Socioecology has traditionally assumed that differences in social form between species derive from selected responses to particular evolutionary environments, while differences within a species reflect plastic responses to contemporary differences in ecology. The issue of behavioural or social plasticity is particularly salient for primatologists as it ties into conceptualizations of the evolution of cognitive capacity. In this regard, savanna baboons Papio hamadryas have provided a focus for research by virtue of their ecological plasticity and a problem for researchers by virtue of marked social differences in one subspecies – hamadryas baboons P. h. hamadryas – that cannot be explained solely by reference to current ecology. It is argued that the problem extends beyond hamadryas and that at least some differences between other populations also reflect selected responses to restricted, local evolutionary conditions. Of particular importance to the understanding of contemporary differences in baboon sociality is the extent to which evolutionary environments have constrained group size and perturbed adult sex ratios and, thereby, structured responses to the ever-present threat of infanticide. The view that there is much to be gained from a phylogenetic approach to population differences in behaviour is endorsed.

Mongolian gazelles Procapra gutturosa were observed, hand-captured and radio-monitored in the eastern steppe of Mongolia during 1998–2003 to understand better their reproduction and survival. During early June, 92% (range = 87–96%) of adult (≥2 years old) females observed (mean n = 735/year) were pregnant, and nearly all gave birth during a 10-day interval (24 June–3 July) each year. Mean mass of neonate (1–2 days old) calves (mean n = 47/year) was greater for males than for females, and masses were directly correlated with mean monthly temperatures the previous winter (December–April). Survival during the first 10 days of life for 111 radio-marked neonate calves monitored during 2000–03 (n = 9–55/year) was 0.83 and did not seem to vary with birth weight. Also, deaths owing to hypothermia, abandonment, or unknown causes (interval cause-specific mortality rate = 0.16) outnumbered deaths owing to predation (0.02) during this interval. Survival rates were similar during the rest of the year (0.86 for 355 days) when most mortalities were owing to predation (interval mortality rate = 0.12 vs 0.01). Annual survival of calves was 0.71 (95% CI = 0.61–0.82). Gazelle births are highly synchronous, probably to take most advantage of the short summer growing season, and perhaps to avoid deleterious spring weather and to minimize predation. High fecundity and relatively high calf survival, especially during the first weeks of life, support the notion that gazelle populations can recover fairly quickly from demographic catastrophes.

Patterns of formation and sequence of ossification of the entire skeleton are described for the snapping turtle Chelydra serpentina, based on new and previously published data. Differences in the sequences of ossification events are described and demonstrate considerable intraspecific variation in these developmental data. The chondrocranium of a late developmental-stage specimen is described and illustrated as baseline data for comparative studies. Patterns of formation and chondrification of forelimb and hind limb elements are generally consistent with those of previous studies; however, conspicuous differences in the patterns of ossification are observed among metapodial and phalangeal elements. In the cranium, patterns of ossification of dermal elements are generally more variable than are those of endochondral elements of the braincase, and as in previous studies, endochondral elements ossify after dermal elements. Documented intraspecific variation in sequence and timing of formation, chondrification, and ossification of skeletal elements should serve as a caveat for those conducting studies of phylogeny, heterochrony, and evolution with these data. Causes of natural and induced variation are discussed briefly.

A new species of Congosorex is described. The new species occurs in Tanzania and is larger in external characteristics than the other two known species in the genus, with the longer tail being especially distinctive. The skull of the new species is wider, on average, than other Congosorex, but intermediate in greatest length. Previously undocumented characteristics that differentiate Congosorex from Myosorex are described. The presence of Congosorex in the Eastern Arc Mountains supports the theory that these mountains are refuges of ancient lineages of organisms with ties to the Guineo-Congolian region of Africa and that there was once a continuous swath of forest connecting these two areas.

