While the changing climate may be leading to more divorce among black-browed albatrosses, researchers have recently found evidence of a more anthropomorphic reason for the split-ups among wandering albatrosses: personality. It turns out, shy guys finish last.
Ruijiao Sun, an MIT-WHOI Joint Program PhD. student, along with WHOI associate scientist with tenure Stephanie Jenouvrier and colleagues from the University of Liverpool and Centre National de la Recherche Scientifique (CNRS), published a study in September, 2022 in the journal Royal Society Biology Letters suggesting that the chance of divorce among wandering albatross can be influenced by how shy, or bold, male birds are. Shy males, according to the study, tend to avoid confrontation so when an albatross “intruder” comes along vying for their female partner’s affection, the shy bird may give up on the relationship and leave the nest. The study found that the shyest male birds were up to twice as likely to divorce as their more aggressive rivals.
To establish a link between personality and divorce, the researchers combined a whopping 70 years of albatross demographic data from a colony on Possession Island in the southern Indian Ocean with more recent “personality” data collected there during breeding seasons since 2008.
The demographic data has been collected during site visits to the nests during each breeding season since the 1950s to determine the identity of parent pairs and their breeding success. Newly born chicks are banded with unique ring number during these site visits.
Measuring albatross personality was more complicated. Researchers had to construct a pole-like track from carbon fiber on which they could glide a foot-high inflatable blue cow—named Betsy—toward the birds. A tiny wide-angle camera was mounted on the cow’s horns to capture the albatross reactions to this object they had never seen before. It was a brilliant setup for a bird personality experiment—at least until Betsy became a target for one of the more aggressive albatrosses.
“During one of the measuring seasons, Betsy got ripped apart by a really bold albatross,” says Sun.
Albatross reactions were scored from 0-4, with lower scores indicating shyness (i.e., little or no reaction) and higher scores indicating boldness (i.e, standing up and calling out). Once the scores were synthesized with the demographic data, the researchers were able to determine that the shyer males—those that showed little or no response—had higher divorce rates and were most likely being forced out of their pair bonds by homewrecking males. The researchers were surprised by the results.
“At the beginning, we thought bold individuals in the colony would have higher divorce rates because we consider divorce as a risky behavior,” says Sun. “If they were bold, we figured they may divorce more often so they can gain more breeding opportunities with different partners. The fact that it was the shy ones getting divorced was opposite to what we were expecting.”
Jenouvrier, Sun’s advisor and senior author of the study, points out that divorces in the colony did not appear to be adaptive—whereby a female leaves her partner to find a better mate for better breeding success.
“Sometimes birds split up to find a better mate and raise more offspring,” Jenouvrier explains. This is called adaptive divorce and has been observed in many bird species. However, in wandering albatrosses, individuals do not have more chicks after a divorce and females are unlikely to benefit from seeking new mates.”
Rather, the couples seemed to experience what Jenouvrier calls “forced divorce”—when a male intruder steals a female away from her timid male partner. The females weren’t actually looking to ditch their shy guys, and personality didn’t play a role in their decision to move on to a bolder bird.