[MARMAM] New publication: Elevated Calf Mortality and Long-Term Responses of Wild Bottlenose Dolphins to Extreme Climate Events

Vivienne Foroughirad vjf5 at georgetown.edu
Thu Mar 11 18:58:07 PST 2021

Dear colleagues,

On behalf of all the co-authors we are pleased to announce our new
publication in the special issue of Small Cetacean Conservation: Current
Challenges and Opportunities in Frontiers and Marine Science.

"Elevated Calf Mortality and Long-Term Responses of Wild Bottlenose
Dolphins to Extreme Climate Events: Impacts of Foraging Specialization and

Janet Mann, Vivienne Foroughirad, Molly H. F. McEntee, Madison L. Miketa,
Taylor C. Evans, Caitlin Karniski, Ewa Krzyszczyk, Eric M. Patterson, John
C. Strohman and Megan M. Wallen

As demands for wildlife tourism increase, provisioning has become a popular
means of providing up-close viewing to the public. At Monkey Mia, Shark
Bay, Australia, up to five adult female Indo-Pacific bottlenose dolphins
(Tursiops aduncus) visit a 100 m stretch of beach daily to receive fish
handouts. In 2011, a severe marine heatwave (MHW) devastated seagrass and
fish populations in Shark Bay. Offspring survival declined precipitously
among seagrass specialists (dolphins that forage disproportionately in
seagrass habitat). As all provisioned dolphins at the site are seagrass
specialists, we examined how provisioned and non-provisioned seagrass
specialists responded to the MHW. Using 27 years of data we compare habitat
use, home range size, calf mortality, and predation risk between
provisioned and non-provisioned females and their offspring before and
after the MHW. Our results show that provisioned females have extremely
small home ranges compared to non-provisioned females, a pattern
attributable to their efforts to remain near the site of fish handouts.
However, weaned offspring (juveniles) born to provisioned females who are
not provisioned themselves also had much smaller home ranges, suggesting a
persistent maternal effect on their behavior. After the MHW, adult females
increased their use of seagrass habitats, but not their home range size.
Provisioned females had significantly lower calf mortality than
non-provisioned females, a pattern most evident pre-MHW, and, in the first
5 years after the MHW (peri-MHW, 2011–2015), calf mortality did not
significantly increase for either group. However, the ecosystem did not
recover, and post-MHW (2016–2020), calf mortality was substantially higher,
regardless of provisioning status. With few survivors, the impact of the
MHW on juvenile mortality post-weaning is not known. However, over three
decades, juvenile mortality among offspring of provisioned vs.
non-provisioned females did not statistically differ. Thus, the survival
benefits accrued to calves in the provisioned group likely cease after
weaning. Finally, although shark attack rates on seagrass specialists did
not change over time, elevated predation on calves cannot be ruled out as a
cause of death post-MHW. We discuss our results as they relate to
anthropogenic influences on dolphin behavioral plasticity and responses to
extreme climate events.

The full article is now available via:


Dr. Vivienne Foroughirad (*she/her*)
Postdoctoral Fellow
Department of Biology
Georgetown University
vjf5 at georgetown.edu
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