bluuebunny/crossref_metadata_2025 huggingface dataset:
Foreflipper propulsion in the California sea lion,Zalophus californianus
Authors: Feldkamp Steven D.
Published: May 2009

The family Otariidae comprises the only group of marine mammals that habitually use their pectoral appendages to generate propulsive forces during swimming. This method of propulsion was examined in the California sea lion (Zalophus californianus), a representative member of the family. High‐speed films were taken as a sea lion swam against a water current generated inside a large flow channel. Thrust production was determined by examining the body's movement at various stages of the propulsive cycle. Sea lions generate thrust continuously throughout the stroke. Over its initial three‐quarters, foreflippers act as hydrofoils creating forward thrust and lift as they move vertically through the water. Thrust production is greatest, however, near the end of the stroke, when flippers are used as paddles and are oriented broad side to the oncoming flow. The force generated by this three‐phased system of propulsion is likely to be greater than that attainable by either an exclusively lift‐based hydrofoil or drag‐based paddling style of swimming.

The kinematic changes that enable sea lions to change speed were also investigated. Film records revealed that stroke amplitude became greater with speed, although total stroke duration remained essentially constant. Sea lions increase stroke frequency with velocity but large variations in the measured values suggest that changes in amplitude and flipper angle of attack are also important parameters for modulating swimming speed.
Reproductive biology of the Tasmanian Bettong (Bettongia gaimardi: Macropodidae)
Authors: Rose R. W.
Published: May 2009

The reproductive biology of the Tasmanian Bettong (Bettongia gaimardi) conforms in many respects to that found in related kangaroos. Gestation and the oestrous cycle are of similar duration (21–22 days), and a postpartum oestrus may result in the formation of a blastocyst that remains quiescent (embryonic diapause) throughout most of pouch life. Oestrous cycles including a gestation are shorter (by 1·5 days) than those cycles without a pregnancy. This ‘maternal recognition of pregnancy’ is extended into pouch life as the furred young always vacates the pouch when a new young is born. Pouch life is relatively short (106 days) and, as the Bettong breeds throughout the year, several young may be reared/year. Both males and females become mature before one year.
The development of the trigeminal jaw adductor musculature and associated skull elements in the lizard Podarcis sicula
Authors: Rieppel Olivier
Published: May 2009

The ontogenetic development of the jaw adductor musculature in Podarcis sicula (Raftnesque) is described in detail and related to patterns of ossification in associated skull elements. It was found that the coronoid bone ossifies in continuity with the developing bodenaponeurosis, whereas the elements of the upper temporal arcade ossify prior to (and seemingly independently of) the realization of an attachment of the developing jaw adductors.

Various aspects of the development of the jaw adductors are discussed in the light of theoretical claims concerning conflicting models of ontogeny, as is the role of ontogenetic studies in the determination of character polarity. It is concluded that the present study supports the model of epigenetic development, and that ontogeny alone is insufficient for the assessment of character polarity. Instead, ontogeny must be interpreted in the context of phylogenetic hypotheses.
Surface changes in the naturally ankylosed teeth of the frog Rana pipiens during growth and maturation: an SEM study
Authors: Howes Robert I.
Published: May 2009

An SEM study of the surface morphology of the major stages of mature and developing teeth of the leopard frog was made using anorganic preparations of the teeth and jaws. After initial development, the crown area changed little during subsequent tooth eruption, ankylosis and maturation. The thin enamel covering extended further down the shaft than expected. After ankylosis, the surfaces of the tooth continued to mature. The unmineralized gap between the crown and the pedestal, which is prominent in most amphibians, gradually filled in as the ankylosed tooth aged. The upper portion of the pedestal initially formed a dentine surface which was globular in appearance due to partial calcification of the surface collagen fibres but became smooth with uniformly calcified fibres as the ankylosed tooth matured. The lower portion of the pedestal was more variable and there was a gradual transition of dentine into a more cellular, bone‐like tissue which contained lacunae and larger fibre bundles. This bone‐like tissue was very distinct in surface morphology from the bone of the adjacent jaw, and as the tooth matured it changed from a coarse, woven appearance to one more like lamellar bone. Resorption bays were present in both the dentine and bony areas of teeth which were being shed. During development, the pedestal, which attaches the tooth to the jaw, formed as a separate calcification site and did not form a complete ring until fusion of its buccal surface with that of the overlying crown. A bony buccal lip formed early as part of the pedestal.
The distribution and population biology of the triclad Phagocata vitta in a Welsh stream
Authors: Armitage M. J. , Young J. O.
Published: May 2009

