When a monk seal hauls out on the beach with wounds on its back, the most common explanation is male-on-female aggression. That’s why earlier this month when a seal rolled onto the beach with a nasty wound on its back, the individual was suspected to be female. Too, the animal was tagged; however, the only visible characters on the very worn tag were “31.” That led to the conclusion the animal was female RF30 (with flipper tags F30 and F31).
However, on a closer look at the animal’s scars and tag in photographs, it was determined the monk seal was not F31. In fact, she wasn’t even a she. The wounded animal was, in fact, adult male RN30–with flipper tag N31. Subsequent photographs confirmed it.
While male-on-male aggression is rare, especially in the main Hawaiian Islands, it’s not novel. The behavior has been witnessed in the Northwestern Hawaiian Islands and is suspected to be related to skewed male-to-female sex ratios. The aggressors tend to be subordinate males ganging up on females. (Like we reported here.) But they can also gang up on adult dominant males.
According to this paper, high concentrations of subordinate males in an area of few females can lead to aggregate aggression. Also, “…much of the evidence gathered to date suggests that aggressive incidents may be more likely to result from a ‘numerical’ failure, where a male that is capable of exerting dominance over 1 or 2 competing males is overwhelmed by a larger number of competitors and is unable to prevent their access to a female.”
The paper shares one particular event: “At the onset of an aggressive onshore attack observed in 1985, an attending male defended a female from a succession of 4 male challengers that remained nearby. Eventually, one of the ‘defeated’ males made a second attempt, and as he fought the attending male, another male rushed in. The defending male rushed back towards the female, followed by all remaining males, and was quickly overwhelmed (Johanos & Austin 1988).”
Earlier this summer, a group of males was video’ed mobbing a female off Lehua, suggesting there may be many subordinate males present off Lehua and Niihau. It’s not known whether N30 is a dominant or subordinate male, but it’s clear he was attacked. Perhaps N30 got mixed up in something similar to the anecdote shared above. Earlier this year, he was observed competing with RN44 for RB00 when she was with PK1. He’s also been sighted at PMRF, a popular spot for seals heading to and/or returning from Niihau. In fact, he was sighted (with no wounds) at PMRF on July 30th. He was next sighted on Kauai’s north shore and reported to the Kauai Hawaiian Monk Seal Conservation Hui on September 4th–bearing the mobbing wounds.
These mobbing wounds can look pretty dramatic. But monk seals have an amazing ability to heal and already, N30’s wounds are healing.
Photo credit: Olry and Megonnell
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