bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of habitat characteristics on small mammals in a Mexican high‐altitude grassland
Authors: Lopez‐Paniagua J. , Romero F. J. , Gomez J. L. , Lopez J. C. , FA J. E.
Published: March 2009

Small mammals in a high‐altitude grassland area close to Mexico City were studied. Populations of 10 species were censused using live traps in 48 sample quadrats. Within each quadrat, vegetation characterization, including complete floristic listings, cover values for species and layers and values of habitat modification, were assessed. Habitats were described according to plant communities identified using ordination and classification methods. Nine different plant communities were obtained. Densities and abundance of all small mammal species were calculated for each of the habitats classified. Peromyscus alsloni was the most abundant species in all habitats, reaching maximum densities of 55 ha−1 in pine forest with dense ground and herb layer. Peromyscus melanotis also occurred in all habitats but at lower densities (maximum 29 ha−1). Reithrodontomys megalotis was found in all habitats except in tall dense grassland. Densities for this species were generally low (1‐9 ha−1) but reached 19 ha−1 in short dense grassland. All other species were largely absent from 4–8 habitats and showed very low densities (0.75–4 ha−1). The densities of the more abundant species were largely correlated with more open habitats and higher indices of habitat modification. Lower altitude grassland habitats have a greater abundance of small mammals and a higher species richness than the medium and higher altitude, physiognomically more complex habitats. Species richness was highest in tall pine‐alder forest with a species‐rich, dense herb layer and lowest in pine forest with dense ground and herb layers. Species richness was positively correlated with overall small mammal density.
Explaining the scaling of transport costs: the role of stride frequency and stride length
Authors: Strang K. T. , Steudel Karen
Published: March 2009

The mechanisms which enable large animals to transport a unit of body mass through a unit distance at a lower metabolic cost than smaller animals have been the subject of numerous studies. Recent investigations have concluded that stride frequency is a main determinant. We examine the role of both stride frequency and stride length in determining the scaling of the cost of transport.

Slopes for regressions between stride frequency and speed and stride length and speed were determined in four species of rodents. These data were pooled with literature values for the slopes of stride frequency, stride length and cost of locomotion (all vs. speed) for a total of 17 species ranging in size from 30 g to 250 kg. Interspecific equations were calculated for each of these slopes versus body mass, and residuals from these allometric lines were calculated. Residuals were compared to see if variation in the rate of cost increase at a given size is related to variation in the rates of stride frequency and/or stride length increase.

The residual analysis revealed that the variation in transport cost is explicable only in terms of the interaction of stride frequency and stride length slopes. The product of the scaling exponents for stride frequency slope and stride length slope is not significantly different from the scaling exponent for the cost of transport. A model seeking to explain the scaling of the cost of transport must therefore consider the influence of both stride length and stride frequency.

We propose that absolutely longer limbs allow large animals to minimize the rate of increase of stride frequency and stride length with speed, and that this allows utilization of muscles with lower intrinsic rates of contraction, which in turn results in a lower mass‐specific cost of transport.
Wing design and scaling of flying fish with regard to flight performance
Authors: Fish F. E.
Published: March 2009

Fin and body dimensions of six genera of flying fish (Exocoetidae) were examined to study variation in morphological parameters in relation to aerodynamics performance. The fins are modified as wings for gliding flight. Fin area and fin span increase with increasing body mass, whereas the percentage of wing area contributed by the pectoral fins and the percentage of the caudal fin area contributed by the hypocaudal lobe remain constant. The aerodynamic design of flying fish approximates the monoplane‐biplane classification proposed by Breder (1930). Scaling relationships for wing loading and aspect ratio indicate that wing morphology in the Exocoetidae is more similar to birds and bats than to other gliders. The flight performance of flying fish is a high‐speed glide with a relatively flat trajectory. The wing, as indicated by the aspect ratio, is designed for high lift with low drag characteristics.
Ontogeny and phylogeny of the trunk lateral line system in cichlid fishes
Authors: Webb Jacqueline F.
Published: March 2009

An examination of the ontogeny of the lateral line trunk canal and the diversity of adult trunk canal patterns among cichlids indicates that bidirectional canal formation is a general ontogenetic pattern in the Cichlidae with the exception of Cichla and those few species with a complete trunk canal pattern. In addition to the tubed scales which make up the trunk canal, some lateral line scales have pits containing superficial neuromasts. These are recognized as components of the lateral line system of the trunk in adult cichlids for the first time. Eight trunk canal patterns that are variations on a simple disjunct pattern are defined among the 17 cichlid genera examined. Using bidirectional canal formation as a developmental model, these patterns can be placed along an ontogenetic spectrum. This suggests that heterochrony (alterations in the timing of development) is an important mechanism of evolutionary change in the lateral line system of the trunk in cichlid fishes.
Morphometric analysis of embryonic development in Alligator mississippiensis, Crocodylus johnstoni and Crocodylus porosus
Authors: Deeming D. C. , Ferguson M. W. J.
Published: March 2009

The size of embryos at various stages of development was determined in three species of crocodilian (Alligator mississippiensis, Crocodylus johnstoni and C. porosus). Various morphometric measurements were taken of embryos throughout development and were described for each stage of development. Increase in size from stage to stage was faster in A. mississippiensis than in C. porosus and C. johnstoni. Hatchlings of A. mississippiensis were large in length but light in mass compared with the hatchlings of C. johnstoni and C. porosus which were heavier per unit length. These morphometric parameters can be used to determine the stage of embryonic development by size. The use of principle component analysis improves this technique further by dampening any anomalous data points.

