By Isabelle Burgun – Agence Science-Presse
Young beluga whales benefit from the sort of care normally associated with babysitting, just like little humans. These caring techniques are “allomaternal,” which means non-maternal infant care when it is performed by any group member other than the mother. So this care is carried out by females that aren’t the mother, but who act as the mother would act.
“We’ve noted behaviors in belugas which are very close to our own. We often say that it takes a village to raise a child, and that could well apply to these marine mammals,” says Jaclyn Aubin, doctoral candidate in the Department of Biological Sciences at the University of Windsor and the principal author of a recent study on the subject.
For her master’s thesis, the biologist followed beluga couples with the help of a drone, looking to film this little-known behavior. The beluga (Delphinapterus leucas) isn’t the only species of odontocete – cetaceans with teeth – that uses nannies: this practice has also been observed among dolphins and sperm whales.
In 2017 and 2018, Aubin was able to capture almost 1,800 observations in the Saint Lawrence River estuary. Perched on a platform constructed for this purpose in Sainte-Marguerite Bay, at the entrance to the Saguenay Fjord, she filmed the movement of young belugas accompanied by adults. This nanny behavior was observed in 17% of her videos.
Also observed in captivity, voluntary “babysitting” implies that there is a complex mechanism behind it. These “aunts” and other closely related females help the young to swim a little behind and to one side (in echelon) or under the tail of another whale – a position that seems to imply protectiveness, as it hides it from potential predators.
“The young, if they even know how to swim at birth, aren’t very good swimmers, and need the accompaniment of these females,” Aubin observes. She is also a researcher at the Groupe de recherche et d’éducation sur les mammifères marins (GREMM), a non-profit organization researching the behavior of whales in the Saint Lawrence.
The particular privilege of swimming in echelon requires the lead adult to spend a lot of energy. This raises numerous questions as to what motivates females to take care of children that are not their own. Is it a sort of maternity apprenticeship for younger females who will one day be mothers? Or is it simply because the young are too “cute” – a natural form of attraction for kids, as it is with we humans?
Aubin has looked in to these reasons and has discovered that adolescent belugas manifest very little interest in babysitting, compared to older females. Moreover, no matter what the “cuteness” of the young beluga, all ages benefit from this alloparental care.
Researchers are leaning towards an explanation involving an enlarged notion of parenthood and the concept of reciprocity. This helps foster a genetic disposition towards mutual assistance when the females eventually become mothers themselves. “It’s possible that there’s mutual aid and reciprocity, even if it’s tough to test. What we know is that there’s inter-female sociability, and that it seems normal for a half-sister or an aunt to care for a little one that isn’t theirs,” Aubin explains.
Belugas can live up to 60 and don’t reach sexual maturity until they are between 8 and 14. Females mature faster. Mature belugas mate every 3 years. Gestation lasts 14 months, and the young are born between June and September. They stay with the females and the juveniles for the first 10 years. Then the males join up with the adults when they are mature, whereas the females stay together.
Toxic algae, pollution, contaminants, disturbances linked to underwater noise… The beluga population in the Saint Lawrence Estuary is on the decline. Over the past 20 years mortality rates for newborns and females have been high. The beluga is a protected species under Canada’s Species at Risk Act.
A Question of Altruism?
Expending energy to take care of the descendants of another female “is something we see among primates, for whom mutual aid is practiced among individuals” says Fanie Pelletier, Professor of Biology at the Université de Sherbrooke. “This sort of parental apprenticeship is also found among emperor penguins, and it improves their reproductive success for those that practice it.” She adds that a preference for relations – sister, aunt, niece, etc. – caring for youngsters is already found in certain species, including the meerkat, a small burrowing mongoose found in southern Africa.
She thinks that the study provides interesting information on the association between members of a group when they teach the young swimming techniques. In reading the study’s four detailed hypotheses, this specialist in behavioral psychology wonders aloud about the authors’ ability to distinguish a mother from other adults.
“It’s very difficult to observe them, especially when it’s the pre-adult that initiates the behavior. Parental and allomaternal care form very complex behaviors to analyze, and it requires you to identify clear links between the different individuals. Not counting random chance, which is never completely absent, could the youth have mistaken another whale for its mother? We see that among ducks who follow another family’s siblings,” Pelletier says.
For a link to the original article: https://www.sciencepresse.qc.ca/actualite/2021/10/25/gardiennage-belugas-saint-laurent