Most Popular Posts
Categories
- Biodiversity (92)
- Climate change (172)
- Community-based conservation (81)
- Economics and conservation (136)
- Endangered species (211)
- Fresh water (48)
- Habitat (221)
- Invasive species (93)
- Marine (123)
- Monitoring (230)
- Restoration (150)
- Socio-political issues (176)
- Tools and technology (101)
Archives
- February 2010
- January 2010
- December 2009
- November 2009
- October 2009
- September 2009
- August 2009
- July 2009
- June 2009
- May 2009
- April 2009
- March 2009
- February 2009
- January 2009
- August 2008
- July 2008
- June 2008
- May 2008
- April 2008
- March 2008
- February 2008
- January 2008
- December 2007
- November 2007
- October 2007
- September 2007
- August 2007
- July 2007
- June 2007
- May 2007
- April 2007
- March 2007
- February 2007
- January 2007
Sep
15
2009
Killer whale declines may be driven by changes in salmon populations
As top predators, killer whales exert a strong influence on the rest of the food web. But now scientists have shown in Biology Letters that it can work the other way around: changes in a single prey species can cause killer whale populations to ebb and flow as well.
Killer whales can eat a wide variety of animals, but individual populations may focus on a narrow set of prey. The authors studied 25 years of data from two killer whale populations off the coasts of British Columbia and Washington State, which typically eat Chinook salmon. The whales’ numbers grew from 1974 until the mid-1990s, then suddenly started dropping. The two populations declined by 17 percent and 8 percent through 2001, when they began to recover.
The whales’ mortality rates corresponded closely to changes in Chinook salmon populations, which followed similar fluctuations in the mid-1990s and early 2000s, the researchers report. They speculate that the whales depended so heavily on Chinook salmon that they became more prone to sickness and death when the fish declined. Other killer whales that specialize in certain prey species may also have trouble switching to alternate food sources if that prey disappears, they say. – Roberta Kwok
Source: Ford, J., Ellis, G., Olesiuk, P., & Balcomb, K. (2009). Linking killer whale survival and prey abundance: food limitation in the oceans’ apex predator? Biology Letters DOI: 10.1098/rsbl.2009.0468
Image © sethakan, iStockPhoto.com
Filed Under Marine |
Email This Post
Did the number of whales in that part of the ocean decline because they died… or because they moved? When you can’t find your dog in your house, does that mean that it died, or maybe that it moved outside?
Hi Paul,
Thanks for your question. According to the paper, the whales were tracked based on photo-identification from natural markings. The authors say that these whales live in “stable societies… from which individuals rarely, if ever, disperse.”
Roberta