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Intraspecific resource partitioning may play a critical role in how predators optimize prey selection. The Black-footed Ferret (Mustela nigripes ; henceforth, ferret) is a highly specialized predator of prairie dogs (Cynomys spp.; henceforth, PDs). Adult ferrets are sexually dimorphic and PDs are of similar size making them a difficult prey item. PD young are born 6 to 8 weeks prior to births of ferrets, producing a crop of smaller prey items during a period when energetic needs of female ferrets are highest. We asked whether relatively small female ferrets select small PDs as prey. We examined survival rates from early to late summer for large and small black-tailed PDs (Cynomys ludovicianus) in Montana and South Dakota as a function of their distance to adult male and female ferrets using capture–mark–recapture of PDs and simultaneous summer monitoring of ferret locations. Survival of small PDs (<600 g) was low when a female ferret was nearby, but distance to nearest female ferret did not affect survival of large PDs. Distance to the nearest male ferret did not influence survival regardless of PD size. Reduced competition from males for a critical food resource needed by females rearing young would benefit fitness of both sexes. If female ferrets depend on young PDs during their reproductive period, existing habitat models may substantially overestimate ferret carrying capacity. [ABSTRACT FROM AUTHOR]

Environmental variation can influence the reproductive success of species managed under human care and in the wild, yet the mechanisms underlying this phenomenon remain largely mysterious. Molecular mechanisms such as epigenetic modifiers are important in mediating the timing and progression of reproduction in humans and model organisms, but few studies have linked epigenetic variation to reproductive fitness in wildlife. Here, we investigated epigenetic variation in black‐footed ferrets (Mustela nigripes), an endangered North American mammal reliant on ex situ management for survival and persistence in the wild. Despite similar levels of genetic diversity in human‐managed and wild‐born populations, individuals in ex situ facilities exhibit reproductive problems, such as poor sperm quality. Differences across these settings suggest that an environmentally driven decline in reproductive capacity may be occurring in this species. We examined the role of DNA methylation, one well‐studied epigenetic modifier, in this emergent condition. We leveraged blood, testes, and semen samples from male black‐footed ferrets bred in ex situ facilities and found tissue‐type specificity in DNA methylation across the genome, although 1360 Gene Ontology terms associated with male average litter size shared functions across tissues. We then constructed gene networks of differentially methylated genomic sites associated with three different reproductive phenotypes to explore the putative biological impact of variation in DNA methylation. Sperm gene networks associated with average litter size and sperm count were functionally enriched for candidate genes involved in reproduction, development, and its regulation through transcriptional repression. We propose that DNA methylation plays an important role in regulating these reproductive phenotypes, thereby impacting the fertility of male ex situ individuals. Our results provide information into how DNA methylation may function in the alteration of reproductive pathways and phenotypes in artificial environments. These findings provide early insights to conservation hurdles faced in the protection of this rare species. [ABSTRACT FROM AUTHOR]

Abstract Environmental variation can influence the reproductive success of species managed under human care and in the wild, yet the mechanisms underlying this phenomenon remain largely mysterious. Molecular mechanisms such as epigenetic modifiers are important in mediating the timing and progression of reproduction in humans and model organisms, but few studies have linked epigenetic variation to reproductive fitness in wildlife. Here, we investigated epigenetic variation in black‐footed ferrets (Mustela nigripes), an endangered North American mammal reliant on ex situ management for survival and persistence in the wild. Despite similar levels of genetic diversity in human‐managed and wild‐born populations, individuals in ex situ facilities exhibit reproductive problems, such as poor sperm quality. Differences across these settings suggest that an environmentally driven decline in reproductive capacity may be occurring in this species. We examined the role of DNA methylation, one well‐studied epigenetic modifier, in this emergent condition. We leveraged blood, testes, and semen samples from male black‐footed ferrets bred in ex situ facilities and found tissue‐type specificity in DNA methylation across the genome, although 1360 Gene Ontology terms associated with male average litter size shared functions across tissues. We then constructed gene networks of differentially methylated genomic sites associated with three different reproductive phenotypes to explore the putative biological impact of variation in DNA methylation. Sperm gene networks associated with average litter size and sperm count were functionally enriched for candidate genes involved in reproduction, development, and its regulation through transcriptional repression. We propose that DNA methylation plays an important role in regulating these reproductive phenotypes, thereby impacting the fertility of male ex situ individuals. Our results provide information into how DNA methylation may function in the alteration of reproductive pathways and phenotypes in artificial environments. These findings provide early insights to conservation hurdles faced in the protection of this rare species.

