ' ecology . together , these analyses provide important insights into the conservation status of the secretarybird in south africa in 2013 , which would not have been possible without the existence of these citizen science data .
although its population is distributed over a vast area covering more than 15 million square kilometres , the secretarybird is generally in decline , and is thought to have completely disappeared from west africa in the last 30 years ( 2 ) ( 5 ) ( 8 ) . this species is increasingly threatened by the expansion of human populations , and the associated spread of cultivation and urbanisation ( 2 ) ( 8 ) . on a smaller scale , some populations of the secretarybird are at risk from hunting and persecution , with several individuals found poisoned or injured in south africa in recent years ( 5 ) .
the secretarybird is easily distinguished from other raptors and cranes by its grey plumage , the orange facial skin with raptor - like beak and the characteristic stealthy stride it takes as it moves through the grass in search of prey . the shape of the body is very similar to that of an eagle but walks on the legs of a stork or crane . the sexes are alike with the males having a slightly longer crest and tail than the female . a full grown secretarybird can reach a mass of 4kg ( max 4 . 5 ) and a reach an astonishing 1 . 4 meters tall with a wingspan of 191 - 220cm . in flight one would think that this bird could be confused with the similar coloured grey crowned crane , but it can easily be distinguished due to its barred tail feathers . with a tail of around 75cm long the secretarybird is the record holder for the longest tail in africa .
bill is short , strong , hocked and pale grey . secretarybird has a patch of bare facial skin , which extends behind and above eyes , orange - red in colour . eyes are dark - brown , with very long black eyelashes . both sexes are similar , with male slightly larger than female .
flight : secretarybird is a very good flier . it uses thermal currents to ascend and it soars for long distances . when it is threatened , the bird runs with spread wings , but it will take off and fly strongly if necessary . it may rise on thermals up to nearly 4000 metres elevation .
the secretarybird is a very distinctive bird , which is the sole member of the genus sagittarius . it is only found in africa , in the grass plains & steppes south of the sahara . it is the only bird of prey predominantly terrestial habits , they may walk up to 20 miles in a day .
as a grassland specialist , it avoids dense bush and rocky habitats . the secretarybird walks purposefully across the veld at up to 3km / h looking for prey . its long legs are exceptionally strong and it uses them to stamp on small animals or hold them down while it tears at them with its beak .
insects form the bulk of its diet but it will take rodents and other small mammals , snakes and birds such as the laughing dove and sabota lark . shangaan traditional healers value the secretarybird for muthi . a concoction using its ground bones is reputed to bring respect and power , and the ability to overcome ones fears .
boshoff af , allan dg ( 1997 ) secretarybird sagittarius serpentarius in : harrison ja , allan dg , underhill lg , herremans m , tree aj , et al . . . , editors . the atlas of southern african birds . vol . 1 : non - passerines . birdlife south africa : johannesburg . pp . 152–153 .
secretarybird lets you focus on writing your poems , taking on the burden of managing your work ; allowing you to keep track of your poems and how they have been : revised , critiqued , read , entered for competitions and submitted for publication . with a few clicks you can sort , filter , classify and catalogue poems , review versions , track critiques and build collections . on startup you can have secretarybird pick up where you left off with your latest draft , making use of a standard or customised template , sequencing each version automatically . and you can have early warning of upcoming competitions . the application is benign , working alongside your existing dtp and text writing software .
as you may imagine , a bird with such long legs is built to do a lot of walking . and the secretarybird does not disappoint . scientists estimate that secretarybirds walk anywhere from 12 to 18 miles ( 20 - 30 km ) a day ! that would be like walking the length of an american football field 300 times or more .
baker n , brouwer j , baker l , sinclair a , harebottle d , et al . . ( 2010 ) the status of the secretarybird sagittarius serpentarius with special reference to tanzania and declines across the continent . a preliminary report to the uk cites scientific authority ( fauna ) , joint nature conservation committee . iringa : tanzania bird atlas project .
distribution of secretarybird in southern africa , based on statistical smoothing of the records from first sa bird atlas project ( © animal demography unit , university of cape town ; smoothing by birgit erni and francesca little ) . colours range from dark blue ( most common ) through to yellow ( least common ) . see here for the latest distribution from the sabap2 .
