Abstract
Evidence for long-term cooperative relationships comes from several social birds and mammals. Vampire bats demonstrate cooperative social bonds, and like primates, they maintain these bonds through social grooming. It is unclear, however, to what extent vampires are special among bats in this regard. We compared social grooming rates of common vampire bats Desmodus rotundus and four other group-living bats, Artibeus jamaicensis, Carollia perspicillata, Eidolon helvum and Rousettus aegyptiacus, under the same captive conditions of fixed association and no ectoparasites. We conducted 13 focal sampling sessions for each combination of sex and species, for a total of 1560 presence/absence observations per species. We observed evidence for social grooming in all species, but social grooming rates were on average 14 times higher in vampire bats than in other species. Self-grooming rates did not differ. Vampire bats spent 3.7% of their awake time social grooming (95% CI = 1.5–6.3%), whereas bats of the other species spent 0.1–0.5% of their awake time social grooming. Together with past data, this result supports the hypothesis that the elevated social grooming rate in the vampire bat is an adaptive trait, linked to their social bonding and unique regurgitated food sharing behavior.
Highlights
IntroductionLong-term cooperative relationships are most evident in primates [1,2,3,4,5,6], but evidence for similar social relationships has been accumulating for several other social vertebrate groups [3, 7, 8], including cetaceans [9, 10], bats [11], elephants [12], hyenas [13,14,15] and ravens [16,17,18,19,20]
After controlling for the effect of species on social grooming rates, we detected no effect of observer (F(6, 119) = 0.19, p~1), feeding rates (F(1,124) = 0.07, p~1), or aggression (F(1,124) = 0.02, p = 0.3)
Are social grooming differences explained by general differences in social structure? The bat species in this study are all group-living in the wild, but vary in their social structures and degree of sociality
Summary
Long-term cooperative relationships are most evident in primates [1,2,3,4,5,6], but evidence for similar social relationships has been accumulating for several other social vertebrate groups [3, 7, 8], including cetaceans [9, 10], bats [11], elephants [12], hyenas [13,14,15] and ravens [16,17,18,19,20]. The functional importance of these complex social relationships across different species may have led to similar cognitive or behavioral mechanisms for manipulating social bonds [19,20,21,22,23,24]. Experimental and observational studies show that primate social grooming can be ‘exchanged’ for multiple social benefits, including reciprocal grooming, social tolerance, access to food, and agonistic support [1, 25,26,27,28,29,30,31,32,33,34,35,36,37]. Most of what is known about social grooming comes from studies of primates, evidence for a role of social grooming in maintaining social ties is emerging
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