The overlap of large carnivores, livestock and people can engender conflicts that often threaten the future viability of carnivore populations in the pastoral systems of Africa. A playback survey of lions Panthera leo, spotted hyenas Crocuta crocuta and black-backed jackals Canis mesomelas and a transect count of wild herbivores was conducted in the Maasai Mara National Reserve and adjoining pastoral ranches to assess the effect of pastoralism and protection on the density and distribution of carnivores in June 2003. Reliability of the prey counts depended on an assumption of similar observability between the protected and pastoral areas, which we assessed using distance sampling in November 2003 and computer simulations and determined to be similar. Estimates of wild prey biomass density was 2.6 times higher in the ranches (14212 kg/km2) than in the reserve (5472 kg/km2) during this wet season count. Apparent hyena density estimates were 1.3 times higher in the ranches (0.561 hyenas/km2) than in the reserve (0.404 hyenas/km2), in correspondence with the regional pattern of prey density. This distribution of hyenas is biased towards the reserve, if it is dependent on prey density. Estimates of apparent jackal density were similar in both areas whereas lion density was anomalously 8.0 times lower in the ranches (0.046 lions/km2) than in the reserve (0.369 lions/km2). Lion and hyena densities and prey biomass did not differ between June 1991 (5172.273 kg/km2) and June 2003 (5472 kg/km2) in the reserve, but jackal density increased in the same period. Lions never responded to playbacks in the ranches, so the potential shift in lion behavioural response for different land use zones is another potential explanation for the patterns found here. We think a real shift in lion populations is a better explanation than a behavioural change in relation to playbacks based on additional data from independent systematic and intensive censuses and playback surveys conducted in the ranches. Lion populations in the pastoral ranches seemed headed for extinction, probably owing to conflicts with pastoralism, necessitating urgent conservation interventions that integrate pastoral economic welfare with large carnivore conservation goals to foster long-term viability of lion populations in the pastoral systems.

Limited resources will inevitably lead to trade-offs between traits. However, trade-offs are not always observed, for a variety of reasons. For example, failure to take into account covariates, and high variation in resource acquisition relative to variation in resource allocation, can obscure the underlying trade-off. In the present paper, the trade-off between offspring size and number was examined in the common lizard Lacerta vivipara. Size–number trade-offs can arise for two different reasons, limited food resources or space constraints. There was no significant trade-off between size and number of young under natural conditions, whereas females captured before ovulation and provided with excess food under laboratory conditions showed a negative correlation between clutch size and offspring size. Food supplementation did not significantly increase reproductive output compared to natural conditions and, thus, the presence of a trade-off under ad libitum conditions was not the result of space limitation in the female reproductive tract. The variance ratio between allocation to investment, however, was twice as high for females ovulating in the laboratory, suggesting that the existence of a trade-off under ad libitum conditions could be a result of less variation among females in resource allocation.

Measurement and dissection of 97 museum specimens provided information on morphology, food habits, and reproduction in the colubrid snake Symphimus mayae. This medium-sized (<910 mm total length) diurnal species from the Yucatán Peninsula is an inhabitant of lowland xerophytic habitats, and an orthopteran dietary specialist. Sexual dimorphism is evident in relative tail length, head length, and numbers of subcaudal scales, but not in the number of ventrals, and males and females attain similar adult body sizes. Symphimus mayae feeds almost exclusively on orthopteroid insects, principally katydids (Tettigoniidae) and crickets (Gryllidae). These taxa jointly accounted for >50% of the total number of prey items recovered from stomachs and had been eaten by >70% of the snakes examined, with little intraspecific or seasonal variation. Other, less frequently used prey groups are (in order of relative importance), stick insects, mantids, Jerusalem crickets, grasshoppers and spiders. All size classes of snakes eat orthopterans, but stick insects are consumed predominantly by adults (>300 mm SVL), and mantids exclusively by large adults (>420 mm SVL). More than 55% of individuals from monthly samples contained recently ingested food, suggesting that feeding in S. mayae occurs year-round and is not significantly curtailed by the local dry season. Reproduction is probably annual, although it does not occur in all females every year, and a single clutch of two to four eggs is produced with oviposition and hatching timed to the wet season.

The behavioural use of rock crevices by rock hyrax Procavia capensis was essential in avoiding harsh environmental conditions during summer. Foraging was the most dominant above-ground behaviour exhibited by rock hyrax during summer. Most ambient temperatures in the early morning of summer fell within the rock hyrax thermoneutral zone, which enabled the animals to forage without the need for prior heating from a solar energy source. Basking was an essential behaviour displayed by rock hyrax in winter. The low quality and scarce food source may be inadequate to meet the metabolic requirements of rock hyrax at low ambient temperatures. It therefore seems that basking is not only an energy conservation mechanism but also essential for the survival of rock hyrax during winter. Juvenile rock hyrax have a higher surface area to volume ratio and are more vulnerable to low ambient conditions than adults. As a result they displayed a different behaviour pattern to adult rock hyrax during winter. Juveniles required larger amounts of food to meet their energetic requirements, while adults spent greater amounts of time basking. The extent to which rock hyrax meet energetic requirements depends on the interaction of ambient temperature, food availability, food quality and foraging efficiency in the presence of predators. The extent to which each of these factors influenced behaviour differed on a daily and seasonal basis.