bluuebunny/crossref_metadata_2025 huggingface dataset:
Arable habitat use by wood mice (Apodemus sylvaticus). 2. Microhabitat
Authors: Tew T. E. , Todd I. A. , Macdonald D. W.
Published: February 2006

Forty‐eight wood mice Apodemus sylvaticus were radio‐tracked over an estimated 1500 h yielding 9000 fixes. The mice were living in three contiguous arable fields, and showed that they respond to weedy microhabitat patches within superficially homogeneous crops. Plant species' abundance and the composition of the seed bank were assessed in quadrats taken in areas in which (a) mice foraged, (b) through which mice travelled, or (c) at random within each home range. Wood mice avoided foraging in areas with a high abundance of bare earth, and selected areas with a high abundance of Alopecurus myosuroides, Stellaria media, Avena fatua, Galium aparine or Bromus sterilis. The food plants apparently selected by wood mice differed markedly between months and between sexes. This may relate to the energetic and nutritional demands incurred by the contrasting reproductive tactics of male and female wood mice. There were no differences between seed bank samples taken from quadrats where the mice foraged, travelled through, or which were selected at random. Our study, the first large‐scale analysis of wood mouse microhabitat preference using radio‐tracking, reveals that whereas the mice do not react to heterogeneity on the scale of the mosaic of crop fields, they are greatly influenced by the dispersion of food plants within the superficially homogeneous crop itself.
Competition for acorns among wild boar (Sus scrofa) and small mammals in a Mediterranean woodland
Authors: Focardi Stefano , Capizzi Dario , Monetti Daniel
Published: February 2006

Observations of the rooting activity of wild boar in a holly‐oak grove showed that in March–April the decrease of acorns in the diet (31%) was lower than their availability (82%). Moreover the occurrence of deep rooting events remains high despite the low occurrence of grass roots in the diet. These observations suggested that wild boar may exploit hoards of acorns collected by small mammals living in the study area (mainly wood mice Apodemus sp.). In order to test this hypothesis two experimental trials were set up to: (1) investigate whether wild boar were able to locate acorns buried in the ground (range 0–30 cm) and (2) establish if mouse burrows were more likely to be excavated than locations without burrows. The results clearly show that wild boar actively search for buried acorns, mainly in March (59%vs 31% in April and nothing in May) and that burrows are excavated significantly more than locations without burrows (ratio 2:1, respectively). Moreover, locations with burrows are characterized by a decline of rooting activity as a function of the distance from their centre (P= 0.02), which is absent in the control locations (P= 0.74). Our results show that wild boar are able to partly compensate for a reduced above‐ground availability of acorns by predating on hoards collected by small mammals. Since this occurs during a critical period for female wild boar when they are giving birth and lactating, this behaviour may strongly influence the population dynamics of both wild boar and small mammals.
Population dynamics of the spiny country rat (Niviventer coxingi) in a subtropical montane forest in central Taiwan
Authors: Wu Hai‐Yin , Yu Hon‐Tsen
Published: February 2006

Population dynamics of the spiny country rat Niviventer coxingi were studied by mark–recapture methods from January 1982 to May 1983 in a subtropical montane forest at Chitou, central Taiwan. The population density was < 8 rats/ha. The annual pattern of population fluctuation was characterized by summer increase, autumn peak and spring decline. Adult recruits occurred mostly in summer and autumn 1982, whereas young rats joined the population as three cohorts: winter 1981, summer 1982 and winter 1982. Growth patterns differed between winter and summer cohorts, which was attributed mainly to the slow body weight increase in summer cohort males. Males, either adult or juvenile, survived the winter better than females, resulting in the shorter lifespans and the lower number of females in the population. Life‐history traits in female N. coxingi, i.e. short reproductive lifespan, few litters per life time and prolonged maternal care, along with the low breeding intensity, rendered the number of females the limiting factor for population increase. However, females may improve the survival and maturation of their offspring by prolonged maternal care.
Endemism, gigantism and extinction in island lizards: the genus Gallotia on the Canary Islands
Authors: Barahona F. , Evans S. E. , Mateo J. A. , García‐Márquez M. , López‐Jurado L. F.
Published: February 2006

In the Canary Islands five extant and two extinct giant lacertid lizards belonging to the endemic genus Gallotia are known. A comparative study of the living and subfossil specimens from the Western Canary Islands demonstrates that the extinct giant species Gallotia goliath and Gallotia maxima are synonymous with the living Gallotia simonyi. Characters formerly used in the diagnosis of the extinct species and subspecies fall within the range of intraspecific variation (ontogenetic and individual) of the living species. The only significant difference between living and subfossil populations of G. simonyi is size, and there is strong evidence to suggest that the reduction in size in living populations reflects shorter life expectancy, a factor that should be taken into account in the current conservation projects on this species.
The effects of bovine tuberculosis (Mycobacterium bovis) on mortality in a badger (Meles meles) population in England
Authors: Wilkinson D. , Smith G. C. , Delahay R. J. , Rogers L. M. , Cheeseman C. L. , Clifton‐Hadley R. S.
Published: February 2006