sabap comparison map for the secretarybird , extracted 19 april 2013 . colour coding of qdgcs as per figure 1 . additional data presented here are the reporting rates and z values used to colour - code qdgcs . the upper number in each square is the sabap1 reporting rate , the middle number is the sabap2 reporting rate , and the lower number is z .
it is quite surprising that we know very little about the biology of this species . we know , for example , very little about the secretarybird ' s population size and trends in south africa and other factors such as territory size . juvenile dispersal and general movements are also poorly understood . this information is needed if we are to conserve this threatened species .
reproduction : secretarybird usually mates for life , and they remain very close , even they hunt in different areas . both adults build a platform of sticks and grasses on the top of a low tree or a bush . their nest may reach 8 feet in diameter . they return each year to the same nest , adding some materials , more sticks and grasses .
roberts vii estimates there are approximately 250 secretarybirds in kruger , with each bird covering a daily foraging territory of about 20 square kilometres . they are known to fly far and wide , presumably for better feeding - a secretarybird ringed in the sabi sabi private reserve next to kruger was found four months later in namibia , over 1 500km away . see veld stalker .
a large and distinctive bird of prey , the secretarybird ( sagittarius serpentarius ) is said to take its unusual name from the strange and distinguishing arrangement of feathers on the back of its neck . this long , raised crest of black , spatula - shaped feathers ( 2 ) ( 4 ) ( 5 ) is said to give the secretarybird the appearance of an old - fashioned secretary who would carry quill - pens tucked behind the ears . more recently , the case has been put forward that the name may actually be derived from the arabic saqr - et - tair . saqr means ‘hunter’ or ‘hawk’ and tair means ‘flight’ or ‘bird’ , and the translation to french may have resulted in the common name that is used today ( 2 ) ( 5 ) .
the secretarybird occurs within some protected areas ( 8 ) , and in some places it has benefited from bush clearance and deforestation of woodlands to make way for agriculture ( 5 ) ( 8 ) . the secretarybird is protected under the african convention on the conservation of nature and natural resources , in the hope that the species will be protected by participating states from hunting , killing , capture or collection ( 9 ) . it is also listed on appendix ii of the convention on international trade in endangered species ( cites ) , meaning that international trade in the species should be carefully monitored ( 3 ) . these actions will hopefully act to safeguard populations of this unusual and charismatic bird of prey , although much will depend on the rate at which vital habitat across its range is lost to human development .
the secretarybird ( sagittarius serpentarius ) was uplisted from near - threatened to vulnerable . in south africa there is considerable concern about the conservation status of the species . a preliminary analysis of sabap1 and sabap2 data shows a considerable reduction in the areas this species previously occupied . this is probably mostly due to habitat loss and habitat degredation , but other threats such as power lines collisions are aslso taking their toll .
the secretarybird also has long , bare legs , which resemble those of a crane but are much more powerful , and end in small , stubby pink toes . juvenile secretarybirds are very similar to the adult , but are grey - eyed , with more brown in the plumage , a shorter tail and a yellow face , until the first moult ( 2 ) ( 4 ) ( 5 ) ( 6 ) .
sometimes described as africa’s ‘marching eagle’ , the secretarybird prefers to move around on foot , easily covering between 20 and 30 kilometres a day when hunting for food ( 2 ) . it spends much of its time stalking across the open ground , periodically stopping and stamping the floor to strike prey , which it will usually crush underfoot or repeatedly kick , before swallowing whole ( 2 ) ( 4 ) ( 5 ) . the secretarybird’s diet primarily consists of large insects and small mammals , mainly rodents . however , it will feed opportunistically on any animal it comes across on its wandering travels , including hares , mongooses , squirrels , snakes , lizards , amphibians , freshwater crabs , and birds up to the size of guineafowl , as well as their eggs . secretarybirds have also been known to take domestic chickens when foraging in areas close to human habitation ( 2 ) ( 5 ) .
the methods developed here represent an important new approach to the analysis of bird atlas data and habitat use data . these methods are applicable to other species covered by sabap and car , and could easily be adapted for use with similar datasets collected in other parts of the world and for other species . they are , however , exploratory and innovative , and necessarily come with caveats regarding their interpretation . that said , our sabap - related findings have received confirmation through an analysis of reporting rate changes for bird families throughout south africa [ 32 ] . this study modelled bird families in relation to the proportion of qdgcs in their range in which reporting rates had increased between sabap1 and sabap2 . sagittariidae ( a single - species family that includes only the secretarybird ) was fourth lowest in a list of 51 families . this implies that the secretarybird is faring particularly badly in comparison with the majority of other south african bird species .
