Search

A multi-year radio-telemetric study of the copperhead Agkistrodon contortrix (Serpentes: Viperidae) was conducted at the north-eastern extreme of its range to determine the relationship of plasma sex steroids of males to the mating season. Blood samples were collected in situ approximately every 2 weeks (repeat-test group) from radio-telemetered males during the 7-month active season (April–October) from 2001 to 2003 and assayed for concentrations of testosterone (T) and progesterone (P4). Blood samples were also obtained from a large number of incidental males (single-test group) for the analysis of seasonal levels of T and P4. The profiles of T and P4 showed a peak in August–September that corresponded to the single mating season (late July to late September). Both T and P4 had similar seasonal profiles, but absolute levels of these steroids were significantly different, with concentrations of T four- to fivefold greater. The mating season of the population we investigated differs from other (e.g. southern) populations, which show two mating seasons (late summer/early fall and spring) before the period of ovulation in mid- to late spring. When a mating season is absent in spring, inseminated females are obligated to store sperm over winter until ovulation in the spring. In studies of A. contortrix that document two mating seasons, peak levels of T in males are coincident with both of these periods. In contrast, we found that peak levels of T and P4 in males coincided with the occurrence of the single mating season, and levels were basal in spring. These results further support the idea that plasma sex steroids influence the expression of sexual behaviour in A. contortrix and other snakes. Nonetheless, confirmation of this view awaits experimental studies. [ABSTRACT FROM AUTHOR]

Information on behavioural and physiological processes of newborn reptiles is often difficult to obtain under natural conditions, especially in lizards and snakes. Consequently, we lack information on a wide range of biological phenomena (e.g. thermoregulation, digestion, circadian activity rhythms) in neonates of these taxa. Here, we report novel behaviour in newborn sibling sidewinder rattlesnakes Crotalus cerastes, a desert-inhabiting species of south-western North America. At the entrances of their natal burrows, neonates formed aggregations (‘balls’) during daylight hours, which involved frequent movements of individuals within these balls. Through the study of two radio-telemetered females and their litters ( n=20 offspring), we obtained temperature data from the mothers, centre of the snake balls, and from multiple sites in the immediate environment for 10 days post-birth, the period that is coincident with maternal attendance and the first cycle of ecdysis. The core temperatures of the snake balls showed significant stability over the extreme thermal ranges of the environment. Although other functions are possible, such as those related to water conservation and antipredator defence, we suggest that frequent movements of individuals within the balls involved selection of a thermal optimum to enhance ecdysis. Based on other studies of aggregation in animals, dynamic aggregative behaviour in newborn sibling C. cerastes implicates self-assembly and suggests that individuals benefit from behavioural interactions with their siblings. One plausible scenario for the evolution of this type of dynamic aggregation involves thermal selection among sibling neonates for optimal basking sites within natal refugia in extreme environments such as desert landscapes. Moreover, it is possibly limited to species of vipers (and other snakes) that are viviparous and where maternal care is present up to the time of shedding in neonates. [ABSTRACT FROM AUTHOR]