The Reproductive Characteristics of the First-generation Hybrid Derived from Three Introduced Purebred Crocodile Species

Abstract: The objective of the present study was to explore the reproductive characteristics of the first-generation hybrid crocodile derived from captive Crocodylus siamensis, C. niloticus and C. porosus introduced from Cambodia, South Africa, and Malaysia. The data for 789 eggs and 651 hatchlings in 26 nests of hybrids of three different crocodile species were collected. Statistical analysis of reproductive variables of hybrid crocodile eggs indicated that the characteristic variables were normally distributed except for the hatching rate. Regression analyses were used to develop the linear equation between egg length, egg width, hatching rate, hatchling weight, and egg mass. The results found a significant correlation between egg mass and other traits except for egg shape index. Significant influences of egg mass and the egg shape index on hatching rate were detected. There was no significant linear relationship between clutch size and egg characteristics. There were several differences in the reproductive characteristic variables between hybrid crocodiles of C. niloticus×C. siamensis and their parental species bred in captivity (variables of the hybrid were generally smaller) and between C. siamensis×C. porosus and their parental species (variables of the hybrid were generally larger). However, there was no difference in the reproductive variables between hybrid crocodiles of C. niloticus×C. porosus and their parental species. These results indicate that careful and rigorous scientific assessments are required on the hybridization of endangered species in particular to fully consider the effects of human intervention on hybridization.