Examination
of two dead gray whales in northern Puget Sound on 28 and 29 April, 2009 reveals
possible traumatic injuries
Summary
by John Calambokidis and Jessie Huggins, Cascadia Research in consultation with
Central Puget Sound Marine Mammal Stranding Network, Whatcom Marine Mammal
Stranding Network, Washington Department of Fish and Wildlife and National
Marine Fisheries Service
Two gray whales were found dead
in northern Puget Sound in the past week and have been examined in the last two
days. While there are some similarities in the timing and some other aspects of
these deaths, they do not appear otherwise related. Overall these represent the
3rd and 4th dead gray whales found this year in Washington
State. This is still below the overall average number of deaths for a year and
well below what occurred during some of the peak years in gray whale deaths.
With close to 20,000 gray whales migrating past Washington and several dozen
coming into Puget Sound, some level of mortality has been normal.
Unlike most of the past gray
whales deaths, however, these animals appeared to have been in much better
nutritional condition and had not starved to death. The Birch Bay whale had very
high levels of fat on its body and the Camano whale had large amounts of feed in
its stomach. These indicate these whales had not died of a long term
debilitating condition but something more sudden. Both showed signs of traumatic
injuries although we are awaiting further tests to be sure these were the
ultimate cause of death. Whales are known to die from ship and boat strikes and
these injuries can sometimes be hard to spot especially once decomposition has
set in.
Additional details on these two
whales are summarized below:
Birch
Bay gray whale stranding
On 28 April, 2009, biologists
from Cascadia Research, Washington Department of Fish and Wildlife, and
volunteers from the Whatcom Marine Mammal Stranding Network examined a 27 foot
juvenile gray whale near Birch Bay, in Whatcom County. The 1-2 year old male was
found floating on 27 April and was towed by the WMMSN staff and BP Refinery to a
suitable location for examination the following day.
The animal was in good body
condition with a thick, oily blubber layer, unlike the emaciated young gray
whales we typically find stranded during this time of year. However, despite
good overall nutritional condition it did not appear to have eaten for a couple
of days prior to death. There was
evidence of both infection and trauma, although the source of the trauma is
unknown and it is possible that the two conditions are linked. Precise cause of
death could not be determined from the field examination, but many samples were
collected for histopathology, genetics, contaminants and disease screening and
will be analyzed in the coming weeks and months.
Camano
Island gray whale stranding
On 29 April, 2009, volunteers
from Central Puget Sound Marine Mammal Stranding Network met biologists from
Cascadia Research and Washington Department of Fish and Wildlife to examine a
large gray whale that was first seen floating off of Camano Island on 26 April,
2009. The 41 foot whale was towed on 28 April by Deception Pass Tours to a
stretch of beach provided by the Whidbey Island Naval Air Station for a necropsy
the next afternoon.
The adult male was moderately
decomposed and in fair body condition. Significant findings from this
examination included a large amount of blood in the body cavity, bruising in
some areas of the blubber layer and in some internal organs, and a stomach full
of recently ingested prey. These findings are suggestive of blunt force trauma,
likely caused by a collision with a large ship.
Researchers
prepare to examine dead whale in Birch Bay, 29 April 2009
Measurements being taken of
Camano Is. Whale on 30 April 2009