unique not only for its name , the secretarybird stands out because of its distinct profile , quite unlike that of any other bird . the feathers on the body are generally grey across the back and paler towards the rump and breast , while the belly , thighs and flight feathers are all black . the underwings are white . the eyes are brown and are surrounded by bare facial skin that is a deep orange - red , and the bill is blue - grey .
birdlife south africa has initiated research on the secretarybird in order to understand aspects of its biology which will assist with its conservation . this research includes tracking the movements of secretarybirds using satellite tracking devices . with these devices the movement of individual birds can be determined in great detail . these devices provide accurate locations to within 10m every 15 minutes from sunrise to sunset . not only will it be possible to determine long distance movement patterns , but also habitat use and territory size .
following a courtship that is performed in flight and includes pendulum displays and calling ( 5 ) , the female secretarybird will lay a clutch of one to three eggs , which are incubated for around 42 to 46 days . the nestling period typically lasts between 65 to 106 days , with a post fledging - dependence period of 62 to 105 days . after this time the juvenile secretarybirds will leave the parental territory and range over long distances , displaying characteristic nomadic behaviour as immature birds ( 7 ) .
envision a large majestic bird of prey , sporting a hooked bill like an eagle and an impressive crest and tail of long , black feathers – but one that also walks along the ground on legs like a stork’s and could easily be mistaken for a crane while in flight . put those pieces together , and you’ve got yourself a secretarybird ! found only in the open grasslands and savannas of sub - saharan africa , the secretarybird looks quite unlike any other bird . it hunts on foot for small mammals , lizards , snakes , tortoises , insects , and young birds , and is most notorious for its ability to kill extremely venomous snakes by stomping them to death ! its name is probably derived from the arabic “saqr - et - tair , ” meaning hunter bird . we often see these birds strolling through the grass , and we’ve even spotted a few of their nests on top of the acacia trees . anything that eats venomous snakes is awesome in our opinion , and these birds are definitely awesome !
kemp , a . c . , kirwan , g . m . , christie , d . a . & marks , j . s . ( 2018 ) . secretarybird ( sagittarius serpentarius ) . in : del hoyo , j . , elliott , a . , sargatal , j . , christie , d . a . & de juana , e . ( eds . ) . handbook of the birds of the world alive . lynx edicions , barcelona . ( retrieved from urltoken on 9 july 2018 ) .
bird atlas data for south africa suggest that the secretarybird population declined across most of the country , and particularly severely in the kruger national park , between the early 1990s and the late 2000s–early 2010s . although these findings are of concern , this time period is relatively short , and in some less accessible areas coverage for sabap2 had not yet reached desirable levels . a longer data series and broader coverage are required before we would be able to state with confidence that the species population had declined significantly in south africa .
kemp , a . c . , kirwan , g . m . , christie , d . a . & marks , j . s . ( 2016 ) . secretarybird ( sagittarius serpentarius ) . in : del hoyo , j . , elliott , a . , sargatal , j . , christie , d . a . & de juana , e . ( eds . ) . handbook of the birds of the world alive . lynx edicions , barcelona . ( retrieved from urltoken on 23 august 2016 ) .
unlike the snail kite , which has a very specialized diet , t he secretarybird will eat just about anything it can catch . it preys on small - to medium - sized mammals such as mice , hedgehogs and hares . it eats other birds and their eggs , too ! it will catch amphibians and various invertebrates , including insects , scorpions , millipedes , and crabs . secretarynirds also eat snakes , including several poisonous species , such as puff adders and cobras , and other reptiles , such as lizards and small tortoises .
the tallest raptor in the world , the secretarybird is unmistakeable . it has long , stork - like legs that are feathered from the thigh to the tarsus . it has a robust body covered in gray , white and black feathers , a feathered black crest and a red - orange and yellow patch of skin around its eye and in front of its strong curved beak . though it looks more like a stork than a raptor when it flies , it is distinguishable from any other bird by the two long tail feathers that extend beyond its feet in flight .
