Humans have been capturing wild Asian elephants for more than 3,000 years for different purposes, and this still continues today despite the fact that the populations are declining. An international team of researchers has now analysed records of timber elephants in Myanmar to understand the effects of capture on the animals and their survival. The study shows that even years after their capture, wild-caught elephants’ mortality rate remains increased, and their average life expectancy is several years shorter compared to captive-born animals. Capturing wild-elephants to replenish captive populations could thus be unsustainable in the long run. Moreover, the discovered differences between captive-born and wild-captured elephants are rarely considered in research and conservation programmes.
Myanmar timber elephant at work.
Image credit: Virpi Lummaa.
Millions of wild animals are captured alive each year for a diverse range of purposes. While members of some species can thrive in captivity and are healthier, live longer, and produce more offspring than their free-living counterparts, many others perform far worse. Elephants, for example, are known to be at a much higher risk of dying when captive in zoos compared to living in the wild. Comparisons like these, however, mainly illustrate the differences in the diet, social environment, exercise possibilities, and disease patterns between zoos and wild environments. They provide little insight to how the capture of wild elephants might affect their long-term well-being in captivity.
Elephants have been employed in logging camps in Myanmar for centuries. Wild-caught and captive-born animals there work and live side by side in forests and are, generally, tamed with the same methods, live in the same environments, and are treated similarly. The detailed records kept by local governments on elephant husbandry provided a rich data set for researchers from the University of Turku, Finland, and the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany. Based on data stretching back nearly a century and including over 5,000 timber elephants, the researchers could establish a robust predictive model on elephant survival after capture. The results of the study are published on 7 August in the journal Nature Communications.
Dr Mirkka Lahdenperä, lead author, Department of Biology, University of Turku, Turku, Finland.
“Our analysis reveals that wild-captured elephants had lower survival chances than captive-born elephants regardless of how they’d been captured, whether by stockade of whole groups, lassoing single elephants, or immobilisation by sedation. This means that all these methods had an equally negative effect on the elephant’s subsequent life. We also found that older elephants suffered the most from capture; they had increased mortality compared to elephants caught at younger ages,” says Dr Lahdenperä.
All elephants face the highest risk of death in the year immediately following capture. Although the risk decreases in subsequent years, these negative effects still last — alarmingly — for around a decade, a surprisingly long time.
“We chose to rely on data from timber camps as — their capture aside — both wild-caught and captive-born elephants have very similar life styles. This unique situation allows a comparison between these two groups unbiased by other factors such as diet or exercise,” explains Dr Alexandre Courtiol, the data scientist of the study.
Capture and taming shorten elephants’ life expectancy considerably
Both captive-born and wild-captured timber elephants in Myanmar live together in semi-captive populations. They work during the day and are released to forests during the night to find food on their own, and can then interact with other captive timber elephants as well as wild elephants. The captive animals are also subjected to the same governmental regulations concerning data recording, workload, and rest periods (working elephants have holidays, maternity leave, and a mandatory retirement age). Both captive-born and wild-caught elephants are tamed and trained before entering the workforce. Wild-captured elephants may, however, be exposed to harsher treatment depending on their age, sex and, personality compared to captive-born calves.
“The long-term overall cost of capture and taming resulted in a median lifespan that is 3 – 7 years shorter than that of captive-born elephants. Capturing elephants to sustain captive populations is, consequently, detrimental, because it not just reduces wild populations of this endangered species, but it also cannot provide a viable solution to sustain captive populations. These wild-caught animals live shorter lives and reproduce poorly in captivity,” says Academy Professor Virpi Lummaa, the senior investigator of the study.
Compared to wild or semi-captive populations, both African (Loxodonta africana) and Asian elephants (Elephas maximus) suffer considerably higher mortality rates in zoos. However, such comparisons do not reveal the effects of origin per se, but instead illustrate management differences because the diet, social environment, exercise possibilities and disease patterns in zoo populations are vastly different to the wild. For example, although not studied in detail, stress levels of captive elephants are reported to increase when interacting with humans. Moreover, a lack of multigenerational family groups in most zoos means that the early maternal environment of those born in captivity is typically different from wild-captured animals. This prevents the differentiation of early parental effects from capture effects among wild-born and captive-born zoo residents. Different zoos also present heterogeneous living conditions, breeding possibilities and climate, and even small variation in factors such as within-year fluctuations in temperature can double the mortality risk of Asian elephants in range countries.
Our results offer interesting comparisons to welfare in zoo collections. In contrast to the situation in our semi-captive Myanmar population, captive(zoo)-born Asian elephants in European zoos have poorer survivorship than wild-captured animals. Although wild-captured female Asian elephants entered zoos at a median estimated age of just 3.4 years, they show better survivorship as adults than zoo-born counterparts. Why do wild-captured individuals fare better than captive-born in zoos, but not in the semi-captive keeping system in Myanmar? Overall, elephants suffer considerably higher mortality rates in zoos when compared to wild or semi-captive populations, such as the timber elephant population studied here. Indeed, captive-born elephants in the Myanmar population show comparable mortality to wild elephant populations, and the contrasting performance of wild-captured animals against the captive-born in zoos and timber camps highlights the problems that zoo elephants face. The reasons for the lower performance in zoos should be studied in detail, for instance, the effects of early-life stress and higher nutritional plane of animals, which have been suggested to cause this controversial pattern. Thus, taken together, rich datasets available for diverse elephants together show that early experience can have profound and sometimes unpredictable effects of wild animals kept in captivity.
Finally, ~1000 Asian elephants currently live in captivity in zoos, safari parks, and circuses world-wide, but these populations are not self-sustaining due to high mortality and low fertility rates. Consequently, 81% of the current European zoo populations were imported from range countries in Asia (75% in North America), 60% being wild-caught and 21% transported from timber camps. Although capturing elephants from the wild may be sometimes necessary e.g., for conservation, veterinary and anti-poaching activities, similar large-scale wild-capture as in our study population to supplement captive population has occurred also elsewhere in Asia, because these captive populations have insufficient reproductive rates to maintain population sizes. Captive-born elephants are regarded by keepers as more intelligent, less aggressive, easier to train, tractable and more reliable in temperament than those captured from the wild. Our study implies that capturing wild individuals in elephants (and potentially among other species with slow life-histories) is costly for individual longevity and alternative methods should be sought to boost captive populations in order to avoid further capture from endangered wild populations.
Above texts are derived from Differences in age-specific mortality between wild-caught and captive-born Asian elephants by Mirkka Lahdenperä, Khyne U. Mar, Alexandre Courtiol & Virpi Lummaa — licensed under a Creative Commons Attribution 4.0 International License
Long-term stress due to capture and taming as well as changes in the social environment are potential reasons for the shorter life of wild-captured elephants.
The results of the study strongly suggest that more studies are necessary to understand and assess how widespread these negative effects of capture are in other species. Whenever capture is unavoidable, animal welfare specialists, veterinarians, and ecologists must work together to improve conservation and management practices. Support and care for the animals is especially critical during the period immediately after capture.
(Source: University of Turku news release, 08.08.2018; license CC BY 1.0 FI)