The black-footed ferret (Mustela nigripes) narrowly avoided extinction to become an oft-cited example of the benefits of intensive management, research, and collaboration to save a species through ex situ conservation breeding and reintroduction into its former range. However, the species remains at risk due to possible inbreeding, disease susceptibility, and multiple fertility challenges. Here, we report the de novo genome assembly of a male black-footed ferret generated through a combination of linked-read sequencing, optical mapping, and Hi-C proximity ligation. In addition, we report the karyotype for this species, which was used to anchor and assign chromosome numbers to the chromosome-length scaffolds. The draft assembly was ~2.5 Gb in length, with 95.6% of it anchored to 19 chromosome-length scaffolds, corresponding to the 2n = 38 chromosomes revealed by the karyotype. The assembly has contig and scaffold N50 values of 148.8 kbp and 145.4 Mbp, respectively, and is up to 96% complete based on BUSCO analyses. Annotation of the assembly, including evidence from RNA-seq data, identified 21,406 protein-coding genes and a repeat content of 37.35%. Phylogenomic analyses indicated that the black-footed ferret diverged from the European polecat/domestic ferret lineage 1.6 million yr ago. This assembly will enable research on the conservation genomics of black-footed ferrets and thereby aid in the further restoration of this endangered species. [ABSTRACT FROM AUTHOR]

Plague, caused by the bacterium Yersinia pestis, is a zoonotic disease of mammalian hosts and flea vectors. Fipronil baits have been used to suppress adult fleas for plague mitigation. The degree and duration of flea control may increase if fipronil also kills other stages in the flea life cycle. We fed grain treated with 0.005% fipronil by weight, or nontreated grain, to black-tailed prairie dogs (Cynomys ludovicianus), which excrete fipronil and metabolites in their feces after consuming fipronil in their diet. We presented prairie dog feces to 331 larval Oropsylla montana (Siphonaptera: Ceratophyllidae). When exposed to feces lacking fipronil or metabolites, 84% of larvae survived for 24 h. In contrast, survival declined to 42% for larvae contacting feces from fipronil-treated prairie dogs. Just 7% of larvae consuming feces from fipronil-treated prairie dogs survived. Fipronil and metabolites may persist in host feces for several months or longer in prairie dog burrows where flea larvae dwell and forage. The lethal effects of fipronil on adult and larval fleas (and perhaps other life stages) may help to explain why fipronil baits are capable of suppressing fleas on prairie dogs for ≥12 mo. [ABSTRACT FROM AUTHOR]

Sylvatic plague is a widespread, primarily flea-vectored disease in western North America. Because plague is highly lethal to endangered black-footed ferrets (Mustela nigripes, BFFs) and the prairie dogs (Cynomys spp., PDs) on which BFFs depend for habitat and prey, minimizing the impacts of plague is a priority at BFF reintroduction sites. We developed a new, flour-based bait pellet containing 0.84 mg of fipronil and weighing ∼1.25 g (FipBits). We measured the degree and duration of flea control on black-tailed PDs (C. ludovicianus) in Montana and on Gunnison's PDs (C. gunnisoni) in Arizona, USA from 2018–2020. FipBits were distributed on treated plots one time at a rate of 125/ha. Fleas were virtually eliminated in Montana from 1 mo posttreatment to 1 yr later and remained substantially depressed 2 yr posttreatment. With the split colony design, we probably underestimated the degree of flea control achieved with FipBits due to crossover edge effects along the arbitrary line dividing the plots. Flea control in Arizona was significant from 1 mo posttreatment to 1 yr later, but flea abundance had recovered by 2 yr posttreatment. Flea control was evaluated from 2020–2021 in South Dakota, USA on four plots treated with three concentrations of fipronil in FipBits (0.68, 0.71, and 0.83 mg/FipBit). Fleas were essentially eliminated for 10 mo on the 0.83-mg plot and were substantially reduced on the two 0.71-mg plots. Fleas were reduced on the 0.68-mg plot, but the degree of control was less than observed on other treated plots. Impacts of plague on PDs and BFFs would probably be greatly reduced by the levels of flea control observed with FipBits. Options for expanded FipBit evaluations are being pursued for what may become a highly practical, affordable, and effective plague mitigation tool. [ABSTRACT FROM AUTHOR]

Sylvatic plague, a primarily flea-borne zoonosis, is a significant threat to prairie dogs (Cynomys spp., PDs) and their specialized predators, endangered black-footed ferrets (Mustela nigripes, BFFs). Host-fed fipronil baits have proven effective in controlling fleas on PDs for the purposes of plague mitigation and BFF conservation. Currently, annual treatments are the norm. We tested the long-term efficacy of fipronil bait treatments with black-tailed PDs (C. ludovicianus, BTPDs) and BFFs in South Dakota, USA. During 2018–2020, we provided BTPDs on 21 sites with grain bait formula, laced with 0.005% fipronil (50 ​mg/kg); 18 non-treated sites functioned as baselines. In 2020–2022, we live-trapped, anesthetized, and combed BTPDs for fleas. Flea control was significant for at least 639–885 days. Flea abundance on the treated sites was < 0.5 fleas/BTPD for ∼750 days. During 2020–2022, we sampled BFFs for fleas on 4 BTPD colonies treated with fipronil grain bait and 8 non-treated colonies. Flea control was significant with BFFs, but flea abundance began to rebound within ∼240 days post-treatment. When feasible, the combination of insecticide treatments, such as fipronil baits, and BFF vaccination against plague provide a “two-pronged” protection approach for these endangered carnivores. If fipronil bait treatments are less effective with predatory BFFs than PDs, as found herein, the “two-pronged” approach might be used to protect BFFs and biennial fipronil bait treatments might be used to protect PDs. If BFF vaccination is not possible, or few BFFs can be vaccinated, annual fipronil bait treatments might be used as a precaution to protect BFFs. Flea densities might be surveyed to determine when/where more frequent treatments seem useful.