the secretarybird is monogamous , living in closely knitted pairs that never stray too far from one another . the mating display includes a ground display where male and female chase each other with wings held up and back ( much like the way they chase prey ) or an aerial display of soaring high with an undulating flight pattern coupled with guttural croaking . mating happens on the ground or on an acacia tree . large flat nests made of sticks are built on top of flat acacia trees ( height : 5 - 7m ) and nests will be visited for almost half a year before the eggs are laid .
like many other wildlife , secretarybird populations are declining throughout much of their range and the species has disappeared entirely in some places . though these birds can spend time in and hunt in some human - created open spaces , habitat loss is still a huge problem for this species . areas that are over - grazed leave little cover for prey animals , so they can be quite empty of wildlife . other areas are being cleared for human settlements and agricultural fields – all places where a secretarbird won ' t find what it needs to survive . these changes in habitat are taking their toll on this lovely bird .
the secretarybird is a long - legged raptor , endemic to africa . it kills its prey ( snakes , lizards ) by stomping . the upper two images of nest - - building in the serengeti are courtesy of michael markussen ( left , 2 - 07 ) and fain zimmerman ( right , 2 - 08 ) . the 2nd , 3rd and right 4th row photos were taken in the serengeti ( 2 - 04 ) . the others were taken in ngorongoro crater ( 9 - 08 ) . click the photo above to see more including a displaying pair , nest - building , incubating , preening and hunting .
description : secretarybird is a very large bird of prey . its plumage is mostly grey , with black primaries , thighs , and a beautiful black crest of about twenty long feathers . tail is grey , barred by two broad black stripes , conspicuous when the bird is flying . tail presents two central feathers , longer than the others . the top of its very long legs is feathered with black . the lower leg is bare and pinkish - grey , covered with scales to protect them while it is walking or when it attacks some snake . toes are short , but very strong , with a powerful talon at the rear .
standing up to 4ft tall , it has very long legs , with black feathered thighs . it has a grey body , black feathers & white wing linings , its tail has two black central streamers . its most distinctive feature are the 20 black crest feathers , resembling quill pens stuck behind its ( invisible ) ears . this combination of features made it resemble a 19 th century clerk or secretary , in those days they were male & often wore tailcoats & knickerbocker trousers & placed their quill pens behind their ears . the head of the secretarybird ( with its yellowish bare patch ) and shape of the beak are very similar to those of the caracara . ( they also have a very long eyelashes , which many modern secretaries would appreciate ) .
during breeding season , secretarybirds perform flight displays . several males perform acrobatic flights , climbing high into the sky , and suddenly dropping down . they soar in wide circles high above the ground , with conspicuous long legs and tail projected behind , and uttering strange groaning . they also execute undulating swoops , downward dives , and both clasp each other talons , like eagles . secretarybird prefers to walk into its range , searching for food . it strides majestically across areas . it can fly very well , but rarely does so , because it hunts on the ground . it is able to walk up to 20 miles in a day . after young fledging , pair continues to roost in the nest at night , and they defend from this nest their territory , about 50 km2 around the nest site .
long - term public participation ( “citizen science” ) projects make it possible for observations made by many different people to be pooled and analysed as a whole [ 6 ] – [ 10 ] . they provide the best opportunity for assessing population trends in species such as the secretarybird . the first and second southern african bird atlas projects ( sabap1 , 1987–1992 , and sabap2 , 2007–present ) offer two snapshots of avian distribution in south africa approximately 15 years apart [ 11 ] , [ 12 ] . the coordinated avifaunal roadcounts ( car ) project ( described below ) , was established in the western cape in 1993 , by 1998 had expanded to cover much of south africa [ 13 ] , and in 2014 was ongoing . we examine the information provided by these datasets for useful insight into the status and ecology of secretarybirds .
secretarybirds feed on snakes , lizards , grasshoppers , mice , birds eggs & the occasional small mammal . it was once thought that snakes were the primary diet ( the latin name translates as
archer of snakes
) , but recent studies indicate that snakes make up only around 2 % of the diet . when feeding on snakes , they ensure are dead prior to eating , as they are not immune to the snakes poison . the secretarybird kills its prey by stamping on it , accurately aiming the rear talon at the skull . occasionally , aided by their height , they will pick the prey up & kill it by dropping it . it is often attracted to bush & grass fires , where it will feed on small animals that failed to avoid the fire . unlike other raptors , they have short stout toes that are unable to grasp .