The ecology of Phagocata vitta (Dugès) in a small mountain stream in North Wales was studied at monthly intervals over two years. The triclad occurred along the length of the stream but was abundant at only three of the 11 sampling sites. The ultimate factor influencing the abundance and distribution patterns was gradient and the proximate factor was the nature of the substratum; greatest numbers were found where the gradient was shallow and higher proportions of finer substrata and flora were present. The roles of other measured abiotic and biotic factors were not major. During the course of a year, low continual recruitment through sexual reproduction, and to a lesser extent through fissioning, took place, distinct cohorts could not be identified, the mean lengths of triclads stayed remarkably constant, and numbers fluctuated apparently erratically with no discernible seasonal pattern. Increases and decreases could not be attributed to changes in birth rates and death rates, respectively, and may have been due to irregular shifts in horizontal and vertical distribution. Factors controlling and regulating population size remain obscure.
How the grass carp (Ctenopharyngodon idella) chooses and chews its food—some clues
Authors: Vincent J. F. V. , Sibbing F. A.
Published: May 2009

Grass carp were allowed to feed on a variety of plants, presented one species at a time. They were filmed and their faeces collected. Canadian pondweed, a grass and a filamentous alga were readily taken; greater duckweed, shining pondweed and the leaves of reedmace were not so acceptable. Limiting factors in feeding seem to vary: with the two pondweeds foraging is limiting, probably because the leaves make it difficult for the fish to extract a single, manageable stem. Transport is limiting with the grass—the fish cannot swallow it quickly enough. Chewing is limiting with reedmace leaves (they are too tough) and the filamentous alga (for no apparent reason). Duckweed is rejected, probably because it has an unpleasant taste. All plants are chewed at the same frequency of jaw movement, independent of the texture of the plant.
Gonadogenesis and sex differentiation in the southern hemisphere lamprey Mordacia mordax
Authors: Hardisty M. W. , Potter I. C. , Koehn J. D.
Published: May 2009

Gonadal development and sex differentiation have been studied in larvae, metamorphosing individuals and young adults of the lamprey Mordacia mordax (Richardson), one of the two anadromous species of the southern hemisphere family Mordaciidae. The parasitic species is remarkable for the fact that its fecundity is so low that it is little greater than those of dwarf nonparasitic species. The relationship between the phasing of gonadal development, pattern of sex differentiation and fecundity in M. mordax is compared with those of nonparasitic and parasitic northern hemisphere lampreys (Petromyzontidae) and with that ofGeoiria australis, the sole representative of the other southern hemisphere family (Geotriidae). Up to lengths of 50 mm, the gonads have only small numbers of germ cells and are small and histologically undifferentiated. A marked increase in germ cell number occurs at body lengths of 50–70 mm, when in future ovaries, many secondary gonia enter meiotic prophase leading to cytoplasmic oocyte growth. Differentiation of the ovaries is generally completed at 90 mm, when they constitute just over half of all gonads. Throughout larval life and even during metamorphosis, the future male gonads remain small, histologically undifferentiated and indistinguishable from earlier undifferentiated stages. As in nonparasitic species, sex differentiation is characterized by the appearance in future male gonads of a high proportion of variable numbers of female orientated germ cells (in meiotic prophase or oocyte growth) destined to undergo atresia. In this respect, M. mordax is closer to the patterns seen in nonparasitic species, than to the more direct or determinate types of gonadal sex differentiation of the parasitic species with high fecundity, such as the southern hemisphere Geolria australis and similar holarctic species. It is suggested that variations in the nature and course of sex differentiation in lampreys may be dependent on initial sex differences in germ cell numbers and hence on the size and rate of growth of the gonad.
Shelter site use and secondary sex ratios in the woodlice Armadillidium vulgare and Porcellio scaber (Crustacea: Isopoda)
Authors: Dangerfield J. Mark , Hassall Mark
Published: May 2009

In grassland populations of the woodlice Armadillidium vulgare and Porcellio scaber (Latreille) the sex ratio in hand collections from beneath wooden offcuts and roofing tiles varied through the breeding season. The proportion of males was higher in these collections from surface refugia than in independent estimates of the population sex ratio taken from soil cores. Collections became female‐biased in June and July when most females were carrying broods, most notably in P. scaber. It is suggested that males use surface shelter between foraging events. A. vulgare males are particularly abundant under boards in May as they become active on the soil surface in order to locate mates. Females may find the higher and more equable temperatures in refugia attractive because they reduce brood development time but the cost of this advantage is the risk of failure to balance moisture requirements. These patterns of habitat use by the sexes have important implications for several population processes, the evolution of life‐history tactics and the development of mating systems in these species.
The use of cover and burrows by a population of rabbits (Mammalia: Oryctolagus cuniculus) in eastern Scotland
Authors: Kolb H. H.
Published: May 2009

Adult rabbits were trapped in the spring on an area of grass and broom in the east of Scotland. They were ear‐tagged and a sample of males and females were fitted with radio‐collars. These were followed for two months to see whether they used burrows or ground cover for shelter during the day. Rabbits found on the surface were disturbed to see whether they bolted to burrows or stayed on the surface. The population was then re trapped to measure the population density, which was estimated to be 12.6 adults/ha in March, allowing for an apparent trapping bias against older females. One hundred and twelve burrow entrances/ha were counted from random quadrats. Males were more likely to be found on the surface than females, and rabbits that were more often on the surface were less likely to bolt to burrows when disturbed. Even when rabbits did bolt to burrows they frequently left them shortly afterwards and returned to the cover of the broom. Males that were most often found on the surface were lighter in weight than those found in burrows. This was not the case for females.
Changes in the skull morphology of the Arctic wolf, Canis lupus arctos, during the twentieth century
Authors: Clutton‐Brock J. , Kitchener A. C. , Lynch J. M.
Published: May 2009

