Role of Grooming in Reducing Tick Load in Wild Baboons (Papio cynocephalus)

Abstract

Nonhuman primate species spend a conspicuous amount of time grooming during social interactions, a behavior that probably serves both social and health-related functions. While the social implications of grooming have been relatively well studied, less attention has been paid to the health benefits, especially the removal of ectoparasites, which may act as vectors in disease transmission. In this study, we examined the relationship between grooming behavior, tick load (number of ticks), and haemoprotozoan infection status in a population of wild free-ranging baboons (Papio cynocephalus). We found that the amount of grooming received was influenced by an individual's age, sex and dominance rank. The amount of grooming received, in turn, affected the tick load of an individual. Baboons with higher tick loads had lower packed red cell volume (PCV or haematocrit), one general measure of health status. We detected a tick-borne haemoprotozoan, Babesia microti, but its low prevalence in the population precluded identifying sources of variance in infection.

Keywords: baboons; grooming; haemoparasitic infections; ticks.

FIGURE 1

Results of the mixed effects regression model of grooming received. Residual values calculated from the multivariate model (Table 2) have been used to illustrate the effects of sex, group, dominance rank, and age on amount of grooming received. A) Females receive more grooming than males after controlling for other variables in the model. B) )Younger animals receive more grooming that older individuals after controlling for other variables. C) Higher ranking animals receive more grooming than the lower ranking animals after controlling for other variables. See Table 2 for parameter estimates for each independent variable.

FIGURE 2

Representative tick specimens obtained from Amboseli baboons. (A) Rhipicephalus simus simus female, (B) R. s.simus male, (C) R. s.simus, engorged female and (D) R. s.simus, ventral view, (E) R. pulchellus male and (F) R. pulchellus female, (G) Hyalomma truncatum female and (H) H. truncatum unknown sex

FIGURE 3

Individuals receiving higher grooming counts had lower tick loads.

FIGURE 4

Clustering of ticks on various body parts of three individuals. A) Tick clusters on the chest; B) on the neck; and C) on the side of the body near the armpit.

FIGURE 5

Results of the multivariate general regression model. Residual values calculated from the model (Table 4) have been used to illustrate the effects of sex and age on PCV (Packed Cell Volume/haematocrit). A) Males had higher PCV than females after controlling for other variables. B) Younger animals exhibited higher PCV than older animals after controlling for other variables.