摘要:

The locomotor behaviour of some large extinct carnivores, including several species of Plio‐Pleistocene sabre‐tooth cats, is here reconstructed, based on a comparison of the cross‐sectional geometric properties and linear dimensions of their femora and humeri with those of large modern carnivores. The long bones are modelled as simple beams, thereby allowing the use of basic beam theory in assessing relevant functional parameters such as second moments of area of the diaphyses when subjected to compressive and bending stresses. Three Pleistocene carnivores,Smilodon fatalis, Homotherium serum, andPanthera atroxseem to have had ecological and functional equivalents among the late Miocene‐Early Pliocene genera,Barbourofelis, Machairodus, andNimravides, respectively.BarbourofelisandSmilodonwere ‘cat‐like’in dental morphology but some structural characteristics of their limb bones had ‘bear‐like’affinities.MachairodusandHomotheriumwere cursorial, whereasNimravidesandP. atroxdisplay the limb morphology of true ambush predators. Various aspects of the postcranial skeleton of some of these extinct carnivores suggest that they may have employed locomotory gaits that

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05402.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Although the quality of foods may change through the seasons, few studies have assessed shifts in food preferences. I studied winter food selection of the Azores bullfinch to evaluate whether physical characteristics (size and accessibility), or phenolic content of food items better explained changes of winter diet. The birds preferred larger items of all winter foods: seeds, sori and flower buds and more accessible seeds. In autumn, seeds seemed preferred to sori, but in spring birds switched from seeds to sori and flower buds, once the latter became larger. Phenols may influence food preference but they did not explain diet shifts or preferences for individual trees. Food selection is a complex mechanism, depending on the alternatives available and seasonal shifts in food preference may continually change the availability of ‘good quality food

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05403.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The musculoskeletal components of the hindlimbs of 20 species of birds, considered non‐runners, were examined. Allometry was used to compare these data with previously published information on the limbs of running birds. In non‐runners the digital flexor muscle and tendon areas scaled approximately isometrically, in contrast to running birds where tendon areas had a lower exponent. Non‐running birds had muscle fibre areas approximately half that of runners of equal mass. In both groups, the muscle:tendon area ratio form. gastrocnemiusincreased as M0.13, suggesting factors other than elastic energy storage are important. Runners exhibited relatively longer tibiotarsi and tarsometatarsi and shorter toes. With very few exceptions, the linear dimensions of bones, tendon cross‐sectional areas, and muscle masses and fibre areas in the legs of the non‐running birds scaled closely according to the requirements for geometric similarity, but the confidence limits are often wide. Deviations from geometric similarity in birds reflect differences in locomotor behaviours and

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05404.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The agonistic behaviour of juvenile pairs of intermoult freshwater crayfishCherax cuspidatus, interacting over space in experimental containers, was examined. The study investigated the effects of differences in Resource Holding Potential (RHP) on social rank, patterns of interaction initiation, and the importance of fighting during encounters between pairs of crayfish. Crayfish were paired with unfamiliar opponents at size classes of 1 : 1, 1 : 0.9, 1 : 0.8, I : 0.7 and 1 : 0.6 using standard carapace length as the RHP index.Larger animals were dominant during significantly more than 50% of replicates at all size classes. Larger animals were dominant at all size ratios lower than 1 : 0.89. Seven smaller animals were dominant at size ratios between 1 : 0.89 and 1 : 0.99. The dominance of smaller animals could not be explained on the basis of morphological measures or age. The influence of prior experience as dominants or subordinates on the behaviour of contestants during these encounters appeared the most likely explanation.Carapace length, body length, and weight were equally reliable RHP indices. Age, number of injuries, and sex were not reliable RHP indices.The probability of initiating the first agonistic bout was independent of relative size for three of the five size classes. Larger initiators of the first bout invariably were successful, while smaller initiators rarely won. The winner of the first bout was the overall dominant during significantly more than 50% of replicates at each size class. The dominant individuals initiated the majority of bouts at all size classes, including the seven replicates where the smaller crayfish was dominant.Fighting (fight time, fight frequency, average bout length), a high intensity behaviour, was an important component of contests at the 1 : 1, 1 : 0.9, and 1 : 0.8 size classes. The significance of fighting was greatly reduced at the 1 :0.7 and 1 : 0.6 classes, indicating that fighting was correlated with the relative size of opponents.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05405.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Growth curves are described for males, pregnant females, and non‐pregnant females using morphometric measurements collected from over 18000 northern fur seals (Callorhinus ursinus) shot at sea between California and the Bering Sea from 1958 to 1974. Seals of all ages experience seasonal increases and decreases in body mass and length. Seasonal fluctuations of body length may be an artefact of mass displacement caused by seasonal changes in mass. Rapid growth and gain in mass occur during a brief one to three month period as the population migrates northward through the coastal waters of northern British Columbia and Alaska on their way to the Pribilof Islands. Body mass of females and immature males is gradually lost while fasting on land and wintering along the coasts of Washington, Oregon, and California. Pregnant females are both heavier and longer than non‐pregnant females of the same age. Body mass in pregnant females levels off with age in contrast with the increasing mass of non‐pregnant females. Growth of northern fur seals does not appear to stop at an upper asymptote, but continues throughout their life

