[MARMAM] New publication: Long-term associations among male sperm whales

Hayao Kobayashi physeter0809 at gmail.com
Fri Jan 8 08:24:20 PST 2021

Dear MARMAM Readers,

My co-authors and I are pleased to announce the publication of our article:

Kobayashi H, Whitehead H, Amano M (2020) Long-term associations among male
sperm whales (*Physeter macrocephalus*). PLoS ONE 15(12): e0244204.

Little is known about the social structure of male sperm whales (*Physeter
macrocephalus*) after they leave their natal units. While previous studies
found no evidence for preferred associations among males, the observation
of mass-strandings consisting exclusively of males, suggest that they have
strong social bonds. To investigate the social associations among male
sperm whales, we used half-weight index of association, permutation tests
and standardized lagged association rate models on a large
photo-identification database collected between 2006 and 2017 in Nemuro
Strait, Japan. Our results suggest that while male sperm whales are not as
social as females, they do form long-term associations, have preferred
companionship, and forage in social proximity to each other. The
best-fitting model to the standardized lagged association rate showed that
associations among males last for at least 2.7 years and as most males
leave the area after 2 years, associations may last for longer. Twenty
dyads were observed associating over more than 2 years, for a maximum 5
years. One dyad was observed associating on 19 different days and clustered
on 7 different days. Male associations may function to enhance foraging or
to fend off predators. Such relationships seem to be adapted to a pelagic
habitat with uncertain resource availability and predation pressure.

The open-access article can be downloaded from

Kind regards,
Hayao Kobayashi

Hayao Kobayashi

PhD. candidate
Graduate School of Fisheries and Environmental Sciences,
Nagasaki University
1-14, Bunkyo-machi, Nagasaki 852-8521, JAPAN
Marine Mammal Research Lab.

Mail:physeter0809 at gmail.com
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