Simple Summary: The black-footed ferret, a member of the weasel family originally found throughout much of Midwestern North America, nearly went extinct prior to the 1980s, in part because of ranchers' persecution of prairie dogs, which make up almost all of the ferret's natural diet. In the 1980s, the few remaining wild individuals of the species were brought into captivity in an effort to breed enough animals to reintroduce a more stable population back into the wild. While this program was successful in expanding the numbers of animals enough to release animals back into the wild, the diet of the captive animals was so substantially different that it caused dramatic dental issues. In the current study, we examined the skulls of 271 adult ferrets and 53 specimens of two species that are closely related to ferrets and found that the captive ferrets differ substantially in skull shape from the wild individuals and that some of these differences are even more substantial than some of the differences between black-footed ferrets and their relatives. Thus, captivity (probably the captive diet) has a substantial negative effect on not only the oral health (gum disease, cavities, etc.) but also on skull shape as well. The black-footed ferret (Mustela nigripes), a North American mustelid species, was once found abundantly throughout the Midwest until the extreme decline in prairie dogs (Cynomys spp.), the black-footed ferret's primary food source, brought the species to near-extinction. Subsequently, the Black-Footed Ferret Recovery Program was created in the 1980s with a goal of bringing all remaining individuals of the species into captivity in order to breed the species back to a sustainable population level for successful reintroduction into the wild. While many components of the ferrets' health were accounted for while in captivity—especially those affecting fecundity—this study aims to assess the effects that captivity may have had on their cranial morphology, something that has not been widely studied in the species. In a previous study, we showed that the captive ferrets had significant oral health problems, and here we aim to document how the captive diet also affected their skull shape. For this study, 23 cranial measurements were taken on the skulls of 271 adult black-footed ferrets and 53 specimens of two closely related species. Skulls were divided based on sex, species, captivity status and phase of captivity and compared for all measurements using stepwise discriminant analysis as well as principal component analysis derived from the combined variables. We found that there are significant differences between captive and wild specimens, some of which are larger than interspecific variation, and that a diet change in the captive specimens likely helped decrease some of these differences. The results suggest that captivity can cause unnatural cranial development and that diet likely has a major impact on cranial morphology. [ABSTRACT FROM AUTHOR]

Black-footed ferrets (BFF; Mustela nigripes) are the only ferret species native to North America and have been listed as endangered since 1967. Starting in 1986, a multi-institutional effort has been breeding this species in captivity with successful reintroductions back into the wild. Enteric coccidiosis is recognized as a frequent cause of juvenile morbidity and mortality in captive breeding programs, and can result in substantial population losses. Despite this, little is known about the etiology of coccidiosis in BFF. Coccidia-positive fecal samples (n=12) and formalin-fixed paraffin-embedded intestinal tissues (n=11) were obtained from BFF in the Toronto Zoo (Ontario, Canada) and Louisville Zoo (Kentucky, USA) Species Survival Plan (SSP) populations. Oocyst morphometrics and sequence genotyping at three loci (nuclear 18S rDNA, mitochondrial cytochrome c oxidase subunit I and mitochondrial cytochrome c oxidase subunit III) were conducted to characterize the coccidium or coccidia responsible for disease outbreaks in these ferrets in different age classes and years. Results suggest that a single Eimeria species, E. ictidea, was the cause of enteric coccidiosis in both SSP populations in both juvenile and adult age classes in all years evaluated. Wider research is indicated to determine whether these findings are representative of the broader captive and wild BFF populations. [ABSTRACT FROM AUTHOR]

The human component in endangered species conservation has the potential to significantly limit the ability to achieve recovery of these species globally. Across the Great Plains of North America there have been significant declines in populations of several grassland‐obligate species, including the black‐tailed prairie dog (Cynomys ludovicianus) and the critically endangered black‐footed ferret (Mustela nigripes). Social surveys conducted in Montana, USA, 27 years ago, immediately prior to reintroduction of black‐footed ferrets, described widely differing attitudes and knowledge among stakeholder groups—with most local and state residents being opposed to conservation and recovery of these two wildlife species. We conducted a mail survey replicating methods of the 1993 study to assess current attitudes and knowledge concerning prairie dogs and black‐footed ferrets among five stakeholder groups (local and statewide ranchers, urban and local residents, and members of conservation organizations). Our results demonstrate that despite concerted outreach efforts and a general rise in knowledge about black‐footed ferrets and prairie dogs across stakeholder groups, similar differences in attitudes persisted among stakeholder groups over time, with local stakeholders adjacent to recovery sites maintaining the most negative attitudes. We also observed that local stakeholders supported a significantly shorter time threshold (<10 years) for abandoning efforts to restore an endangered species should recovery goals not be met. Given the reliance on local public support for conserving these species, and other endangered species globally, our findings highlight the importance of continually reassessing stakeholder attitudes and knowledge over time to assess challenges and identify opportunities for endangered species restoration. [ABSTRACT FROM AUTHOR]

