The following article on killer whale attacks on humpback whales as discerned 
through rake mark scars has recently been published:

Steiger, G.H., J. Calambokidis, J.M. Straley, L.M. Herman, S. Cerchio, D.R. 
Salden, J. Urbán-R, J.K. Jacobsen, O. von Ziegesar, K.C. Balcomb, C.M. 
Gabriele, M.E. Dahlheim, S. Uchida, J.K.B. Ford, P. Ladron de Guevara-P, M. 
Yamaguchi and J. Barlow.  2008.  Geographic variation in killer whale attacks 
on humpback whales in the North Pacific: implications for predation pressure. 
Endangered Species Research 4:247-256.



ABSTRACT: We examined the incidence of rake mark scars from killer whales 
Orcinus orca on the flukes of humpback whales Megaptera novaeangliae throughout 
the North Pacific to assess geographic variation in predation pressure. We used 
3650 identification photographs from 16 wintering or feeding areas collected 
during 1990 to 1993 to determine conservative estimates in the percentage of 
whales with rake mark scarring. Dramatic differences were seen in the incidence 
of rake marks among regions, with highest rates on wintering grounds off Mexico 
(26 vs. 14% at others) and feeding areas off California (20 vs. 6% at others), 
2 areas between which humpback whales migrate. Although attacks are rarely 
witnessed, the prevalence of scars demonstrates that a substantial portion of 
animals are attacked, particularly those that migrate between California and 
Mexico. Our data also suggest that most attacks occur at or near the wintering 
grounds in the eastern North Pacific. The prevalence of attacks indicates that 
killer whale predation has the potential to be a major cause of mortality and a 
driving force in migratory behavior; however, the location of the attacks is 
inconsistent with the hypothesis that animals migrate to tropical waters to 
avoid predation. Our conclusion is that, at least in recent decades, attacks 
are made primarily on calves at the wintering grounds; this contradicts the 
hypothesis that killer whales historically preyed heavily on large whales in 
high-latitude feeding areas in the North Pacific.


The article can be downloaded for free from the publishers website:
http://www.int-res.com/articles/esr2008/4/n004p247.pdf

 

or from Cascadia Research:

http://www.cascadiaresearch.org/reports/Steiger-etal.2008.pdf

Gretchen H. Steiger

Research Biologist

Cascadia Research

Olympia, Washington

360.943.7325

 

_______________________________________________
MARMAM mailing list
MARMAM@lists.uvic.ca
https://lists.uvic.ca/mailman/listinfo/marmam

Reply via email to