The Number of Louse Eggs on Wild Japanese Macaques (Macaca fuscata) Varies with Age, but Not with Sex or Season

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.

Breeding behavioral activities of captive red pandas in Nepal

“…The female was regularly observed grooming the male while sleeping. Allogrooming in solitary species is typically observed only during the breeding or rearing of young and facilitates courtship, bonding, cleanliness, and social rank (Sachs 1988;Smolinsky et al 2009;Ishii et al 2017).…”

Host‐related and environmental factors influence long‐term ectoparasite infestation dynamics of mouse lemurs in northwestern Madagascar

“…Among the most widely stated host‐related determinants of parasite richness and prevalence are species, sex, age, and body condition (e.g., Clough et al, 2010; Durden et al, 2021; Ishii et al, 2017; Klein et al, 2018). The impact of host species on parasite infections can result from differences in ecology and sociality.…”

“…Since older individuals could show immunosenescence (Haberthur et al, 2010; Palacios et al, 2007; Zohdy, 2012), or juveniles could have less developed immune systems (Attanasio et al, 2001; Foerster et al, 1997), age has been argued and shown to impact parasitic infections. In a study on wild Japanese macaques ( Macaca fuscata ), Ishii et al (2017) found that juvenile hosts harbored more louse eggs than adult macaques. As a consequence of nutritional stress, hosts in poorer body conditions are often more susceptible to infections than individuals in better conditions (Beldomenico & Begon, 2010; Kiene et al, 2020; Wikel, 1982).…”