A transgenic animal such as a transgenic snake or other reptile that expresses a heterologous expression product is described, along with methods of making the same. In general, the animal comprises cells containing a sequence encoding the heterologous expression product. The sequence encoding the heterologous expression product is integrated into the genome of the animal (e.g., in some or all cells thereof, and in some embodiments into germ cells thereof). The sequence encoding the heterologous expression product is, in general, operatively associated with an expression sequence or promoter. The animals are useful for, among other things, testing of repellents, testing of toxicological compounds, as teaching aids, for venom production, etc.