The rate of embryonic growth in A. mississippiensis appeared to be under greater genetic control than in the two species of Crocodylus. The evolutionary advantages of this phenomenon probably relate to the biology of A. mississippiensis. Due to the northerly range of this species it is advantageous for alligators to hatch as soon as possible, as large as possible, to maximize the period prior to winter hibernation and reduce predation. Tropical crocodiles have fewer selection pressures for rapid development and have slower rates of embryonic growth. Genetic aspects of crocodilian embryonic development have been largely ignored but may help explain some aspects of crocodilian growth under farming conditions.
A classification of pythons (Serpentes, Pythoninae)
Authors: Underwood G. , Stimson A. F.
Published: March 2009

The Central American Loxocemus and the pythons are assigned to sister subfamilies Loxoceminae and Pythoninae, within the weakly characterized family Boidae. They share the character of the left cerebral artery foramen being larger than the right. Within the Henophidia, paired subcaudal scales associate these subfamilies with Xenopeltis and the Uropeltidae.

Twenty‐nine discrete variables were coded as 52 binary characters. Nine continuous (meristic) variables were examined. A method is described by which 18 binary characters were selected from seven of these variables, for inclusion in the data set. With Loxocemus and Xenopeltis as outgroups, the data were analysed by a compatibility method. The Pythoninae are resolved into tribes Pythonini and Moreliini on the basis of complementary synapomorphies. The Pythonini have only the genus Python, for the African and Asiatic species, including reticulatus and timoriensis. The Moreliini have all of the Australasian species, in two genera: Aspidites and Morelia.

A phylogenetic analysis of the two tribes is presented, with incomplete resolution of the Moreliini. The two tribes overlap in the areas of the Moluccas and Timor. It is postulated that: Loxocemus plus Pythoninae represent a Laurasian stock; south‐east Asia was the primary centre of radiation of the Pythoninae; by the Miocene dispersal to Australasia had occurred, where there was a second radiation.
Seasonal variation in gut morphology in wild rabbits (Oryctolagus cuniculus)
Authors: Sibly R. M. , Monk K. A. , Johnson I. K. , Trout R. C.
Published: March 2009

It is shown experimentally that diet composition affected the sizes of several digestive organs in juvenile rabbits collected from the wild. Stomach weight, small intestine volume and colon length were larger in rabbits reared on diets higher in fibre. Small intestine weight, however, was lower.

Analysis of natural variation in wild adult rabbits showed that all digestive organs (except for the appendix) were larger in rabbits living on chalk soils than in those living on sand or clay. Seasonal variation was more marked in males than in females, probably because of the sexes' different breeding requirements. Thus most male digestive organs were smaller between December and June than at other times of year. Female digestive organs did not show this pattern, and were largest in May/June, when the demands of pregnancy and lactation are highest. However, food quality may have been important too. Food quality is probably highest in April, and most digestive organs were then smallest (both sexes). The dry weights of stomach and small intestine did not fit these patterns. Stomach weight increased with the presence of the nematode parasite Graphidium strigosum and small intestine and caecal volumes with the presence of cestodes. Numbers of nematodes (Trichostrongylus retortaeformis and Passalurus ambiguus) in the caecum or colon, however, had no effects on organ sizes.

Data are presented on variation in intensity and prevalence of these helminth parasites with season and soil type.
Seasonal and spatial differences in food selection by otters (Lutra lutra) in Shetland
Authors: Kruuk H. , Moorhouse A.
Published: March 2009

Otters Lutra lutra in Shetland feed almost exclusively in the sea. Their diet was assessed from direct observations of 13, 313 dives, of which 27% were successful, and 2028 prey could be identified. The results are compared with published data on the availability offish for different seasons, time of day, state of tide, and different types of coast. The most frequently taken prey was eelpout Zoarces viviparus (34%), but they were relatively small, and rocklings Ciliata mustela dominated the diet in terms of biomass (18%, against eelpout 15%). Small eel‐shaped, bottom‐living species dominated in the diet at all times, but of those, otters took the larger fishes in the populations (median weight of prey 28 g). The size and species composition of prey of males was the same as that of females with cubs, but females without cubs took smaller fish.

In spring, prey was smaller than at other times, and otters were least successful when diving. Diving success and mean prey weight was highest in winter, although prey availability was highest in summer.

Eelpout were caught mostly along sheltered coasts, rocklings in more exposed areas. It is argued that for optimal exploitation of the seasonal availability of different species of prey, otters need to use different types of coast, and the size of their ranges would be related to the spacing of coastal types.

Most fishes were caught in daytime, and around high tide otters fed less than at other times; hunting therefore took place during periods of inactivity of prey. For the main prey species, Ciliata mustela, it was estimated that otters took a substantial part of the total population.
Trophic relationships of common frog (Rana temporaria) and pigmy shrew (Sorex minutus) in upland Co. Antrim, Northern Ireland
Authors: Meharg M. J. , Montgomery W. I. , Dunwoody T.
Published: March 2009

The common frog and the pigmy shrew are common vertebrate predators in the uplands of Co. Antrim, Northern Ireland. This report concerns their habitat preference and trophic biology which are poorly documented at higher altitudes. Frogs preferred damp, grassy, reclaimed habitats while pigmy shrews appeared to favour moorland dominated by Calluna vulgaris. Both frogs and shrews were absent from pitfall trap collections from December to February and numbers of both were low until late spring. This corresponded to the period of lowest invertebrate abundance. Examination of stomach contents suggests that frogs are less selective feeders and utilize a greater diversity of prey items than pigmy shrews. Although sample size is low early in the year, diversity of the diet of pigmy shrews apparently increased from the first to the second quarter and again in the third quarter of the year. This led to an increase in food niche overlap with frogs in late summer but at a time of year when food supply was greatest. It is unlikely, therefore, that dietary overlap constitutes a basis for interspecific competition between frogs and shrews. This is likely to be ameliorated by habitat and behavioural differences between the two predators.
The anatomy and function of the feeding apparatus in two armadillos (Dasypoda): anatomy is not destiny
Authors: Smith KathleenK. , Redford K. H.
Published: March 2009

The morphology and function of the masticatory apparatus in two armadillos, Dasypus novemcinctus and Euphractus sexcinctus are compared. Euphractus sexcinctus, a species restricted to South America, is omnivorous, eating a wide range of foods, including significant amounts of plant material and carrion. Dasypus novemcinctus is geographically the most widespread of all armadillos, ranging from northern Argentina into the United States. It is insectivorous‐omnivorous, apparently consuming whatever it encounters in the leaf litter. In South and Central America, this leads to a diet with a large proportion of ants and termites; in North America, the diet is considerably broadened. The teeth, jaws and jaw musculature of E. sexcinctus are large and the configuration of the jaws maximizes force production. Dasypus novemcinctus possesses derived morphology relative to the primitive condition in armadillos and exhibits many characteristics of ant and termite‐eating mammals, including reduced jaw muscles, teeth and facial bones. The apparent morphological specializations for myrmecophagy in D. novemcinctus do not, however, constrain its diet to ants and termites. It is broadly omnivorous, especially in North America. Our data highlight the difficulties in predicting diet from morphological analysis and raise questions concerning the behavioural limits imposed by morphological specialization.
Ontogenetic changes in the mechanical properties of the femur of the polar bear Ursus maritimus
Authors: Brear K. , Currey J. D. , Pond Caroline M.
Published: March 2009

The mechanical properties of the bone material of femora of five wild polar bears, ranging in age from three months to seven and three‐quarter years, were compared with those of humans and axis deer. There are changes in mechanical properties in all three species with age, but their time course and extent vary greatly between species. The age‐related changes in mechanical properties are attributable mainly to changes in mineralization. At any age, the properties of the polar bear's bones lie between those of humans and the deer. The architecture of the bear's bones, and the mechanical properties of their bone material, were related to the weight of the bears. The calculated stresses in the bones, and their deflection under load, were relatively constant compared with the very large differences in the weights of the bears and the sizes of their bones.
On the optimal growth of the alimentary tract in avian postembryonic development
Authors: Konarzewski M. , Lilja C. , Kozłowski J. , Lewonńczuk B.
Published: March 2009

It was shown in the mathematical model described elsewhere that when growth rate of the chicks is maximized and not constrained by the food availability, the optimal relationship between body mass and alimentary tract mass should conform to a single straight line, or two‐, or three‐segmented straight lines. Here, we present the data on growth of 11 bird species, and we test the model using the mass of intestines as an indicator of growth of the alimentary tract. The results support the predictions of the model for altricial species and contradict them for precocials. Since precocial species examined here were not food‐limited, we suggest that the lack of optimal growth of their alimentary tract is inherent to their mode of development. This may account for their lower growth rate, as compared to altricials. The existence of the optimal growth of the alimentary tract in altricial nestlings suggests that under natural conditions the food is much more abundant than it is generally assumed.
A novel method of self‐righting in the springtail Sminthurus viridis (Insecta: Collembola)
Authors: Brackenbury John
Published: March 2009

Photographic evidence shows that the ventral tube can be used as a tentacle‐like mechanical aid for self‐righting from an inverted position. It is proposed that the extraordinary length of the vesicles of the ventral tube in globular springtails has been evolved in order to combat postural instabilities resulting from spherical symmetry of body form.
Fruit patch size and frugivory in the lowland tapir (Tapirus terrestris)
Authors: Bodmer Richard E.
Published: March 2009

