1BIOENERGETIC CHANGES FROM 1986 TO 2001 IN THE SOUTHERN RESIDENT KILLER WHALE POPULATION
of killer whales (Orcinus orca) has decreased from a high of 98 individuals to a low of 79 animals, which is a reduction of 20 % of the entire population in only 6 years (pers. obs. 2002, Bain 2002). While at this point we do not understand the entire web of causation for this decline, several contr...
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| Format: | Text |
| Language: | English |
| Published: |
2002
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.612.7469 http://www.earthisland.org/immp/orca/docb6.pdf |
| Summary: | of killer whales (Orcinus orca) has decreased from a high of 98 individuals to a low of 79 animals, which is a reduction of 20 % of the entire population in only 6 years (pers. obs. 2002, Bain 2002). While at this point we do not understand the entire web of causation for this decline, several contributing factors have been reported, such as prey availability and the decrease in salmon stocks, the exposure to toxic chemicals and in particular PCB’s (Ross 2001, Dahlheim et.al. 2000), as well as the increase in commercial and private vessels mostly for whale watching over the last 10 years (Bain 2002). Studies determining the impact of vessel traffic on different whale species have shown that the animals change their swimming behavior and/or avoid boats (Bauer et.al. 1986, Fraker et.al. 1995). In the northern resident community of killer whales it was shown that the whales swam significantly faster, increasing the angle between successive dives or choosing less direct paths in their swimming direction in order to avoid boats when vessels were in the vicinity (Williams et.al. 2002, Kruse 1991). These changes in behavior were determined with only one boat situated a distance of 100 m from the closest whale. This distance (100 m) has been the suggested distance any boat should be from the closest whale in order to minimize disturbance (Johnstone Strait Killer Whale Committee 1996). Trites and Bain (2000) estimated theoretically that the male killer whales added an extra 13 % in traveling distance when followed by boats. In order to measure physiological data on the actual energy expenditure in killer whales potentially increased due to boat traffic, a study which had been |
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