摘要:

Skulls of red deer (Cervus elaphusof known age were examined. A scoring procedure devised for fallow deer (Dama dama) was used to relate tooth wear to a particular age (Brown&Chapman, 1990). The precise sequential nature of tooth wear as it appeared on the slopes and tips of cusps, on the marginal ridges and links between cusps was recorded. From these data a base has been provided from which estimates of age may be made of animals of unknown age. The variability for the scores are given for 95% prediction intervals from the regression of age on total molar wear score.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03783.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The breeding behaviour of male grey sealsHalichoerus grypusof known age and weight was studied on Sable Island, Nova Scotia. Branded males ranged in age from 8 to 16 years and although there was a positive relationship between age and weight, there was a large overlap between age classes. In general, there was an increase in length of tenure and rates of copulation with increasing male age but this was less marked among males between the ages of 13 and 16 years. Compared to older ones, males of 8 and 12 years were observed at more sites, travelled more extensively around the breeding colony, were transient more frequently and were unable to lie as close to females. There was no correlation between male body weight and either length of tenure or rates of copulation when males of age 8 (the smallest males) were excluded from the analysis. Most agonistic behaviour was made by larger, older males towards smaller, younger ones and appeared to be responsible for the short length of tenure and low reproductive rates of young bulls.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03784.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Cryptomys damarensisis one of the few subterranean rodents which is social. This species is found in the semi‐arid regions of southwestern and central Africa. The Damaraland mole‐rat occurs in coloniesof up to 25 individuals, in which reproduction is limited to one or two of the largest males and the largest female in the colony.The mean colony size is 18 mole‐rats (n=6 colonies). The mean colony biomass is 2.32 kg and the sex ratio is female biased (0.71–0.78). The number of mole‐rats in each colony, the mean body mass and the sex ratio are described for six field‐captured colonies, three of which were captured in their entirety.The dominance hierarchy of two colonies ofC. damarensiswas found to be linear with a value of between 0.94 and 1.00 calculated from Landau's linearity index. Dominance was found to be related to gender, with the males more dominant than females. The reproductive individuals are the dominant animals within each respective gender. The non‐reproductive females rank lowest in

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03785.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The hind limb kinematics of American alligators (Alligator mississippiensis) executing the high walk were analysed using cineradiography. The stance phase is characterized by hip extension of 60–80d̀, knee extension of 30–40d̀ and a flexion (30–40d̀)—extension (80–90d̀) sequence of the ankle. At initial foot contact with the substratum, the femur is positioned 20–25d̀ from the sagittal plane of the sacrum. During retraction the femur is abducted to a maximum angle of 40–50d̀ near foot lift‐off. A slight medial rotation about the femoral axis takes place to maintain the orientation of the femoral condyles. The sacral region undergoes rotation about a vertical axis of 20–30d̀ and transverse roll of 10–12d̀ with each stride. One individual used an atypical limb posture in which the femur was adducted to 20d̀ rather than abducted during the stance phase.Although the crocodilian high walk appears to be a good example of a ‘semi‐erect’ posture that is intermediate between ‘sprawling’ and ‘fully erect’, the current system of postural grades hampers our understanding of locomotor variability and diversity. Grades must be considered categorical abstractions until enough data can be acquired to demonstrate that postural divisions are based on well‐defined kinematic parameters and functional mechanisms. The indiscriminate use of postural grades, particularly in fossil taxa, blurs differences between members of each grade and artificially broadens dist

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03786.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Hair follicle activity and fibre growth were studied using histological sections from the skin of five adult feral does sampled every four weeks for 18 months. The main period of guard hair growth in primary follicles was from November to April. Secondary follicles grew fine, long, nonmedullated fibres (cashmere) from December to June. Shedding of these fibres from secondary follicles had commenced by July and cashmere was absent from the fleece by November. From September to December a subsidiary hair cycle occurred in many secondary follicles which produced minute (vellus) fibres, less than 2.4 mm in length. Some secondary follicles probably shed their cashmere fibres and remain quiescent over spring. Annual pelage changes were therefore achieved with one main growth period, although many secondary follicles underwent another brief hair cycle in spring.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03787.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Orkney volesMicrotus arvalisshow avoidance of red foxVulpes vulpesfaecal odours, both in the laboratory and in the wild. Since these voles have been isolated from foxes since Neolithic times it is likely that these responses are innate rather than learned.When applied to young Scots pine saplings, the fox odour inhibited feeding by voles when alternative foods were available.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03788.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Idotea wosnesenskiiBrandt, a valviferan isopod, has five pairs of pleopods within a branchial chamber enclosed by modified uropods (operculae). The pumping mechanism of resting isopods was videotaped to observe ventilation, and particularly to determine whether or not the swimming pleopods (first three pairs) and the gas exchange pleopods (last two pairs) have ventilatory roles. Observations on intact animals (to observe water flow into and out of the branchial chamber) and on animals with operculae propped open or with parts of their abdominal wall removed (to study the actual pumping movements of the pleopods) revealed that all five pairs of pleopods function in ventilation. The ventilatory stroke has two phases: an opening phase in which the pleopods move medially and ventrally, opening spaces between pleopods (analogous to the swimming recovery stroke), and a closing phase, wherein the pleopods move laterally and dorsally, reducing the gaps between succeeding pleopods (analogous to the swimming power stroke). Ventilatory strokes may be continuous or they may be separated by resting phases. Both the frequency and amplitude are variable: the frequency changes greatly due to the wide variation in resting phase duration. By opening the operculae the amplitude can increase so that ventilatory strokes grade into swimming strokes. The ventilatory stroke pattern at rest is generally similar to the swimming stroke pattern but differs in its slower and nearly simultaneous dorsoventral movements and its lower frequencies. Dye and particle movements around intact animals and those with exposed pleopods show that water typically takes about three strokes to pass through the branchial chamber.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03789.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The regional variation in the pupping season of the harbour seal (Phoca vitulina) was reviewed using the birth periods reported for 65 colony sites distributed over a range from 30.4d̀ to 78.5d̀ North latitude. The birth timing ofP. v. vitulinawas not related to latitude, but birthing inP. v. concoloralong eastern North America exhibited a latitudinal cline. The timing of birth inP. v. richardsivaried in three distinct patterns: (1) a significant unidirectional latitudinal cline extending between Baja California and the west coast of Washington; (2) a cluster comprised of Puget Sound, Washington and Vancouver Island, British Columbia colonies in which birthing occurred an average of 65 days later than on the Washington coast; and (3) a cluster from northern British Columbia and Alaska which did not demonstrate a latitudinal cline. Insufficient data were available for the analysis ofP. v. mellonaeorP. v. stejnegeri.We found great regional variation in the timing of birth among all colonies, with mean birth dates occurring as early as 15 March and as late as 3 September. Little variation existed north of 50d̀. To the south of 50d̀, however, most of the variation could be attributed to correlation with latitude or to affiliation with the Puget Sound, Washington‐Vancouver Island, British Columbia geographic area.Clinal variation in pupping could result from: (1) geographic variations in a selective factor with perhaps gene exchange between contiguous populations playing a role in smoothing the variation; or (2) for populations between Mexico and the west coast of Washington, regional variation in a non‐selective environmental variable, such as phot

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03790.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Patterns of seismic communication and somatosensory responses were studied in four chromosomal species (2n= 52, 54, 58, 60) of blind subterranean mole‐rats, belonging to theSpalax ehrenbergisuperspecies in Israel. The patterns involved head thumping signals and surface‐recorded cerebral potentials evoked by vibrational signals. The patterns correspond to the differences in territory size and population density which characterize the four species. It is suggested that this correspondence is related to the adaptive significance of the seismic communicat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03791.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Reproduction in a population of European wild rabbits occupying parkland habitat in East Anglia showed an annual seasonality in terms of numbers of emergent young, male testes size and an index of female oestrous status. Weather conditions showed marked variation over the four‐year study period with significantly higher minimum ground temperatures and hours of daily sunshine, and less snowfall recorded during the second two years. Parailel shifts in reproductive seasonality were found with male testes size peaking in January and February as opposed to May and April, first female oestrus recorded one month earlier (January compared to February), and young emerging over an average of 5.5 instead of 4.5 months each year and their first appearance above ground advanced by two months from April to February. Mean annual productivity increased from 7.2 and 6.1 emergent young per female, to 10.1 and 9.1 over the four years, while the number of adults present in the population at the start of the breeding season increased from 22 to 45, with females always outnumbering males. The usefulness is demonstrated of a noninvasive index of vulva appearance, and morphometric measures of testes to determine female oestrous status and estimates of male testicular weight in wild populations.The reported changes in reproduction are probably mediated through the influence of climatic variables on the quality or quantity of food available to the rabbits. These data demonstrate the possible effects of predicted global warming on productivity in the rabbit and highlight the major influence of climate on reproductive seasonality in this important pest specie

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03792.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY