Christopher T. Winne, John D. Willson and J. Whitfield Gibbons
University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken,
SC 29802 USA
Summary
1. Capital breeding is an ideal reproductive strategy for many ectotherms
because it provides a disassociation between feeding and reproduction,
a necessary requirement for animals that become anorexic during pregnancy.
Among ectotherms, some viviparous snakes (e.g. Viperidae) exemplify the
capital breeding strategy because many species (i) do not feed during
pregnancy due to behavioural conflicts between reproduction and foraging,
and (ii) take more than one season to accumulate sufficient energetic
stores for reproduction.
2. Isolated wetlands often exhibit extreme annual fluctuations in environmental conditions with prolonged droughts periodically leaving wetlands completely dry and devoid of prey. Following droughts, however, wetlands can be extremely productive, rendering prey resources virtually unlimited for some species.
3. This study examines drought survival strategy and reproductive ecology of a small aquatic snake Seminatrix pygaea (Cope) in an isolated wetland. Seminatrix pygaea are atypical from most sympatric snake species in that (i) their small body size, reliance on aquatic prey, and high rates of evaporative water loss make them ill-suited to overland movement, and (ii) they may not be subject to costs typically associated with feeding during pregnancy.
4. We hypothesized that S. pygaea would survive periodic multiyear droughts by aestivating within the dried wetland, a survival strategy heretofore undocumented in snakes. Further, we hypothesized that if S. pygaea rely on 'typical' snake reproductive strategies of 'adaptive anorexia' and capital breeding, reproductive output would be reduced in the first wet year following drought.
5. By encircling a 10-ha wetland with a continuous drift fence before it refilled we were able to demonstrate that S. pygaea were present within the dried wetland prior to the onset of spring rains that refilled the wetland in 2003. Our results suggest that S. pygaea are capable of surviving multiyear droughts by aestivating within the dried wetland.
6. Despite having presumably depleted energy reserves during the drought, S. pygaea reproduced with the same frequency and fecundity during the first season following refilling of the wetland as in pre-drought years.
7. The ability of S. pygaea to rebound rapidly from the stresses of prolonged drought is due in part to their reproductive ecology. Seminatrix pygaea readily feed throughout pregnancy and consequently can rapidly translate high prey abundances into reproductive output through income breeding.
Key-words
climatic variation, foraging ecology, migration, reproductive allocation,
reptile
Correspondence
Christopher T. Winne, University of Georgia, Savannah River Ecology Laboratory,
Drawer E, Aiken, SC 29802, USA
Tel: 803 725 0422 (work), 803 640 6033 (cell). Email: winne@srel.edu
SREL
Reprint #2985
Winne, C. T., J. D. Willson and J. W. Gibbons. 2006. Income breeding allows an aquatic snake Seminatrix pygaea to reproduce normally following prolonged drought-induced aestivation. Journal of Animal Ecology 75: 1352-1360.