Measurements of a large series of skulls of the Arctic wolf, Canis lupus arctos. have shown that since 1930 there has been an overall reduction in the size of the skulls, together with widening of the cranium, shortening of the facial region, and reduction in size of the teeth. This suggests that hybridization and subsequent introgression occurred with huskies (Canis familiaris) during the 1930s, which is consistent with historical accounts. Since 1950 there has been a reversion in skull morphology to a more ‘wolf‐like’ form, suggesting that hybridization is no longer occurring.

The skull of a wolf/dog hybrid is intermediate in size between the skulls of wolves and huskies but its shape is allometrically dissimilar. Skulls of wolves from the period 1930–50 are moi‐e similar to the skull of this hybrid than in the other time periods.

The skull of a male canid from a carcass collected on Ellesmere Island and presented to the Natural History Museum. London, in 1986 was at first thought to be from a wolf/dog hybrid but analyses of the measurements show that it is more likely to be from an Arctic wolf with severe abnormalities to the jaws.
A possible acoustic function for the casque structure in hornbills (Aves: Bucerotidae)
Authors: Alexander G. D. , Houston D. C. , Campbell M.
Published: May 2009

Various theories suggest functions for the casques of hornbills, including feeding, fighting and sex and species recognition. This study tests whether these structures, most of which are predominantly hollow, could act as resonating chambers, amplifying or otherwise modifying the loud calls of these birds. Fibreglass replicas were made of the casque cavities of 15 hornbills of eight species, using museum skins and x‐rays as guides. Analyses of the resonance characteristics of the replicas were then compared with analyses of the calls of each of the eight species. Within each species the range of resonance frequencies was found to correspond closely to that of the fundamental frequencies of the calls but not with that of the dominant frequencies of the calls, except in one instance. There was, therefore, no evidence that the casque specifically amplifies the dominant notes in the call. We suggest that there may be an amplification effect operating through a feedback mechanism from the casque to the syrinx, along with reasons why some species possess hollow casques while others do not.
Locomotor patterns and costs as related to body size and form in teiid lizards
Authors: White T. D. , Anderson R. A.
Published: May 2009

Stride parameters and gaits were examined in seven species of teiid lizards in an attempt to understand size‐dependent variation of locomotor patterns. Scaling of body dimensions to body mass revealed that axial measures conformed to geometric similarity, whereas the limb segments exhibited an allometry which was statistically significantly less than geometric similarity. Variations in the relationships between stride lengths, stride frequencies and duty factors (% of the stride that foot contacts ground) represented locomotor specializations and were not strictly size‐dependent among species. At body length equivalent velocities, stride length and stride frequency scaled to body mass0.40±0.06 and 0.09±0.03, respectively. Cost during locomotion at body length equivalent velocities could be estimated by the square of the product of stride length and stride frequency. Plotting the cost during locomotion for geometrically similar lizards against body mass yielded an estimate of the cost during locomotion that was proportional to mass0.62±0.11. An estimate of the mass‐specific cost during locomotion at body length‐equivalent velocities scales to mass−0.38±0.11. Because the limbs of these lizards exhibit an allometry less than geometric similarity, a correction of the estimate of the mass‐specific cost during locomotion could be obtained by factoring in the effect of increased locomotor costs associated with relatively shorter pelvic limbs in larger lizards. The allometrically corrected estimate of the mass‐specific cost during locomotion was proportional to mass−0.31. This estimated regression, which is the relatiue cost of transport for a single, morphologically conservative family of lizards, predicts a slope quite close to that derived from studies of oxygen requirements during locomotion in lizards of several families (slope= ‐0.28, John‐Alder, Garland & Bennett, 1986) and in mammals (slope= ‐0.32, Taylor, Heglund & Maloiy, 1982).
Trochus kotschyi, the first Indian Ocean record of the genus Osilinus (Mollusca: Gastropoda: Trochidae)
Authors: Herbert D. G.
Published: May 2009

The species Trochus kotschyi Philippi, 1849, and Priotrochus obscurus (Wood, 1828) have been much confused in the past. Consistent differences between these taxa in respect of shell morphology, external anatomy and radular and opercular form are demonstrated. The distribution of T. kotschyi and the extent to which it and P. obscurus are sympatric are discussed. T. korschyi is referred to the genus Osilinus Philippi, 1847, a new combination and the first record of the genus from the Indo‐West Pacific. The species is thought to be a pre‐Miocene relict reflecting a mid‐Tethyan origin of the genus. A note on the type species designation ofOsilinus is provided.
Dispersion and site fidelity of breeding female grey seals (Halichoerus grypus) on North Rona, Scotland
Authors: Pomeroy P. P. , Anderson S. S. , Twiss S. D. , McConnell B. J.
Published: May 2009

Female grey seals (Halichoerus grypus) formed breeding aggregations on the island of North Rona, Scotland. Aggregations of females were associated particularly with gullies leading from the sea, leaving large areas of available space unoccupied. Changes in the degree of aggregation of females during the breeding season were similar in 1987, 1988 and 1989. Pronounced aggregations occurred in the early and late parts of each breeding season.

