Behavior brief

Orcas splash to kill

Orcas hunting in a group
Image: Wikimedia commons, Wolfgang Hagele

When killer whales splash around in the water, it's not all for fun and games. linkurl:Research;http://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.2010.00453.x/abstract in Marine Mammal Science describes a hunting behavior in one group of orcas, dubbed "pack ice killer whales," in which the whales swim as a group toward a seal lying on a chunk of ice, pumping their tails in unison to create waves that wash the resting seal into the water where they can kill and eat it. While this behavior, first described in 1981, has been observed occasionally in the last 30 years, the current study describes 22 instances of wave-washing hunting in just 75 hours of observation, suggesting the technique may be more widespread than previously suspected. (Hat tip to linkurl:ScienceNOW;http://news.sciencemag.org/sciencenow/2011/04/slideshow-killer-whales-devise-l.html )Oxidative stress influences greenfinch personalitiesThough some remain skeptical of the idea of animal personalities, linkurl:growing evidence;http://www.the-scientist.com/2010/3/1/34/1/ suggests that dogs, cats, birds and even fish display meaningful and consistent individual differences in behavior among organisms. New linkurl:research;http://jeb.biologists.org/content/214/10/1732.abstract published in the Journal of Experimental Biology shows that greenfinches not only have variable personalities, but that such differences are reflected in the birds' levels of oxidative stress, which could be linked to variations in their metabolism, stress hormones, and lifespan.

Is this greenfinch, Carduelis chloris, bold or timid?
Image: Wikimedia commons, Ken Billington

When the researchers measured each bird's boldness, they found that the most timid birds, which took as long as 30 minutes to approach a new colored food, also had high levels of an oxidative stress marker, malondialdehyde, in their blood. Bolder birds, which investigated the new item in as little as a few seconds, had lower levels of the marker. However a test of curiosity, measured by interest in a new toy, had different results: the birds with the strongest reactions -- the most and least curious -- had the same amount of malondialdehyde, while birds with intermediate reactions had much higher levels. These two descriptions of personality potentially reflect different and complex approaches to information and food gathering, the authors wrote in their paper, and may predict how personality relates to physiology and survival in the wild.Orangutans spear fish with sticks

An orangutan hanging out by a pond -- maybe he's thinking about fishing
Image: Wikimedia commons, Nilfanion

Arboreal orangutans sometime take a break from their treetop habitats to explore the local ponds -- and perhaps catch a fish or two while they're there. In one day, anthropologist Anne Russon noted 17 instances of orangutans trying, sometimes successfully, to catch fish, occasionally poking them with sticks before immediately devouring them. She presented these details at a meeting of the American Association of Physical Anthropologists on April 14. While this is the first documentation of orangutan fishing, Russon told linkurl:Science News,;http://www.sciencenews.org/view/generic/id/72895/title/Gone_fishing,_orangutan-style the behavior has been observed in other primate species such as chimpanzees, macaques and baboons. Sex differences in dogs

Image: Wikimedia commons, Mdk572

When a small ball rolls behind a tree and reemerges as a large ball, humans immediately recognize the error -- objects don?t change their basic properties just because we can't see them. Testing this ability in dogs, researchers found that female dogs were better than male dogs at identifying such changes, according to linkurl:research;http://rsbl.royalsocietypublishing.org/content/early/2011/04/20/rsbl.2011.0287 published in Biology Letters online on April 27 -- females looked at the balls that emerged a different size nearly twice as long as those that stayed the same. This difference could be explained evolutionary by the greater need for females to be able to differentiate between her puppies and thus have better physical understanding, but cognitive biologist Corsun Muller has no evidence for this. However, this study does indicate that sex differences should be taken into account when doing animal studies, he told linkurl:ScienceNOW.;http://news.sciencemag.org/sciencenow/2011/04/female-dogs-arent-easily-fooled.htmlCity birds aren't bird-brained

Image: Flickr, linkurl:deadendmind;http://www.flickr.com/photos/deadendmind/3515269705/in/photostream/

While urbanization drives some species towards extinction, some birds are appear to be adjusting quite well to city life, such as linkurl:crows;http://www.youtube.com/watch?v=BGPGknpq3e0 that crack nuts by dropping them into traffic and linkurl:blue tits;http://www.bbc.co.uk/nature/life/Blue_Tit#p00by6vm that pierce aluminum foil tops of milk jugs to drink the rich cream. Animal ecologist Alexei Maklakov and his colleagues found passerine birds that were better at adapting to city life belonged to families with bigger brains. They published their linkurl:results;http://rsbl.royalsocietypublishing.org/content/early/2011/04/26/rsbl.2011.0341 in Biology Letters online on April 27. While brain size is generally not a good indicator of intelligence, the larger brains in these families may lead to "enhanced behavioral plasticity," Maklakov told linkurl:Discovery News,;http://news.discovery.com/animals/brainy-birds-city-urban-110427.html leading to their greater survival in cities, which "provide a variety of ecological opportunities that require changes in behavior in order to be exploited."
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[31st January 2011]*linkurl:Friends of a feather;http://www.the-scientist.com/news/display/57922/
[17th January 2011]