) . the main exceptions were eastern karoo ( winter ) , north - eastern eastern cape ( winter ) and steenkampsberg ( both seasons ) . the eastern karoo result may seem surprising , because the sign tests indicate that a preference for natural habitats was expressed on a highly significant majority of routes . however , the proportion of available habitats that were transformed was extremely low ( less than 2 % ; unpublished data ) , so a similarly low proportion of birds needed to be seen on transformed land for the jacobs index to indicate that they were expressing a preference for that habitat . the karoo biomes are semi - desert , and in general the land is too dry for cultivation or pastures . where crops or pastures are grown , the land is usually irrigated , which may cause the biomass of potential secretarybird prey species ( rodents , reptiles , small birds , insects ) to increase . if this is the case , it would make sense for secretarybirds to prefer transformed habitats where they are available in the karoo . in fact secretarybirds are thinly distributed in the karoo , preferring grassland and savanna habitats
habitat selection in relation to habitat availability was analysed by comparing the proportions of natural and transformed land available to the proportions of birds seen in each type of land in each precinct . the proportions of natural and transformed land available were calculated using all three nlc maps . all classes of land other than natural vegetation classes and waterbodies were combined to form a single “transformed” land class , and the remaining categories were combined to form a “natural” class ( man - made and natural waterbodies , including wetlands , are not distinguished in the maps ) . a caveat to this analysis is the distinction between transformed , modified , and natural land [ 3 ] . land classified as “transformed” is that on which the vegetation structure has been completely altered , e . g . pastures and cultivated fields . the “natural” habitats mapped in the national land - cover maps are in fact mostly modified habitats , i . e . habitats in which the overall structure and main components of the natural vegetation remain , but in which important changes have been made , e . g . the naturally occurring community of herbivores has been replaced by livestock . in 1989 it was estimated that only 7 % of south africa ' s land surface remained fully natural and undisturbed [ 27 ] . thus in these analyses when we refer to natural habitats , we are in fact mostly referring to modified habitats . however , the extent to which they had been modified and to which they differed functionally from natural habitats , from the perspective of a secretarybird , would be variable .
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del hoyo , j . , collar , n . j . , christie , d . a . , elliott , a . and fishpool , l . d . c . 2014 . hbw and birdlife international illustrated checklist of the birds of the world . volume 1 : non - passerines . lynx edicions birdlife international , barcelona , spain and cambridge , uk .
a very large and distinctive terrestrial raptor , which stands c . 1 . 2 m tall ( ferguson - lees and christie 2001 ) . it is grey , whitish and black in all plumages , with small bill and head , bare face , relatively long neck , exceptionally long , bare legs , and long graduated tail with greatly elongated central rectrices . it has a distinctive crest of black - tipped spatulate feathers ( ferguson - lees and christie 2001 ) .
this species is classified as vulnerable because recent evidence from across its range suggests that its population is experiencing a rapid decline , probably owing to habitat degradation , disturbance , hunting and capture for trade .
. it is variably described as common to rare ( only 10 pairs or less in waza - logone west , cameroon [ j . brouwer
although the species occurs across a vast range , surveyed densities suggest that the total population size does not exceed a five - figure number .
2014 ) . on the basis of this evidence the species is suspected to be undergoing a rapid decline overall .
2014 ) . it ranges from sea - level to 3 , 000 m . juveniles can move a long way after leaving their nest site , but will return to their natal area ( retief and smit - robinson 2014 ) . a variety of prey is consumed , primarily insects and rodents , but also other mammals , lizards , snakes , eggs , young birds and amphibians . breeding occurs throughout the year and the species typically nests in a flat - topped
. disturbance by humans , probably most often herders , is likely to negatively affect breeding . the species is captured and traded in apparently small numbers ; however , it is unknown how many die in captivity and transit . direct hunting and nest - raiding for other uses and indiscriminate poisoning at waterholes are also potential threats . these human - induced threats may compound the effects of severe droughts in some areas ( baker
cites appendix ii . it occurs in a number of national parks and other protected areas across its large range .
