Animals have personalities too—and some animal couples raise their young better based on how well their personalities match.
Greylag geese, which mate in long-term monogamous relationships, have better success hatching chicks if their personalities are a good match, according to a new paper in the journal Animal Behavior.
This matching of partner personalities allows the pair to coordinate more successfully when incubating their eggs, leading to increased thermal stability and protection from predators.
"Like in humans, the personality of both parents and their similarity in personality traits can influence their success as parents," study co-author Lauren Common, a Flinders University Ph.D. candidate now based at the University of Vienna, said in a statement.
"Successful pair bonds where partners were similar in their boldness, mainly by responding to risky situations in the same way, can have higher hatching success. This bold parenting style can lead to consistency and responsiveness, which can result in successful reproductive output and survival of young and fledgling success."
Greylag geese are native to Europe and Asia, and are monogamous, often pairing for life. They nest in dense reeds, on islands, or in open areas, with the female laying 4 to 6 eggs, and both parents protecting and raising the young. Between 14 and 20 percent of these geese pairs are homosexual, and birds whose heterosexual mate has died subsequently pair up with a member of the same sex over half the time.
In the paper, the researchers describe how they studied over 100 captive greylag geese across three breeding seasons, measuring their personalities, how many eggs they laid, how many chicks they hatched, and how many of those chicks made it to adulthood.
The geese were measured for certain personality traits—activity, boldness, and aggression—using special behavioral tests.
"Animal personality was once considered a figment of human imagination and, worse, anthropomorphism," study co-author Sonia Kleindorfer, a professor at the University of Vienna and founder of the BirdLab at the College of Science and Engineering at Flinders University, said in the statement. "This study adds to a growing body of work showing that animals such as greylag geese have consistent individual differences in behavior, also called personality," she says.
"But more than that, personality traits in animals can be linked to successful love matches and reproductive success. Therefore, these traits may be targets of natural and sexual selection."
They found that individual geese reliably tested for one of these traits, however, the geese didn't appear to take personality into account when choosing a mate. If the two geese both had the same level of boldness, the researchers found that they had better hatching success than those who were mismatched. This same trend was not seen for clutch size or fledging success, however.
"In species with biparental care and monogamy, reproductive output and success may be influenced not only by the personality of each individual but also the behavioral compatibility of the pair," Kleindorfer said. "This kind of pairing in greylag geese is linked to their well-developed cognitive capacity and social awareness and individuals consistently differ in personality traits such as boldness, aggressiveness, sociability and other behavioral traits."
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References
Common, L. K., Katsis, A. C., Frigerio, D., & Kleindorfer, S. (2024). Effects of assortative mating for personality on reproductive success in greylag geese, Anser anser. Animal Behaviour. https://doi.org/10.1016/j.anbehav.2024.08.004
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