Of 67 breeding females marked in 1985, 62 (93%)) returned to N. Rona to breed in at least one season up to 1989, but 18 (27%) were present in all five years. Females came ashore up to 14 days before giving birth and 82% were observed first in the vicinity of their subsequent pupping site. Between 1985 and 1989, marked females which returned were faithful to their previous pupping sites, even when the previous pup had died. There was no evidence of a gradual change in the location of individual pupping sites over time. This pupping site fidelity may generate aggregations whose location, timing and composition is predictable.
The inheritance of patterns of metameric variation in the mouse (Mus musculus) vertebral column
Authors: Johnson D. R. , O'higgins P.
Published: May 2009

In this paper, we examine the patterns of metameric variation shown by different dimensions of vertebrae from the mouse vertebral column. We examine differences in metameric variation between variables within an inbred strain and compare patterns of metameric variation between inbred strains and between inbred strains and their F1 S. We make both visual and numerical comparisons, the latter being based upon a novel application of Fourier analysis. Comparisons between dimensions within a strain reveal two distinct patterns of metameric variation within the column. The first, shown only by the antero‐posterior (dorso‐ventral) diameter of the neural canal, is relatively simple: dimensions become progressively smaller caudally. The second is more complex, with two peaks, and appears more closely related to somatic structures. The second pattern may be modified according to the temporal pattern of development of different vertebral elements. Comparisons between mouse strains suggest that those variables which complete growth early, and which preserve the basic patterns of metameric variation in a relatively unmodified form, are best suited to discriminating between inbred strains. The Fl S between inbred strains show patterns of metameric variation which in some cases are more like those of one parental strain and in others more like those of the other parental strain. We consider the significance of these findings in relation to further studies of mammalian vertebral column genetics, development and evolution.
Ecomorphological relationships among Caribbean tetraodontiform fishes
Authors: Turingan Ralph G.
Published: May 2009

The anatomy of the oral jaw apparatus, lever‐arm mechanics and the diet of six species of Caribbean fishes in the order Tetraodontiformes were investigated to explore the relationships between trophic morphology and feeding habit in these fishes. Tetraodontiforms use their oral jaw apparatus to capture and reduce a broad range of prey types such as plankton, polychaete worms, holothuroids, sea urchins, crabs, molluscs, gorgonians and algae. The different feeding habits of tetraodontiforms are reflected by differences in the morphological and biomechanical features of their oral jaw apparatus that appear to enhance their abilities to feed on hard prey organisms. Species that bite and crush hard, benthic prey organisms had more massive bones and muscles, longer jaw‐opening in‐levers, and higher jaw‐closing lever ratios than the planktivorous, suction‐feeding species. Masses of the jaw and suspensorium bones and lower jaw adductor muscles as well as the jaw‐opening in‐levers and jaw‐closing lever ratios of crushers were greater than those of biters. In contrast, the mass of the adductor muscle of the upper jaw did not vary among species with different diets, indicating that this muscle may not be central to the factors that determine patterns of prey use in these fishes. The diversity of feeding behaviours and the wide range of feeding habits among fishes in the order Tetraodontiformes illustrate the versatility of the oral jaw apparatus as a single functional feeding system in fishes.
Hymenopteran wing kinematics: a qualitative study
Authors: Brackenbury J. H.
Published: May 2009

(With 9 plates and 2 figures in the text)

Wing deformations were studied in representatives of several hymenopteran families during free Right in hovering or near hovering conditions. The claval furrow, costal break, stigma and a variety of flexion lines occupying the wing apex are all involved in regulating forewing profile during the flight cycle in lchneumonidae and Tenthredinidae. In these families, as well as in the sphecid Sphex rujocincius, the median flexion line of the hindwing is also active in the terminal stages of supination. The plaiting fold of the vespid forewing plays an important role in profile control during the upstroke, reversing its polarity compared to rest. Little wing distortion was observed in the large scolids Scotia flavifrons and S. hirta, possibly attributable to the presence of strengthening ridges and grooves in the wing apex.
Body elongation and decreased reproductive output within a restricted clade of lizards (Reptilia: Scincidae)
Authors: Griffith Hugh
Published: May 2009

