Greater Short-nosed Fruit Bat

Greater short-nosed fruit bats share food both with relatives and with unrelated individuals, allowing researchers to separate kinship effects from reciprocity effects. Related bats share more—kin selection operates. But unrelated bats also share, and sharing among non-relatives follows reciprocal patterns: bats share more with partners who've shared with them.

The dual system reveals complementary mechanisms. Kin selection provides a baseline of sharing that doesn't require reciprocity tracking—you share with relatives even if they've never shared with you. Reciprocity adds sharing with non-relatives who've proven cooperative. The combination creates broader food security than either mechanism alone.

Roost fidelity creates repeated interaction. These bats return to the same roost sites, creating stable social groups. The repeated interaction enables reciprocity tracking—you'll encounter the same individuals repeatedly, making defection costly and cooperation rewarding. Roost stability is a precondition for reciprocity.

Social grooming predicts food sharing. Bats who groom together also share food. Grooming serves as relationship maintenance that enables food sharing during scarcity. The investment in grooming relationships pays off when food runs short—grooming partners become sharing partners.

For organizations, these bats demonstrate that kinship and reciprocity can operate simultaneously. Nepotism provides baseline cooperation; merit-based relationships add additional cooperation. Organizations needn't choose between family business and meritocracy—they can layer both systems.