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Dryad

Using retrospective life-tables to assess the effect of extreme climatic conditions on ungulate demography

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Oct 06, 2022 version files 85.49 KB

Abstract

In Mediterranean areas, severe drought events are expected to intensify in forthcoming years as a consequence of climate change. These events may increase physiological and reproductive stress of wild populations producing demographic changes and distribution shifts.

We used retrospective life tables to understand demographic changes on a wild population after severe drought events. We studied the impact of two extreme events (2003 and 2005) on the population dynamics of our model species, the red deer (Cervus elaphus). During both years, population density was high (40 and 36 ind/100 hectares, respectively). Thus, we reconstructed retrospectively the age-structure of the female part of the population for the period 2000-2010 by using data of known-age individuals culled during the period 2000 to 2019 (n = 4176). Also, based on previous studies results, we aimed to validate this methodology.

Both extremely dry years, 2003 and 2005, produced marked and lasting cohort effects on population demography. Age pyramid the following years (2004 and 2006) revealed that the extreme drought caused the female fawn cohort to be similar or even smaller than the yearling cohort. Furthermore, these cohort effects were still perceptible 3 years after theses severe events. Results agree with previous findings that showed a negative effect of severe drought events on female pregnancy rates and conception dates.

Although simple, this study provides an empirical quantification of the demographic effects of severe drought events for a wild population which might be useful to understand future demographic changes under the context of climate change.