Relationships between body shape and relative abdominal size were compared among differentially elongate species within the scincid lizard genus Brachymeles, to investigate how morphological evolution affects the proportion of body volume available to hold eggs and offspring. Relative abdominal size is inversely related to elongation, suggesting that relative clutch mass decreases with addition of abdominal body segments. Shape‐volume relationships contradict trends seen in comparisons among distantly related limbed and limbless squamates (lizards and snakes), in which snakes have relatively more abdominal volume. Comparison within a phylogenetically restricted group allows the identification of functional and ontogenetic factors potentially limiting reproductive output. In Bruchymeles, constraining factors include retention of anterior body segments bearing parasternal ribs, which prevents extension of the clutch anteriorly within the body, and reduction of allometry of abdominal segments, which provides extended series of uniformly‐sized vertebrae for limbless locomotion, but reduces the relative size of the abdomen. The latter trait is associated with overall size reduction, which affects relative egg‐size and packing. Factors constraining abdominal volume in this genus are probably common to other elongate lizards, a morphological group that has been rarely represented in comparative studies of life history.
Aberrant anogenital distance in XXSxv (‘sex‐reversed’) pseudomale mice
Authors: Atkinson T. G. , Blecher S. R.
Published: May 2009

Anogenital distance (AGD). a sex differentiation marker in mice (Mus musculus), is thought to be a secondary sexual trait exclusively regulated by androgens during development. However, recent studies suggest that some so‐called secondary sexual traits may be influenced by sex‐chromosomal genotype. To explore this question further we studied the AGD of the XXSxr 'sex‐reversed’mouse, which has adequate androgens for masculinization.

The AGDs of adult and prepubertal XY, XYSxr carrier, XXSxr 'sex‐reversed’and XX mice were measured. We found that adult XXSxr 'sex‐reversed’mice (which we refer to as pseudomales) and XYSxr carriers have shorter mean AGDs than their XY siblings. Prepubertal XXSxr animals also have shorter mean AGDs than their XY siblings when AGD is expressed as a proportion of body length. XX adult and prepubertal mice have significantly shorter AGDs than the other genotypes at similar stages of development. The differences in AGD between adult and prepubertal XY and XXSxr sibs, and adult XY and XYSxr sibs, reported here, do not appear to be due to androgen levels, since adult testicular and serum testosterone levels are higher in pseudomales and carriers than in XY mice, and fetal pseudomale androgen levels also appear to be at least as high as those of normal males. Furthermore, the AGD differences between genotypes are not correlated to differences in testis size. We conclude that the differences are likely to be due to a tissue specific effect of the genetic constitution of the individuals, as is the case with scrotal development in the marsupial Macropus eugenii (the tammar wallaby).
Urea production and accumulation in the green toad, Bufo viridis
Authors: Hoffman Joy , Katz Uri
Published: May 2009

The toad, Bufo viridis, can live for several months without access to free water, absorbing soil‐bound water down a water‐potential gradient created, mainly, by accumulating urea in its body fluids. We investigated if the retention of urine was sufficient to account for the rate of accumulation or if an increased rate of urea production was needed in order to do so. The basal rate of urea production in unfed animals in the absence of osmotic stress was estimated by two methods; first, analysis of the bathing medium and, secondly, collection and analysis of urine at two‐hourly intervals. This was then repeated with animals fed a weight‐maintaining diet. Generally similar results were obtained by either method in both fed and unfed animals, although higher urea production rates were found in the former. Although it had been planned to apply the short interval method to toads with free access to water, the control condition for toads transferred to soil, it proved to be impracticable. Some animals did not bathe for almost a day, during which time minute quantities of urine were obtained. Larger volumes were only produced during or after bathing. Consequently, animals which were partially immersed in water were substituted as controls. Total urea content was determined in these and in toads after a week on soil. The calculated increase was compared to that which could be expected from urine retention. It was found that urea accumulated at more than twice the predicted rate. When rates of accumulation were calculated over longer periods, urine retention alone was sufficient to account for them within three weeks on soil, the usual period required for acclimation. We concluded that B. viridis increased its rate of urea production only for a short period, until a favourable water potential gradient was achieved.
Seasonal variation in the activity patterns of the Orkney vole Microtus arvalis orcadensis
Authors: Reynolds P. , Gorman M. L.
Published: May 2009

In captivity, Orkney voles Microtus uruulis orcudensis show an activity pattern that consists of regularly alternating periods of rest and activity with a periodicity of about 2.8 hours. Captive voles kept under ambient conditions are equally active day and night at all times of the year. Free‐living voles also show a regular short‐term rhythm of activity but in addition the partition of activity between day and night varies seasonally. At two sites on Orkney Mainland cyclic variation in diurnality with a period of 12 months were recorded. Although surface activity occurred during both the day and night throughout the year, day activity predominated, particularly during the winter months. The cycle appeared to be synchronous at the two study sites.

Seasonal variation in diurnality appeared to be associated with population density and due largely to the proportion of juveniles in the population. Given the 12‐month cycle of diurnality found in the Orkney vole, phase relationships with photoperiod are likely to be consistent between years. This may explain why populations of this subspecies do not appear to undergo multi‐annual population cycles.