Large non‐ruminant ungulates consume the more abundant low‐quality forage because this gives them the advantage of reducing search effort. However, large‐bodied herbivores would be predicted to search for high‐quality fruit patches if these patches were of large size and the fruits rich in nutrients. Diets of lowland tapir (Tapirus terrestris), a large non‐ruminant of the Amazon basin, were examined from animals of north‐eastern Peru to investigate this relationship between high‐quality fruit, lower‐quality browse and searching behaviour. Lowland tapir consumed on average 33% fruit, which is relatively high for a large non‐ruminant ungulate. The fruit portion of lowland tapir diets was dominated by the nutritious Mauritia flexuosa (Palmae) drupes, which were selected by tapir more frequently than other fruit types. M. flexuosa palms grow in virtually monotypic stands and occur in larger patches than other fruit trees used by terrestrial herbivores of the Amazon. Lowland tapir encountered fruits more frequently when ranging in M. flexuosa palm forests than in non‐palm forests, because they changed their searching behaviour once they entered palm forests by turning more abruptly. It appears that lowland tapir can consume greater proportions of fruit than other large non‐ruminant ungulates, because they exploit a nutritious fruit that occurs in large patches and that meets the energy demands of their large body size.
Morphological adaptations to an unusual defensive strategy in the mantid Orthoderella ornata (Insecta: Mantidae)
Authors: Brunner Dani , Gandolfo Daniel
Published: March 2009

The behaviour of Orthoderella ornata Giglio Tos, 1897, a cryptically coloured mantid, is described with reference to some morphological adaptations that conceal the typical insect outline.

The modification of the typical morphology of the head in mantids is analysed with special mention of the internal structure, the tentorium, and by comparison with the disposition of two other species with a different defensive strategy.

The hypothesis that O. ornata has short legs in correlation with its resting position is supported by a morphometric comparison with five other species of mantids which show different behaviour and positions in their cryptic strategy.
Ranging behaviour of the Cape grey mongoose Galerella pulverulenta in a coastal area
Authors: Cavallini P. , Nel J. A. J.
Published: March 2009

Five Cape grey mongooses (Galerella pulverulenta (Wagner, 1839)) were radio‐tracked from November 1988 to February 1989 in the West Coast National Park, Cape Province, South Africa. Animal locations numbering 2253 were recorded. Radio‐tagged mongooses were diurnally active and frequented thick mediterranean‐type scrub; sightings of untagged mongooses followed the same pattern. Home range size (95% harmonic mean) of resident animals in the study period ranged from 21 to 63 ha. One female had the smallest range; the other, a juvenile, ranged more widely, possibly dispersing, and utilized a more varied habitat. Home ranges overlapped widely, both within and between sexes, although territoriality among adult females cannot be ruled out. Males showed some degree of sociality. Possible reasons for this spatial system are discussed.
Skeletal growth and function in the California gull (Larus californicus)
Authors: Carrier David , Leon Lisa R.
Published: March 2009

Although the bones of rapidly growing animals are composed of weak tissue, they often must function in locomotor activity. We address the conflict between development and skeletal function by analysing the ontogeny of skeletal strength in the California gull, Larus californicus. Changes in shape and mechanical properties of the femur, tibia, tarsometatarsus, humerus, ulna and carpometacarpus were analysed in a complete post‐hatching growth series. During post‐hatching growth, strength and stiffness of the skeletal tissue increases six‐ to ten‐fold. At hatching, long bones of the wing are relatively weak and they remain so throughout the major portion of the growth period. However, in the hind limb, relatively thick bones in juveniles compensate for the weak tissue such that the force required to break the bones remains constant relative to body mass. This difference between hind limb and wing parallels the development of locomotor function; young gulls begin to walk within a day or two of hatching, but they do not fly until they are fully grown. Thus, in the bones of the hind limb, the conflict between rapid growth and skeletal function is solved by negative allometry of bone thickness.

After young gulls reach adult size, the breaking strength of the wing bones increases three‐ to four‐fold, the mass of the pectoralis muscle triples and the surface area of the wing doubles. The one aspect of wing development that is not delayed until shortly before fledging is linear growth of the bones. Bones of the wing increase in length at a rapid and relatively constant rate from the time of hatching to the attainment of adult size. Relatively early initiation of linear growth of the wing bones suggests that the rate at which bones grow in length may be the rate limiting factor in wing development.
Immune responses of the common seal (Phoca vitulina) to canine distemper antigens during an outbreak of phocid distemper viral infection
Authors: Carter S. D. , Hughes D. E. , Bell S. C. , J. R. Baker , Cornwell H. J. C.
Published: March 2009

