April 11, 2002

Researchers Study Animal Recognition of Kin

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Prof. Robert Johnston, psychology, and his fellow researchers have found that many animals such as hamsters and other rodents can recognize their kin in a matter of seconds. Their findings have been published in journals including Animal Behaviour and Proceedings: Biological Sciences, a journal of The Royal Society, Britain’s national academy of science.

Although there is still little known about the sense of smell, the Johnston lab is trying to find the answers to the mysteries of olfactory communication and how it relates to social recognition and memory for individuals and kin.

Recognition

Kin recognition is important in that an animal may employ a variety of different behaviors depending on if the other animal is kin or not. Jill Mateo, Cornell psychology researcher in Johnston’s lab, has found that Belding’s ground squirrels (Spermophilus beldingi) are nepotistic and show preferential treatment toward their kin.

“The squirrels may risk their lives for kin by giving risky alarm calls to warn off predators, and as a result are twice as likely to be eaten. But they only exhibit this costly behavior for close relatives because by helping them, they save their own genes,” Mateo said. In addition, the Belding’s ground squirrels show cooperative defense of territories to prevent infanticide.

Helena Yu ’03, an undergraduate working in the Johnston laboratory, adds, “This is important because animals use recognition to establish dominance hierarchies, mate choice and all these other things that are key to their survival.”

Johnston described recognizing an individual using the sense of smell by giving an analogy to recognizing a face.

“Although there are many different elements in a face, you see the whole image and look at the relationship between the individual parts to recognize a face. This is the same thing for odors but the elements are individual chemical compounds. Each individual of the same species has the same chemical compounds but has different ratios of each compound and consequently a distinct odor,” Johnston said.

Odors

In the case of the Belding’s ground squirrels, they produce two odors that can be used as kin-labels, or cues that are more similar among kin than non-kin. One kin label, secretions from the oral gland, is detected by “kissing” among the squirrels. They are also known to secrete another kin-label from their dorsal gland by “twist marking” on the ground, a stick or a rock.

Johnston and Mateo have also shown how hamsters can distinguish between kin and strangers by “self-referent phenotype matching,” commonly known as the “armpit effect.” This mechanism is used to compare other animals’ odors to their own and discriminate between strangers and unfamiliar kin. “Theoretically, the best way to distinguish between your relatives and strangers is by comparing them to your own characteristics. This is extremely difficult to prove but we have best evidence for the armpit effect,” Johnston said.

Johnston and Mateo took newborns and, within a few hours of birth, cross-fostered the animals. When they became adults, the animals were tested to see if they could recognize their real kin and foster kin. Results showed that they could distinguish between their relatives and non-relatives, evidence for self-referent phenotype matching.

Tests

In addition, the researchers ran other laboratory tests where the hamsters showed differential treatment of relatives and non-relatives. They used behavioral assays, more specifically, scent marking behaviors, to demonstrate kin recognition. Johnston and Mateo found that the hamsters used scent marking for aggressive behaviors and sexual advertisements toward non-kin more than toward kin.


Archived article by Joann Kang