You lick me, I like you: understanding the function of allogrooming in ungulates

Abstract

Allogrooming is a common affiliative behaviour with hygienic, physiological and social consequences, and has historically been examined in non‐human primates in order to understand the evolution of sociality. In primates, allogrooming is well‐known to have evolved for an antiparasitic function, leading to physiological consequences and further adoption of the behaviour for social functions. This includes exchanging benefits in a biological market, post‐conflict reconciliation and long‐term social bond formation. The relevant importance of these functions is largely undetermined in many non‐primate taxa, including ungulates. We aimed to evaluate the current evidence for allogrooming function in ungulates, asking whether the behaviour serves a social function, and if so, to what magnitude. Ungulates show large differences in their allogrooming behaviour, but the variation of these has not been truly understood. We find that although allogrooming in ungulates has been co‐opted for social purposes such as bond formation, the variety of these has not been fully explored. Identifying species‐specific allogrooming functions can help to clarify the context of behaviour; this allows us to improve our knowledge of how individuals and groups interact within a population, and understand the implications of this behaviour when deducing animal state and sociality. We conclude that there is great potential for additional research into the benefits of affiliative behaviour in ungulates, and we encourage further exploration into the social functions of allogrooming in ungulates.

Programmed Grooming after 30 Years of Study: A Review of Evidence and Future Prospects

“…In an experimental study with impala, the removal of ticks from control subjects resulted in a reduction in the rate of allogrooming, again supporting a tick-control function [9]. Hodgson et al [57] has suggested that ungulates are a promising taxa for comparative allogrooming research, to explore the social and ecological factors impacting the evolution of sociality.…”

“…Allogrooming involves one individual grooming the body of another to remove debris or ectoparasites. While primates use their fingers to groom manually, other mammals use oral grooming methods such as licking, chewing, nibbling, and scraping to remove ectoparasites and comb through the hair [57]. Baboons that received more allogrooming had, in turn, lower tick loads and a higher packed red cell volume or hematocrit, a general measure of health status [58].…”

“…Baboons that received more allogrooming had, in turn, lower tick loads and a higher packed red cell volume or hematocrit, a general measure of health status [58]. Although allogrooming in primates likely evolved to remove parasites from inaccessible body regions, it has often taken on social functions such as conflict reconciliation, tension relief, and bond formation [57], and this may be the case in other taxa. Allogrooming is associated with physiological changes, such as an increase in endorphins and neuropeptides, indicative of pleasure; reduced glucocorticoids, indicative of tension reduction; and reduced heart rates, suggestive of positive welfare [57].…”

“…Although allogrooming in primates likely evolved to remove parasites from inaccessible body regions, it has often taken on social functions such as conflict reconciliation, tension relief, and bond formation [57], and this may be the case in other taxa. Allogrooming is associated with physiological changes, such as an increase in endorphins and neuropeptides, indicative of pleasure; reduced glucocorticoids, indicative of tension reduction; and reduced heart rates, suggestive of positive welfare [57]. In ungulates, phylogenetic evidence supports the evolution of allogrooming for parasite defense, with higher grooming rates concentrated in taxa with greater ectoparasite exposure [35].…”

Personality homophily drives female friendships in a feral ungulate

“…Therefore, while the general herd-level social associations in space use patterns may strengthen group cohesion and help avoid predators through 'many eyes' 83 , preferential social associations or friendships can still be sustained. As evident in a species like water buffalo, where direct affiliative interactions, like allogrooming, are predominantly absent 45 , spatial proximity patterns can be of vital importance for maintaining friendships (cf. 46 ).…”