Reproductive inefficiency in male blackfooted ferrets (Mustela nigripes)

The black-footed ferret (Mustela nigripes), once considered extinct, has be nefited from captive breeding and subsequent reintroduction into native hab itat. A high proportion of females (>90%) exhibit estrus in captivity durin g the spring breeding season. However, many males considered to be prime-br eeding age (1-3 years old) fail to sire offspring. Breeding records in 1995 revealed that 40 of 73 males (55%) managed under the Black-Footed Ferret S pecies Survival Plan did not reproduce, despite being provided opportunity. The present study was conducted to determine the incidence and etiology of male reproductive failure in 1996 and 1997. In 1996, 38 of 69 (55%) 1- to 3-year-old males failed to sire offspring. Likewise, 35 of 60 (58%) males d id not reproduce in 1997. Overall, 21% of adult males failed to sire young in three consecutive breeding seasons (1995-1997). Electroejaculate traits (ejaculate volume, sperm concentration, motility, morphology, and acrosomal integrity) from 29 proven breeder males were not different (P > 0.05) from those of 23 males that did not sire young (nonproven breeders). However, s ix categories of reproductive failure were identified for the 73 prime-bree ding age, nonproven males: 1) underdeveloped testes (22%); 2) improper bree ding position with the female (25%); 3) excessive aggression toward estrous females (9%); 4) copulation with no sperm detected at postcoital lavage (1 9%); 5) copulation with sperm in the vaginal lavage but no resulting pregna ncy (18%); and 6) copulation with no vaginal lavage performed and no result ing pregnancy (7%). These data indicate that combined behavioral and physio logic factors, but not overall sperm quality, influence reproductive perfor mance in male black-footed ferrets managed in captivity. Zoo Biol 19:517-52 8, 2000. (C) 2000 Wiley-Liss, Inc.