Abstract The human component in endangered species conservation has the potential to significantly limit the ability to achieve recovery of these species globally. Across the Great Plains of North America there have been significant declines in populations of several grassland‐obligate species, including the black‐tailed prairie dog (Cynomys ludovicianus) and the critically endangered black‐footed ferret (Mustela nigripes). Social surveys conducted in Montana, USA, 27 years ago, immediately prior to reintroduction of black‐footed ferrets, described widely differing attitudes and knowledge among stakeholder groups—with most local and state residents being opposed to conservation and recovery of these two wildlife species. We conducted a mail survey replicating methods of the 1993 study to assess current attitudes and knowledge concerning prairie dogs and black‐footed ferrets among five stakeholder groups (local and statewide ranchers, urban and local residents, and members of conservation organizations). Our results demonstrate that despite concerted outreach efforts and a general rise in knowledge about black‐footed ferrets and prairie dogs across stakeholder groups, similar differences in attitudes persisted among stakeholder groups over time, with local stakeholders adjacent to recovery sites maintaining the most negative attitudes. We also observed that local stakeholders supported a significantly shorter time threshold (

The black-footed ferret (Mustela nigripes), a North American mustelid species, was once found abundantly throughout the Midwest until the extreme decline in prairie dogs (Cynomys spp.), the black-footed ferret’s primary food source, brought the species to near-extinction. Subsequently, the Black-Footed Ferret Recovery Program was created in the 1980s with a goal of bringing all remaining individuals of the species into captivity in order to breed the species back to a sustainable population level for successful reintroduction into the wild. While many components of the ferrets’ health were accounted for while in captivity—especially those affecting fecundity—this study aims to assess the effects that captivity may have had on their cranial morphology, something that has not been widely studied in the species. In a previous study, we showed that the captive ferrets had significant oral health problems, and here we aim to document how the captive diet also affected their skull shape. For this study, 23 cranial measurements were taken on the skulls of 271 adult black-footed ferrets and 53 specimens of two closely related species. Skulls were divided based on sex, species, captivity status and phase of captivity and compared for all measurements using stepwise discriminant analysis as well as principal component analysis derived from the combined variables. We found that there are significant differences between captive and wild specimens, some of which are larger than interspecific variation, and that a diet change in the captive specimens likely helped decrease some of these differences. The results suggest that captivity can cause unnatural cranial development and that diet likely has a major impact on cranial morphology.

The Black-footed Ferret Recovery Implementation Team Executive Committee is conducting a project to develop, and (hopefully) eventually implement, a plague vaccination program for prairie dogs. The project is a component of the Western Association of Fish and Wildlife Agencies Grasslands Conservation Initiative. An effective, field-worthy vaccine against plague could be the biggest breakthrough in recovery efforts for the black-footed ferret since the 1981 rediscovery of wild ferrets near Meeteetse, Wyoming. If proven efficacious, the vaccine could help agencies and stakeholder cooperators maintain specific populations of prairie dogs at robust levels, thus enhancing range-wide conservation of those species, as well recovery of the ferret, while enabling control of other prairie dog populations to resolve site-specific agricultural and human health concerns. The results of laboratory and field-testing in the early stages of developing this vaccine are preliminary but mostly encouraging. A plan for broad-scale application is being developed for possible use when testing has been completed and (if warranted) the vaccine is registered for governmental use. An overview of all aspects of the project is discussed.

In western North America, sylvatic plague (a flea-borne disease) poses a significant risk to endangered black-footed ferrets (Mustela nigripes) and their primary prey, prairie dogs (Cynomys spp.). Pulicides (flea-killing agents) can be used to suppress fleas and thereby manage plague. In South Dakota, US, we tested edible "FipBit" pellets, each containing 0.84 mg fipronil, on free-living black-tailed prairie dogs (Cynomys ludivicianus). FipBits were applied along transects at 125 per ha and nearly eliminated fleas for 2 mo. From 9–14 mo post-treatment, we found only 10 fleas on FipBit sites versus 1,266 fleas on nontreated sites. This degree and duration of flea control should suppress plague transmission. FipBits are effective, inexpensive, and easily distributed but require federal approval for operational use. [ABSTRACT FROM AUTHOR]

