Stress Takes Toll on Elephants Forced to Work in Myanmar’s Timber Industry
Stress kills for generations to come.
That’s the message from a new study examining the health of Asian elephants working in Myanmar’s timber industry. Researchers found that elephant mothers that give birth during the most stressful times of the year produce calves with a much lower survival rate than those born in other months. Those young that do survive mature faster, start breeding at a younger age, and ultimately have fewer offspring.
The effect is not unlike what happens in humans, where conditions in early life can lead to later health problems such as heart disease and diabetes, said Hannah Mumby, a research fellow at the University of Cambridge and the study’s lead author. The goal of the study was to see if other long-lived animals outside of the human-primate evolutionary tree also experienced rapid aging or other health effects owing to stress early in life.
That’s especially important in Myanmar, where the elephant population has declined from about 10,000 in 1960 to fewer than 5,000 today. The pachyderms there face numerous threats—including habitat loss and poaching—but the new study could provide further clues about their decline.
The majority of Myanmar’s elephants lead semi-captive lives working in the country’s timber industry, where they push and drag massive logs from forests to roads or rivers. This highly managed, government-run industry provided Mumby and her fellow researchers with detailed birth and health records of more than 10,000 elephants going back nearly a century. They also tested living elephants for hormones associated with stress.
Those stress hormones, they found, were highest from June to August, a period that corresponds with monsoon season. Elephants in those months often have to pull trees through heavy mud, a physically taxing process. The calves born during this period had the lowest survival rates and later in life experienced lower reproductive success.
Interestingly, the research showed that the stressed elephants in Myanmar actually do better than Asian elephants in zoos because they do lead semi-wild lives.
“They’re kept in groups and released into the forest at night,” Mumby said. This allows them to forage for their food and have relationships with other elephants. “They even have some opportunity—probably less now than earlier—to mate with wild elephants.”
The research could offer some clues to help improve management for these working elephants, whose jobs are actually starting to disappear.
“Just as wild elephants are experiencing a kind of reduction in the available habitat that they have, these working elephants are at a kind of crossroads as well,” Mumby said. “Until recently the timber industry’s been such an important economic powerhouse in Myanmar, but these resources aren’t infinite. The future is actually quite uncertain about what’s going to happen with these elephants.”
Many elephants and their handlers have already become unemployed, forcing them into lives of begging on city streets.
How the research relates to the health of other Asian elephants—let alone those living through the poaching crisis in Africa—is not yet clear, but Mumby said understanding the effects of stress on these long-lived animals will play a role in conserving them.
“Elephants look big and strong, but they seem to be quite sensitive to their environments,” she said. Understanding the big picture of their health, mortality, and fertility, therefore, will be relevant for their long-term survival.