Assessing significant (>30%) alopecia as a possible biomarker for stress in captive rhesus monkeys (Macaca mulatta)

Abstract

Hair loss is common in macaque colonies. Very little is known about the relationship between psychological stress and hair loss. We initially examined alopecia and hair cortisol concentrations in 198 (89 male) rhesus macaques from three primate centers and demonstrated replicability of our previous finding that extensive alopecia (> 30% hair loss) is associated with increased chronic cortisol concentrations and significantly affected by facility. A subset of these monkeys (142 of which 67 were males) were sampled twice approximately 8 months apart allowing us to examine the hypotheses that gaining hair should be associated with decreases in cortisol concentrations and vice versa. Hair loss was digitally scored using ImageJ software for the first sample. Then visual assessment was used to examine the second sample, resulting in 3 categories of coat condition: 1) monkeys that remained fully haired, 2) monkeys that remained alopecic (with more than 30% hair loss), or 3) monkeys that showed more than a 15% increase in hair. The sample size for the group that lost hair was too small to be analyzed. Consistent with our hypothesis, monkeys that gained hair showed a significant reduction in hair cortisol concentrations but this effect only held for females. Coat condition changed little across sampling periods with only 25 (11 male) monkeys showing a greater than 15% gain of hair. Twenty (7 male) monkeys remained alopecic, whereas 97 (49 males) remained fully haired. Hair cortisol was highly correlated across samples for the monkeys that retained their status (remained alopecic or retained their hair).

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

“…It should be noted that chronic and acute cortisol measures are not always correlated. In rhesus monkeys, chronic hair cortisol concentrations (typically representing three months) were positively correlated with hair loss, and monkeys that grew new hair showed a reduction in hair cortisol concentrations . In contrast to these chronic assessments, fecal cortisol concentrations were inversely associated with alopecia .…”

Fatty acid supplements improve hair coat condition in rhesus macaques

“…A link between stress and alopecia in macaques is supported by the following findings. Severe alopecia is associated with markedly elevated hair cortisol concentrations, and spontaneous regrowth of hair in females with this condition is associated with significantly decreased hair cortisol concentrations . PUFA treatment has been shown to reduce HPA axis activity in mice and hypothetically may restore hair growth cycles in alopecic animals.…”

“…In a follow‐up 8 months later, most severely alopecic monkeys maintained their status. However, a subset of female monkeys that gained hair also showed reduced hair cortisol concentrations . Severe alopecia is less common than mild alopecia.…”

“…However, a subset of female monkeys that gained hair also showed reduced hair cortisol concentrations. 4 Severe alopecia is less common than mild alopecia. Monkeys with mild hair loss did not show HPA axis elevation, and their hair loss may be related to other factors, such as low-grade inflammation.…”

Hair plucking, stress, and urinary cortisol among captive bonobos (Pan paniscus)

“…We hypothesized that individuals that frequently hair plucked would exhibit high levels of cortisol. Novak et al [in press] examined changes in coat condition and hair cortisol among captive rhesus macaques and found that female macaques that gained hair had reduced cortisol concentrations over an 8‐month study period. Using urinary cortisol as a biomarker for physiological stress, we can determine if hair plucking is associated with chronic stress among captive bonobos.…”