Risk factors for barbering in laboratory mice.

Barbering is a common abnormal behavior in laboratory mice, where mice pluck their own fur and/or the fur or whiskers of their cage mates. Barbering mice are a concern for welfare and research quality, as well as serving as a spontaneous model of trichotillomania (a hair-pulling disorder in humans). Causes and prevention of barbering are poorly understood, although there is evidence that both biological and environmental factors play a role in its prevalence. Since initial work in this area was done 20 years ago, mouse husbandry has changed dramatically. We provide an updated analysis of risk factors for barbering in laboratory mice based on point prevalence of hair loss in 2544 cages over one year (7007 mice). We analyzed the effects of biological, environmental, and husbandry factors that are known to be stressors for mice. We found that certain risk factors for barbering, such as sex and breeding status, have persisted despite changes in housing. We additionally identified differences in prevalence based on genetic background, housing system, time of year, and a "hotspot" effect showing spatial clustering of barbering. Our findings can be used to increase understanding of this behavior and to inform changes in husbandry to reduce its prevalence.