Despite intense levels of predation by raptors, including the short‐eared owl which switches between nocturnal and diurnal hunting, Orkney voles exhibit a relatively simple and highly predictable cycle of diurnality. This cycle is unlikely therefore to have evolved as a means of preventing predator specialization with respect to time of day, season or year.
Reproductive suppression in eusocial Cryptomys darnavensis colonies: socially‐induced infertility in females
Authors: Bennett N. C. , Jarvis J. U. M. , Millar R. P. , Sasano H. , Ntshinga K. V.
Published: May 2009

Inhibition of reproduction occurs in colonies of the Damaraland mole‐rat (Cryptomys damarensis), where one female and usually one male are reproductively active. They remain the sole reproductive animals thoughout their stay in the colony, which in the field may exceed five years.

An 18‐month study on a captive colony of C. damarensis shows that non‐reproductive females remain anovulatory and always have concentrations of urinary progesterone lower than that of the reproductive female 10.7 8.8 nmols/mmol creatinine (n = 85), although their progesterone concentrations are slightly elevated when the reproductive female is early in pregnancy. In contrast the reproductively active female has elevated concentrations of progesterone 63.3 70.1 nmols/mmol creatinine (n= 14).

Standard histological together with immunohistochemical examination of the ovarian structure shows that follicular development in the non‐reproductive females is halted at varying stages prior to ovulation and that the unruptured follicles luteinize. These unruptured luteinized follicles stain positive for 3β hydroxysteroid dehydrogenase—the enzyme catalysing the synthesis of progesterone from pregnenolone. It is possible that the low levels of circulating progesterone produced by the luteinized follicles in the non‐reproductive females in the colony are sufficient to feedback on the hypothalamo‐pituitary axis and prevent the surge of LH necessary for ovulation.

Behavioural studies provide corroborative evidence for sexual suppression. Thus the non‐reproductive females in the colony are never involved in courtship or copulatory behaviour. nor do they actively solicit males in the colony. The reproductive female, however, plays an active role in mate selection and is the initiator in courtship behaviour.

The suppression of ovulation in non‐reproductivc females is maintained for as long as there is a reproductive female in the colony.
Diet and condition of wild boar, Sus scrofu scrofu, without supplementary feeding
Authors: Groot Bruinderink G. W. T. A. , Hazebroek E. , Van Der Voot H.
Published: May 2009

From 1987 to 1992 diet and condition of two populations of wild boar which received no supplementary feeding were studied in the Veluwe area, a large area of heathlands and forests in The Netherlands, and were compared with those obtained in a previous study (1974–1976), when supplementary food was provided. Composition of stomach contents depended mainly on season, mast availability, and area‐specific factors, whereas sex and age were of little or no importance. Density dependence was found for the decrease in mast (tree seed) consumption from autumn to winter. In autumn, and in winters of rich mast years, mast was the main constituent of the diet. In winters of poor mast years this was replaced by broadleaved grasses in one area and by broadleaved grasses, wavy hairgrass, and roots in the other. We found no important differences between the stomach contents of animals receiving no supplementation, and the natural fraction during a period of supplementary feeding. Variation in body weight was related mainly to age and sex, but also to mast availability. Judged by relative loss of body weight and decrease of bone marrow fat, juveniles seemed to suffer more from poor mast availability than adults. The decrease in body weight from autumn to winter was greater when population density was high. In poor mast years, recruitment into the population receiving no supplementation depended on the availability of broadleaved grasses; in rich years, recruitment was still lower than in populations receiving supplementary feeding. In populations receiving supplementary feeding, recruitment seemed independent of mast availability.
Determination of age in Cantabrian chamois (Rupicapva pyvenaica pavva) from jaw tooth‐row eruption and wear
Authors: Pearez‐Barberiaa F. J.
Published: May 2009

A tooth eruption and wear pattern useful to determine ten age classes when the horns are not available for this purpose, is described for Cantabrian chamois (Rupicapra pyrenaica parva) inhabiting the Cantabrian Mountains (north of Spain). In animals under eight years old, age is not significantly over‐ or under‐estimated when using the method, however, the age of animals older than eight years is significantly under‐estimated.
Allometric relations in three species of finches (Aves: Fringillidae)
Authors: Bjourklund Mats
Published: May 2009

Static nestling, adult and ontogenetic allometry were analysed in three species of finches. Static nestling allometry was very similar across age in early ontogeny and among species and could be approximated by a single matrix of phenotypic variances and covariances. The first eigenvector of this matrix showed negative allometry of bill and tarsus to mass, but positive for wing length to mass. Adult static allometry was also very similar among species, but differed from nestling pattern. In adults the bill had a positive allometry in relation to tarsus and wing, but negative to mass, while tarsus and wing were unrelated to mass. The ontogenetic allometry in each species was very similar to nestling static allometry. Viewed in relation to final size, bill characters grew more slowly than body characters, but for a longer time, which created the difference between adult and nestling allometric patterns. There were differences among species both with regard to elevation and slope of allometric coefficients, suggesting that the differences among species came about by changes in the three fundamental ontogenetic parameters namely growth rate, onset of growth and offset of growth.
Dispersion and site fidelity of breeding male grey seals (Halichoevus grypus) on North Rona, Scotland
Authors: Twiss S. D. , Pomeroy P. P. , Anderson S. S.
Published: May 2009

The daily locations of socially active male grey seals were recorded during three successive breeding seasons on North Rona (Outer Hebrides, Scotland). Areas of occupancy were defined for 38 individually identified males. Socially active males showed a high degree of site fidelity, determined from the overlap of areas and distance moved by individuals between seasons. The degree of site fidelity displayed by individuals was not related to measures of individual mating success, dominance, date of arrival to the colony, length of stay at the colony or changes in these values between seasons. As both male and female grey seals display site fidelity on N. Rona, individual recognition of potential opponents and mates is possible. There is also potential for the production of full sibling offspring in successive seasons.
Interrelationships of crural muscles and tendons in a range of birds
Authors: Bennett M. B.
Published: May 2009

The crural musculature in 19 species of birds was examined. New data on the mechanical properties of avian tendons showed a mean linear elastic modulus of about 1.3 GPa and failure stress of 74MPa. Physiological cross‐sectional areas were calculated for 12 muscles in each species, together with the cross‐sectional areas of their attached tendons. Investigation into potential various sources of error demonstrate this is a robust method for studying muscle‐tendon units. The mode for calculated peak tendon stresses was 17.5 MPa. The results were compared to those obtained from mammal limbs by Ker, Alexander & Bennett (1988). It appears that the muscle‐tendon units in birds are not as strongly optimized for the minimization of mass as those in the limbs of mammals. This may reflect a compromise between optimization for minimum mass and other functional requirements.
Use of salmonid carcasses by vertebrate scavengers
Authors: Hewson R.
Published: May 2009

The use of salmonSalmo salarcarrion by ottersLutra lutraand other scavengers along the River Dee in north‐east Scotland was studied by radio‐tagging and individual marking of fish carcasses. More carcasses were available on the Dee than on tributary streams used for spawning, indicating that salmon returned to the river after spawning and died there. The amount of salmon carrion available to terrestrial and avian scavengers along the Dee varied from 6.7 kg. km‐1on an upstream study area to 36 kg. km‐1downstream. Fish carcasses in the Dee were moved by spates up to 20 km but in streams used for spawning less than 1 km. Of 86 carcasses examined in 1990/91, 64 were available to terrestrial and avian scavengers on the bank or awash and of these 45 had been fed upon by otters and 16 by birds. In 1991/92, 23 of 30 carcasses were available to terrestrial and avian scavengers. All had been fed upon, 19 by otters, four by birds. Other carcasses, in shallow water, were not available to terrestrial and avian scavengers. Subsequent scavenging was mainly by otters and continued for up to three weeks after the carcasses were found. HeronArdea cinerea, great black‐backed gullLarus marinusand crowCorvus coronealso scavenged salmon carcasses along the Dee. Great black‐backed gulls were the most frequent scavengers, but heron (dominant to black‐backed gull) was a major scavenger in 1990/91. Crows, subordinate to other scavengers, waited, often in pairs, upon dominant scavengers. There were more scavenging birds downstream and numbers did not change between years. Of 20 salmon carcasses placed in spawning areas eight were probably, two possibly, removed by otters. Otters continued to scavenge carcasses for up to a month. Scavenging by foxesVulpes vulpesand birds followed the removal of fish carcasses from the water by otters. Radio transmitters were removed by otters and left lying alongside carcasses.
The diet of the wood mouse Apodemus sylvaticus on set‐aside land
Authors: Rogers L. M. , Gorman M. L.
Published: May 2009

The diet of wood mice on set‐aside consisted of 87% plant material, 65% of which was green leaf materials. This diet contains very much less seed or animal material than does that of wood mice studied in other habitats. The poor diet reflected what was available in the area.
Effects of site of tactile stimulation on the escape swimming responses of hatchling Xenopus laevis embryos
Authors: Boothby K. M. , Roberts A.
Published: May 2009

Hatchling Xenopus laevis embryos usually swim when the skin is touched with a fine hair. Less common are small, local V‐flexions and more general C‐flexions. Simple flexions or the initial flexion at the start of swimming occur predominantly on the opposite side to the stimulus to direct the animal away from the stimulus. Strokes to the midline lead to random sidedness of responses.

The reliability of the sidedness of flexions and the first flexions of swimming decreases the more rostrally the stimuli are given. The range of directions of swimming paths are larger with more rostral stimuli so responses to head stimuli are unpredictable in direction.

In animals immobilized in α‐bungarotoxin, strokes to the skin produce electrically recorded motor output which corresponds to: V‐flexions, C‐flexions and swimming. Fictive activity generally starts on the side opposite to the stimulus. The fictive responses suggest that the three basic behaviour patterns observed can be generated entirely within the central nervous system without any sensory feedback.