The mortality rates of badgers Meles meles were estimated, using data from a long‐term capture–mark–recapture study of an undisturbed badger population in south‐west England. Two life table methods were used: fusion and discounting. Badgers were allocated to a particular TB status for all or part of their lives according to their degree of infection with bovine tuberculosis Mycobacterium bovis. Separate life tables were created for animals with each TB status, and for males and females, and the estimated mortality rates were compared statistically. The progression of M. bovis infection, and the positions of M. bovis lesions were also analysed. The main findings are: (a) uninfected male badgers have a significantly higher mortality rate than uninfected females, (b) infected badgers which are not excreting M. bovis do not have a significantly higher mortality rate than uninfected badgers, (c) badgers which are excreting M. bovis have a much higher mortality rate than uninfected badgers, (d) male badgers appear to cope with M. bovis infection less well than females, and (e) there may be sex differences in the mode of spread of M. bovis in badgers.
Weapon strength and competitive success in the fights of shore crabs (Carcinus maenas)
Authors: Sneddon L. U. , Huntingford F. A. , Taylor A. C. , Orr J. F.
Published: February 2006

Weapon size has been shown to be a better predictor of competitive success than body size (carapace width) in fights between shore crabs, Carcinus maenas. However, when the weapon size disparity is small between two opponents, it is still difficult to predict the victor. The role of weapon strength in pairwise fights between male shore crabs was investigated, to determine if relative force influences contest content, duration and outcome. Weapon strength was ascertained using a force transducer on live crabs, then fights between crabs were staged between size matched males. Winning crabs had major (crusher) claws and minor (cutter) claws that exerted a significantly greater force than losing crabs even when claw length was the same. Winners and losers were matched for carapace width, claw length and dactyl length but not claw height or claw length minus the dactyl. Winners had greater claw height and claw length to the dactyl in the major claw giving them a higher mechanical advantage when closing the claw and thus exerting a greater force. The forces exerted by the major and minor claws were analysed for any relationship between force and morphological measurements. Winning crabs appear to be fitter in having a better claw structure which exerts a greater force and they are more successful in agonistic interactions.
Orbit orientation and the function of the mammalian postorbital bar
Authors: Noble Vivian E. , Kowalski Erica M. , Ravosa Matthew J.
Published: February 2006

The visual predation hypothesis of primate origins was introduced by M. Cartmill in the 1970s. In outlining a series of predictions regarding changes in orbital orientation, he further posits that the formation of a bony postorbital bar is correlated with greater orbital convergence, which in turn appears to be linked to selection for increased stereoscopic visual acuity in a nocturnal milieu. A series of predictions related to this model is tested in living analogues that vary in postorbital bar formation: felid and herpestid carnivorans and the pteropodid megabats. Bivariate correlations and regressions, ANOVA and ANCOVA are used to assess the intrinsic allometric and non‐allometric factors thought to affect two aspects of orbital orientation, convergence and frontation. These angles of orbital orientation are then examined in an effort to determine how they are associated with the development of a postorbital bar. Cartmill suggested that convergent orbits develop from changes in relative orbit diameter and relative interorbital breadth. This study indicates that felids show only weak support for these predictions, while herpestids do not provide support and pteropodids show some support. Instead, in response to natural selection, convergence seems to develop to improve stereoscopic vision and depth perception in nocturnal predators. As predicted, felids show a significant positive relationship between orbital frontation and relative brain size. Analyses in herpestids, however, do not show significant relationships between frontation and relative palate length or relative brain mass. Pteropodids also do not support the model regarding intrinsic frontation factors. In both carnivoran groups, convergence and frontation are positively correlated, whereas they are not correlated in Pteropodidae. In partial contrast to Cartmill's predictions, we found that orbital convergence and/or orbital frontation are generally higher in carnivorans and bats with postorbital bars. Therefore, a greater emphasis on nocturnal stereoscopic visual predation and increased relative brain size both move the orbital aperture out of the plane of the temporal fossa and a postorbital bar thus provides adequate rigidity to the lateral orbital margin. In the more encephalized Felidae, orbital frontation is positively correlated with relative brain size; as smaller mammals have relatively larger brains, this explains why postorbital bars tend to be found in smaller felids. In herpestids and pteropodids, postorbital bars tend to occur in larger taxa which are more convergent than smaller forms.
Environmental factors influencing the presence and abundance of a log‐dwelling invertebrate,Euperipatoides rowelli(Onychophora: Peripatopsidae)
Authors: Barclay S. , Ash J. E. , Rowell D. M.
Published: February 2006

The microenvironments of decaying logs support a large invertebrate fauna, but are vulnerable to the effects of logging and land‐clearing. We present an analysis of the relationship between a number of environmental variables and the occurrence and abundance of the onychophoranEuperipatoides rowelliwithin decomposing logs in a forest in south‐eastern Australia. Aspect of slope is strongly associated with most of the environmental variables and is a good predictor of both presence and abundance of animals in logs; south‐easterly slopes show higher levels of log colonization, larger populations within logs and a larger median weight of both males and females than north‐westerly facing slopes. Degradation state of logs, log length, presence of termites and shrub cover are also associated with the presence of onychophorans, while log volume shows the most marked association with abundance.Euperipatoides rowelliprefers wetter logs, although there is considerable overlap between relative water content of logs with and without onychophorans. Log degradation state, an important factor in the presence of animals, is associated with years since felling, and our data indicate that logs become capable of supporting large populations ofE. rowelliafter a minimum of 45 years of decay. Thus future logging practices have important implications for the maintenance of suitable log environments for this species, and this result may be generalized to other log‐reliant fauna.
Pheromonally mediated colonization patterns in the velvet worm Euperipatoides rowelli (Onychophora)
Authors: Barclay S. D. , Rowell D. M. , Ash J. E.
Published: February 2006

