What's killing killer whales?
Orca report covering a decade of necropsies identifies threats

Date:
December 3, 2020
Source:
University of British Columbia
Summary:
Pathology reports on more than 50 killer whales stranded over nearly
a decade in the northeast Pacific and Hawaii show that orcas face a
variety of mortal threats -- many stemming from human interactions.



FULL STORY ========================================================================== Pathology reports on more than 50 killer whales stranded over nearly
a decade in the northeast Pacific and Hawaii show that orcas face a
variety of mortal threats -- many stemming from human interactions.


==========================================================================
A study analyzing the reports was published today in the journal PLOS
ONE. The study findings indicate that understanding and being aware
of each threat is critical for managing and conserving killer whale populations. It also presents a baseline understanding of orca health.

The study was conducted by a team of marine mammal and orca specialists
led by the British Columbia Ministry of Agriculture and coordinated
through the SeaDoc Society, a Washington-based program of the University
of California, Davis' School of Veterinary Medicine. The lead author,
Dr Stephen Raverty, and coauthor, Dr John Ford, are adjunct professions
at the University of British Columbia Institute of Oceans and Fisheries
and Department of Zoology, respectively.

The whales include those from healthy populations as well as endangered species, such as the southern resident whales regularly sighted off the
coasts of British Columbia, Washington and Oregon.

Of 52 whales stranded between 2004 and 2013, causes of death were
determined for 42 percent. For example, one calf died from sepsis
following a halibut hook injury. Another starved from a congenital
facial deformity. Two whales died from the blunt force trauma of vessel strikes. Additional causes of death include infectious disease and
nutritional deficiencies.

'We can do better' Despite there being no singular common cause of death,
the study found a common theme: Human-caused deaths occurred in every
age class -- from juveniles to subadults and adults.

"In British Columbia, we lost nine southern resident killer whales:
2 adults, 2 subadults and 1 calf died from trauma; one was a confirmed propeller strike, with one adult and two subadults from suspected ship strikes," said lead author Stephen Raverty, a veterinarian pathologist
with the BC Ministry of Agriculture and adjunct professor at UBC's
Institute for the Oceans and Fisheries. "One of these iconic species
passed away from an infection secondary to satellite tagging. Another
death was due to natural causes and the other two undetermined. Half of
the southern killer whale deaths identified in this study were caused
by human interactions." "Nobody likes to think we're directly harming animals," said co-author and SeaDoc Society Director Joe Gaydos, a
wildlife veterinarian with the Karen C.

Drayer Wildlife Health Center in the UC Davis School of Veterinary
Medicine.

"But it's important to realize that we're not just indirectly hurting
them from things like lack of salmon, vessel disturbance or legacy
toxins. It's also vessel strikes and fish hooks. That humans are directly killing killer whales across all age classes is significant; it says
we can do a better job." In 2004, Raverty and Graydos co-developed a standardized killer whale necropsy protocol. Revised in 2014 with help
from Judy St. Leger, a pathologist working for SeaWorld, this guide
helped improve examinations of deceased whales.

"The results from systematic necropsies of dead killer whales in this
review is unique and will establish critical baseline information to
assess future mitigation efforts," Raverty said. "This work contributes
to a better understanding of the impacts that ongoing human activities and environmental events have on killer whales." The authors acknowledge the report is an incomplete picture of orca health and mortality. Necropsies
can only be performed on whales found in an adequate state to receive
them, and even then, the cause of death cannot always be determined. But
the report offers one of the most comprehensive looks yet at the multitude
of human and environmental threats affecting killer whales and can help
inform strategies to better protect them.


========================================================================== Story Source: Materials provided by University_of_British_Columbia. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Stephen Raverty, Judy St. Leger, Dawn P. Noren, Kathy Burek
Huntington,
David S. Rotstein, Frances M. D. Gulland, John K. B. Ford,
M. Bradley Hanson, Dyanna M. Lambourn, Jessie Huggins, Martha
A. Delaney, Lisa Spaven, Teri Rowles, Lynne Barre, Paul Cottrell,
Graeme Ellis, Tracey Goldstein, Karen Terio, Debbie Duffield,
Jim Rice, Joseph K. Gaydos.

Pathology findings and correlation with body condition index in
stranded killer whales (Orcinus orca) in the northeastern Pacific
and Hawaii from 2004 to 2013. PLOS ONE, 2020; 15 (12): e0242505 DOI:
10.1371/ journal.pone.0242505 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/12/201203173446.htm

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