September 21 (UPI) – Only children can be exposed to stigma, but for humans, growing up without siblings isn’t really dangerous. The same cannot be said of elephants.
According to a new study published on Tuesday in the Journal of Animal Ecology, young elephants that grow up with older siblings have higher survival rates and reproduce at a younger age than calves that grew up without siblings.
Females reared with older sisters had higher long-term survival rates and reproduced on average two years younger.
Elephants that start breeding earlier tend to generate more offspring in their lifetimes.
Male calves had slightly lower survival rates when raised alongside older sisters rather than older brothers. However, having older sisters was associated with higher body weight for male baby calves.
The researchers suggest that the phenomenon “live fast, die young” may explain the difference, as male elephants that mature faster can sacrifice their long-term health.
“Our research confirms that fraternal relationships shape the lives of individuals, particularly in social species, such as elephants, where cooperative behaviors are essential for the development, survival and reproductive potential of individuals,” said Vérane Berger , lead author of the study, researcher at the University of Turku. in Finland, said in a press release.
Studying wild elephants over long periods of time is quite difficult, making it almost impossible to study long-term behavior and health impacts of siblings.
For the latest study, the researchers studied semi-captive wood elephants living in Myanmar.
During the day, elephants are used as working animals. Local people ride the elephants and use the large mammal to pull plows and transport goods. At night, elephants live in the forest unsupervised.
Semi-captive elephants mate and interact with wild and tame elephants. The calves are raised by their mothers for five years until they are trained for the job by the local people.
Regulations established by the Myanmar Timber Enterprise limit the types and amount of work for which elephants can be deployed.
“Because elephants live in their natural habitats, there are many similarities to wild elephants, such as foraging for natural food and the lack of reproductive support,” said the study co-author, Mirkka Lahdenperä, in the press release.
“Although there are differences – in nature the family groups are probably larger – there are more similarities than differences and we could assume that some of the associations found in our study would also be true for wild elephants. But of course these should be studied, ”said Lahdenperä, postdoctoral researcher in the Elephant and Human Projects in Turku.
Researchers have studied the use of elephants for work in Myanmar for years, and records of wood elephant populations go back decades.
For the study, scientists analyzed information on the body mass, reproduction, sex and survival of 2,344 calves born between 1945 and 2018.
Because the researchers lacked information on the quality of maternal care and other external factors, they could not control for all of the variables that might influence survivability and sexual maturity.
“By collecting more information on mothers’ body mass at birth, we hope to disentangle the maternal effects from the effects on siblings,” Berger said.
“More data will also allow us to explore the effects of the environment on sibling relationships and to go into more detail on the effects siblings have on specific aspects of a young calf’s health,” such as immunity, muscle function, and hormonal variations, ”Berger said.