We demonstrate that the males of the peripatopsid Euperipatoides rowelli secrete a pheromone from crural papillae, which acts as an attractant to both males and females of the species. Patterns of colonization of decomposing logs and differences in sex ratio between incipient vs established populations indicate that males are the initial dispersers and colonizers, finding suitable log habitats in an exploratory fashion, while females subsequently colonize logs. This results in a disproportionately high frequency of males in newly colonized logs, followed by a gradual increase in female proportion. We argue that females use the aggregating pheromone secreted by males to target appropriate rotting log microhabitats, resulting in a clumped distribution of females compared to a more random distribution for males among recently colonized logs. This mode of colonization reduces the time that animals, especially females, spend outside the safety of suitable logs, and the risk‐taking strategy of male exploration may explain the marked sex ratio bias in favour of females in the population. Rapid and non‐random dispersal may also account for the contradictory evidence of unexpectedly high rates of colonization of new logs, yet a paucity of animals in leaf litter samples. The possibility that pheromone trails play a part in the dispersal process is discussed.
Reproductive biology of the onychophoran Euperipatoides rowelli
Authors: Sunnucks Paul , Curach Natalie C. , Young Anthony , French Jordan , Cameron Ray , Briscoe Dave A. , Tait Noel N.
Published: February 2006

The reproductive biology of the ovoviviparous peripatus Euperipatoides rowelli was investigated from field collections and laboratory cultures. The sexes have different demographics. The frequency distribution of individual weight is essentially L‐shaped in females, but closer to normality for males: thus the sexes must exhibit different patterns of growth and/or mortality. Males are generally much smaller and rarer than females. The primary sex ratio seems to be 1:1 with equal investment in the sexes, while the tertiary ratio is highly female‐biased. Logs with fewer individuals tend to be male‐biased while well‐populated logs tend to be female‐biased. Males mature at 15–30% of the bodyweight of mature females. The weight frequency distribution of males without developed sperm in their tracts is strongly skewed to the lower weights, while that of males with sperm is more normally distributed, indicating that sperm production occurs as soon in life as possible. Males mature in their first year of life, if growth rates in culture may be extrapolated to the wild. In contrast to this rapid maturity in males, females may mature as late as their second or third years. Most mature females, and many prior to maturity, carry sperm in their spermathecae. After maturity, there is an approximately linear relationship between body mass and number of developing embryos. Reproduction in E. rowelli is significantly seasonal despite high individual variance, with a major bout of parturition in November–December (summer). A female can harbour one developed and one undeveloped batch of embryos in each uterus. Excesses of developed embryos in one uterus are counterbalanced by deficits of undeveloped ones, indicating that females can use their paired reproductive tracts independently. Individual females in culture can experience episodes of parturition approx. 6 months apart without re‐mating, thus gestation may be 6 months or more. Sperm in spermathecae remain capable of vigorous swimming for at least 9.5 months.
Higher testicular activity in laboratory gerbils compared to wild Mongolian gerbils (Meriones unguiculatus)
Authors: Blottner S. , Franz C. , Rohleder M. , Zinke O. , Stuermer I. W.
Published: February 2006

The Mongolian gerbil has been used as laboratory animal since 1935. Breeding gerbils as an isolated laboratory population for decades may have led to a domestication process whose effects include changes in brain size. Quantitative changes in testicular activity could be assumed. Comparative intraspecific measurements were performed in 34 adult males of the laboratory strain (LAB) and in males raised as offspring of wild Mongolian gerbils (WILD) caught in central Mongolia (F1, n= 16; F2, n= 17). LAB and WILD were examined in January. Testicular spermatozoa were counted, proportions of different cell types were analysed using DNA flow cytometry, and mitotic and meiotic activity was calculated from DNA histograms. Intratesticular testosterone concentrations were measured with an enzyme immunoassay. In the WILD, testicular activity was lower and varied more. The overall weight, the efficiency of spermatogenesis (sperm/g testis) and resulting total sperm per testis were significantly less in offspring of wild gerbils. This corresponded with lower levels of haploid cells, total germ cell transformation of diploid cells to spermatids and meiotic transformation of spermatocytes to spermatids. The most profound difference was found in testicular testosterone concentration: the mean level was 405.7 ± 41.2 ng/g testis in LAB vs 6.4 ± 2.0 ng/g in WILD F1. All parameters changed in WILD F2 generation compared with F1 and diminished the differences with LAB. Differences between F1 and F2 were significant for testis mass, testis/body weight ratio, percentages of haploid cells and cells in G2/M phase, both germ cell transformations and testosterone concentration. The results suggest rapid, adaptive changes of male reproductive physiology in the early offspring generations from wild populations under laboratory breeding conditions. The breeding of Mongolian gerbils in the laboratory has influenced the testicular function resulting in increased spermatogenic activity and highly stimulated testosterone production.
Roosts used by the golden‐tipped bat Kerivoula papuensis (Chiroptera: Vespertilionidae)
Authors: Schulz M.
Published: February 2006

