Dear Colleagues,
On behalf of the Orca Behavior Institute, I'm pleased to announce our latest publication in PeerJ:
2018. Increased presence of mammal-eating killer whales in the Salish Sea with implications for predator-prey dynamics. PeerJ 6:e6062 https://doi.org/10.7717/peerj.6062
Abstract: The inland waters of Washington State and southern
British Columbia, collectively known as the Salish Sea, comprise
key habitat for two regional populations of killer whales (Orcinus
orca): the mammal-eating West Coast Transients and the
endangered fish-eating Southern Residents. These two populations
are genetically distinct and may avoid each other. Transient
killer whale usage of the Salish Sea has been previously assessed
over two seven-year time periods, showing an increase from 1987 to
2010. We documented a continued significant increase in
mammal-eating killer whale presence in the Salish Sea from 2011 to
2017, with intra- and inter-annual variability and with record
sightings in 2017. This continued increase, likely in response to
abundant marine mammal prey, is related to both a growing
population and an increase in the number of West Coast Transients
visiting the area. Additionally, a negative binomial regression
shows that absence of Southern Residents is correlated to
transient presence. Finally, both populations of killer whales
have been linked to regional harbor seal populations; harbor seals
are salmonid-eating competitors of the Southern Residents and are
prey for the mammal-eating transients. With Southern Residents
listed as endangered, culling harbor seals has been proposed as a
measure to help in their recovery. With this in mind, we developed
an energetic model to assess the minimum number of harbor seals
consumed by transient killer whales. Using the actual number of
whales present in each age-sex class for each day of the year, we
estimate that, at a minimum, transients in the Salish Sea consumed
1090 seals in 2017. This is more than 2% of the 2014 estimated
harbor seal population the Salish Sea. The population controlling
effects of transient killer whale predation on harbor seals should
be considered when evaluating any pinniped management actions in
the Salish Sea.
Full paper available open access here: https://peerj.com/articles/6062/
Best regards,