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Learn how animal defenses were evolved

Posted on Feb 08 2014 | IANS

New York, Feb 8 : Why some animals use noxious scents while others live in social groups to defend themselves against predators?

This question of animals being either social or stinky led researchers to find out the answer through a comprehensive analysis of predator-prey interactions among carnivorous mammals and birds of prey.

"The idea is that we're trying to explain why certain anti-predator traits evolved in some species but not others," said Theodore Stankowich of California State University, Long Beach.

Stankowich, along with biologist Tim Caro and geographer Paul Haverkamp from University of California, Davis collected data on 181 species of carnivores, a group in which many species are small and under threat from other animals.

They ran a comparison of every possible predator-prey combination to create a potential risk value that estimates the strength of natural selection due to predation from birds and other mammals.

They found that noxious spraying was favoured by animals that were nocturnal and mostly at risk from other animals.

Living in groups was favoured by animals that were active during the day and potentially vulnerable to birds of prey.

According to Stankowich, this study breaks new ground in the methodology of estimating predation risks.

"Spraying is a good close-range defense in case you get surprised by a predator, so at night when you can't detect things far away, you might be more likely to stumble upon a predator," Stankowich said.

Conversely, small carnivores like mongooses and meerkats usually are active during the day which puts them at risk from birds of prey.

Living in a large social group means "more eyes on the sky" in daytime, when threats can be detected further away, added the study appeared in the journal Evolution.

The social animals also use other defenses such as calling out a warning to other members of their group or even mobbing together to bite and scratch an intruder to drive it away.

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