Abstract
During grooming, primates remove harmful ectoparasites, such as ticks and lice, and there is direct evidence for a health benefit of tick removal. Grooming behaviors differ among primates with respect to age and sex. Moreover, the number of ectoparasite may exhibit seasonal variation. Therefore the number of ectoparasites on a host may vary with effects, host age and sex, and season. However, these effects have not been a focus of louse infestation studies of primates. Grooming in Japanese macaques is related to sex and age, with developmental changes in behavior corresponding to the timing of tooth eruption. Moreover, behavioral data for Japanese macaques suggest that lice load may differ with the season. Thus, we examined whether the number of louse eggs varies according to host macaque sex, age, and season, and whether it changes in response to tooth eruption. We counted unhatched and hatched eggs attached to the hair on six 1-cm2 areas on the left wrist skin of culled macaques, using a stereoscopic microscope. We sampled five winter coats and three summer coats for each age class: infant, juvenile, adolescent, and adult. The number of unhatched and hatched eggs was related to age, but not to sex and season. There were significant differences in the number of unhatched eggs between infants and adults, juveniles and adults, and adolescents and adults. There were also significant differences in the number of hatched eggs between infants and adults, juveniles and adults, adolescents and adults. Tooth eruption did not influence the number of louse eggs. These results suggest that researchers should consider the age of host animals when assessing the relationship between grooming and ectoparasites.
Highlights
Grooming is a major defense strategy against ectoparasites, and is performed by various species, including insects, fishes, birds, and mammals (Sparks 1967)
Our results indicate that the number of louse eggs on hair shafts close to the skin varies significantly among macaque age groups, but not by sex and season
There was a significant difference in unhatched eggs between infants and adults, juveniles and adults, and adolescents and adults
Summary
Grooming is a major defense strategy against ectoparasites, and is performed by various species, including insects, fishes, birds, and mammals (Sparks 1967). Ticks and lice transmit protozoa and bacteria, which cause serious infections, such as babesiosis (Kjemtrup and Conrad 2000; Ruebush et al 1981), epidemic typhus (Blanc and Woodward 1945; Burgess 1995; Roux and Raoult 1999), trench fever (Roux and Raoult 1999), and relapsing fever (Burgess 1995; Durden 2001) They suck the blood of host animals and cause anemia in humans (Guss et al 2011; Speare et al 2006) and a wide range of wild mammals (Durden 2001), including spider monkeys (Ateles: Ronald and Wagner 1973). In light of the negative health effects that result from tick and lice infestation, removal of ectoparasites by grooming may play a significant role in maintaining host health
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