Use of roosts by the golden‐tipped bat Kerivoula papuensis was investigated principally in the Richmond Range National Park, north‐eastern New South Wales and Mt Baldy State Forest in north‐eastern Queensland, Australia. Roosts were located primarily using radiotelemetry; although others were found by light tagging, visual location and nest searching techniques. In the main study site in the Richmond Range a total of 54 K. papuensis diurnal roosts were located, 96.5% occurring in the suspended nests of the yellow‐throated scrubwren Sericornis citreogularis (Pardalotidae) (93%) and the brown gerygone Gerygone mouki (Pardalotidae) (3.5%). At Mt Baldy, K. papuensis displayed greater variation in day roost selection, although 73% were in S. citreogularis nests. In both sites, day roosts were confined to the lower stratum of rainforest with a small proportion in eucalypt tall open forest with a rainforest subcanopy. Diurnal roosts were located at distances varying from 20 to 1200 m to the nearest major vegetation ecotone, ranging from along watercourses upslope to ridgelines. Diurnal roosts were predominantly occupied by single bats, with a maximum group size of eight individuals. All roosts in hanging nests were modified by the presence of a basal hole. Strong circumstantial evidence was provided that K. papuensis modified these roost structures in a manner allied to tent‐making bats. A single maternity roost was located in the hollow of a rainforest canopy tree, Flindersia australis (Rutaceae).
Ultrastructure of the neck membrane in dragonflies (Insecta, Odonata)
Authors: Gorb Stanislav N.
Published: February 2006

This study describes and quantifies the microsculpture and ultrastructural design of the neck membrane of adult Odonata using scanning and transmission electron microscopy. The membranous cuticle has a complex pattern of microfolds, which appear to have a specialized mechanical function. The membrane has two layers of cuticle: the epicuticle and exocuticle. The outermost layer is the electron‐opaque epicuticle, which repeats the shapes of the microfolds. The epicuticle has no fibrillar elements. The exocuticle is electron‐lucent and rather thin (0.5–1.5 μm) compared with the sclerite cuticle. The cuticle microfibrils in successive lamellae are at angles to each other. The epidermal cells underlying the membrane have an electron‐lucent matrix filled with electron‐opaque spherical vesicles of 0.1–0.4 μm in diameter. The behaviour of the membrane folds under loading was studied by shock‐freezing experiments; these showed that the shape of the folds changed in response to head movements, and stretched under loading. A comparison of the surface patterns of the membrane in 10 odonate species from seven families (Zygoptera: Coenagrionidae, Lestidae, Megapodagrionidae; Anisoptera: Cordulegastridae, Aeshnidae, Corduliidae, Libellulidae) had not revealed any correlation of the measured parameters with the size, sex or systematic position of species studied.
Interspecific scaling of the hindlimb skeleton in lizards, crocodilians, felids and canids: does limb bone shape correlate with limb posture?
Authors: Blob Richard W.
Published: February 2006

During locomotion, lizards and crocodilians generally use a more sprawling limb posture than most mammals and experience substantial axial rotation of the femur. Consequently, the limb bones of most mammals are loaded predominantly in bending, but the limb bones of lizards and crocodilians are loaded primarily in torsion. As body size increases, torsional shear stress in limb bones is expected to increase more than bending stress; therefore, limb bone diameters of lizards and crocodilians might be expected to scale with relatively greater positive allometry than limb bone diameters of mammals that use upright posture. To test this hypothesis, scaling patterns of the femur and tibia in lizards (iguanians and varanids) and crocodilians were compared with patterns in felid and canid mammals, using both non‐phylogenetic statistical methods and phylogenetically independent contrasts. Comparisons with theoretical models indicate that size‐related changes in limb bone geometry do not completely compensate for size‐related increases in limb bone stress in the lizard or crocodilian lineages examined. Unless lizards and crocodilians compensate for size‐related increases in limb bone stress through other mechanisms (e.g. changes in limb kinematics or the mechanical properties of limb bones), limb bone stresses are predicted to be relatively greater among larger species of these lineages. However, limb bone diameters appear to scale with greater positive allometry (relative to body mass) in varanids than in iguanians, suggesting that larger lizard lineages might compensate for increased stress through changes in bone geometry to a greater degree than smaller lineages. Allometric scaling patterns for many limb bone diameters among iguanians are more similar to those of felids and canids than to those of varanids; thus, sprawling locomotor habits do not correlate clearly with a particular pattern of limb bone scaling. This suggests that similarity of interspecific scaling patterns of limb bone lengths and diameters is not sufficient to justify inferences of similar locomotor function.
Female nesting behaviour, pup growth and ontogeny in Brants' whistling rat (Parotomys brantsii)
Authors: Jackson T. P.
Published: February 2006