initiate a coordinated continent - wide monitoring programme to obtain an up - to - date population estimate and track the species ' s trends . in areas where the species is declining , raise awareness of threats amongst local people , particularly livestock herders . monitor and tackle the capture and trade of the species .
to make use of this information , please check the < terms of use > .
is found throughout africa south of the sahara , except the extreme deserts of the namib coast and the forested region around the equator in western africa . secretary birds do not occur in the southern areas of guinea , cote d ' ivoire , ghana and nigeria , and are entirely absent from the sub - saharan countries of sierra leone and liberia .
secretary birds prefer open savannahs and grasslands , although they also live in semi - deserts and lightly wooded or scrub areas . in grasslands , secretary birds choose areas where the grass is one meter or less in height so their view is not obstructed . they are common near agricultural areas that offer hunting opportunities . secretary birds are never found in true deserts with extreme aridity , or heavily wooded areas . these birds are found from sea - level to around 3 , 000 m .
( ferguson - lees and christie , 2001 ; hosking , et al . , 1988 ; steyn , 1983 )
secretary birds stand around 0 . 9 to 1 . 2 meters tall and weigh between 2 . 3 to 4 . 27 kg . females tend to be slightly smaller than males . wingspans of females range from 1 . 2 to 1 . 32 m , while those of males range between 1 . 26 to 1 . 35 m .
these large raptors have very distinctive morphology . the plumage is generally gray in color , perhaps with some white feathers . they have black flight feathers on the wings and a crest of black - tipped feathers on the back of the head . the bare face is orange to red in color . they have a relatively small head , a gray - white beak , a long neck , and an eagle - like body . unlike an eagle , however , the bare , pinkish legs are very long and end in stubby toes with blunt claws . the tibial portions of the legs are covered in black plumage that give the bird the appearance that it is wearing shorts . the long tail has especially long central rectrices that are often tipped with black .
( ferguson - lees and christie , 2001 ; hosking , et al . , 1988 ; mackworth - praed and grant , 1980 ; steyn , 1983 )
are similar in appearance to adults with a few exceptions . first , the bare skin on the face is yellow rather than orange or red . second , juveniles show black coloration on the tips of the wing shoulder feathers , as well as brown to black barring on the underwing coverts . lastly , juveniles also tend to have shorter central tail feathers and crests than adults .
with any other bird of prey , mainly due to their very long legs . from a distance secretary birds are mistaken for
secretary birds are monogamous and are thought to pair for life . in courtship , they give a croaking call while displaying in the air and on the ground . aerial displays consist of high soaring and diving performed by a single individual ( usually the male ) , or by the pair when the male will dive toward the female and she will half - turn to present her claws . this courtship behavior is very similar to that of other birds of prey . on the ground , their displays are very crane - like with the two birds dancing around with their wings outstretched . sometimes small groups of secretary birds will all join in this ground display behavior . after courtship displays , mating will usually take place on the ground , although some pairs mate in trees .
may breed throughout the year , although there are peaks in breeding from august to march . both the male and female will construct a large nest on a flat - topped tree ( usually an acacia tree or some other thorny tree ) . the nest is usually a saucer - shaped platform made of sticks and lined with a thick layer of grass , wool , dung , and other such materials . a pair of secretary birds will usually reuse the same nest for many years , adding to the structure each year to create a nest that can range from 1 . 5 to 2 . 5 meters in diameter . a frequently reused nest will be abandoned if the structure becomes too large and heavy to be supported by the tree and seems likely to collapse .
the female lays a clutch of 1 to 3 eggs , with each egg laid two to three days apart . the eggs are chalky - white with reddish - brown streaks and are pyriform in shape . eggs are variable in size and can range from 68 to 92 mm in length and 52 to 61 mm in width . incubation of the eggs begins as soon as the first egg is laid . incubation duties are shared by both the male and female , although more frequently by the female . the male brings food to the nest for the female during this time . in 42 to 46 days , the semi - altricial young hatch . young generally hatch 2 to 3 days apart , but no siblicide has been observed . however , in a clutch of three eggs , the smallest chick usually dies of starvation because it cannot compete with its larger nest mates .
