Belding’s ground squirrel (Spermophilus beldingi) is one of the interesting species of mammals that recognizes its kin and treats them with special deference, a concept know as nepotism, . In fact, there seems to be a positive correlation between the cooperation between two individuals and their degree of relatedness (how related they are) in Belding's ground squirrel (Sherman 1980 qtd. in Sherman 1981). Several of the squirrels’ behaviors can be considered nepotistic, specifically cooperative nesting territory defense and alarm calling. Interestingly, only females show nepotistic behaviors.

Recognizing Kin:

In order to show favoritism towards their kin, S. beldingi must be able to recognize which individuals are their kin. The prominent theory behind kin recognition in S. beldingi is that they are able to recognize the scent of their kin by phenotypic matching (Holmes 1986). To match phenotypes, individuals compare their own phenotype, or that of their relatives (assumedly imprinted during their early life) to that of the individual they encounter. If the encountered individual’s phenotype matches the template phenotype, then this individual may be kin (Holmes 1986). Interestingly, Holmes determined that siblings are less likely to be agonistic towards each other than non-siblings, even if they are reared apart, because the squirrels can use their own phenotype as a template. In addition, juveniles will behave less agonistically towards each other if they have been raised with each other’s siblings (if they are raised with individuals that are genetically related to the individual they are introduced to). Therefore, both genetic relatedness and rearing can affect kin recognition in S. beldingi, but genetic relatedness has the greatest effect. In nature, females may also learn their sister's phenotypes as templates to determine relatedness of unfamiliar females (Holmes 1986), because they are raised in the same burrow and because they interact (play and sleep) mainly with their relatives after emergence from the natal burrow (Holmes 1994).

When a Belding’s ground squirrel compares its phenotype to that of another individual, it is comparing smells. Belding's ground squirrels have a very noticeable odor. Turner detected that they have anal and dorsal scent glands that leave a "pungent" odor in the dust bathing areas (Turner 1972). The odors produced by S. beldingi are excreted from oral and dorsal glands change based on genetic relatedness (other smells, such as those from the anal glands and from the urine do not change with relatedness). All the different odors are unique for each individual (Mateo and Johnston 2000). Thus, each individual has its own repertoire of scents that others can use to recognize it. Significantly, Mateo and Johnston discovered that juvenile S. beldingi are not be able to differentiate between the scents of previously familiar and non-familiar individuals after hibernation, but they are always able to differentiate between the scents of kin and non-kin (2000).

Why is it important to recognize other individuals?

Being able to recognize other individuals is extremely important to the Belding’s ground squirrel. First, females will be able to recognize their sisters, non-litter mate sisters (1/2 sisters born in different litters), mothers, and daughters. This will allow them to know who to behave nepotistically towards when defending nesting territories and alarm calling. Females will also be able to recognize males that have a history of winning fights, and will thus be able to breed with the most successful male (Mateo and Johnston 2000).

Cooperative Nesting Territory Defense:

Female Belding's ground squirrels have evolved the interesting behavior of assisting their closely related female kin (mothers, daughter, litter mate sisters, and non-litter mate sisters) to other protect newborn offspring from infanticide. To do so, they chase other conspecifics out of their kin's territories and assist those that are being chased. Interestingly, the very age groups that are most likely to commit infanticide, young males and non-resident females, are chased the most (Sherman 1981b). On the other hand, females do not chase each other from their respective territories and do not fight when they come into contact. In addition, closely related females will occasionally share food and shelter (Sherman and Morton 1979). Mothers and daughters are more cooperative than siblings, and litter mate sisters are more cooperative than non-litter mate sisters. In fact, non-litter mate sisters only help in chases and fights. On the other hand, grandmothers and granddaughters, aunts and nieces, and first cousins do not cooperate. In fact, these individuals are treated in exactly the same manner as other conspecifics (competitively) (Sherman 1981a).

Alarm calling:

The use of alarm calls in response to predation is found widely in nature, despite the fact that these calls make the animal more noticeable to predators, leading scientists to study their adaptive significance. Many different adaptive benefits of alarm calls have been proposed. First, they may call the predator's attention to other prey when they respond or prevent the predator from following its prey by confusing it when they flee. Second, it may serve to alert relatives or to warn others that may later reciprocate the behavior. Third, it may discourage the predator from returning. In Belding's ground squirrels (Spermophilus beldingi), alarm calls do not cause bedlam among the squirrels and thus do not confuse the predator, nor do they discourage the predator in any manner. But, alarm calls do serve to warn relatives of a terrestrial predator. Adult and one-year-old female Belding's ground squirrels are much more likely to give alarm calls than males (who disperse away from their kin), and female squirrels with nearby kin are more likely to give alarm calls than those without living kin nearby. In addition, the chance that females will give alarm calls increases with age. For example, at Tioga Pass, California, Paul Sherman determined that females call more often than males in response to terrestrial predators (both males and females call in response to aerial predators), especially those that had kin near by (Sherman 1977).See also alarm calling page!

So, why do we care about Nepotism?

Because female ground squirrels are nepotistic, they are able to further the chance that their genes (or at least an incredibly similar set of genes) are passed on to the next generation. Females living with their relatives will use less energy establishing and protecting their burrows, and will have access to food on the territories of their kin. This will allow them to better care for their young. In adddition, increased protection of the nesting territory helps to decrease the occurance of infanticide. Females will also alarm call to warn close relatives of predators, which could allow relatives time to escape (Sherman and Morton 1979). Thus, they will be able to reproduce and raise young, passing the "family genes" onto the next generation