This study examines aspects of the nesting behaviour of Brants' whistling rat Parotomys brantsii, a medium‐sized rodent indigenous to southern Africa. In the semi‐arid regions in which it occurs P. brantsii breeds opportunistically, modifying its breeding period in relation to rainfall. Within a winter rainfall area, females produced up to four litters of three to four young during the winter–spring period following a gestation period of c. 38 days, with females showing a post‐partum oestrus. The behaviour of females was modified by the birth of their pups, after which they spent extended periods underground, interspersed with bouts of food‐collecting activity. With the emergence of pups above‐ground, females increased their vigilant activity. At 5 weeks pups had developed all the important behavioural characteristics of adults, such as creating their own overnight food stores, collecting nesting material and defending a warren area against conspecifics. This was also the age at which the young dispersed from their natal nest area as well as the time at which females could reach sexual maturity, despite physical immaturity. The high reproductive output of female P. brantsii, as well as the rapid ontogeny of their young, compared to other otomyine rodent species, may represent an adaptation for maximizing reproductive potential in the semi‐arid areas they inhabit.
The highly specialized secretory epithelium in the buccal cavity of the alkalinity adapted Lake Magadi cichlid, Oreochromis alcalicus grahami (Teleostei: Cichlidae): a scanning and transmission electron microscope study
Authors: Maina J. N.
Published: February 2006

Oreochromis alcalicus grahami is a small cichlid fish that lives in the hot, highly alkaline, highly saline peripheral lagoons of Lake Magadi, Kenya. The fish faces profound diurnal oscillations of oxygen concentration. During the day, from photosynthetic activity of cyanobacteria (blue‐green algae), the water is supersaturated with oxygen but after sunset when photosynthetic activity stops the water is virtually anoxic as a result of bacterial respiration. During the night and after explosive exercise, O. a. grahami characteristically skims the surface of the water with the mouth agape, suggesting that the buccal cavity is used as a gas‐exchange organ. Contrary to expectation, however, the buccal cavity was found to be conspicuously non‐vascularized: the surface epithelial lining was fundamentally of a mucus secretory type. In addition, certain cells in the deeper layers showed extensive lateral labyrinths similar to the epithelium of the renal tubules. These morphological features respectively indicated roles of secreting a protective film and regulation of ions taken across the epithelial lining of the buccal cavity. The allocation of gas‐exchange to the gills and the air‐bladder, osmoregulation essentially to the gills, and mucus secretion/protection to the buccal cavity displays an adaptive trade‐off process in an elite animal. Effective use of the buccal cavity as a gas‐exchanger would entail air‐gulping followed by brief retention of it in the cavity to allow oxygen uptake. During such interval, both the gills and the air‐bladder would of necessity be rendered temporarily non‐functional. Skimming the top layer of water with the mouth open ensures that the gills are passively ventilated with well aerated water and the air‐bladder is simultaneously used for gas‐exchange, a strategy that should enhance oxygen acquisition, especially at higher ambient temperatures.
Factors affecting the duration of activity by pine martens (Martes martes) in the Białowieża National Park, Poland
Authors: Zalewski Andrzej
Published: February 2006

The duration of activity bouts by pine martens Martes martes was studied in the pristine deciduous forests in Białowieża National Park (north‐eastern Poland). From 1991 to 1996, 14 martens were monitored by radio‐tracking throughout 5823 h. On average, male martens were active for 9 h/day and females for 8.5 h/day. The duration of the martens' diel activity varied greatly among bimonthly periods (from 2.8 h/day in February–March to 12 h/day in June–July). Martens decreased their activity from 13 h/day on warm days to 2.5 h/day on cooler days. In the winter months, when martens curtailed their activity, they often hunted larger prey or scavenged ungulate carcasses. On average, 69% of the martens' active time was during the night. The number of activity bouts per day varied from one to six (mean 2.6) and increased with growing ambient temperature. Activity bouts of males were significantly longer (4 h, on average) than those of females (3 h) and were not related to ambient temperature. The duration of short inactive bouts increased in the cold season and inactivity lasted longer in females than in males.
Food habits and livestock depredation of two Iberian wolf packs (Canis lupus signatus) in the north of Portugal
Authors: Vos J.
Published: February 2006

Two Iberian wolf Canis lupus signatus packs were studied in the north of Portugal during spring and summer 1996. The study areas are located in two mountainous areas close to the Spanish border. Both regions presented a very low density of wild ungulates and intensive livestock production. The food habits and the livestock depredation of the wolves were considered. The study material included 87 dropping samples, interviews with shepherds, carcass investigation and government reports of livestock depredation. Prey preference was measured in both areas. Wolves fed exclusively on livestock, especially goats. Wolf attacks on goats affected mostly large flocks of > 100 heads, but where there were horses, wolves preyed preferentially on horses. In both study areas, sheep was recorded as a regular prey by the government reports but never appeared in the scat analysis results. This apparent contradiction will be discussed. The wolf's dependence on livestock can be explained by the scarcity of wild prey and the high density of livestock. Conservation of wolves in such impoverished areas depends on an efficient livestock depredation management plan and the reintroduction of native prey species.
The influence of body size on dive duration of underyearling southern elephant seals (Mirounga leonina)
Authors: Irvine Lyn G. , Hindell Mark A. , van den Hoff John , Burton Harry R.
Published: February 2006

