Review: Sperm cryopreservation in wild small ruminants: morphometric, endocrine and molecular basis of cryoresistance

•Cryopreserved sperm can be used to improve the diversity of wildlife populations.•Epididymal sperm shows higher cryoresistance than ejaculated sperm.•Seasonal changes in testosterone and prolactin are involved in sperm cryoresistance.•Aquaporins may be involved in androgen-related variation of sperm cryoresistance.•Testicular tissue may provide a suitable source of male gametes.