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“Although the trade-off between offspring size and the number of offspring is a critical component of life-history theory, many empirical tests fail to show that such trade-off exists. Although this may be due to statistical issues (i.e. failure to control for maternal body size), other complications such as female body shape may play a role as well. Here, we examined reproductive traits in two species of viviparous garter snakes with very different body

morphologies (Thamnophis marcianus and T. proximus) to see how female body shape affects this trade-off. In the more slender species (T. proximus), we found a strong, negative relationship between brood size and offspring size, with the effect most notable in smaller females. However, in the more robust snake selleck products (T. marcianus), there was no significant p38 protein kinase trade-off seen in either the sample as a whole or for either larger or smaller females. Our data support earlier work on ectotherms, which indicates that body shape can act to constrain how offspring size and clutch or litter size are related. “
“We investigated

locomotor activity rhythms in the little-studied wild-caught eastern rock sengi (Elephantulus myurus) from Goro Game Reserve, Limpopo Province, South Africa. To assess whether locomotor activity is endogenously entrained by the light–dark cycle, animals (n = 13) were subjected to three different light-cycle regimes: a 12 h light/12 h darkness (LD) cycle, a total darkness (DD) cycle and an inverse of the LD cycle (DL). Ten animals exhibited strong light entrainment under LD1 with the total percentage of activity during the light phase (56.5% ± 11.9%) significantly higher than during the dark phase (43.5% ± 11.9%). Eleven animals expressed distinct endogenous free-running rhythms under DD (mean τ = 23.6 h ± 0.6 h; range: 22.9 h–24.5 h), with significant inter-individual variation. Under DL, the

total percentage of activity was approximately equal during the light (50.4% ± 7.8%) and dark phase (49.6% ± 7.8%). E. myurus was on average active 25% of the 24-h day with a nocturnal–diurnal ratio of 0.8 under LD1 and exhibited locomotor activity under controlled conditions similar to that of closely related species in the wild. In 62% of the animals, activity was highest around dawn, lowest during ID-8 the afternoon and intermittently expressed throughout the night. Little quantitative data are available on the daily locomotor activity rhythms of sengis particularly in response to the light–dark cycle. This study provides valuable quantitative data on locomotor activity rhythms in E. myurus. “
“Because environmental conditions vary seasonally in most regions, many small mammals reproduce at a specific time of the year to maximize their reproductive success. In the tropics and subtropics, the breeding season is usually determined by the extent of the dry and rainy seasons.