In 1988, there was a marked increase in the mortality rate of the common seal (Phoca vitulina) in European waters which was shown to be associated with a canine distemper‐like virus (CDV), recently named Phocid Distemper Virus (Cosbyet al., 1988). Investigations were carried out to determine the ability of common seals to respond immunologically and to determine the levels of antibody produced. Common seal immunoglobulins were purified, analysed and shown to be similar to those of other mammals. A simple immunoassay to measure seal antibodies to CDV was developed and showed striking differences between the susceptible seals (low levels of antibodies) and the surviving common seals (high amounts of anti‐distemper antibodies). Similar results were obtained with a neutralization test currently used to measure antibody titres to canine distemper virus in the dog. The adult common seals had high antibody titres and may be protected for future years, whereas the younger seals did not develop high levels of antibodies. This may be because either the younger seals had not encountered the virus or had not developed effective immunity.
The distribution, density and biomass of terrestrial reptiles in Dominica, West Indies
Authors: Bullock D. J. , Evans P. G. H.
Published: March 2009

Fourteen species of reptiles have been recorded from the island of Dominica, Lesser Antilles. As part of a larger study of the ecology of Dominica's forests, the distribution, density and biomass of three widespread lizard species (Anolis oculatus, Ameiva fuscata and Mabuya mabouya) were estimated in all major vegetation types. No consistent differences between seasons occurred for any of the three species, and at no site was a definite breeding season detected. Densities, estimated mainly by plot counts, were highest in coastal woodlands where mean densities reached 2148 Anolis per hectare, 379 Ameiva per hectare, and 751 Mabuya per hectare. Densities in rain forest sites were often very low. Combined biomass for the three species also reached a maximum in coastal woodlands of 44.7 kg/ha. This value is amongst the highest recorded for terrestrial reptile assemblages, and suggests that Dominica's coastal woodlands are unusually favourable habitats for reptiles.

Previous studies of Caribbean lizards have suggested that either competition or predation from birds may influence lizard densities. The present study, however, found no such relationships, and it was concluded that lizard density was independent of bird density.
Biological protective substances in Marthasterias glacialis (Asteroidea) epidermal secretion
Authors: Canicattí C. , D'Ancona G.
Published: March 2009

Marthasterias glacialis secretes a watery mucous liquid consisting of 14% carbohydrate and 86% protein. The mucous secretion possesses different biological active molecules responsible for lysozyme‐like, protease and haemolytic activities. These substances could constitute a molecular barrier playing a protective role against the penetration by bacteria, fungi and parasites. The secretory apparatus consists of two unicellular glands, a large goblet cell and a granular cell, which open directly into the epidermis.
Sexual dimorphism in leg length among orb‐weaving spiders: a possible role for sexual cannibalism
Authors: Elgar M. A. , Ghaffar N. , Read A. F.
Published: March 2009

The degree and direction of sexual dimorphism across different species is commonly attributed to differences in the selection pressures acting on males and females. The extent of these differences is especially apparent in species that practise sexual cannibalism, where the female attempts to capture and eat a courting male. Here, we investigate the relationship between sexual dimorphism in size and leg length, sexual cannibalism and courtship behaviour in three taxonomic groups of orb‐weaving spiders, using morphological data from 249 species in 36 genera. Females are larger than males in all three taxonomic groups, and males have relatively longer legs than females in both the Araneinae and Tetragnathidae. Across genera within each taxonomic group, male body size is positively correlated with both female body size and male leg length, and female body size is positively correlated with female leg length. Sexual size dimorphism is negatively correlated with relative male leg length within the Araneinae, but not within either the Tetragnathidae or the Gasteracanthinae. There was no negative correlation between sexual size dimorphism and relative female leg length in any taxonomic group. We argue that the relationship between sexual size dimorphism and relative male leg length within the Araneinae may be the result of selection imposed by sexual cannibalism by females.
Optimum stiffness for leg bones
Authors: Alexander R. McN. , Ker R. F. , Bennett M. B.
Published: March 2009

A limb bone will be lighter if it is made thinner. However, thinner bones are more flexible (for given length and shape of cross‐section) so their muscles must shorten more to move the distal end of the bone against a resisting force. To shorten more, a muscle needs longer muscle fibres and so must be heavier. Thus a particular thickness for the bone will enable the combined mass of bone plus muscle to be minimized. Peak stresses due to bending moments, in bones that were optimized according to this criterion, would be about ±70 MPa. Stresses of about this magnitude have been found in leg bones of various mammals, in strenuous activities such as running and jumping. However, similar stresses might be predicted on grounds of strength requirements, to give adequate factors of safety.
The idiosomal chaetotaxy of astigmatid mites
Authors: Griffiths D. A. , Atyeo W. T. , Norton R. A. , Lynch C. A.
Published: March 2009