The dive duration of 16 underyearling (6–12 months old) southern elephant sealsMirounga leoninaduring their second trip to sea was investigated using geolocating time–depth recorders. Underyearling seals had a lesser diving ability, with respect to duration and depth, than adult southern elephant seals. Individual underyearlings dived for average durations of up to 20.3 min and depths up to 416 m compared to durations and depths of 36.9 min and 589 m, respectively for adults. Dive duration was positively related to their body mass at departure, indicating that smaller seals were limited to shorter dive durations, perhaps as a result of their lesser aerobic capacity. All seals often exceeded their theoretical aerobic dive limit (average of 22.1 ± 18.1%). The number of dives exceeding the theoretical aerobic dive limit was not related to mass, suggesting that factors other than mass, such as foraging location or prey availability, may have been responsible for differences in diving effort. Foraging ability, indicated by the ability of the seals to follow vertically moving prey, was positively related to seal mass, indicating that small mass restricted foraging ability. The shorter dive durations of the smaller seals inferred that they had shallower dive depths in which to search for prey, thus restricting foraging ability. Although foraging ability was restricted by size, foraging success was found to be inversely related to mass, the smaller seals gaining a higher proportion of blubber than larger seals during their foraging trips. Thus, despite smaller seals being restricted to shallower depths and shorter durations, their foraging success was not affected.
Growth, survival and behaviour of larval long‐toed salamanders (Ambystoma macrodactylum) exposed to ambient levels of UV‐B radiation
Authors: Belden L. K. , Wildy E. L. , Blaustein A. R.
Published: February 2006

Mortality is the most extreme effect of ultraviolet‐B radiation (UV‐B; 280–315 nm) on living organisms, but sublethal effects of UV‐B may also be important. Moreover, there may be population differences in response to UV‐B, but this aspect has not been well explored for animal populations. Amphibians have been a model system for studying the detrimental effects of UV‐B. However, previous research on the effects of UV‐B on amphibians has mainly focused on embryos. Few studies have investigated how UV‐B affects larvae. We examined potential sublethal effects of UV‐B on the long‐toed salamander Ambystoma macrodactylum from two different populations. Observational data from field transects indicated that larvae are potentially exposed to UV‐B in their natural habitat. Choice tests indicated that larvae select shaded regions more often than those in the sun, but do not directly distinguish between regions with high and low UV‐B. Laboratory experiments indicated a survivorship difference between individuals from low‐ and high‐elevation sites. When exposed to relatively low levels of UV‐B individuals from low‐elevation sites experienced higher mortality than controls (no UV‐B). There were no differences in mortality between UV‐exposed and non‐exposed larvae from the high‐elevation population. Although mortality of UV‐B exposed larvae was not significantly different from controls in the high‐elevation population, sublethal effects on growth were observed. Individuals from the high‐elevation site grew significantly less when exposed to UV‐B than individuals shielded from UV‐B. Our study demonstrates that larval A. macrodactylum are exposed to UV‐B in nature, that UV‐B exposure can cause mortality as well as having sublethal effects on growth and that there are potential population differences in sensitivity to UV‐B radiation.
Environmental determinants of the composition of desert‐living rodent communities in the north‐east Badia region of Jordan
Authors: Scott Dawn M. , Dunstone Nigel
Published: February 2006

The spatial and temporal compositions of rodent communities in habitats of the Badia region of north‐east Jordan were investigated between 1996 and 1997. Live grid‐trapping and spot‐lighting techniques were employed to estimate rodent densities. Sixteen environmental variables including soil content, vegetation cover and relief were recorded within the study sites. TWINSPAN was used to derive six habitat classes based on the similarity of their rodent communities. These were hammada, harrat, marab, wadi and two types of sand dunes. The derived classifications were similar to the original categorization of habitat types based on ground‐truthed observations of the sites selected from satellite imagery. Multivariate statistical analyses (TWINSPAN and DECORANA) revealed three major rodent groups in relation to local habitat types: (1) petrophiles: Gerbillus dasyurus, Acomys russatus and Meriones tristrami; (2) open hammada‐dwelling species: Jaculus jaculus, Gerbillus henleyi and Meriones crassus; (3) psammophiles: Meriones libycus, Gerbillus nanus and Gerbillus cheesmani. Species richness was highest in marabs and lowest in red sand dunes. Species diversity (Hill's index) was highest in sand dunes and lowest in red sand dunes. Rodent biomass was highest in sand dunes and lowest in wadis. CANOCO showed rodent community composition to be correlated with vegetation parameters and soil content. TWINSPAN grouping and DECORANA ordination of rodent species provides some evidence for habitat preference, size disparity and competition as mechanisms of resource partitioning facilitating coexistence.
Maximum dive depths of common diving petrels (Pelecanoides urinatrix) during the annual cycle at Mayes Island, Kerguelen
Authors: Bocher Pierrick , Labidoire Bruno , Cherel Yves
Published: February 2006