The plague bacterium, Yersinia pestis, is a generalist pathogen of flea (Siphonaptera) vectors and mammalian hosts. In colonies of prairie dogs (PDs, Cynomys spp.), Y. pestis causes occasional epizootics, killing ≥90% of PDs within weeks to several months. We evaluated the effectiveness of deltamethrin, a pyrethroid insecticide, as a tool for preventing plague epizootics among three PD species. Specifically, we studied PD population growth on paired plots treated with deltamethrin for flea control or left untreated as baselines. We also evaluated PD population growth relative to flea abundance and PD density. All epizootics occurred on nontreated plots. Epizootics occurred on plots with very low PD densities as well as high densities. Mean population change, assessed by comparing visual counts of PDs in years before and during epizootics, was +88% for treated plots and −97% for nontreated plots. For comparison, an experimental oral vaccine against plague had an average change in population index or estimate during epizootics of −69% on vaccine plots compared with −83% for associated nontreated (placebo) plots. In our study and on plots not treated with deltamethrin, PD population growth was negatively correlated with flea abundance in the year before the epizootic, lending support to the hypothesis that flea abundance plays a critical role in plague transmission under natural conditions. Generally speaking, deltamethrin is a highly effective tool for plague management on PD colonies. That said, continued study is needed to refine deltamethrin treatments and to develop a more integrated strategy for plague management. [ABSTRACT FROM AUTHOR]

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® 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® 5% carbaryl; Dusta-cide® 6% malathion; Alpine® 0.25% dinotefuran with 95% diatomaceous earth; and Tri-Die® 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. [ABSTRACT FROM AUTHOR]

A 47-day-old black-footed ferret (Mustela nigripes) kit was found dead in June 2016. Histologic examination revealed pyogranulomatous tubulointerstitial nephritis, pneumonia, and encephalitis, with intralesional microsporidia. Transmission electron microscopic examination showed microsporidia with ultrastructural characteristics consistent with Encephalitozoon spp. Polymerase chain reaction (PCR) and direct sequencing confirmed the presence of Encephalitozoon cuniculi genotype II. This organism has been reported in other Carnivora (i.e., canids, felids, mustelids, procyonids, otariids). In humans, it is generally described as an opportunistic pathogen in immunocompromised individuals. The source of infection in the quarantine facility remains unknown, although two groups of frozen feeder rat kidneys tested positive for E. cuniculi genotype II via PCR. Feeding whole prey to various zoo taxa carries some potential disease transmission risk. [ABSTRACT FROM AUTHOR]

Plague is a flea-borne disease of mammalian hosts. On the grasslands of western North America, plague stifles populations of Cynomys spp. prairie dogs (PDs). To manage plague, PD burrows are treated with 0.05% deltamethrin dust that can suppress flea numbers and plague transmission. Here, we evaluate the degree and duration of deltamethrin flea control with three PD species at six sites across four U.S. states. Data were simultaneously collected at paired plots. Burrows from one randomly assigned member of each pair were treated with deltamethrin; non-treated plots served as experimental baselines. Flea control was strong =two months after treatment, remained moderate one year later, and was statistically detectable for up to two years at some sites. Flea abundance was lower in plots with higher rates of deltamethrin application. After burrow treatments, flea abundance increased over time, reaching >one per PD within 255 to 352 days. Nevertheless, annual treatments of burrows with deltamethrin provided PDs with substantial protection against plague. Even so, deltamethrin should be further evaluated and combined with other tools under an integrated approach to plague management. Integrated plague management should help to conserve PDs and species that associate with them, including the endangered black-footed ferret (Mustela nigripes). [ABSTRACT FROM AUTHOR]

Sylvatic plague poses a substantial risk to black-tailed prairie dogs (Cynomys ludovicianus) and their obligate predator, the black-footed ferret (Mustela nigripes). The effects of plague on prairie dogs and ferrets are mitigated using a deltamethrin pulicide dust that reduces the spread of plague by killing fleas, the vector for the plague bacterium. In portions of Conata Basin, Buffalo Gap National Grassland, and Badlands National Park, South Dakota, US, 0.05% deltamethrin has been infused into prairie dog burrows on an annual basis since 2005. We aimed to determine if fleas (Oropsylla hirsuta) in portions of the Conata Basin and Badlands National Park have evolved resistance to deltamethrin. We assessed flea prevalence, obtained by combing prairie dogs for fleas, as an indirect measure of resistance. Dusting was ineffective in two colonies treated with deltamethrin for >8 yr; flea prevalence rebounded within 1 mo of dusting. We used a bioassay that exposed fleas to deltamethrin to directly evaluate resistance. Fleas from colonies with >8 yr of exposure to deltamethrin exhibited survival rates that were 15% to 83% higher than fleas from sites that had never been dusted. All fleas were paralyzed or dead after 55 min. After removal from deltamethrin, 30% of fleas from the dusted colonies recovered, compared with 1% of fleas from the not-dusted sites. Thus, deltamethrin paralyzed fleas from colonies with long-term exposure to deltamethrin, but a substantial number of those fleas was resistant and recovered. Flea collections from live-trapped prairie dogs in Thunder Basin National Grassland, Wyoming, US, suggest that, in some cases, fleas might begin to develop a moderate level of resistance to deltamethrin after 5–6 yr of annual treatments. Restoration of black-footed ferrets and prairie dogs will rely on an adaptive, integrative approach to plague management, for instance involving the use of vaccines and rotating applications of insecticidal products with different active ingredients. [ABSTRACT FROM AUTHOR]

