Elephant seal bulls are not exactly known for their gentle behavior towards other members of their species, especially during the breeding season. They don’t win any prizes as fathers either, because they don’t take care of rearing the pups in their harem (most of which are not their own anyway). But one specimen seems to be the famous exception to the rule, as it showed researchers a completely different behavior and saved a pup from drowning despite the high costs in energy expenditure.
It sometimes takes a good portion of luck for scientists making extraordinary observations. For Dr. Sarah Allen and Matthew Lau, it was a walk on the beach at Point Reyes National Seashore in California on a mild January day. The two staff members of the protected area administered by the US National Park Service were conducting an assessment of the northern elephant seal population on the beach. While doing so, they witnessed an elephant seal bull gently push a two-week-old cub from the waves back to the safety of the beach before it would drown. Such altruistic behavior by a bull had never been observed before and has now been published in the journal Marine Mammal Science.
A female elephant seal and her pup were suddenly hit by strong tidal waves on a stretch of beach. The cub, barely two weeks old, was caught by the strong current and pulled further into deeper water. “The weather on January 27 was sunny, mild and windless,” the team of authors writes in their paper. “We noted that the pup was unable to swim as it struggled to keep its head above water, calling.” The female kept calling out, attracting the attention of the bull of the associated harem. After a quick check, the big bull rushed into the water and picked up the young animal, which was now in around 3 meters of water and on the verge of drowning. “He positioned his body so that he was gradually and gently pushing the pup with his head and body while swimming towards shore. When waves drew back, he physically assisted the pup by providing shelter and an anchor with his body, and thus preventing it from being drawn out to sea again”, Allen and her co-authors describe the scenes. The mother then made more calls towards the bull and returned to a higher position and the bull let out its familiar roar before resting a little.
It is possible that the bull had not rescued his own pup, because females choose the best place to give birth to the previous year’s young every year and the turnover of bulls in such places is extremely high. In Point Reyes, the case is somewhat different, as previous genetic studies have shown that the animals are more often related to each other than in other places. And altruistic behavior within close relatives would be a possible explanation for the observation.
In any case, for the authors of the study, the bull’s behavior is the first documented case of altruism (voluntary, costly action to help another individual) by an elephant seal bull. “For an alpha male, this cost might be substantial because he would need to conserve energy while fasting for several months, defending his position against other males, and mating with many females,” explains the team of authors. But at the same time, the rescue operation could also have an advantage for the bull. Females remain in the harem and mate with the bull if they do not lose the young. That way, he at least secures his offspring the following year, even if the female elephant seal then decides to mate with another bull.
What remains for the bull in the whole story is not only the fact that he saved the life of a pup and thus created an advantage for his reproduction. He will also go down in the history of behavioral research with the work published.
Dr Michael Wenger, PolarJournal
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