Mortality of Siberian polecats and black-footed ferrets released onto prairie dog colonies

Black-footed ferrets (Mustela nigripes) likely were extirpated from the wild in 1985–1986, and their repatriation depends on captive breeding and reintroduction. Postrelease survival of animals can be affected by behavioral changes induced by captivity. We released neutered Siberian polecats (M. eve...

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Bibliographic Details
Published in:	Journal of mammalogy 2011-08, Vol.92 (4), p.721-731
Main Authors:	Biggins, Dean E., Miller, Brian J., Hanebury, Louis R., Powell, Roger A.
Format:	Article
Language:	eng
Subjects:	Abundance Animal behavior Animals Biological and medical sciences Birds Body mass Burrows Canis latrans Captive breeding Captivity Colonies Cynomys Cynomys ludovicianus Dogs ecological equivalent ecological surrogate Environmental protection Ferrets Fundamental and applied biological sciences. Psychology Hunting Mammalia Mammalogy Mortality Mustela Mustela eversmanii Mustela nigripes Prairies Predation Predators Prey Reintroduction SPECIAL FEATURE Species reintroduction Survival translocation Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution Wildlife conservation
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Summary:	Black-footed ferrets (Mustela nigripes) likely were extirpated from the wild in 1985–1986, and their repatriation depends on captive breeding and reintroduction. Postrelease survival of animals can be affected by behavioral changes induced by captivity. We released neutered Siberian polecats (M. eversmanii), close relatives of ferrets, in 1989–1990 on black-tailed prairie dog (Cynomys ludovicianus) colonies in Colorado and Wyoming initially to test rearing and reintroduction techniques. Captive-born polecats were reared in cages or cages plus outdoor pens, released from elevated cages or into burrows, and supplementally fed or not fed. We also translocated wild-born polecats from China in 1990 and released captive-born, cage-reared black-footed ferrets in 1991, the 1st such reintroduction of black-footed ferrets. We documented mortality for 55 of 92 radiotagged animals in these studies, mostly due to predation (46 cases). Coyotes (Canis latrans) killed 31 ferrets and polecats. Supplementally fed polecats survived longer than nonprovisioned polecats. With a model based on deaths per distance moved, survival was highest for wild-born polecats, followed by pen-experienced, then cage-reared groups. Indexes of abundance (from spotlight surveys) for several predators were correlated with mortality rates of polecats and ferrets due to those predators. Released black-footed ferrets had lower survival rates than their ancestral population in Wyoming, and lower survival than wild-born and translocated polecats, emphasizing the influence of captivity. Captive-born polecats lost body mass more rapidly postrelease than did captive-born ferrets. Differences in hunting efficiency and prey selection provide further evidence that these polecats and ferrets are not ecological equivalents in the strict sense.
ISSN:	0022-2372 1545-1542