Maximum dive depths of common diving petrels Pelecanoides urinatrix were measured monthly over > 1 year, from January 1995 to February 1996, with miniature gauges attached to the birds at Mayes Island, Kerguelen Archipelago. Overall, maximum dive depths of 347 diving petrels averaged 31 ± 6 m (range: 8–64 m), with a mode at 30–35 m. Mean maximum dive depths differed significantly over the study period. The lowest value (22 ± 8 m) was obtained in winter and it was associated with euphausiid crustaceans, suggesting a change in foraging behaviour associated with a shift in the main prey consumed. During the breeding season, birds fed mainly upon the hyperiid amphipod Themisto gaudichaudii (66% of the total number of prey), followed by the large carnivorous copepod Paraeuchaeta antarctica (15%) and zoea larvae of the crab Halicarcinus planatus (13%). Comparison of the diving capabilities of diving petrels (genus Pelecanoides) with those of other diving seabirds suggests that, relative to body mass, diving petrels can dive deeper than penguins and also possibly than alcids, and are thus the most proficient divers among birds.
Variation in home range and use of habitat in the striped skunk (Mephitis mephitis)
Authors: Bixler Andrea , Gittleman John L.
Published: February 2006

We studied home‐range size, home‐range overlap and use of habitat in a population of striped skunksMephitis mephitisin eastern Tennessee. Variables determined to influence home‐range size were season and body weight: skunks had larger ranges in the spring than in winter and heavier females had larger ranges. Habitat, sex and sample sizes of radio‐fixes did not correlate with home‐range size. All home ranges overlapped by 1.4–100% of the range area. There was no pattern of greater intersexual than intrasexual overlap; this differs from many other carnivore studies. Movements of individuals and distribution of den sites indicated that striped skunks, irrespective of sex or size, prefer edge habitat in comparison to forest or field.
Tooth succession in the greater cane rat Thryonomys swinderianus (Temminck, 1827)
Authors: van der Merwe M.
Published: February 2006

Tooth succession was followed in captive greater cane rats Thryonomys swinderianus of known ages with the aid of regular radiographs. The incisors and single premolar tooth (dP 4/4) in each quadrant are persistent deciduous teeth that are not replaced by permanent teeth. Tooth succession is relatively slow, with eruption of the lower cheek teeth in advance of the upper ones. During the first 5 months of post‐natal development, three cheek teeth per quadrant become functional. Another 5 months elapse before the fourth cheek tooth erupts. The same slow growth can be seen in the increase in mass, which only doubles 5 months after puberty (5 months).
The mechanical properties of down feathers from gentoo penguins (Pygoscelis papua)
Authors: Bonser Richard H. C. , Dawson Colin
Published: February 2006

In a recent paper, Dawson et al. (1999) investigated how the morphology of the contour and downy afterfeathers of gentoo penguins Pygoscelis papua function as thermal insulators. Their model considered how the morphology of individual feather barbs interact to create an efficient insulatory barrier. They noted that, during diving, the feathers must be compressed and return to their original configuration due to stored strain energy. In addition, the downy feathers of penguins have to withstand significant wind loading whilst the birds are on land (Taylor, 1986). Despite the obvious necessity for mechanical competence and resilience of down feathers, we still know little about their mechanical performance.
Genetic tests of the taxonomic status of the ring‐tailed lemur (Lemur catta) from the high mountain zone of the Andringitra Massif, Madagascar
Authors: Yoder Anne D. , Irwin Jodi A. , Goodman Steven M. , Rakotoarisoa Soava V.
Published: February 2006

A recent survey of the high‐mountain zone of the Madagascar Parc National (PN) d'Andringitra revealed the presence of an apparently isolated troop of the ring‐tailed lemur Lemur catta. These animals display phenotypic and ecological characteristics that are unusual for the monotypic genus Lemur, thus raising the possibility that they are members of a different undescribed species. We present analyses of two mitochondrial genes to test the hypothesis that L. catta from Andringitra should be considered a distinct species. The results indicate that taxonomic revision is not warranted under the expectations of the phylogenetic, coalescent, or biological species concepts. Rather, the genetic patterns observed among the Andringitra and lowland mitochondrial haplotypes are consistent with those expected for a single species.
Social and population structure of a gleaning bat, Plecotus auritus
Authors: Entwistle A. C. , Racey P. A. , Speakman J. R.
Published: February 2006

Brown long‐eared bats Plecotus auritus occupying 30 summer roosts in north‐east Scotland were studied over 15 years. During this time 1365 bats were ringed, and a further 720 recaptures were made. Individual bats showed a high degree of roost fidelity, returning to one main roost site; < 1% of recaptured bats had moved among roost sites, and all recorded movements (n= 5) were < 300 m. Adults of both sexes were loyal to the roost sites at which they were first captured, indicating long‐term use of roosts. At least some juveniles (n= 32) of both sexes returned to the natal roost. Mark–recapture estimates indicated that colonies of this species were substantially larger (c. 30–50 individuals) than assumed in previous studies. Plecotus auritus differs from most other temperate zone, vespertilionid species in that there was no evidence of sexual segregation during summer, with males present in all colonies throughout the period of occupancy. Population structure in summer seems to be consistent with a metapopulation model, with discrete sub‐populations showing minimal interchange. The group size, colony composition and population structure described in this species may be associated with the wing shape (particularly aspect ratio) and foraging behaviour of P. auritus. It is postulated that relative motility, linked to wing structure, may affect the distribution of individuals, and may have implications for the genetic structure of this species. Correlations between aspect ratio and both colony size and migratory behaviour, across British bat species, indicate that wing shape could be an important factor contributing to patterns of social behaviour and genetic structuring in bats.
Adult dispersal in the co‐operatively breeding Damaraland mole‐rat (Cryptomys damarensis): a case study from the Waterberg region of Namibia
Authors: Hazell R. W. A. , Bennett N. C. , Jarvis J. U. M. , Griffin M.
Published: February 2006

