 Research is being done on the environmental cues that have to be replicated before captive animals can be persuaded to breed . Common species such as the tiger salamander and the mudpuppy are being given hormones to stimulate the production of sperm and eggs , and the role of arginine vasotocin in courtship behaviour is being investigated . Another line of research is artificial insemination , either in vitro or by inserting spermatophores into the cloacae of females . The results of this research may be used in captive @-@ breeding programmes for endangered species . 
