Population augmentation with translocated individuals has been shown to alleviate the effects of bottlenecks and drift. The first step to determine whether restoration for genetic considerations is warranted is to genetically monitor reintroduced populations and compare results to those from the source. To assess the need for genetic restoration, we evaluated genetic diversity and structure of reintroduced (n = 3) and captive populations of the endangered black-footed ferret (Mustela nigripes). We measured genotypic changes among populations using seven microsatellite markers and compared phenotypic changes with eight morphometric characters. Results indicated that for the population which rapidly grew postreintroduction, genetic diversity was equivalent to the captive, source population. When growth languished, only the population that was augmented yearly maintained diversity. Without augmentation, allelic diversity declined precipitously and phenotypic changes were apparent. Ferrets from the genetically depaupertate population had smaller limbs and smaller overall body size than ferrets from the two populations with greater diversity. Population divergence (F ST = 0.10 ± 0.01) was surprisingly high given the common source of populations. Thus, it appears that 5-10 years of isolation resulted in both genotypic divergence and phenotypic changes to populations. We recommend translocation of 30-40 captive individuals per annum to reintroduction sites which have not become established quickly. This approach will maximize the retention of genetic diversity, yet maintain the beneficial effects of local adaptation without being swamped by immigration.
Plague, a flea-borne disease, hampers efforts to restore populations of black-footed ferrets (Mustela nigripes), which occupy colonies of prairie dogs (Cynomys spp.) in North America. Plague is managed by infusing prairie dog burrows with DeltaDust Ò 0.05% deltamethrin, a pulicide that kills fleas. Experiments are needed to identify pulicides that can be used in rotation with DeltaDust for integrated plague management. In South Dakota, USA, we tested the efficacy of four pulicide dusts when applied at a rate of 8 g per burrow on colonies of black-tailed prairie dogs (Cynomys ludovicianus): Sevin Ò 5% carbaryl; Dusta-cide Ò 6% malathion; Alpine Ò 0.25% dinotefuran with 95% diatomaceous earth; and Tri-Die Ò 1% pyrethrum with 40% amorphous silica and 10% piperonyl butoxide. We also tested systemic 0.005% fipronil, which was distributed as ½ cup of laced grain per burrow. We sampled prairie dogs on 3294 occasions and detected 10,041 fleas. Sevin and Dusta-cide suppressed fleas but only for 1 month. Neither Alpine nor Tri-Die had any noticeable, consistent effect on fleas. Fipronil suppressed fleas by 97-100% for 3 months. The residual effect of fipronil persisted for *12 months. Efficacy of fipronil seems comparable with DeltaDust, which exhibited a residual effect for *10 months in prior studies. Continued research is needed to optimize fipronil treatments for plague management on prairie dog colonies.
Effective conservation planning for endangered species depends on an understanding of space use patterns. Blackfooted ferrets Mustela nigripes depend on prairie dogs Cynomys sp. as prey and use their burrow systems for shelter. The availability of areas with high densities of active prairie dog burrows is the major factor thought to affect their selection of sites and resources. However, we have little knowledge about how the spatial distribution of active prairie dog burrows might influence the spatial organization and home-range size of ferrets. We monitored the movements of black-footed ferrets on a black-tailed prairie dog C. ludovicianus colony in South Dakota to document ferret space use patterns. Home ranges of female ferrets were 22.9 -95.6 ha in size (x¼56.3 ha, SE¼19.7, N¼6), while male ferret home ranges were on average more than twice as large as those of females (x¼128.3 ha, SE¼68.5, N¼3). The home-range size of female ferrets was correlated with mean active prairie dog burrow utilization distribution (UD) value within ferret home ranges, where home-range size decreased as active prairie dog burrow UD value increased (r 2 ¼ 0.974, P , 0.001, N ¼ 6). Ferret space use overlapped more extensively than previously reported, with up to 43% UD overlap between a ferret and the nearest adjacent ferret of the same sex. Areas of overlap tended to have higher active prairie dog burrow UD values, suggesting that the spatial distribution of active prairie dog burrows influenced both home-range size and the amount of space use overlap between ferrets. These findings emphasize the potential influence of resource distribution on carnivore sociobiology and the importance of considering that distribution in assessing habitat for the reintroduction of specialized species.
In an attempt to save the species from extinction, the last remaining 18 black-footed ferrets (Mustela nigripes) were trapped up from the wild to initiate a captive breeding program. Nearly 30 years later more than 8,000 black-footed ferrets have been produced in captivity and approximately 4,100 animals have been reintroduced into 20 sites in eight US states (Arizona, New Mexico, Utah, Colorado, Kansas, Wyoming, South Dakota and Montana), Mexico and Canada. However, full recovery of the species has yet to be achieved, mainly due to limited viable habitat, disease and reduced fecundity. This chapter will highlight the advances in the black-footed ferret recovery program over the last 10 years including: (1) adaptive management techniques employed for the captive population; (2) development of new reintroduction sites and associated challenges facing wild black-footed ferrets; and (3) optimization of assisted reproductive techniques to secure the future of this rare species.
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