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Winter weather affects asp viper Vipera aspis population dynamics through susceptible juveniles
 

Summary: Winter weather affects asp viper Vipera aspis population dynamics
through susceptible juveniles
Res Altwegg, Stefan Dummermuth, Bradley R. Anholt and Thomas Flatt
Altwegg, R., Dummermuth, S., Anholt, B. R. and Flatt, T. 2005. Winter weather
affects asp viper Vipera aspis population dynamics through susceptible juveniles.
/ Oikos 110: 55/66.
Detailed studies on mammals and birds have shown that the effects of climate variation
on population dynamics often depend on population composition, because weather
affects different subsets of a population differently. It is presently unknown whether
this is also true for ectothermic animals such as reptiles. Here we show such an
interaction between weather and demography for an ectothermic vertebrate by
examining patterns of survival and reproduction in six populations of a threatened
European snake, the asp viper (Vipera aspis), over six to 17 years. Survival was lowest
among juvenile and highest among adult snakes. The estimated annual probability for
females to become gravid ranged from 26% to 60%, and was independent of whether
females had reproduced in the year before or not. Variation in juvenile survival was
strongly affected by winter temperature, whereas adult survival was unaffected by
winter harshness. A matrix population model showed that winter weather affected
population dynamics predominantly through variation in juvenile survival, although
the sensitivity of the population growth rate to juvenile survival was lower than to adult

  

Source: Altwegg, Res - Avian Demography Unit, Department of Statistical Sciences, University of Cape Town

 

Collections: Environmental Sciences and Ecology