Characterizing Husbandry Risk Factors Associated with Metastatic Soft Tissue Mineralization in Zoo-Housed Komodo Dragons (Varanus komodoensis) in the United States

Abstract

Metastatic soft tissue mineralization has emerged as a major cause of death in captive Komodo dragons (Varanus komodoensis). A cross-sectional survey-based study was performed to evaluate husbandry-related risk factors for metastatic mineralization in zoo-housed Komodo dragons in the United States. Nineteen institutions participated, nine of which (47.4%) had a history of metastatic mineralization within their collections. Husbandry at participating institutions varied in temperature gradients, outdoor exposure, artificial lighting, and diet items offered. Differences in husbandry were tested between institutions with and without a history of mineralization by using univariate analyses, and variables resulting in a significance level of ≤0.10 were entered into a multinomial logistic regression model. The only variable demonstrating a significant difference during univariate analyses was the number of Komodo dragons per enclosure (P = 0.036), whereas the only significant predictive variable after modeling was humidity approximation. Zoos that approximated rather than measured humidity were 12.0 times as likely to have a history of mineralization in their Komodo dragons (odds ratio [OR] = 12.0, P = 0.045). These variables likely reflect the under- or overestimation of exhibit humidity levels and the tendency to house males and females together. Based on postmortem findings for 27 Komodo dragon mortalities from these institutions, the presence of mineralization at necropsy was significantly associated with female dragons (OR = 18.2, P = 0.0044) and yolk coelomitis or embolism (OR = 6.76, P = 0.046). Although this study did not identify definitive links between husbandry and the prevalence of mineralization at the institutional level, the survey revealed high variation in husbandry conditions and potential deficiencies in management based on the Association of Zoos and Aquariums and the European Association of Zoos and Aquaria guidelines.