Life expectancy and longevity of varanid lizards (Reptilia:Squamata:Varanidae) in North American zoos

Abstract

In zoos, life expectancy-the average lifespan of individuals within a population, and longevity-the maximum lifespan within a population, can be useful parameters for evaluating captive husbandry and animal welfare. Using life history and demographic data derived from regional studbooks, this study examined life expectancy and longevity in a total of 782 wild-caught (WC) and captive-bred (CB) varanid lizards of seven species maintained in North American zoos since 1926. The average lifespans for WC and CB animals were 6.3 ± 0.3 and 9.3 ± 0.4 years, respectively, with CB males living significantly longer than females (P = 0.009). A total of 26.4% of WC and 22.5% of CB animals experienced mortality during their first 2 years in captivity, with mortality during this period greatest among Varanus rudicollis and V. prasinus. A positive correlation was observed between life expectancy and adult body mass in captive-bred individuals (r = 0.981; P = 0.002). Wild-caught females with a history of successful reproduction had a significantly greater average lifespan than non-reproducing females (P < 0.0001). Results from this study suggest that varanids have not been reaching their lifespan capacities in North American zoos. In light of these findings, several husbandry-related factors which may be affecting the welfare and lifespans of varanids in zoos are identified and discussed. This study also highlights the utility of demographic and life history data in captive animal management, and offers a general framework for future herpetological studies of a similar nature.

How long do dolphins live? Survival rates and life expectancies for bottlenose dolphins in zoological facilities vs. wild populations

“…Kaplan-Meier survival analysis-Finally, a number of studies have used the Kaplan-Meier survival analysis to assess life expectancy in a variety of animal species (e.g., Ostermann et al 2001, White et al 2005, Nuss and Warneke 2010, Jett and Ventre 2015, Mendyk 2015, Robeck et al 2015. This analysis is similar to a life table, with the notable exception that the time intervals analyzed are much smaller (i.e., a day rather than a year).…”

The Cephalic Osteoderms of Varanus komodoensis as Revealed by High‐Resolution X‐Ray Computed Tomography

“…He was 19.5 years old when he died on 4 March 2013, weighing 59.2 kg and measuring 2.6 m in total length. Mendyk () estimated the average longevity of male captive‐bred V. komodoensis at approximately 14.4 years, with the oldest‐living captive male aged 15.4 years. However, the studbook for the species estimates a median life expectancy for captive males to be 19.5 years, with the oldest captive male aged 26 (Boyer et al, ).…”

Exceptional longevity of a male Madeira rock lizard Teira dugesii maintained in captivity for 41 years

“…M aintaining reptiles in captivity can give clues about their longevity. As expected, longevities in captivity have increased with the development of better care and husbandry; the first reports on reptiles life spans achieved in zoological gardens (Flower, 1925) are shorter than those reported in more recent studies (Bannert, 1998;Slavens & Slavens, 1999;Mendyk, 2014b). Herein, we recount the remarkably 41 year lifespan of a captive male Teira dugesii (Milne-Edwards, 1829).…”