Abstract:
In arid habitats, recent increases in summer temperatures associated with global warming are adversely affecting many animal populations. However, annual rainfall also varies widely in many of these areas, and we do not yet fully understand the relative impact of variation in temperature and rainfall on the demography of arid-zone species. Here, we examine the effects of temperature and rainfall variation on the demography of meerkats Suricata suricatta in the southern Kalahari over the last 25 years. During this period, average maximum monthly air temperatures at our study site increased by around 1.5°C to 3.2°C, while annual rainfall fluctuated without a consistent trend. We show that annual changes in female fecundity and recruitment were more closely correlated with variation in rainfall. Increasing air temperatures were associated with reductions in the recruitment of pups and the survival of some age classes but, in most cases, the demographic consequences of high temperatures were modest compared to the effects of low rainfall, which in some years led to the near cessation of successful reproduction and the extinction of many smaller groups. For instance, exceptionally low rainfall in 2012–2013 was associated with low recruitment and with declines in group size and population density, which fell by over 50%. Unusually hot years did not have similar consequences. Following the 2012–2013 drought, intermittent years of low rainfall and frequent droughts continued to suppress recruitment and slowed the population's recovery. Future changes in temperature may affect the dynamics and size of the meerkat population, but our work suggests that over the last 25 years, annual changes in rainfall have exerted a stronger influence on meerkat demography. Our study demonstrates the importance of long-term, individual-based data for determining how changes in climate affect the dynamics of animal populations, especially in arid environments where bottom–up processes often dominate.
