Using semi-captive Asian elephants to examine population dynamics in long-lived mammals

Amidst the global biodiversity crisis, understanding the processes that underpin population decline in a changing environment is crucial to develop effective conservation management strategies. External drivers of population decline such as human disturbance and climate change have an immediate influence on population vital rates such as survival and reproduction, which has implications for population dynamics. However, anthropogenic activity may also have long-lasting demographic consequences for wildlife populations, influencing vital rates for several years and affecting demographic structure. Long-lasting demographic effects may be particularly important in long-lived species that experience years or decades of environmental variation, but long-term demographic data is needed to pick apart the drivers of population dynamics. Here, I explore the drivers of population dynamics in semi-captive Asian elephants using a long-term, individual-based demographic dataset collected between 1951-2014 from timber camps in Myanmar. First, in chapter 2 I demonstrate that capture from the wild reduced lifetime reproductive success in female elephants, and that the negative effects of wild-capture lasted for over a decade and affected survival in subsequent generations. In chapter 3, I further explore the role of wild-capture for population dynamics and find that the sustainability of this semi-captive population was dependent on capture from the wild for decades. Furthermore, long-term projections suggest that without wild-capture, there may be transient population declines lasting for over half a century. Wild-capture influenced the age-structure of the population, and in chapter 4 I investigate the contribution of population age-structure to short-term population growth rates. Age-structure varied substantially across the study period and was a critical driver of transient population dynamics in this disturbed population. Finally, to assess other potential drivers of population dynamics, in chapter 5 I tested whether the past climate influenced vital rates in semi-captive elephants under contrasting mechanisms of delayed climate effects and find little evidence for delayed climate effects at this temporal scale. I highlight that the negative effects of human activity on wildlife populations can last for decades, and the important role of transient population dynamics in long-lived species. These results provide novel insight into the impact of human disturbance on population dynamics in a long-lived species.