Grooming site preferences determined by lice infection among Japanese macaques in Arashiyama

Abstract

I investigated the effect of the density of louse eggs (Pedicinus obtusus and P. eurygaster) on grooming site preferences in Japanese macaques (Macaca fuscata). Louse eggs were more often found on the outer side of the body (upper back, lower back, outer arms, and outer legs) than on the inner side of the body (chest, belly, inner arms, and inner legs). Japanese macaques were more likely to be groomed on the outer side than the inner side of the body by allogrooming and autogrooming. Such grooming site preferences correlated with the distribution of louse eggs but not with the areas of body parts. Thus, the ecology of lice might affect grooming behavior of Japanese macaques. Five hundred and fifty louse eggs were estimated to parasitize an adult female Japanese macaque. Considering the intrinsic rate of natural increase of lice, monkeys need to be groomed almost every day. This suggests that Japanese macaques need grooming partners and form social bonds with others for everyday grooming.

Manipulating grooming by decreasing ectoparasite load causes unpredicted changes in antagonism

“…The reduction in allogrooming following a treatment for ectoparasites confirms the finding of previous correlational studies (e.g. Sanchez-Villagra et al 1998;Perez & Vea 2000;Zamma 2002;Radford & Du Plessis 2006) that allogrooming serves, at least partially, a hygienic role specifically targeted at removing ectoparasites. Surprisingly, individuals experiencing our control treatment, receiving water instead of Advantix, also exhibited decreased parasite loads.…”

“…Groomers target especially infected or inaccessible regions of their partner's bodies (Perez & Vea 2000;Zamma 2002;Radford & Du Plessis 2006) and, across populations, grooming rate correlated with ectoparasite load, suggesting a hygienic function (SanchezVillagra et al 1998). Reducing ectoparasites' levels reduces the need for hygiene maintenance and could reduce grooming levels.…”

Frequency of removal movements during social versus self-grooming among wild chimpanzees

“…Others focused on the hygienic function of removal movements. For example, Zamma (2002a) found that in Japanese macaques, the total daily number of removal movements (self-and social grooming) was almost identical to the daily increase in louse eggs. Freeland (1981) compared removal movements between selfand social grooming and found that more particle-removal movements were observed during social grooming than during self-grooming in three species of Cercopithecidae (however, scratching was included in the category of grooming).…”

Reporting social behaviours of mixed-species troops formed by Callithrix jacchus and Callithrix penicillata (Primate, Callitrichidae)

“…Allogrooming is a social behaviour common in primates. It is well known that it has a hygienic function by the removal of ectoparasites (Zamma, 2002) and reduction of social tension by the production of endorphins (Schino et al 1988). It is also linked to group cohesion (Lehmann et al 2007), and the strengthening of links between individuals (Sánchez-Villagra et al 1998).…”