[MARMAM] New publication on the sex life of harbor porpoises

Bill Keener bill.keener at comcast.net
Mon Nov 19 15:47:26 PST 2018

Dear MARMAM community,

On behalf of my co-authors, I’m pleased to announce the publication of our article:

The Sex Life of Harbor Porpoises (Phocoena phocoena): Lateralized and Aerial Behavior

William Keener, Marc A. Webber, Isidore D. Szczepaniak, Tim M. Markowitz and Dara N. Orbach. Aquatic Mammals, Vol 44, Issue 6, 2018.


The Golden Gate Bridge in San Francisco Bay provides a non-invasive aerial platform where harbor porpoises (Phocoena phocoena) can be observed mating. We photographed 144 mating events over an eight-year period (2010 to 2018) occurring in all seasons. The mating habits of free-ranging male harbor porpoises are systematically described, a first for any member of the family Phocoenidae. The males’ rapid sexual approaches toward females were characterized by high energy and precision timing as males rushed to contact females surfacing to breathe. Males always attempted to copulate by positioning their ventral sides on the females’ left side. This extreme laterality in sexual approach has not been reported for any cetacean. Males approached females with force and speed that often resulted in male aerial behaviors (69% of mating attempts). These behaviors, observed exclusively in mating contexts, included leaps and splashes that counter the species’ reputation for inconspicuous behavior. Males also displayed their ventrum or penis toward females without attempting to copulate. The penis was visible in 60% of the 96 mating events for which the ventrum could be observed, with intromission confirmed in one event. Males always initiated mating and approached lone females in 62.5% of mating events. Calves accompanied females during 25% of mating events. Calves were temporarily separated from their mothers by the approaching males in approximately half of these events. Additional adults were observed in 12.5% of groups, although no male-male interactions were observed. Our findings on the unique mating pattern exhibited by male harbor porpoises validate some predictions made about their behavior based on their reproductive biology and anatomy. The data support the hypothesis that males compete primarily by sperm competition and not contest competition.

The full article, is available at https://doi.org/10.1578/AM.44.6.2018.620 and is open access as part of a special issue of Aquatic Mammals in honor of Bernd Wursig. To see the video clips of mating behavior, go to the online supplemental material page: https://www.aquaticmammalsjournal.org/index.php?option=com_content&view=article&id=10&Itemid=147 https://www.aquaticmammalsjournal.org/index.php?option=com_content&view=article&id=10&Itemid=147

To request a PDF copy, please email me at bill.keener at comcast.net mailto:bill.keener at comcast.net


Bill Keener
Golden Gate Cetacean Research

Corte Madera, California, USA
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