hatchlings are covered in off - white down and have large heads that seem too heavy for their bodies . at two weeks of age , they attain a thick coat of gray down , and in three weeks the crest begins to appear . development is slow in secretary birds and it takes six weeks before the hatchlings can stand on their own . at this stage , they learn to feed themselves from prey brought to the nest . by seven weeks , nestlings are fully feathered . around 60 days , the young begin flexing their wings , often flapping and lifting small distances into the air before dropping back to the nest . in 64 to 106 days , the offspring will fledge . the offspring remain around the nest tree for an additional 62 to 105 days , during which time they are dependent upon the parents for food and training in foraging techniques .
breeding interval secretary birds can raise two broods within ten months under desirable conditions .
both male and female secretary birds invest heavily in the young . both sexes share incubation duties . after the eggs hatch , parental care is constant . both the male and female feed the young via regurgitation , although the female mostly regurgitates food that the male has brought back to the nest for her . after about a month , parental care drops significantly , with the parents only returning to the nest to feed the chicks . after six weeks , the parents stop feeding via regurgitation and bring larger prey items that they give the chicks to eat directly . when the chicks fledge and leave the nest , the parents will teach the chicks how to hunt for prey . once the offspring know how to provide for themselves and are independent , they generally head off on their own , leaving the parents’ territory . however , in some circumstances the parents will still tolerate having the juveniles in their territory and even allow the now - independent offspring to join in their hunts and share the nest tree as a roost . it is important to note that juveniles are not dependent on the parents during this time . they are just temporarily sharing a territory . two months is the average amount of time that independent juveniles are allowed to remain in the parents’ territory before being chased away so that the parents can breed again .
is sometimes solitary , but is more often found in pairs or family groups consisting of up to five individuals . larger aggregations of secretary birds may form near an abundant food source or a watering hole , but these groups do not remain together long . secretary birds become active about two hours after the sun has risen , when the grass is no longer wet with morning dew . these birds spend the day walking around and feeding until late afternoon , at which point they return to their roosts . secretary birds prefer to walk rather than fly , and average about 20 to 30 km a day on foot . when hurried or confronted with a threat they run before taking flight . when they do fly , they fly well and often at great heights .
a pair of secretary birds defends an area that can range from 20 to 500 square kilometers depending on the density of secretary birds and food resources in the area . any conspecifics caught intruding in a pair ' s territory will be chased out forcefully .
is generally sedentary and will remain in its own territory , but they are sometimes nomadic . in most cases , these nomadic tendencies are caused by a search for food .
secretary birds are generally silent . when they do call , they typically give a deep , trisyllabic croaking wail that can be heard for quite some distance . this call , along with a drawn - out growling sound , is used in conjunction with aerial and ground displays during the courtship process . a softer version of the main call is used when feeding young . an occasional whistle is given from time to time . the young have their own calls to solicit food from their parents , which start off as a quiet squealing , then becoming a loud ' chok - a - chok - a - chok - a - chok ' .
is an opportunistic predator with a broad prey base . the majority of the diet is made up of arthropods ( including grasshoppers , beetles , spiders , scorpions , wasps , etc . ) and small mammals ( including mice , rats , hedgehogs , hares , mongooses , etc . ) . other recorded prey of secretary birds includes small and young birds , eggs , amphibians , freshwater crabs , lizards , small tortoises , chameleons and snakes . although this species is famed for killing and eating snakes , these reptiles are not eaten as often as is generally believed . however , the snakes taken as prey are often adders , cobras , and other venomous species .
secretary birds hunt exclusively on the ground , either alone or in pairs ( usually with their mate ) . the birds will set out across a grassy area at a steady pace searching for movement . if a particularly thick tuft of grass is encountered , the bird will stamp on it to flush out any potential prey . once prey is spotted , the bird quickens its pace to take the prey by surprise . if a chase commences , the bird will flap its wings and run after the prey until catching up to it . with small prey , the bird will merely bend down and capture it in its bill . larger prey , especially snakes , are stamped to death with the bird ' s blunt feet . a secretary bird will strike a snake just behind its head to snap its neck or stun it . secretary birds are said to pick up a stunned snake , fly high into the air and drop the snake to its death , but this behavior has not been well documented . once the prey is stunned or killed , the bird will swallow it whole through its large gape . if the prey proves too large , then the bird will tear it apart much like an eagle , using its feet to hold the prey down .