Phylogenetic comparative methods: Harnessing the power of species diversity to investigate welfare issues in captive wild animals

Abstract

This paper reviews a way of investigating health and welfare problems in captive wild animals (e.g., those in zoos, aviaries, aquaria, or aquaculture systems) that has great potential, but to date has been little used: systematically comparing species with few or no health and welfare issues to those more prone to problems. Doing so empirically pinpoints species-typical welfare risk and protective factors (such as aspects of their natural behavioral biology): information which can then be used to help prevent or remedy problems by suggesting new ways to improve housing and husbandry, and by identifying species intrinsically best suited to captivity. We provide a detailed, step-by-step "how to" guide for researchers interested in using these techniques, including guidance on how to statistically control for the inherent similarities shared by related species: an important concern because simple, cross-species comparisons that do not do this may well fail to meet statistical assumptions of non-independence. The few relevant studies that have investigated captive wild animals' welfare problems using this method are described. Overall, such approaches reap value from the great number and diversity of species held in captivity (e.g., the many thousands of species held in zoos); can yield new insights from existing data and published results; render previously intractable welfare questions (such as "do birds need to fly?" or "do Carnivora need to hunt?") amenable to study; and generate evidence-based principles for integrating animal welfare into collection planning.

What’s new from the zoo? An analysis of ten years of zoo-themed research output

“…Consequently, equally important research candidates remain understudied due to this lack of baseline information. Use of ecological information on species' habitat choices can be used to inform housing (Mason, 2015, Kroshko et al, 2016, Mellor et al, 2018 and suitability of husbandry can be evaluated via individual preference testing (Mehrkam and Dorey, 2015, Troxell-Smith et al, 2017a, Troxell-Smith et al, 2017b. Therefore, constructing "in-zoo" questions based on manipulations that can yield species-specific information means that these poorly understood species can be researched and improvements to their husbandry be made on an evidence-based approach.…”

Large Lemurs: Ecological, Demographic and Environmental Risk Factors for Weight Gain in Captivity

“…Environment and living conditions also contribute to weight gain [13] and, should these covary with our wild ecology predictors, could be confounds [63]. Therefore, using the information on living conditions we collected in our survey, we calculated six husbandry variables (see Table 1) believed a priori to likely influence body weight so we could later statistically control for their effects if necessary.…”

“…Our sampling method of captive animals is non-random, as we recruited Species360 member zoos. Using survey responses from different people likely introduced noise into our data (see [63]). Being observational rather experimental also means there may be other unmeasured variables not considered here, e.g., calorie intake (sensu [13]), which could affect our outcome and/or be confounded with our predictors.…”

“…Relative body mass as a proxy for body condition and the accuracy of its obesity threshold now requires validation, e.g., using lifespan (e.g., from [69]) and/or the prevalence of reproductive problems and other comorbidities of obesity (e.g., from records in ZIMS [142] or from [143]; but see Mellor et al [63]). If the current threshold of ≥1.5 does correspond with obesity, then such animals should have reduced lifespan and higher prevalence of comorbidities.…”

“…Here, we use two complementary methods (cf. [63]) to better understand susceptibility to weight gain in captive lemurs. We use phylogenetic comparative methods to test the hypotheses relating species-typical ecology to captive weight gain described above, aiming to identify species-level effects, i.e., ecological risk factors.…”