A Male Grey Seal May Have Commited 'Fatal Sexual Interaction' With 11 Harbour Seals
Over a span of 41 days in Winter 2018-2019, eleven dead female harbour seals washed up along a confined stretch of Germany's North Sea shoreline. Curiously, all were pregnant or had recently been pregnant, and six had lacerations to the genitals. All apparently died of septicemia, an infection of the blood, in this case by bacteria. DNA extracted from the vaginal tracts of the deceased seals revealed the apparent perpetrator of the killings: a bull grey seal.
In the animal kingdom, sex isn't always consensual. Sexual coercion is widespread and takes a variety of forms. And, as the present case elucidates, it doesn't always occur between members of the same species.
Grey seals and harbour seals may be closely related, but grey seals are vastly larger. Male grey seals can weigh more than 600 pounds while female harbour seals weigh closer to 200. During sex, such a size disparity can be deadly. Given the DNA evidence, the researchers suspect that at least one male grey seal – likely a large juvenile – attempted to forcibly copulate with unreceptive female harbour seals, inflicting physical trauma and lacerations upon the victims which subsequently resulted in bacterial infection and death. The killings coincided with grey seals' breeding season in the North Sea.
"The present study is the first one reporting fatal interspecific mating attempts of at least one male grey seal with pregnant harbour seals in the German Wadden Sea. It remains unclear if the described cases are an exception caused by one individual on a local scale," the researchers wrote.
Source: Rohner, S., Hülskötter, K., Gross, S. et al. Male grey seal commits fatal sexual interaction with adult female harbour seals in the German Wadden Sea. Sci Rep 10, 13679 (2020). https://doi.org/10.1038/s41598-020-69986-w