Within the Astigmata, setal homologies with the general chaetotaxic systems developed for acariform mites by F. Grandjean have never been convincingly established. This study deals with all body regions, exclusive of legs and gnathosoma, mostly utilizing as models astigmatid species from three different families. Six hypotheses which attempt to explain the ontogeny of segments, setae and cupules in the caudal bend region are compared using three‐dimensional views obtained by scanning electron microscopy. The hypotheses are evaluated by in‐group comparisons testing their consistency with presumed segmental boundaries, and by out‐group comparisons with oribatid mites. The strongest, most parsimonious hypothesis suggests that larval astigmatid mites possess segment F, but not its setae, and the two pairs posterior to segment F are hl and h2, whilst the five setae added in the protonymph are h3, f2 and ps1–3. Six pairs of structures on the deutonymphal anal plate are identified as modified setae, and evidence supporting their homologies with setae of other instars is discussed for the first time. A comparison of the principal chaetotaxic systems used for the dorsal and anal regions of the Astigmata is presented. Application of Grandjean's setal signatures to these regions, as well as to the coxisternal and genital regions, is discussed and illustrated by examples.
Factors affecting differential mating success in male crested newts, Triturus cristatus
Authors: Hedlund Linda
Published: March 2009

This study investigates differences in mating success in male crested newts, Triturus cristatus. In experiments, mating success varies considerably between individual males. Male size affects mating success, but the maximal height of the male's crest is more important. Male size and crest height are correlated, but in partial correlation analysis only crest height is significantly correlated with mating success. Motivation is also an important factor in determining male mating success as males that had been isolated for a week were more successful than freshly caught males. Newts might be limited in their ability to produce spermatophores, and isolation gives the male time to produce more spermatophores. It is likely that motivational state is less important in a natural population than size and crest height, because wild males are often interrupted during courtship before spermatophore deposition and hence are highly motivated to mate.
Energy requirements during reproduction and reproductive effort in shrews (Soricidae)
Authors: Genoud M. , Vogel P.
Published: March 2009

The energy requirements of reproducing and non‐reproducing females of three species of Crocidura (C. russula, C. viaria, C. olivieri), and two species of Sorex (S. coronatus, S. minutus) were measured. Members of these two genera show different rates of metabolism and reproductive strategies (extreme altriciality and larger litter size in Sorex). During pregnancy, the daily energy intake (on either an absolute or a mass‐specific basis) remained close to the non‐reproductive value in all species. The absolute energy intake increased strongly after parturition and was influenced by the litter size. Peak energy intake of lactating females was extremely high, typically between 100% and 200% above the non‐reproductive requirements in the Crocidura and about 300% above the non‐reproductive intake in the Sorex. The mass‐specific daily energy intake was reduced during lactation in the three smaller species but not in C. viaria and C. olivieri. This decrease probably involves the different thermoregulatory abilities and/or basal rate of metabolism of the pups. Average reproductive effort was about 50%, in the Crocidura species and above 150% in the Sorex species. The higher effort in the latter is partly due to a larger litter size. But in addition, extreme altriciality in the Sorex leads to an earlier increase in the energy requirements and thus is an energetically more expensive reproductive mode. The present results support the hypothesis that a higher basal rate of metabolism is associated with a higher reproductive effort in shrews.
Selection of gastropod prey by a tropical freshwater crab
Authors: Dudgeon David , Catherine Cheung Pui Shan
Published: March 2009

Prey selection by Somaniathelphusa sinensis (Parathelphusidae) among five gastropod species (two prosobranchs, three pulmonates) was associated with two snail attributes. First, the degree of defence of the tissues by the shell, approximated by shell weight (SW)/tissue dry weight (M). Snails with the heaviest shells (Sinotaia quadrata: Viviparidae) could not be attacked successfully by any crabs, and those with somewhat lighter shells (Melanoides tuberculata: Thiaridae) were protected from small crabs. Secondly, among those light‐shelled snails which could be attacked successfully, prey value (M/handling time, Ht) determined rank order of preference. Biomphalaria straminea (Planorbidae), with the highest M/Ht, was the species most readily eaten. When presented with a single snail species, crabs selected among different‐sized B. straminea in a way which maximized M/Ht. This preference was most strongly exhibited by small crabs. A lack of size selection for Radix plicatulus (Lymnaeidae) prey was in agreement with an absence of a clear influence of size on Ht for this species. Manipulation of M/Ht by attaching plastic discs to B. straminea shells (thereby increasing Ht) resulted in patterns of prey selection in accordance with the hypothesis that foraging S. sinensis maximized M/H1.

Partial consumption of R. plicatulus, and to a lesser degree Physella acuta (Physidae), was common when groups of snails were presented to individual crabs, and occurred more frequently when large snails were offered. Partial consumption and subsequent rejection of large snails may have masked selection for small prey which were rarely abandoned before being completely eaten.

The implications of patterns of prey selection were discussed with reference to the influence of crab predation on snail distribution and abundance in Hong Kong fresh waters.
Behaviour and social organization in a colony of the Damaraland mole‐rat Cryptomys damarensis
Authors: Bennett N. C.
Published: March 2009

This paper reports qualitative and quantitative behavioural studies of the social mole‐rat C. damarensis. The behaviours were subdivided into four major categories: nest, maintenance, interactive and auto‐behaviours. Social interactions and behavioural types were analysed by sex, age category and caste. The nest area is a focal point in the burrow system with individuals spending more than 70% of the day there. Many of the interactive behaviours occurred there and the mole‐rats showed definite preferences with regard to which individuals they rested next to or avoided.

