Differences in age-specific mortality between wild-caught and captive-born Asian elephants

Abstract

Wild-capture of numerous species is common for diverse purposes, including medical experiments, conservation, veterinary interventions and research, but little objective data exists on its consequences. We use exceptional demographic records on Asian elephants from timber camps in Myanmar to investigate the long-term consequences of wild-capture during 1951–2000 on their mortality (N = 5150). We show that captured elephants have increased mortality compared to captive-born elephants, regardless of their capture method. These detrimental effects of capture are similar for both sexes but differ substantially according to age. Elephants captured and tamed at older ages show a higher increase in mortality after capture than elephants captured and tamed young. Moreover, the increased mortality risk following capture and taming is still perceived several years after capture. Our results are timely given the continued capture of elephants and other wild animals to supplement captive populations despite the alarming declines of wild populations globally.

Maternal age at birth shapes offspring life‐history trajectory across generations in long‐lived Asian elephants

“…We excluded calves without known mothers and calves without complete records of their mothers from our analyses. Birth dates are known precisely for captive-born individuals (72.8% of individuals included in this study), whereas the age at capture (and thus approximate birth year) of wild-caught individuals is estimated by comparing their height and body size with captive-born elephants of known age, and through morphological assessment (Lahdenperä, Mar, Courtiol, & Lummaa, 2018;Mumby, Chapman, et al, 2015a). Calf data were available for 11 regions in Myanmar (see Regions in Figure SI age at first reproduction varied between 8 and 31 years of age (mean = 19.18 ± 4.35, median = 19), and reproductive daughters produced between 1 and 9 calves during their lifetime or followup period (mean = 2.25 ± 1.32, median = 2).…”

“…We included the mothers' (F1) birth origin (captive-born or wild-caught) as a fixed factor. We also included an interaction between the birth origin of the mother (F1) and the number of years between the time of capture and the birth of the calf (F2; no main effect), and an interaction between the birth origin of the mother and her age at capture from wild (no main effect) to account for the fact that for wild-caught animals only, the traumatic effects of capture may decrease with time and age (Lahdenperä et al, 2018). We included calf birth season (dry or monsoon season) and calf sex as binomial factors (Mumby, Mar, Hayward, et al, 2015b).…”

Taming age mortality in semi-captive Asian elephants

“…The MTE keeps detailed records of all of their elephants, enabling us to monitor the life events (e.g. birth and death) of individual animals 4,24,27 . Each elephant has a unique ID number permanently marked on their rump, and veterinarians and other authorised personnel maintain a logbook throughout their life recording important demographic and health events.…”

“…Each elephant has a unique ID number permanently marked on their rump, and veterinarians and other authorised personnel maintain a logbook throughout their life recording important demographic and health events. These include exact birth and death dates 24 , cause of death determined by post-mortum 23 , location, and maternal information 28 . Here, we use this information to investigate factors associated with mortality risk during taming age for captive-born calves.…”

“…Consequently, first born calves with inexperienced mothers, and those born to ageing mothers with decreased body condition, have generally been found to experience higher juvenile mortality 9 . Another factor with the potential to influence calf survival is their mother's birth origin, as females caught from the wild and not born in captivity have previously been found to show compromised reproduction, survival themselves and calf survival compared to mothers born in captivity 4,24,25 . However, whether similar impacts extend to their calves during the critical period of taming is unknown, as are the effects of maternal investment.…”