Kate C. Baker’s research while affiliated with Wisconsin National Primate Research Center and other places

Animal care in facilities housing nonhuman primates has undergone a transformation in the past two decades, as the scientific community has learned more about the effects of husbandry practices on behavior and physiology of captive nonhuman primates. Today, husbandry consists of more than simply feeding animals and removing waste. Husbandry practices cover all aspects of animal care, from ensuring the animals’ nutritional needs to providing adequate shelter, monitoring the health of the animals, and refining procedures so that they reduce stress and distress. As such, husbandry is integral to providing optimal animal welfare. This chapter will summarize four main areas of husbandry (health monitoring, nutrition, shelter, and humane handling) and discuss how each can influence aspects of the welfare of captive nonhuman primates living in a research environment.

Promoting welfare should be a goal of all facilities housing nonhuman primates. However, determining whether that goal has been met can be challenging. One means of measuring primate welfare is by assessing the animal’s behavior. Herein, we review commonly used behavioral indices for measuring welfare. The first is abnormal behavior, which is defined as behavior that differs in kind or degree from natural behavior. Abnormal behavior can indicate past or present adverse experiences, but it is also impacted by intrinsic factors such as species, temperament, age, and sex. Although abnormal behavior may in some way help an animal to cope with its environment, the presence of abnormal behavior is of concern and interventions may be warranted. Low well-being can also be measured by the display of anxiety-related self-directed behaviors such as scratching and yawning, as well as fear-related facial expressions and vocalizations, freezing, and fleeing. The benefit of utilizing normal species-appropriate anxiety behaviors is that, unlike with abnormal behavior, they are ubiquitous and can function as a “warning system,” which allows for earlier identification of environmental deficiencies and intervention. Species normative behaviors that are reflective of positive emotional states can be used to identify animals experiencing positive welfare, but determining appropriate levels of these behaviors in captivity can be challenging. Regardless of the behaviors being assessed, an understanding of the species’ behavioral repertoire is critical when using behavior as a measure of welfare. When accurately assessed, an animal’s behavior, whether normal or abnormal, can be utilized as an indicator of well-being in nonhuman primates.

The social setting of animal subjects in the research environment has known effects on a variety of dependent measures used in biomedical research. Proper evaluation of the robustness of published research is dependent upon transparent, detailed, and accurate reporting of research methods, including the animals' social housing conditions. However, to date, most research articles utilizing nonhuman primates (NHPs) provide only partial data on this topic, hampering transparency, and reproducibility. Therefore, we call for the inclusion of information pertaining to the social aspects of the animals' housing conditions in publications involving NHPs to improve transparency. We argue that including this information in scientific publications is crucial for the interpretation of research findings in the appropriate context and for understanding unexplained variability in study findings. Finally, the inclusion of this information in publications will additionally familiarize scientists with how other researchers conducting similar studies are housing their animals and will encourage them to consider the implications of various housing conditions on their research outcomes.

Social housing of rhesus macaques (Macaca mulatta) is considered to be the cornerstone of behavioral management programs in biomedical facilities. However, it also involves the risk of socially inflicted trauma. The ability to avoid such trauma would contribute to the animals' well-being and alleviate staff's concerns, thus paving the path for more introductions. Here, we sought to address the conflict between the need to socially house rhesus macaques and the need to bring social wounding to a minimum by identifying behaviors expressed early in social introductions, that may serve as predictors of later wounding events. We employed logistic regression analysis to predict the occurrence of wounding for 39 iso-sexual, adult pairs in the 30 days following the introduction into full contact using the levels of behaviors that were observed at the onset of the introduction. The results show that the levels of submissive behaviors were the only significant predictor to later stage wounding. Higher levels of submissive behaviors expressed during the early phases of the introduction were associated with a decreased likelihood of wounding. Interestingly, levels of affiliative behaviors have not added any power to the predictability of the statistical model. Therefore, it may be suggested that the exchange of submissive signals at the earliest stages of the introduction is critical in the determination of relative rank and preclude the need to establish dominance via aggression when allowed full contact. While the observation of clear-cut dominance relationships is commonly considered a harbinger of success, our findings suggest that it is the acknowledgment of subordination, rather than the expression of dominance that underlies this observed pattern. The value of our findings for guiding social housing decision-making may be strongest in situations in which the composition of potential partners is constrained, and therefore requiring that wise decisions be relied upon early behaviors.

Environmental enrichment (EE) gives laboratory animals opportunities to engage in species-specific behaviors. However, the effects of EE devices on normal physiology and scientific outcomes must be evaluated. We hypothesized that the spectral transmittance (color) of light to which rats are exposed when inside colored enrichment devices (CED) affects the circadian rhythms of various plasma markers. Pair-housed male Crl:SD rats were maintained in ventilated racks under a 12:12-h light:dark environment (265.0 lx; lights on, 0600); room lighting intensity and schedule remained constant throughout the study. Treatment groups of 6 subjects were exposed for 25 d to a colored enrichment tunnel: amber, red, clear, or opaque. We measured the proportion of time rats spent inside their CED. Blood was collected at 0400, 0800, 1200, 1600, 2000, and 2400 and analyzed for plasma melatonin, total fatty acids, and corticosterone. Rats spent more time in amber, red, and opaque CED than in clear tunnels. All tubes were used significantly less after blood draws had started, except for the clear tunnel, which showed no change in use from before blood sampling began. Normal peak nighttime melatonin concentrations showed significant disruption in the opaque CED group. Food and water intakes and body weight change in rats with red-tinted CED and total fatty acid concentrations in the opaque CED group differed from those in other groups. These results demonstrate that the color of CED altered normal circadian rhythms of plasma measures of metabolism and physiology in rats and therefore might influence the outcomes of scientific investigations.