IMAGE: WIKIMEDIA COMMONS, WOLFGANG HAGELE
Orcas splash to kill
When killer whales splash around in the water, it's not all for fun and games. Research 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 ScienceNOW )
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
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 Science News, the behavior has been observed in other primate species such as chimpanzees, macaques and baboons.
Sex differences in dogs
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 research 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 ScienceNOW.
City birds aren't bird-brained
While urbanization drives some species towards extinction, some birds are appear to be adjusting quite well to city life, such as crows that crack nuts by dropping them into traffic and blue tits 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 results 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 Discovery News, leading to their greater survival in cities, which "provide a variety of ecological opportunities that require changes in behavior in order to be exploited."