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891.
Christian Ramp Wilhelm Hagen Per Palsbøll Martine Bérubé Richard Sears 《Behavioral ecology and sociobiology》2010,64(10):1563-1576
Analyses of social structures in baleen whales are rare, and so far, they are thought to consist of mostly short and unstable
associations. We investigated the association patterns of individual humpback whales from a summer feeding aggregation in
the Gulf of St. Lawrence from 1997 to 2005. Photo-identified animals were sexed using genetic methods and were grouped into
five categories: juvenile males/females, mature males and lactating/non-lactating females. We calculated half-weight association
indices within and between the groups and found that 45% of the observation showed single animals and another 45% small groups
(two to three) consisting mainly of mature animals besides lactating females. Using permutation tests, we found evidence for
long-term associations between mature males and non-lactating females as well as among non-lactating females. Standardised
lagged association rates revealed that these male–female groups disassociated quickly over about 2 weeks, whereas associations
increased again towards the beginning of the breeding season. Non-lactating females of similar age engaged in multi-seasonal
stable pairs for up to six consecutive feeding seasons; no mature male–female association was observed in consecutive years.
The females with the most stable and long-term associations also had the highest reproductive output. While the risk of predation
could not explain these long-term bonds, feeding cooperation seemed the most plausible explanation for group forming behaviour
during the summer months. 相似文献
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Michael P. Harris Doug Beare Reidar Toresen Leif Nøttestad Matthias Kloppmann Hendrik Dörner Kevin Peach Derek R. A. Rushton Judy Foster-Smith Sarah Wanless 《Marine Biology》2007,151(3):973-983
Since the early 2000s routine fish surveys have recorded increasing numbers of snake pipefish, Entelurus aequoreus, in the northeast Atlantic. Fishermen and divers have also commented on this increase and pipefish have started to appear
in the diet of seabirds and other marine predators. This paper collates information from these diverse sources and assesses
the current status of snake pipefish. We found compelling evidence of a dramatic increase in the abundance of snake pipefish
starting around 2003 and continuing up to the present (2006) and a range expansion northwards to Spitzbergen and the Barents
Sea. Since 2004 snake pipefish have been increasingly recorded in the diet of many species of seabird breeding in colonies
around the coast of the UK, and in Norway, Iceland and the Faeroe Islands. Information on the nutrient value of snake pipefish
is currently lacking but their rigid, bony structure makes them difficult for young seabirds to swallow and there are numerous
records of chicks choking to death. Thus, in the case of avian predators during the breeding season, it appears unlikely that
increased abundance of snake pipefish will provide a useful alternative prey. The reason for the rapid and dramatic increase
in numbers of snake pipefish is currently unclear but such events are characteristic of marine ecosystems and will almost
certainly have an effect on food web dynamics. 相似文献
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