Body condition of the red kangaroo (Macropus rufus) in arid Australia: The effect of environmental condition,sex and reproduction

The body condition of live-caught male and female red kangaroos (Macropus rufus Desmarest 1842) was assessed in environmental conditions described by a period of high (two years) followed by low (one year) rainfall. Changes in pasture biomass and quality closely followed rainfall fluctuations in these years. Fluctuations in standardized body mass, in turn, lagged behind changes in pasture biomass with a delay of three months. Male and female body condition was best predicted by green grass biomass. Kangaroos caught during the high rainfall period reached an above average plane of condition. In the low rainfall period that followed, the condition of kangaroos declined, and was greater for small males (14–41 kg), large males (45–89 kg), and females (18–36 kg) with small or no pouch young than for female subadults (< 22 kg) and females with large pouch young (20–34 kg). Female subadults were also significantly older and the ratio of females:females with young-at-foot was higher in the low rainfall period. This suggests a mechanism for age/sex class differences in survivorship. The lagged synchrony of body condition with pasture biomass can be explained by body-size related digestive constraints, reflecting sex differences in adaptation to a stochastic environment.     

蝙蝠科三种蝙蝠的G-带和C-带

对肺、心等进行组织培养,用空气干燥法制作染色体标本,对贵州3种蝙蝠即中华鼠耳蝠(Myotis chinensis)、西南鼠耳蝠(M.altarium)和亚洲长翼蝠(Miniopterus fuliginosus)进行了G-带、C-带带型分析。结果表明,2种鼠耳蝠的G-带基本相同,亚洲长翼蝠的G-带与两种鼠耳蝠有一定同源性;C-带核型中,中华鼠耳蝠和亚洲长翼蝠只有着丝粒带,而西南鼠耳蝠有的染色体有插入C-带和端位C-带。根据带型异同分析讨论了鼠耳蝠和长翼蝠间的进化关系。     

Ecological selection and sexual dimorphism in the sooty oystercatcher,Haematopus fuliginosus

Male and female sooty oystercatchers (subspecies Haematopus fuliginosus fuliginosus; Haematopodidae) have an average difference in bill length of 19%. We studied the relationship between this sexual dimorphism and foraging ecology at coastal sites in southern New South Wales, Australia. Intersexual foraging divergence was most striking in diet, with seven prey classes eaten exclusively by one sex (male: 4, female: 3), and all shared prey classes eaten in different proportions. Intersexual diet partitioning was also observed in energetic rewards gained from foraging, with females gaining highest energetic benefits from eating ascidians and males from eating limpets. Furthermore, within the most commonly consumed prey item, limpets, females gained higher energetic benefit from eating smaller sizes while males gained greater rewards from the largest limpet sizes. Intersexual divergence was also observed in several aspects of foraging behaviour. Finally, there was a significant effect of tidal cycles upon intersexual niche partitioning in this species; the degree of diet divergence varied between tide conditions and females had a consistently more efficient dietary intake on neap tides than males. Diet divergence in the sooty oystercatcher is greater than previously observed in any oystercatcher, and is correlated with the largest sexual bill dimorphism recorded in this family. It is argued that intersexual competition between territorial pairs is operating to diverge male and female bill morphology.     

Sexual segregation in western grey kangaroos: testing alternative evolutionary hypotheses

In sexually dimorphic ungulates, sexual segregation is hypothesized to have evolved because of sex-specific differences in body size and/or reproductive strategies. We tested these alternative hypotheses in kangaroos, which are ecological analogues of ungulates. Kangaroos exhibit a wide range of body sizes, particularly among mature males, and so the effects of body size and sex can be distinguished. We tested predictions derived from these hypotheses by comparing the distribution of three sex–sex size classes of western grey kangaroos Macropus fuliginosus , in different habitats, and the composition of groups of kangaroos, across seasons. In accordance with the predation risk-reproductive strategy hypothesis, during the non-breeding season, females, which were more susceptible to predation than larger males, and were accompanied by vulnerable young-at-foot, were over-represented in secure habitats. Large males, which were essentially immune to predation, occurred more often than expected in nutrient-rich habitat, and small males, which faced competing demands of predator avoidance and feeding, were intermediate between females and large males in their distribution across habitats. During the breeding season, females continued to be over-represented in secure habitats when their newly emerged pouch young were most vulnerable to predation. All males occupied these same habitats to maximize their chances of securing mates. Consistent with the social hypotheses, groups composed of individuals of the same sex, irrespective of body size, were over-represented in the population during the non-breeding season, while during the breeding season all males sought females so that mixed-sex groups predominated. These results indicate that body size and reproductive strategies are both important, yet independent, factors influencing segregation in western grey kangaroos.