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05406.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Milk consumption was measured in pouch young of the northern brown bandicoot,Isoodon macrourus, using the22Na turnover technique. Milk consumption rates increased from about 2.3 ml young−1d−1at 23 days post‐partum to about 17.2ml young−1d−1at 52 days, just prior to weaning. Young increased in mass from 8.5 g to around 112 g over the same period. Masś gained for each ml of milk consumed ranged from 0.28 to 0.65 gml−1. The efficiency with which young converted milk energy and protein into body energy and protein ranged from 16.1 to 39.6% and 38.4 to 82.3%,

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05407.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Occlusal variants of a total of 6252 teeth of 246 specimens of cape hares and 42 specimens of savanna hares were studied. Most hares were collected in the Great Rift Valley (Kenya) during 1967‐1968. Some savanna hares were obtained from the Queen Elizabeth National Park (now Ruenzori NP, Uganda) in the same period. In total, 61 variants concerning enamel folds, plication, and lakes were described. Only three teeth (I2, M3, I1) proved invariant in both species. In each species, three regional units (sampling locations) were specified. Quantitative analyses of nonmetric (epigenetic) variability and geographic divergence between the regional units and between the two species were based on 31 dichotomized (0/1 scores) characters. They were created from the commonly encountered variants. A high degree of bilateral symmetry was revealed in most characters, but characters varied independently from one another. This indicated a lack of complex morphotypes in the occlusal patterns. The frequencies of all character states were calculated for all regional units and the combined species samples. No categorical differences were found in occlusal characters between the two species. The interindividual epigenetic variability was calculated as the mean of standard deviations of single characters in each sample based on the character scores. It did not differ between the two species and among the regional units within each species. Only in savanna hares from the Queen Elizabeth Park was the tendency of folding and plication of enamel structures somewhat reduced. Divergence of occlusal character states between the two species and among regional units was assessed by using C. A. B. Smith's ‘mean measure of divergence’as a distance measurement. Thirteen of 15 pairwise morphological distances differed significantly from zero. A UPGMA dendrogram based on these distance measurements revealed distinct epigenetic separation of the two species. Within each species, slight geographic divergence corresponded to the spatial distribution of the regional units. In cape hares, spatial divergence also paralleled some changes in climatic conditions. In view of the lack of complex occlusal types and the larger interspecific divergence as compared to the intraspecific, character variation is likely to be caused by phylogenetic rather than by ecogenetic proc

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05408.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A significant negative correlation between the numbers of earthworms and the flatworm was demonstrated in fromalin‐sampled lawns. Their distributions, recorded by a transect from a shrub border where the flatworm is suspected to have been introduced, indicated that predation may lead to earthworm extinction. Two different vermarium designs demonstrated a gradation of earthworm vulmerability to the flatworm due to depth within the soil and burrow width rather than perference for specific earthworm species. A strong correlation between the level of earth worm predation and flatworm movement implied active hunting. A predation rate was found to be 0.67 of an earthworm per flatworm per week with a metabolic conversion rate of 10

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05409.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Activity schedules of dormice were investigated in relation to weather and seasonal factors, by automatic monitoring of temperatures in nests of free‐living animals. Data were obtained for two years and 294 dormouse‐nights. The principal exogenous factor influencing pan‐seasonal activity was photoperiod, activity beginning about 30 min after sunset and ending about 50 min before sunrise. However, on a seasonal scale, activity start time, end time and length were all strongly affected by ambient temperature and rainfall; higher temperatures appeared to lengthen activity, whereas rainfall reduced it. Diurnal activity was rare and took place when ambient air temperatures at midnight fell below 9°C. There were large differences in activity shedules between years, which were also correlated with weather conditions. Dormice are directly affected by weather, which also strongly influences the availability of their food. Weather may in general heavily influence small hibernators, because they can utilise facultative torpor to overcome adverse conditions. Our results imply that weather may have a profound effect on dormouse life history, especially in Britain's maritime climate where summers are frequently cool a

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05410.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Recent advances in reproductive technologies for animal breeding, together with improvements in techniques for storage of gametes and embryos, have encouraged the view that the time is now appropriate for developing systematic policies of germplasm banking. Such activities would aim to support more conventional breeding programmes for threatened species, by providing the opportunity to store valuable genetic material for use on some future occasion. A number of pertinent issues should be addressed, however, before embarking upon the large scale implementation of genetic bank programmes. This review raises and discusses some of the issues involved.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05411.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY