Taming age mortality in semi-captive Asian elephants

Jennie A H Crawley,Virpi Lummaa,Zaw Min Oo,Hnin Nandar,Mirkka Lahdenperä,Win Htut

doi:10.1038/s41598-020-58590-7

Abstract

Understanding factors preventing populations of endangered species from being self-sustaining is vital for successful conservation, but we often lack sufficient data to understand dynamics. The global Asian elephant population has halved since the 1950s, however >25% currently live in captivity and effective management is essential to maintain viable populations. Here, we study the largest semi-captive Asian elephant population, those of the Myanma timber industry (~20% global captive population), whose population growth is heavily limited by juvenile mortality. We assess factors associated with increased mortality of calves aged 4.0–5.5 years, the taming age in Myanmar, a process affecting ~15,000 captive elephants to varying degrees worldwide. Using longitudinal survival data of 1,947 taming-aged calves spanning 43 years, we showed that calf mortality risk increased by >50% at the taming age of four, a peak not seen in previous studies on wild African elephants. Calves tamed at younger ages experienced higher mortality risk, as did calves with less experienced mothers. Taming-age survival greatly improved after 2000, tripling since the 1970’s. Management should focus on reducing risks faced by vulnerable individuals such as young and first-born calves to further improve survival. Changes associated with reduced mortality here are important targets for improving the sustainability of captive populations.

Highlights

Understanding factors preventing populations of endangered species from being self-sustaining is vital for successful conservation, but we often lack sufficient data to understand dynamics
The global Asian elephant (Elephas maximus) population has halved since the 1950s, and its range has shrunk to 5% of its original size, leaving it endangered[2]
Taming age varies across the countries where captive elephant populations are common, but how calves of different ages cope with taming and how this affects their mortality risk is unknown

Summary

Introduction

Understanding factors preventing populations of endangered species from being self-sustaining is vital for successful conservation, but we often lack sufficient data to understand dynamics. Taming is currently a necessary process for the Myanmar population of timber elephants, to ensure a safe and effective working environment These large animals can pose great risks to their handlers, or mahouts[12], and have been reported in the past to cause 10–20 mahout fatalities per year within the MTE7. The effect of stress on factors affecting a calf ’s susceptibility to diseases such as the Elephant Endotheliotropic herpesvirus (EEHV), which currently threatens both African and Asian elephant calves globally[17], is poorly understood and taming stress could exacerbate disease susceptibility Calf traits such as body size and condition in turn vary with many factors such as a calf ’s environmental and early life conditions, their sex, age and the maternal care they receive. It remains unclear whether taming-age mortality of calves has changed over time as veterinary care, taming practices and general management have shifted in the modern day[26]

Methods

Results

Conclusion