The Damaraland mole‐rat colonies show some division of labour, into frequent and infrequent worker groups; these castes differed significantly in the amount of both digging and soil movement undertaken.
Intraspecific variation in egg composition and yolk formation in the common guillemot (Uria aalge)
Authors: Hatchwell B. J. , Pellatt J.
Published: March 2009

Common guillemot eggs were collected and analysed in two years on Skomer Island, Wales, to investigate the effects of environmental conditons during the pre‐laying period on egg formation and composition. Pre‐laying attendance at breeding colonies indicated more favourable environmental conditions in 1987 than in 1986. The size of eggs did not differ between years, but eggs were laid earlier in 1987 and the time taken for yolk deposition was also shorter in 1987. Two distinct effects of environmental conditons on yolk formation were indicated: first, on the timing of initiation of yolk deposition; and secondly, on the duration of the yolk deposition period. Egg composition also differed significantly between years with a higher proportion of albumen and a higher proportion of lipid and non‐lipid solids in yolks in 1987. These results are discussed with respect to environmental conditions and the constraints on egg production.
Population variables and causes of mortality in a hedgehog (Erinaceous europaeus) population in southern Sweden
Authors: Kristiansson Hans
Published: March 2009

A hedgehog population in southern Sweden was studied by capture‐mark‐recapture during 1972–1979. Each animal was weighed, sexed and marked with one numbered clip in each ear.

The number of subadult and adult hedgehogs was about 20 in the first two years, 1972–1973. Numbers then increased and approximately doubled and the population peaked in 1978. A decrease came in 1979.

The estimated number of juveniles produced varied between years with the lowest figure (15 juv.) in 1974 when the population was low and the highest in 1977 (39 juv.) when the population was high. As no captured subadult female had suckled young, estimates of recruitment rate assumed that females did not reproduce until they were adult. The average number of juveniles per adult female was 2.8. Recruitment rate did not show any correlation with non‐juvenile population densities.

For both juveniles and non‐juveniles the annual mortality varied greatly between years. Average yearly mortality was 47% for non‐juveniles and 34% for juveniles.

For non‐juveniles, most of the total mortality occurred during winter, ranging between 26% and 43% (average 33%), and increased with increasing densities of non juveniles. Juvenile winter mortality varied between 6% and 94%, averaging 33%.

Summer mortality of non‐juveniles averaged 15%, ranging between 3% and 22%. Traffic kills were the predominant cause of death. Only a few juveniles were found dead during summer and autumn.

There were no statistical differences in age‐specific survival rate between males and females and, generally, no differences in survival rate between the age categories within each sex. It is argued that the population size appears to be more influenced by environmental factors, such as food availability, winter nest sites and winter climate, than by density‐dependent factors.
Effects of sea water on thermal insulation of the otter, Lutra lutra
Authors: Kruuk H. , Balharry D.
Published: March 2009

Otters Lutra lutra L. which feed in the sea in Scotland frequently wash in fresh water. Experiments were carried out with otter pelts and with captive otters, to study the biological function of this behaviour. In vitro, the fur of otters lost much of its thermal insulation after five soakings in sea water and subsequent drying. Otters were fed in sea water or fresh water, with or without simultaneous access to alternative fresh water. When fed in sea water, otters used the alternative fresh water much more than when fed in fresh water, they were more reluctant to enter sea water if no alternative fresh water was present, and without this alternative fresh water they showed signs of hypothermia. After swimming in sea water the animals spent more time grooming and rolling. Without fresh water present the otters' fur lost its capacity for retaining air under water. These observations suggest an explanation for the restricted distribution of otters living along the coast, and for the lack of use of marine habitats by small mammals in general.
Living fast and dying young: A comparative analysis of life‐history variation among mammals
Authors: Promislow D. E. L. , Harvey P. H.
Published: March 2009

Recent comparative studies point to the importance of mortality schedules as determinants in the evolution of life‐history characteristics. In this paper, we compare patterns of mortality from natural populations of mammals with a variety of life histories. We find that, after removing the effects of body weight, mortality is the best predictor of variation in life‐history traits. Mammals with high levels of natural mortality tend to mature early and give birth to small offspring in large litters after a short gestation, before and after body size effects are factored out. We examine the way in which life‐history traits relate to juvenile mortality versus adult mortality and find that juvenile mortality is more highly correlated with life‐history traits than is adult mortality. We discuss the necessity of distinguishing between extrinsic sources of mortality (e.g. predation) and mortality caused by intrinsic sources (e.g. costs of reproduction), and the role that ecology might play in the evolution of patterns of mortality and fecundity. We conclude that these results must be explained not simply in the light of the demographic necessity of balancing mortality and fecundity, but as a result of age‐specific costs and benefits of reproduction and parental investment. Detailed comparative studies of mortality patterns in natural populations of mammals offer a promising avenue towards understanding the evolution of life‐history strategies.
The structure of the intrapigmented aesthetes and the properiostracum layer in Callochiton achatinus (Mollusca: Polyplacophora)
Authors: Baxter J. M. , Sturrock M. G. , Jones A. M.
Published: March 2009

