Black-footed ferrets (Mustela nigripes) apparently were extirpated from all native habitats by 1987, and their repatriation requires a combination of captive breeding, reintroductions, and translocations among sites. Improvements in survival rates of released ferrets have resulted from experience in quasi-natural environments during their rearing. Reestablishment of a self-sustaining wild population by 1999 provided the 1st opportunity to initiate new populations by translocating wild-born individuals. Using radiotelemetry, we compared behaviors and survival of 18 translocated wild-born ferrets and 18 pen-experienced captive-born ferrets after their release into a prairie dog colony not occupied previously by ferrets. Translocated wild-born ferrets moved significantly less and had significantly higher short-term survival rates than their captive-born counterparts. Using mark–recapture methods, we also assessed potential impacts to the established donor population of removing 37% of its estimated annual production of kits. Annual survival rates for 30 ferret kits remaining at the donor subcomplex were higher than rates for 54 ferret kits at the control subcomplex (unmanipulated) for males (+82%) and females (+32%). Minimum survival of translocated kits did not differ significantly from survival of those at the control subcomplex. Direct translocation of young, wild-born ferrets from site to site appears to be an efficient method to establish new populations.
Mortality of Siberian polecats and black-footed ferrets released onto prairie dog colonies
Biggins, D.E., B.J. Miller, L.R. Hanebury, and R.A. Powell
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.
Genetic consequences of trumpeter swan (Cygnus buccinator) reintroductions
More than twenty years have passed since the discovery, in 1981, of the last known wild population of black-footed ferrets near the small town of Meeteetse, Wyoming. This secretive, nocturnal member of the weasel family was thought to be extinct, or nearly so. The black-footed ferret was known to be very dependent on large colonies of prairie dogs, but little else was known about these rarely seen animals.
What started with excitement over their discovery, however, soon degraded into a frantic effort to save the last of a dying population. Distemper and plague, both introduced diseases, were discovered on the prairie dog colony that supported the ferret population. Between 1981 and 1987 the Meeteetse ferret population dropped from an active community consisting of many family groups to only 14 individuals captured to save the species. Those 14 animals became the future of the black-footed ferret recovery program...
Experimental repatriation of boreal toad (Bufo boreas) eggs, metamorphs, and adults in Rocky Mountain National Park
The boreal toad (Bufo boreas) is an endangered species in Colorado and is considered a candidate species for federal listing by the United States Fish and Wildlife Service. Boreal toads are absent from many areas of suitable habitat in the Southern Rocky Mountains of Colorado presumably due to a combination of causes. We moved boreal toads from existing populations and from captive rearing facilities to habitat which was historically, but is not currently, occupied by toads to experimentally examine methods of repatriation for this species. Repatriation is defined as the release of individuals into areas currently of historically occupied by that species (Dodd and Seigel, 1991). This effort was in response to one of the criteria for delisting the boreal toad in Colorado stated in the conservation plan and agreement for the management and recovery of the Southern Rocky Mountain population of the boreal toad (Loeffler, 1998:16); “…there must be at least 2 viable breeding populations of boreal toads in each of at least 9 of 11 mountain ranges of its historic distribution.” Without moving eggs from established wild populations, or from captivity to historical localities, it is doubtful whether the recovery team will attain this ambitions goal.
Translocation of Utah Prairie Dogs
Although methods for translocating threatened Utah prairie dogs (Cynomys parviden) have been refined over the past 25 years, post-release loss rates remain high at many sites, and persistence of populations is low. Reestablishment of viable populations on public lands is critical to the security of the species. This task is testing methods to improve the short-term retention and survival of prairie dogs at release sites. These include visual barrier fences and electric fencing to temporarily restrict the post-release movements of prairie dogs, and artificial burrow structures and mowing to increase the attractiveness of sites to prairie dogs. Additional longer-term studies are being conducted to investigate effects of plague and habitat quality on population attributes. Because translocations and reintroductions are rapidly becoming necessary for conservation of other prairie dog species, study results will have broad application.