A University of Alberta researcher has discovered a rare practice by red squirrels that seems to have human-like dimensions of altruism, but at its heart is also a survival tactic.
U of A researcher Jamieson Gorrell was observing a red-squirrel population when he discovered a female had adopted a newborn squirrel abandoned by its biological mother.
Gorrell, a PhD candidate in evolutionary biology, found a baby red squirrel had been taken from its mother-absent home nest and was being cared for by another female in a nearby tree. Researchers think it’s likely the biological mother was taken by a predator.
Squirrels are among the most solitary animals, having little to do with one another, so the adoption of a foundling struck Gorrell as an anomaly. But while checking through nearly 20 years of research gathered by the U of A on this particular red squirrel population in the Yukon, Gorrell made a breakthrough finding: On four other occasions, over the life of the study, female red squirrels had adopted abandoned baby squirrels and in every case Gorrell determined the foundling was related to its adoptive mother.
Unlike social animals such as chimpanzees, the solitary, antisocial squirrels were able to identify kinship without making contact with one another.
The researchers think that before the biological mother disappeared, the adoptive mother-to-be recognized a genetic link between them. Gorrell’s team theorized that the constant vocalizing or chattering a squirrel uses to mark its territory and ward of intruders contains signals describing its genetic history. The adopting mother knew the biological mother was family and after it disappeared she recognized her genetic connection to the abandoned baby.
This research is significant because it proves a long-accepted theory of evolutionary biology is correct for a solitary, non-social animal. Hamilton’s Rule, dating back to 1963, explains that despite the so-called law of the jungle and survival of the fittest, altruistic behavior can exist. But this altruism is restricted to family members only.
Female red squirrels will only adopt an abandoned baby it shares common genes with and will only pick one lucky squirrel from an entire litter of foundlings.
Gorrell says the adopting squirrel, already a single mother supporting her own family, will adopt just one family-linked foundling. Having an extra family member helps the adopting mother ensure a continuation of the gene pool. But adopting more than one foundling is out of the question because the cost to the adoptive mother and her biological offspring outweighs the potential benefit.
The work of Gorrell and his colleagues at McGill University and Guelph University was published online by Nature Communications on Tuesday, June 1.
For still photos of the adopting red squirrel please follow this link: http://www.redsquirrel.ca/KRSP/Media.html