Captive breeding is used for the conservation of endangered species, but inbreeding can result when a small number of founders are used to establish populations. Inbreeding can reduce the proportion of normal sperm in an ejaculate, but may also have effects on sperm size and shape (morphometry). We investigated the effects of inbreeding on sperm morphometry of black-footed ferrets ( Mustela nigripes (Audubon and Bachman, 1851)) and red wolves ( Canis rufus Audubon and Bachman, 1851) from captive breeding programs to determine if more inbred males produced sperm of poor quality (bulky head, small midpiece, short tail). We measured sperm head length, head width, midpiece length, midpiece width, and tail length on 10 sperm from each male of both species. A negative relationship between variation in sperm tail length and inbreeding coefficient ( f) was found in black-footed ferret, suggesting that more inbred individuals will have reduced genetic and phenotypic variation. Analyses indicated a negative relationship between sperm head width and f and a positive relationship between sperm tail length and f in red wolf, suggesting that more inbred male red wolves could have faster sperm. These results indicate that inbreeding affects functionally important aspects of sperm morphometry, but that these effects may not be entirely negative. [ABSTRACT FROM AUTHOR]

ABSTRACT Reducing coyote (Canis latrans) predation can be an important management objective. Here, we evaluated the efficacy of electronet fencing for excluding coyotes from focal areas on black tailed prairie dog (Cynomys ludovicianus) colonies, measured the effect of fencing on wild‐born black‐footed ferret (Mustela nigripes) kit survival, and modeled costs and benefits of fencing. From 27 July to 2 October 2010 in north‐central Montana, USA, we erected and maintained 7.7 km of electronet that enclosed 108 ha on portions of 2 prairie dog colonies. We monitored 2 female ferrets and 6 kits inside exclosures and 3 females and 12 kits outside of exclosures. Percent of coyote sightings in the protected areas was 6 times less than expected during the exclosure period (42% pre‐exclosure, 7% exclosure, 47% post‐exclosure). We conclude that the electronet fencing was effective for dramatically decreasing coyote activity in focal areas where black‐footed ferret litters were being raised. We found evidence that survival of kits living primarily in protected areas was 22% higher, but we qualify this finding because of low sample sizes and because our monitoring activity on the study site may have influenced coyote activity. We estimated one‐time costs for fencing to be US$4,464/km and operation and/or maintenance costs for the 68 days of fence operation to be US$641/km. If fencing increased survival by 20–30%, then total cost per ferret kit not lost to coyote predation would range between US$5,400 and $3,600, or US$2,550 and $1,700 if fence set‐up–take‐down labor and use of an all‐terrain vehicle were donated. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Sylvatic plague, a primarily flea-borne zoonosis, is a significant threat to prairie dogs ( Cynomys spp., PDs) and their specialized predators, endangered black-footed ferrets ( Mustela nigripes , BFFs). Host-fed fipronil baits have proven effective in controlling fleas on PDs for the purposes of plague mitigation and BFF conservation. Currently, annual treatments are the norm. We tested the long-term efficacy of fipronil bait treatments with black-tailed PDs ( C. ludovicianus , BTPDs) and BFFs in South Dakota, USA. During 2018-2020, we provided BTPDs on 21 sites with grain bait formula, laced with 0.005% fipronil (50 ​mg/kg); 18 non-treated sites functioned as baselines. In 2020-2022, we live-trapped, anesthetized, and combed BTPDs for fleas. Flea control was significant for at least 639-885 days. Flea abundance on the treated sites was < 0.5 fleas/BTPD for ∼750 days. During 2020-2022, we sampled BFFs for fleas on 4 BTPD colonies treated with fipronil grain bait and 8 non-treated colonies. Flea control was significant with BFFs, but flea abundance began to rebound within ∼240 days post-treatment. When feasible, the combination of insecticide treatments, such as fipronil baits, and BFF vaccination against plague provide a "two-pronged" protection approach for these endangered carnivores. If fipronil bait treatments are less effective with predatory BFFs than PDs, as found herein, the "two-pronged" approach might be used to protect BFFs and biennial fipronil bait treatments might be used to protect PDs. If BFF vaccination is not possible, or few BFFs can be vaccinated, annual fipronil bait treatments might be used as a precaution to protect BFFs. Flea densities might be surveyed to determine when/where more frequent treatments seem useful., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 Published by Elsevier B.V.)

