Stress doesn’t just take a toll on humans, but elephants, too—according to a new study in Scientific Reports.
The researchers discovered that Asian elephants born during times of high maternal stress produce significantly fewer progeny in their lifetime than elephants born in other times, and decline much more rapidly in older age.
This is the first study to investigate the effects of stress on non-human species with lifespans similar to ours.
“Poor early life conditions have been linked to many disease outcomes in humans, but is unknown whether stress in early life also speeds up ageing rates in long-lived species,” Dr. Hannah Mumby, lead author, explained in a press release. “We found that the decline in reproduction with age is much steeper in the elephants born at the poorer time of year. Even though they reproduce slightly more when they’re young, this still doesn’t compensate for the steep decline and they end up with fewer offspring.”
The team, which is out of the University of Sheffield, came upon this discovery while examining records of elephants from Myanmar. The records spanned three generations and documented the lives and deaths of more than 10,000 elephants that worked for the timber industry.
Then, to determine the most stressful time of year, the researchers measured the amounts of stress hormone metabolites in the fecal matter of 37 female elephants on a monthly basis for 12 months. They found that three particular months spiked stress levels by 46%: June, July, and August.
Why is this time period so stressful?
Those three months span the monsoon season, when elephants work extra hard to drag logs to rivers. The number of calves born during this time is much lower, and those born are least likely to survive. Further, we now know they don’t live as long or reproduce as much as calves born in other seasons.
These results add further weight to the notion that maternal stress (in any species) is likely to affect the offspring, and may help conservationists increase elephant populations. Improving developmental conditions could encourage longer-lived and more reproductive elephants, guaranteeing the survival of one of the world’s best-loved animals.
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Feature Image: University of Sheffield
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