The ultrastructure of the intrapigmented aesthetes which occur in specific areas of the different valves of Callochiton achatinus are described. The possible functions of the aesthete and the pigmented body are discussed in the light of their ultrastructure and the ecological requirements of the animal. The properiostracum in C. achatinus is unusually thick and has a structure very similar in appearance to that of collagen.
The relative age structure and body masses of complete wild‐captured colonies of two social mole‐rats, the common mole‐rat, Cryptomys hottentotus hottentotus and the Damaraland mole‐rat, Cryptomys damarensis
Authors: Bennett N. C. , Jarvis J. U. M. , Wallace D. B.
Published: March 2009

The relative ages of individuals in a complete wild‐captured colony of 13 Cryptomys hottentotus hottentotus and a complete wild‐captured colony of 25 Cryptomys damarensis were determined by means of tooth wear and eruption patterns and through the degree of ossification of their skeletons.

From sequential tooth wear and eruption patterns four relative age classes were discerned in C. h. hottentotus and five in C. damarensis. These relative age class allocations were supported by the studies on the ossification of the skeletons.

In C. damarensis, older animals are not necessarily the larger‐sized individuals. In C. h. hottentotus, however, older animals are usually the larger‐sized individuals. The reproductive pair in each of the Cryptomys species are the oldest or amongst the oldest individuals in the colony.

Individuals in a second colony of C. damarensis kept under laboratory conditions for three years maintained greatly disparate body masses which were correlated with the role of the individual within the colony and not, where it was known, with the age of the animal.

An analysis of 13 body and skull measurements performed on a complete colony of 13 C. h. hottentotus and a complete colony of 25 C damarensis revealed that only C. damarensis showed sexual dimorphism. This dimorphism was apparent from an early age but became more pronounced in older animals.
Anti‐predator defences of Pholcus phalangioides (Araneae, Pholcidae), a web‐building and web‐invading spider
Authors: Jackson R. R. , Brassington Roxanne J. , Rowe R. J.
Published: March 2009

The behaviours used by Pholcus phalangioides (Fuesslin) (Araneae, Pholcidae) to evade its predators were studied with particular attention being given to a special defence behaviour, whirling. To whirl, this long‐legged web‐building spider swings its body around in a circle, with its legs remaining on the silk. Experiments were carried out to determine the types of stimuli that elicited whirling. Touching the spider or its web elicited whirling, as did air movement over the spider, but there was no evidence that chemical stimuli from potential predators were important. Small juveniles differed from adult females and larger juveniles by more often dropping from the web instead of whirling when confronted by a potential predator. Besides catching prey on its own web P. phalangioides invades other spiders' webs to catch the other spiders. By whirling in alien webs, P. phalangioides could deter attacks by the resident spider, but P. phalangioides was less inclined to whirl when in an alien than when in its own web.
Predator‐prey interactions between jumping spiders (Araneae, Salticidae) and Phokus phalangioides (Araneae, Pholcidae)
Authors: Jackson Robert R.
Published: March 2009

Portia is a genus of specialized web‐invading salticids that use aggressive mimicry. Some other salticids leap into webs to catch spiders but do not use aggressive mimicry. Pholcus phalangioides is a web‐building spider with a special defensive behaviour—called whirling—in which it swings its body around in a circle while keeping its long legs on the silk. Pholcus phalangioides is preyed on by Portia and probably other salticid spiders in nature. Interactions between P. phalangioides and 13 species of salticids were studied in the laboratory to compare how effective salticids with different styles of predation were at catching the pholcids. Four species of Portia were studied and each was more efficient at catching P. phalangioides than were the other nine salticids tested. For one species—Portia fimbriata—individuals from three different populations were studied. The Queensland P. fimbriata used aggressive mimicry more consistently and were more efficient at catching P. phalangioides than were the other species of Portia and the other populations of P. fimbriata. The salticids that were the most efficient at catching pholcids were also better able to avoid setting off whirling by the pholcids. An experiment in which pholcids were artificially induced to whirl whenever the predator was near provided additional evidence that whirling is an effective defence of pholcids against predation by salticids.
Web‐building and predatory behaviour of Spartaeus spinimanus and Spartaeus thailandicus, primitive jumping spiders (Araneae, Salticidae) from South‐east Asia
Authors: Jackson R. R. , Pollard S. D.
Published: March 2009

Behavioural data are provided for the first time for two species of Spartaeus, S. spinimanus from Singapore and Thailand and S. thailandicus from Thailand. These jumping spiders (Araneae, Salticidae), from the primitive subfamily Spartaeinae, build large sheet webs on tree trunks and they capture prey—especially moths—on or near the web by walking to and lunging at them. When walking, Spartaeus waves its palps and legs in an unusual way. In formal tests, Spartaeus captured moths more frequently than flies and captured both moths and flies more readily when with their webs than without their webs.