Kin recognition and the ‘armpit effect’: evidence of self–referent phenotype matching

Abstract

In species with multiple paternity or maternity, animals may best assess their relatedness to unfamiliar conspeci¢cs by comparing their own phenotype(s) with those of unidenti¢ed individuals. Yet whether animals can recognize kin through self-matching is controversial. Because golden hamsters (Mesocricetus auratus) mate multiply and can produce multiply sired litters, they were tested for their ability to use selfmatching for kin recognition. Hamsters that were reared only with non-kin since birth responded di¡erentially to odours of unfamiliar relatives and non-relatives. Postnatal association with kin was not necessary for this discrimination. Prenatal learning was unlikely because of delayed production and perception of social odours. To our knowledge, this is the ¢rst demonstration that a vertebrate can use its own phenotype for kin-recognition purposes without prior experience with kin. By using itself as a referent, rather than its siblings or parents, a golden hamster may be better able to direct nepotism towards the most appropriate individuals. Kin discrimination via self-inspection may be especially important in nepotistic contexts (to identify most closely related conspeci¢cs), whereas inclusion of the phenotypes of close kin as referents may be favoured in mate-choice contexts (to identify all related individuals).

Genomic imprinting and the social brain

“…As the F1 mice had never been exposed to these maternal odours previously (all the animals were embryo transferred to foster mothers of a separate strain), the most parsimonious explanation for this behavioural parent-of-origin effect was that it was genetic in basis, and is therefore probably due to imprinted genes. Further investigations into the neurobiological basis of this behaviour suggested that this was not due to selfreferent phenotype matching (Mateo & Johnston 2000), as the urinary odours produced by the reciprocal F1 mice themselves were indistinguishable (Isles et al , 2002. Therefore, the action of this imprinted gene effect is most probably exerted via the neural systems controlling olfactory cue perception and/or information processing.…”

Germ-line chimerism and paternal care in marmosets ( Callithrix kuhlii )

“…Although the exact mechanisms of kin recognition are unknown in primates, baboons appear to be capable of recognizing paternal offspring, which may involve phenotype matching (18). Phenotype matching has been conclusively demonstrated to occur in at least one mammal species (19). If chimerism in marmosets involves more than hematopoietic tissues, then we predict differential parental behavior toward chimeric and nonchimeric infants and altered estimates of relatedness from those expected for nonchimeric mammals.…”

Preferences of newborn mice for odours indicating closer genetic relatedness: is experience necessary?

“…As a result, hamsters responded to odours of conspecifics, whether familiar or unfamiliar, in a graded fashion based on the degree of similarity with their own phenotype . Subsequent studies have also explored the simultaneous use of individual recognition and selfreferencing in hamsters (Mateo & Johnston 2000). In another cross-fostering study in which pups from two species of wild mice (Mus spicilegus and Mus musculus)…”