A total of 104 Damaraland mole‐rats was collected in 1988, 1990, 1991 and 1993 from an open water canal in the Otjiwarongo district of Namibia. The mole‐rats were apparently dispersing above ground when they fell in and drowned; they had travelled at least 20 m in distance from their natal burrow systems. The dispersing mole‐rats of both sexes were significantly larger than 73 animals trapped from a nearby control population. Sequential tooth wear and eruption patterns showed that dispersers were adult animals. There was a bias towards male mole‐rats dispersing. Furthermore, in years with lower rainfall (< 300 mm) it was found that dispersal became even more male biased. Eighty per cent of males and 40% of female dispersers showed signs of reproductive readiness, with more males than females being ready to breed. Thus it appears that, in these otherwise totally subterranean mammals, at least one form of dispersal occurs, above ground, and that adult mole‐rats are the principal dispersers.
Mesenchytraeus antaeus, a new giant enchytraeid (Annelida, Clitellata) from the temperate rainforest of British Columbia, Canada, with a revised diagnosis of the genus Mesenchytraeus
Authors: Rota Emilia , Brinkhurst Ralph O.
Published: February 2006

Mesenchytraeus antaeus sp. n., an unpigmented giant enchytraeid inhabiting Carmanah valley (48°37′N, 124°44′W), Vancouver Island, is described. With its 102–127 segments and the size of fixed specimens reaching 61×2.9 mm (diameter maximal at midbody), this species qualifies as one of the largest members of the Clitellata family. The body wall comprises: a surprisingly thin cuticle (0.002 mm), the epidermis (0.02–0.04 mm), circular muscles (0.02 mm), plus thick longitudinal muscles (eight‐layered, totally 0.16–0.18 mm) divided into seven unequal fields. The chaetae are grouped in bundles of two to seven but show some unusual traits which suggest interesting convergences with the lumbricids. For instance, the most lateral chaeta in a bundle is always the largest; the larger chaetae exceed in length one‐third of a millimetre; the ectal tips of the chaetae are oriented in opposite directions in the anterior and posterior halves of the body. The spermathecal pores are prominent and open laterally in the middle of V, an unprecedented location among enchytraeids. The nature of the spermathecal ampullae (free, diverticulate and greatly elongate) indicates a close relationship to a group of species that seems to be confined to the Pacific coast of North America and the Arctic coast of Siberia. This amphi‐Beringean lineage includes other gigantic forms such as M. harrimani Eisen, 1904 and M. maculatus Eisen, 1904, from which, however, M. antaeus is clearly differentiated by the lack of pigmentation, the different size distribution of the chaetae within bundles, and the unique arrangement of the male apparatus. The latter includes unusually long sperm funnels (extending over 10 segments) and two groups of large accessory glands opening through two circular papillae at the base of each penial bulb, independently of the penial pores. All other congeners known to possess this type of glands (e.g. M. franciscanus Eisen, 1904) are at most only half as large as M. antaeus. The chaetal muscles of M. antaeus are heavily infested by encysted nematodes.
Developmental responses to pond desiccation in tadpoles of the British anuran amphibians (Bufo bufo, B. calamita and Rana temporaria)
Authors: Brady L. D. , Griffiths R. A.
Published: February 2006

Tadpole development was compared in three amphibian species (Bufo calamita, B. bufo and Rana temporaria) that suffer different risks of pond desiccation in nature. Using a replicated pond system, development was monitored in desiccating and non‐desiccating ponds, and in vertical‐sided and gently shelving (‘shoreline’) ponds. In desiccating ponds, tadpoles suffered from crowding effects and metamorphosed at a smaller size, but development was not accelerated in response to desiccation in any of the three species. Desiccating ponds had higher maximum temperatures but also lower minimum temperatures, which may explain the lack of any difference in development time between desiccating and non‐desiccating ponds. Although shoreline ponds were slightly warmer than vertical‐sided ponds, development under these conditions was also consistent with a crowding, rather than a temperature, effect. In shoreline ponds, metamorphosis generally took longer, was less synchronized between individuals, and resulted in a smaller size at metamorphosis, compared to development in vertical‐sided ponds. The lack of species‐by‐desiccation interactions indicated that there were no differences between the three species in developmental plasticity. Developmental constraints may place a limit on the degree of plasticity that can evolve in a species such as B. calamita, which breeds only in ephemeral ponds with a variable hydroperiod. Alternatively, low genetic variability within British populations of B. calamita may have constrained the evolution of adaptive plasticity in this species.