Young female elephants benefit from growing up with siblings, especially older sisters, leading to them living longer lives and having calves earlier.
Researchers from the UK, Myanmar and Finland studied semi-captive Asian elephants (Elephas maximus) in Mayanmar and found that being raised with siblings had a big impact on the development of elephant calves.
The researchers found that “Being raised with older siblings strongly increased calves’ long-term survival compared to not having a sibling, with elder sisters having a bigger impact than elder brothers.”
They found that female elephants raised with older sisters lived longer and reproduced on average two years earlier than those raised with brothers.
Male elephants raised with older sisters had slightly shorter life spans but weighed more compared to those raised with older brothers.
The study noted that “Reproducing at an earlier age is generally associated with more offspring over the course of an elephant’s lifetime.”
Dr Verane Berger, the lead author of the study, said: “Our research confirms that sibling relationships shape individual lives, particularly in social species, such as the elephants, where cooperative behaviours are essential to the development, survival and reproductive potential of individuals.”
The effect of siblings on development in the long term is often understudied in animals with long lifespans such as elephants because of the logistical challenges faced by studying the animals in the field for their whole lives.
The semi-captive lifestyles of the elephants in this study allowed the researchers to overcome many logistical issues presented by studying completely wild elephants.
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The elephants are government-owned and extensive records are kept about their lives from the day they are born.
The researchers explained: “These elephants are used during the day as riding, transport and draft animals. At night the elephants live unsupervised in forests and can interact and mate with both wild and tame elephants.”
The calves are raised by their mothers until they are five years old, at which point they undergo training for work.
The Myanmar Timber Enterprise (MTE) strongly regulates the amount of work the elephants can carry out per day.
Dr Mirkka Lahdenpera, a co-author of the study, said: “Because the elephants live in their natural habitats, there are many similarities to wild elephants, such as natural foraging and no assistance in breeding.”
She added: “While there are differences – in the wild, family groups are probably bigger – there are more similarities than differences and we could assume that some of the associations found in our study would also hold true for wild elephants. But of course, these should be studied.”
Berger said that the next steps in the research would involve “collecting more information on the body mass of mothers at birth (to) hope to disentangle maternal effects from sibling effects.”
She added: “More data will also let us explore the effects of the environment on sibling relationships and go into more detail on the effects siblings have on specific aspects of a younger calf’s health, such as immunity, muscular function and hormonal variations.”
The study analysed data on 2,344 calves born between 1945 and 2018 and was published titled ‘The elephant in the family: Costs and benefits of elder siblings on younger offspring life-history trajectory in a matrilineal mammal’ in the Journal of Animal Ecology on 20th September.
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Story By: Peter Barker, Sub-Editor: William McGee, Agency: Newsflash
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