The ability to recognize individuals to which one is genetically related. This is often the result of early experience. For example, Belding's ground squirrels (Citellus beldingi) are born underground, but mother and offspring do not learn to recognize each other until the young emerge above ground at 3½ weeks old. Only then will there normally be any chance of confusion. Ground squirrels that are cross-fostered in nature (raised by a foster family following the death of their mother) treat their foster family as their own. This occurs only if the cross-fostering occurs before the squirrels are weaned and emerge above ground. Underlying this imprinting effect there may also be a genetic effect. If squirrel pups are reared apart and then tested together, siblings are less aggressive than unrelated individuals.
Most ground squirrel litters are fathered by more than one male, and littermates may be full siblings or half siblings. Observations in nature show that female squirrels are more altruistically inclined towards their full siblings than their half siblings. The ability of the female to make this discrimination must be due to some kind of phenotypic matching, an ability to compare one's own phenotype with that of others.
Subjects: Evolutionary Biology — Zoology and Animal Sciences.