How to estimate body condition in large lizards? Argentine black and white tegu (Salvator merianae, Duméril and Bibron, 1839) as a case study

Body condition is a measure of the health and fitness of an organism represented by available energy stores, typically fat. Direct measurements of fat are difficult to obtain non-invasively, thus body condition is usually estimated by calculating body condition indices (BCIs) using mass and length. The utility of BCIs is contingent on the relationship of BCIs and fat, thereby validation studies should be performed to select the best-performing BCI before application in ecological investigations. We evaluated 11 BCIs in 883 Argentine black and white tegus (Salvator merianae) removed from their non-native range in South Florida, United States. Because the length-mass relationship in tegus is allometric, a segmented linear regression model was fit to the relationship between mass and length to define size classes. We evaluated percent, residual, and scaled fat and determined percent fat was the best measure of fat because it was the least associated with snout-vent length (SVL). We evaluat..., Species description
The Argentine black and white tegu is a large teiid lizard native to eastern and central South America that has become established in several areas of central and southern Florida, United States. Tegus can be classified as omnivores as well as generalist meso-predators which consume fruit, plant material, and animal prey (arthropods, gastropods, reptiles, birds, and small mammals), with evidence of diet changing based on seasonal abundance. Tegus are also known to scavenge upon carrion and regularly consume eggs of ground-nesting vertebrates such as alligators, turtles, and birds. This species is considered invasive in Florida with potential negative impacts on native fauna through egg predation and competition for burrowing sites. To combat this threat, management programs have been established in Florida to reduce the population of invasive tegus and halt their expansion into ecologically sensitive areas, such as nesting sites of threatened species such as American...,