In 2008 and 2009, we evaluated the duration of prophylactic deltamethrin treatments in white-tailed prairie dog ( Cynomys leucurus) colonies and compared effects of autumn or spring dust application in suppressing flea numbers and plague. Plague occurred before and during our experiment. Overall, flea abundance tended to increase from May or June to September, but it was affected by deltamethrin treatment and plague dynamics. Success in trapping prairie dogs (animals caught/trap days) declined between June and September at all study sites. However, by September trap success on dusted sites (19%; 95% confidence interval [CI] 16-22%) was about 15-fold greater than on undusted control sites (1%; CI 0.3-4%; P≤0.0001). Applying deltamethrin dust as early as 12 mo prior seemed to afford some protection to prairie dogs. Our data showed that dusting even a portion of a prairie dog colony can prolong its persistence despite epizootic plague. Autumn dusting may offer advantages over spring in suppressing overwinter or early-spring flea activity, but timing should be adjusted to precede the annual decline in aboveground activity for hibernating prairie dog species. Large colony complexes or collections of occupied but fragmented habitat may benefit from dusting some sites in spring and others in autumn to maximize flea suppression in a portion of the complex or habitat year-round. [ABSTRACT FROM AUTHOR]

Black-footed ferrets (Mustela nigripes (Audubon and Bachman, 1851)), a North American species of mustelid, faced near extinction after westward expansion during the 20th century destroyed a majority of the population of prairie dogs (genus Cynomys Rafinesque, 1817), their primary food source. Fearing extinction of the black-footed ferret, the U.S. Fish and Wildlife Service captured the entire population between 1985 and 1987 and began a captive breeding program. While in captivity, the fertility and genetic diversity of the species was closely monitored; however, there is little information about other health consequences of this breeding program. For instance, the black-footed ferrets have been fed a diet that is very different than what they consume in the wild. How did the composition of this diet affect the oral health of these animals? An analysis of dentition of wild and captive black-footed ferrets reveals that calculus accumulation and periodontal diseases occurred with greater severity in captive black-footed ferrets, suggesting that such oral pathologies arose from the unnaturally soft diet fed to them. These findings offer insight into how mechanical properties of diet can affect oral health and how these dietary properties should be considered, not only in regard to the health of black-footed ferrets but also to the health of all mammals including humans. [ABSTRACT FROM AUTHOR]

Interspecies somatic cell nuclear transfer (iSCNT) could benefit recovery programs of critically endangered species but must be weighed with the risks of failure. To weigh the risks and benefits, a decision-making process that evaluates progress is needed. Experiments that evaluate the efficiency and efficacy of blastocyst, fetal, and post-parturition development are necessary to determine the success or failure or species-specific iSCNT programs. Here, we use the black-footed ferret (Mustela nigripes) as a case study for evaluating this emerging biomedical technology as a tool for genetic restoration. The black-footed ferret has depleted genetic variation yet genome resource banks contain genetic material of individuals not currently represented in the extant lineage. Thus, genetic restoration of the species is in theory possible and could help reduce the persistent erosion of genetic diversity from drift. Extensive genetic, genomic, and reproductive science tools have previously been developed in black-footed ferrets and would aid in the process of developing an iSCNT protocol for this species. Nonetheless, developing reproductive cloning will require years of experiments and a coordinated effort among recovery partners. The information gained from a well-planned research effort with the goal of genetic restoration via reproductive cloning could establish a 21st century model for evaluating and implementing conservation breeding that would be applicable to other genetically impoverished species. [ABSTRACT FROM AUTHOR]

In western North America, endangered black-footed ferrets M ustela nigripes are conserved via reintroduction to colonies of prairie dogs C ynomys spp., their primary prey. Predation is an important source of mortality; coyotes C anis latrans appear to be the most problematic predator, accounting for 67% of known predation events on radio-tagged ferrets. Little is known about what factors affect spatial use of prairie dog colonies by coyotes, or how other animals might affect interactions between coyotes and ferrets. During June- October 2007-2008, we used spotlight surveys to monitor coyotes and ferrets (both years) and rabbits S ylvilagus spp. (first year) on a 452-ha colony of black-tailed prairie dogs C ynomys ludovicianus in the Conata Basin, South Dakota. Coyotes appeared to select areas of the colony used by rabbits, suggesting coyotes hunted rabbits, a common item in their diet. Between midnight and sunrise, ferrets were most commonly observed during early morning (01:00-03:00 h), whereas coyotes were observed mostly during dawn (04:00 h - sunrise) when ferrets were rarely seen. These temporal differences in the timing of observations suggest ferrets tend to remain underground in burrows when coyotes are most active. Coyotes appeared to be attracted to rabbits in both space and time, suggesting the risk of predation for ferrets might relate to the abundance and locations of rabbits in prairie dog colonies. [ABSTRACT FROM AUTHOR]

