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Why do Belding's ground squirrels give alarm calls more often when relatives are nearby?

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Serengeti National Park, Tanzania: herd of gnu (wildebeests) — Animal social behavior Herd of gnu (wildebeests) in the Serengeti National Park, Tanzania.

Belding's ground squirrels (Spermophilus beldingi) give alarm calls more frequently when close relatives are nearby because this behavior is an example of altruism driven by kin selection.

While the act of calling warns other group members of a predator's approach, it also puts the caller at risk by attracting the predator's attention. According to the theory of inclusive fitness, individuals can increase their genetic success not only by reproducing themselves but also by assisting the survival and reproduction of relatives who share their genes.123

Hamilton's rule explains that such self-sacrificial behavior can evolve when the benefit to the recipients, weighted by their genetic relatedness to the donor, exceeds the cost to the donor. By warning kin, the squirrel promotes the survival of individuals who carry copies of its own genes, thereby enhancing its indirect fitness. This behavior is a fundamental illustration of how natural selection favors genetic success over individual survival alone.21