We discuss possible mechanisms for the generation of ‘protean’ responses to head stimulation which are unpredictable in direction.
Morphometric variation in the Nearctic collared lemming (Dicrostonyx)
Authors: Eger Judith L.
Published: May 2009

A. H. Macpherson suggested that much of the current geographic diversity in Canadian Arctic mammals resulted from isolation in refugia during the Wisconsin glacial stage. This study evaluates the refugium hypothesis, insofar as it applies to Nearctic Dicrostonyx, by means of a statistical analysis of geographic variation in 13 skull characters. Overall, geographic variation among samples is not significant, although D. hudsonius and D. unalascensis are geographically and morphologically distinct. Some variation in skull shape is correlated with winter temperature. Partitioning tests on other measures of shape variation indicate some discontinuities consistent with the refugial hypothesis. Discrete samples reflect possible refugial populations in northern North America, Eastern Beringia and two southern periglacial refugia, one in eastern North America and at least one in western North America.
Energetic constraints and steroid hormone correlates of male calling behaviour in the túngara frog
Authors: Marler C. A. , Ryan M. J.
Published: May 2009

We investigated physiological constraints on calling behaviour in the túgara frog, Physalaemus pustulosus. First, we examined the hypothesis that energetic factors limit calling. Time spent in chorus activity is the best predictor of male mating success (Ryan, 1985). Manipulation of food availability demonstrated that males given supplemental food were more likely to call than males without supplemental food. Males without supplemental food were less likely to call even though their lipid reserves were only slightly less than males given the supplemental food, suggesting that part of the increased energy obtained from the supplemental food may have been channelled into calling to attract females. Secondly, we examined the role of steroid hormones in switching between reproductive and non‐reproductive behaviours. Calling males had higher levels of plasma testosterone than silent males. Experimental elevation of corticosterone decreased testosterone levels and the likelihood of calling, thus linking both of these steroid hormones to calling behaviour. Males who responded to supplemental food by increasing calling had higher levels of testosterone than those without supplemental food, but there was no difference in plasma corticosterone levels. Overall, the results suggest that energetic factors affect calling behaviour and that one potential mechanism for this affect is through plasma testosterone levels. Corticosterone can decrease calling behaviour, however, corticosterone does not appear to mediate the effect of energetic factors on calling behaviour. These data are consistent with the hypothesis that energetic factors ultimately constrain sexual selection for calling behaviour.
Diet of arctic foxes (Alopex lagopus) in Iceland
Authors: Hersteinsson P. , Macdonald D. W.
Published: May 2009

Arctic foxes, Alopex lagopus, live in low productivity arctic and northern tundra habitats, where they generally prey heavily on lemmings. In Iceland, however, no lemmings are present, and the foxes have a very varied diet, including plants such as seaweed and black crowberries, a wide range of birds and invertebrates, and carcasses of large mammals such as seals, reindeer, and sheep. Marked seasonal, geographical and inter‐annual differences confirm arctic foxes in Iceland as opportunistic feeders. There are coastal and inland foxes: coastal foxes feed mainly on prey derived directly or indirectly from the ocean, particularly various seabirds and seals, while inland foxes feed largely on migrant birds, such as geese, waders and passerines in summer, and ptarmigan in winter. Despite their reputation for killing lambs, in this study, lamb carcasses were found at only 19.4% of 1125 fox dens, 44% of which had only one carcass. The distance to the nearest farm and the physical condition of lambs were major determinants of the number of carcasses found at a den. We discuss the implications of arctic foxes' diet for population dynamics and group formation, and for management practices.
Population differences in behaviour and morphology in the snailLittorina saxatilis:phenotypic plasticity or genetic differentiation?
Authors: Johannesson B. , J.ohannesson K.
Published: May 2009

The ovoviviparousLittorina saxatilis(Olivi) can be found in many intertidal habitats. Winkles from different habitats have different morphologies and behaviours, which are usually argued to reflect adaptations. Whether the different forms are caused by genetic differentiation or due to phenotypic plasticity is, however, less discussed. Our aim was to document morphological and behavioural differences among one exposed rock poulation, one sheltered boulder population, and one mud flat population, and we reared offspring in a common laboratory environment to see if the differences persisted.

We used principal component analysis (PCA), based on 19 measurements, to compare size and shape differences. We also used PCA and linear regression to study allometry and compare growth trajectories. Behavioural differences were studied in three laboratory trials.

Littorina saxatillisfrom the rock were relatively small, had small aperture lips, thin shells, blunt spires, and wide columellae. They preferred to stay in cracks and to be above the water surface, and they quickly emerged out of their shells after disturbance.L. saxatillisfrom the boulder shore were relatively large, had large lips, thick shells, pointed spires, and narrow columellae. They preferred open surfaces, submergence, and after disturbance they slowly emerged out of the shell.L. Saxatilisfrom the mud flat were relatively small, had small lips, think shells, pointed spires, and narrow columellae and most behaved similarly to the boulder shore snails. Although less pronounced, most of these morphological and behavioural differences persisted in the snails that we reared in the common environment. This indicates some genetic differentiation. All groups grew allometrically, and most groups differed in growth trajectories, Despite similar ages, the reared females were generally larger than the reared males, indicating higher growth rate in females. Sexual maturation seemed to be reached at a certain size rather than at a certain age. Theories predict genetic diferentiation in intertidal snail species with low dispersal, but some investigations show results that contradict the theories, while others agree with them. Our study confirms the prediction thatL. saxatilisshould be genetically differentiated.