We evaluated how American badgers (Taxidea taxus) might exert selective pressure on black-footed ferrets (Mustela nigripes) to develop antipredator defenses. In a colony of black-tailed prairie dogs (Cynomys ludovicianus) in South Dakota, badgers concentrated their activities where burrow openings and prairie dogs were abundant, a selective behavior that was exhibited by ferrets in the same colony. Badgers excavated burrows more often when in areas recently used by a ferret, suggesting that badgers hunt ferrets or steal prey from ferrets, or both. We also conducted an analysis of survival studies for ferrets and Siberian polecats (M. eversmanii) released onto prairie dog colonies. This polecat is the ferret's ecological equivalent but evolved without a digging predator. Badgers accounted for 30.0% of predation on polecats and 5.5% of predation on ferrets. In contrast, both polecats and ferrets have evolutionary experience with canids, providing a plausible explanation for the similar relative impact of coyotes (Canis latrans) on them (65.0% and 67.1% of predation, respectively). We hypothesize that ferrets and badgers coexist because ferrets are superior at exploitation competition and are efficient at avoiding badgers, and badgers are superior at interference competition. [ABSTRACT FROM AUTHOR]

Questions and problems that emerged during operational conservation of black-footed ferrets (Mustela nigripes) have been addressed by a wide variety of studies. Early results from such studies often were communicated orally during meetings of recovery groups and in written form using memoranda, unpublished reports, and theses. Typically, implementation of results preceded their publication in widely distributed journals. Many of these studies eventually were published in journals, and we briefly summarize the contents of 8 volumes and special features of journals that have been dedicated to the biology of ferrets and issues in ferret recovery. This year marks the 30th anniversary of rediscovery of the black-footed ferret, and the 7 papers of the following Special Feature summarize data collected over nearly that span of time. [ABSTRACT FROM AUTHOR]

Radiotelemetry was used during 1983 and 1984 to collect information on short-term areas of activity for black- footed ferrets (Mustela nigripes) near Eyeteeth, Wyoming. This population ultimately provided ferrets for the captive-breeding program that bred and released offspring into the wild since 1991. We fitted 5 adult ferrets and 13 juveniles with radiotransmitters and followed their movements during late summer and fall. Adult males had 7-day areas of activity that were >6 times as large as those of adult females. Activity areas of adult males varied little in coverage or location on a weekly basis, but females sequentially shifted their areas. Unlike juvenile females, juvenile males tended to leave their natal colonies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ecologically equivalent species serve similar functions in different communities, and an ecological surrogate species can be used as a substitute for an equivalent species in a community. Siberian polecats (Mustela eversmanii) and black-footed ferrets (M. nigripes) have long been considered ecological equivalents. Polecats also have been used as investigational surrogates for black-footed ferrets, yet the similarities and differences between the 2 species are poorly understood. We contrasted activity patterns of radiotagged polecats and ferrets released onto ferret habitat. Ferrets tended to be nocturnal and most active after midnight. Polecats were not highly selective for any period of the day or night. Ferrets and polecats moved most during brightly moonlit nights. The diet activity pattern of ferrets was consistent with avoidance of coyotes (Canis latrans) and diurnal birds of prey. Similarly, polecat activity was consistent with avoidance of red foxes (Vulpes vulpes) in their natural range. Intraguild predation (including interference competition) is inferred as a selective force influencing behaviors of these mustelines. Examination of our data suggests that black-footed ferrets and Siberian polecats might be ecological equivalents but are not perfect surrogates. Nonetheless, polecats as surrogates for black-footed ferrets have provided critical insight needed, especially related to predation, to improve the success of ferret reintroductions. [ABSTRACT FROM AUTHOR]

We investigated postbreeding resource selection by adult black-footed ferrets (Mustela nigripes) on a 452-ha black-tailed prairie dog (Cynomys ludovicianus) colony in the Conata Basin of South Dakota during 2007-2008. We used resource selection functions (RSFs) to evaluate relationships between numbers of ferret locations and numbers of prairie dog burrow openings (total or active), distances to colony edges, and connectivity of patches of burrow openings. In both years ferrets selected areas near edges of the prairie dog colony where active burrow openings were abundant. In the interior of the colony ferrets selected areas with low abundance of active burrow openings. At times, prairie dog productivity (i.e., pup abundance) might be greatest at colony edges often characterized by grasses; ferrets are likely to select areas where refuge and vulnerable prey are abundant. Ferrets could have used interior areas with few active burrow openings as corridors between edge areas with many active burrow openings. Also, in areas with few active burrow openings ferrets spend more time aboveground during movements and, thus, are likely to be more easily detected. These results complement previous studies demonstrating importance of refuge and prey in fine-scale resource selection by ferrets and provide insight into factors that might influence edge effects on ferret space use. Conservation and restoration of colonies with areas with high densities of burrow openings and prairie dogs, and corridors between such areas, are needed for continued recovery of the black-footed ferret. RSFs could complement coarse-scale habitat evaluations by providing finer-scale assessments of habitat for the black-footed ferret. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]