Social hair pulling in captive rhesus macaques (Macaca mulatta)

Abstract

Alopecia is common among captive populations of nonhuman primates. There are many potential causes of alopecia, including physiological conditions such as hormonal imbalance and infection, features of the captive environment such as housing type, ground substrate, and group density, as well as behavioral abnormalities such as self-plucking. A potential behavioral cause of alopecia in group-housed primates is social hair pulling, where one animal pulls hair from a conspecific. While social hair pulling has been conflated with overgrooming in some of the alopecia literature, other authors have categorized it as a form of aggression rather than a form of excessive grooming. In this study we examined social hair pulling, grooming, and aggression within 7 groups of rhesus macaques (Macaca mulatta) (N=319). We took weekly 30-minute behavioral observations on each group for one year to assess the patterns of hair pulling and grooming, which monkeys were receiving and initiating these behaviors, as well as aggression and other behaviors indicating dominance. We also assessed the amount of alopecia on each individual monthly. While grooming tended to be directed “up” the hierarchy (i.e., monkeys were more likely to groom animals of a higher rank than lower rank), most hair pulling was directed “down” the hierarchy. Further, hair pulling seldom co-occurred with aggressive behaviors, suggesting that it was not a form of aggression. Hair pulling also usually resulted in ingestion of the pulled hair. Hair pulling was correlated with alopecia; monkeys who were frequent recipients of hair pulling scored higher on monthly alopecia ratings than those who were less often observed having hair pulled. Our results suggest that social hair pulling is a behavior distinct from either grooming or aggressive behavior, and that it may contribute to alopecia in socially housed macaques.

Alopecia in rhesus macaques (Macaca mulatta): Association with pregnancy and chronic stress

“…Although weight loss and alopecia have been associated with protein deficiency in gorillas,10 the macaques in the present study were fed a nutritionally complete diet and none were noted to be clinically underweight during their physical examination. Weight loss and alopecia have also been associated with lower social rank 5,6,49. Perhaps in the present study, weight and alopecia were associated because of their respective relationships with social rank.…”

“…Patterns of missing hair can vary from small discrete patches to diffuse hair loss covering most of the body. Although often presented as a welfare issue in non‐human primates, alopecia is a complex condition that can occur in response to a number of diverse variables including age, sex, seasonal changes, nutritional deficits, pregnancy, stress, hormonal changes, genetic factors, temperament, infection, parasites, and hair‐pulling …”

Increased produce enrichment reduces trauma in socially‐housed captive rhesus macaques (Macaca mulatta)

“…In captive or semi‐provisioned settings, foods are easily processed and extracted, and provided in predictable ways, and these primates may spend as little as 20% of their day foraging/feeding (Altmann & Muruthi, ; Beisner & Isbell, ). This can result in a greater frequency of social hair pulling and hair ingestion (Beisner & Isbell, ; Heagerty, Wales, Prongay, Gottlieb, & Coleman, ), aggression (Beisner & Isbell, ), and self‐directed behaviors and stereotypies (Gottlieb et al, ; Lutz & Novak, ). As such, common enrichment devices for captive primates focus on foraging based strategies, such as puzzle feeders (Gottlieb et al, ; Novak, Kinsey, Jorgensen, & Hazen, ), foraging boards (Bayne et al, ; Lutz & Novak, ), and distribution of food under woodchips and shavings (Boccia & Hijazi, ; Byrne & Suomi, ; Doane et al, , Lutz & Novak, ), which have been shown to alleviate some, but not all, unwanted behaviors.…”

Prevalence and characteristics of hair plucking in captive bonobos (Pan paniscus) in North American zoos

“…Hair plucking is reported to occur in a number of captive primate species, including rhesus macaques (Heagerty, Wales, Prongay, Gottlieb, & Coleman, ; Lutz, Coleman, Worlein, & Novak, ; Reinhardt, Reinhardt, & Houser, ), and all the great apes (Birkett & Newton‐Fisher, ; Brand & Marchant, ; Edwards & Snowdon, ; Hill, ; Jacobson, Ross, & Bloomsmith, ; Less, Kuhar, & Lukas, ; Miller & Tobey, ; Nash, Fritz, Alford, & Brent, ; Pizzutto, ). The behavior has been observed to be both self‐directed and directed toward conspecifics (Heagerty et al, ). In captive macaques, the occurrence of hair plucking is related to a number of variables including sex, age, dominance rank, and reproductive status.…”

“…Adolescents were reported to have an increased likelihood of hair plucking compared to adults (Reinhardt et al, ). When directed toward conspecifics, hair pulling has been reported to be directed toward lower‐ranking individuals in two different studies (Heagerty et al, ; Reinhardt et al, ) although the nature of social hair plucking was different. Reinhardt and colleagues (1986) found the behavior to be agonistic, resulting in behavioral responses in the recipients reflecting fear, and pain.…”