When Asian elephants are born into stressful situations, they tend to age faster but have fewer offspring, according to researchers from the University of Sheffield.
"Poor early life conditions have been linked to many disease outcomes in humans, but it is unknown whether stress in early life also speeds up aging rates in long-lived species," Dr. Hannah Mumby, lead author of the study, said in a news 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 researchers from that university's Department of Animal and Plant Sciences examined records of elephant births and deaths in Myanmar, Southeast Asia. In total, they studied 10,000 individuals, spanning three generations over the course of a century. Their elephant subjects had been semi-captive animals working in the timber industry.
To better understand this aging effect, the researchers examined which months are stressful for pregnant elephants, by measuring the hormone glucocorticoid metabolites, which is associated with stress, according to the release.
The researchers concluded that from June to August, during monsoon season, the elephants experience the most stress. During this time the elephants are required to drag logs to rain-swollen rivers.
"Fertility and reproductive rate decline with age for all of us, but for some faster than others -- and this variation was how we measured differences in aging," Dr. Virpi Lummaa, senior author, said in the release.
Their study highlights the correlation between maternal stress and offspring aging. While this has important implications for Asian elephants, the researchers also suggest that by improving developmental conditions, reproductive aging could be delayed in various species.
Their findings were recently published in Scientific Reports.
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