| Commercial farming of snakes greatly reduces the exploitation of wild snake resources by providing sustainable snake products to the market. However, snake farming would lose its conservation significance and become a stimulator of poaching if the origin of snakes on sale could not be identified during law enforcement when poached snakes enter the market with the name of farmed ones. Therefore, effective methods for forensic identification of snake origin are required. However, there has no such methods been reported up to the present.Snakes in farms live in small cages with stable environmental factors and sufficient food supply. The movement is restricted to a low intensity. In contrast, snakes in the wild live in complex and fluctuating environment with instable food source but high intensity of movements. It could hypothesized that farmed snakes are fast and stable in growth rate in comparison to wild individuals. This might result in morphological differences which could be used to establish methods for origin discrimination.We chose the king rat snake, Elaphe carinata, as model (wild group:n=32; farm group:n=27), and measured 15 measurements namely body mass (W), body length (L), snout-vent length (Ls-v), tail length (Lt), head length (Lh), head height (Hh), mouth width (Wm), space between front canthusi (Sae), space between hind canthusi (Spe), space between nostrils (Si), liver weight (Wt), heart weight (Wh), gall weight (Wg), weight of subcutaneous fat at neck (Wnf), weight of abdominal fat (Waf).16 indices were set up based on these measurements including Ls-v/L, Lt/Ls-v, Lh/Ls-v, Hh/Ls-v, Wm/Ls-v, Sae/Ls-v, Spe/Ls-v, Si/Ls-v, Wl/W, Wh/W, Wg/W, Wnf/W, Waf/W, H/W, W/Ls-v3, Wf/W. Meanwhile, density of growth lines of vertebra (Dbl) and fat content of skeletal muscle (Mf/M) were also tested for origin discrimination.Results showed that 10 morphological indices (Ls-v/L, Lt/Ls-v, Wl/W, Wnf/W, Waf/W, Wf/W, H/W, Mf/M, W/Ls-v3 and Dbl) are effective to discriminate the origin of the king rat snake, among which Waf/W, Wl/W, W/Ls-v3 and Wf/W were significantly affected with sexual dimorphism and highly effective for discrimination snakes only if the sex is known, and indices Ls-v/L, Lt/Ls-v, Wnf/W, H/W, Mf/M and Dbl showed no sexual dimorphism effects and could be applied without necessity of sex concerns. Because the mode of commercial snake farming is similar to that of the king rat snake, the methods we developed in this study are potentially applicable to other snakes. |
