Switcheroo! Kangaroo mothers adopting unrelated young observed for the first time
Sherbrooke, le 13 mai 2015 – DNA lab tests reveal a startling discovery. She’s been dutifully nursing a baby for several months that is not hers! Even more surprising, her own offspring is being exclusively taken care of by the new baby’s biological mother.
Is this the premise of a reality show? No: it’s a finding on eastern grey kangaroos by a multi-institutional team of Canadian and Australian researchers, led by Professor Marco Festa-Bianchet of the Biology Department at the Université de Sherbrooke. A 6-year study published today in the scientific journal PLOS ONE reveals a previously unobserved phenomenon in wild kangaroos: adoption of juveniles by unrelated mothers, often while abandoning their own offspring.
“Adoptions are very rare in wild animals,” said Prof. Festa-Bianchet. “And when they do occur, the mothers involved are usually related. Our study is the first to document adoptions in wild kangaroos. There are very few scientific reports of exclusive nursing by unrelated females in the wild”.
“During our research, we noted four cases where mothers switched offspring,” adds Wendy King, doctoral student at the University of Queensland and first author of the study. “We really weren’t expecting that since one of our goals was to keep track of how many offspring female kangaroos were raising each year. Our working hypothesis is that a disturbance causes juveniles to quickly hop into other females’ pouches before getting their identity checked. Then once inside the pouch, the adopted young likely take on the female’s odour and are not easily distinguished from the original offspring in a more relaxed setting.” In seven cases, the adoptee took the place of a pouch occupant that died shortly after. However, the research shows that the “switcheroo” has as close a relationship with the new mother as normal offspring-mother pairs, and that the adoptive mother continues providing milk and care for a further 6-8 months. Survival of the adopted young and future reproduction of the adoptive mother were not affected by the change. While there thus seems to be no benefit to the young, this phenomenon can be very detrimental to those adoptive mothers who lose their own young that year.
DNA testing and body measurements were used to determine the kinship relationships and body conditions of kangaroos in this study, which was based on capturing 326 young born to 194 mothers at Wilsons Promontory National Park, Australia. The research was conducted in partnership with the Universities of Queensland and Melbourne in Australia, as well as Bishop’s University in Canada.
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Johanne Leroux, communications agent
Faculté des sciences | Université de Sherbrooke
819 821-8000, ext. 67085 | Johanne.Leroux2@USherbrooke.ca