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Recovery Strategy for the Black-footed Ferret (Mustela nigripes) in Canada

1. Background

1.1 Species assessment information from COSEWIC

Date of Assessment: May 2000

Common Name: black-footed ferret

Scientific Name: Mustela nigripes

Status: Extirpated

Reason for Designation: This ferret no longer occurs in the wild in Canada. Prairie dogs, the ferret's necessary and preferred prey species, are now limited to a small area of Saskatchewan.

Occurrence: Alberta, Saskatchewan, Manitoba

Status History: Extirpated by 1974. Designated Extirpated in April 1978. Status re-examined and confirmed in May 2000. Last assessment based on an existing status report.

1.2 Description

The black-footed ferret is a nocturnal, intermediate-sized member of the weasel family (Mustelidae). Both sexes have yellowish-buff fur with lighter under parts, a nearly white face and throat, black legs, a black-tipped tail and a black mask across the eyes. Adult ferrets weigh 0.75 to 1.2 kg and have a total length of approximately 0.5 meters (Anderson 1986). Females are usually about 10% smaller than males (Fitzgerald 1994).

1.3 Populations and distribution

Black-footed ferrets are the only ferret species native to North America. Their distribution is tightly linked to that of their primary prey, black-tailed prairie dogs (C. ludovicianus), white-tailed prairie dogs (Cynomys leucurus) and Gunnison's prairie dogs (C. gunnisoni) (Biggins 2003). As prairie dog control measures and sylvatic plague devastated prairie dog populations, black-footed ferret populations crashed. Black-footed ferrets were thought to be globally extinct until 1981 when a small population was discovered near Meeteetse, Wyoming. All current populations of black-footed ferrets descend from this last remaining population.

Canadian Distribution

Currently extirpated from Canada, the historical range of black-footed ferrets included southwestern Saskatchewan and southeastern Alberta (Figure 1; COSEWIC 2000). The last confirmed record of black-footed ferrets in Canada occurred in 1937 near Climax, Saskatchewan, in the vicinity of the Frenchman River valley. Despite the close ecological relationship between prairie dogs and black-footed ferrets, the black-footed ferret's range in Canada also appears to have extended beyond that of prairie dogs (Laing & Holroyd 1989). This implies that historically, black-footed ferrets exploited alternative prey sources and habitats in Canada, possibly preying on Richardson's ground squirrels (Spermophilus richardsonii). Although there are relatively few historical records of ferrets in areas near prairie dog colonies in the Frenchman River valley, this is likely due to the fact that the colonies were in a remote area of Saskatchewan where incidental observations were unlikely and systematic surveys had not occurred.

Global Distribution

Black-footed ferrets are classified as extinct by the IUCN Red List and are listed on Appendix 1 of CITES (IUCN 2006a). However, the IUCN listing has not been updated since 1994 when only preliminary reintroduction of ferrets had occurred. In the U.S., the Endangered Species Act lists black-footed ferrets as 'Endangered' throughout their range. However, most extant wild populations are classified as 'Experimental/Nonessential' pursuant to the Act. Reintroduction efforts have resulted in black-footed ferrets currently occurring in Montana, South Dakota, Wyoming, Arizona, Colorado and Utah.

Black-footed ferrets are not officially listed by the Mexican government. Reintroduction efforts have occurred in the Chihuahua region.


Figure 1. Black-footed ferret's historical range and reintroduction locations

Black-footed ferret's historical range and reintroduction locations (see long description below).

Livieri, pers. comm.

Description of Figure 1

Figure 1 is a map that displays the source population of Black-footed ferret sites, their release sites, their historical range and the Grasslands National Park.


Conservation breeding program

Between 1985 and 1987, 18 wild black-footed ferrets were brought into captivity from the Meeteetse, Wyoming population in an attempt to develop a conservation breeding program. Successful breeding and husbandry techniques have been developed, and currently seven breeding facilities exist in North America. This program has produced approximately 5800 ferrets since 1987 (Marinari pers. comm.), all descended from seven founder animals. Genetic diversity and kit production are maximized within the breeding program through the Association of Zoos and Aquariums (AZA) Black-footed Ferret Species Survival Plan (SSP). This successful conservation breeding program has provided ferrets for 11 separate reintroduction sites across six U.S. states and in Mexico (Lockhart pers. comm.). Captive-bred ferrets are allocated for release by the U.S. Fish & Wildlife Service (USFWS).

The Toronto Zoo, a member of the AZA Black-footed Ferret SSP and a partner of the U.S. Black-footed Ferret Recovery Implementation Team (BFFRIT), is the only Canadian organization actively breeding black-footed ferrets for reintroduction. Since 1992, the Toronto Zoo has raised 269 kits (young), the majority of which have been reintroduced into the wild in the U.S. and Mexico. The Toronto Zoo's participation in this conservation breeding program has added a Canadian component to international ferret recovery efforts over the past 15 years.

1.4 Needs of the black-footed ferret

1.4.1 Habitat and biological needs

The black-footed ferret is a prairie species that inhabits semi-desert shrubland, short-grass and mixed-grass ecosystems where prairie dogs are present. Black-footed ferrets require active prairie dog colonies for their year-round habitat throughout all stages of their lifecycle. Prairie dogs comprise approximately 90% of the black-footed ferret's diet (Campbell et al. 1987; Sheets et al. 1972). Black-footed ferrets also rely on prairie dog burrows for shelter, escaping predators, and rearing their young (Miller & Forrest 1996).

Black-tailed prairie dogs, the only species of prairie dog occurring in Canada, are limited to southwestern Saskatchewan. In 2006, prairie dog colonies occurred on two privately managed ranches, as well as the Masefield Agri-Environment Services Branch Community Pasture, the Dixon Provincial Community Pasture and Grasslands National Park of Canada. Of the 1000 hectares (ha) of prairie dog colonies occurring in Canada, approximately two-thirds are located within Grasslands National Park. Overall, surveyed colonies have been stable or increasing in size since 1994 (R. Sissons, unpublished data). Prairie dogs co-exist with cattle grazing.

Vegetation and topography have indirect effects on black-footed ferrets as they influence prairie dog colony establishment and size (Sheets et al. 1971). Both the size of the prairie dog colony and the density of prairie dogs are critical components of black-footed ferret habitat (Biggins et al. 1998); however, the relationship between these two habitat components is not well understood. The relationship between black-footed ferrets and vegetation or topography has not been studied directly. Throughout the black-footed ferret's historical range, prairie dog colonies occurred in a diversity of grass and shrub/grass communities with differing topographical relief.

This suggests that size and density of prairie dog colonies may be more important elements of black-footed ferret habitat than vegetation or topography (Forrest et al. 1985; Knowles 2005).

Prairie dog density

Biggins et al. (1993) estimated that a minimum density of 3.63 prairie dogs/ha is needed to meet the breeding requirements of black-footed ferrets. They noted that prairie dog colonies below this threshold may still support non-breeding ferrets and play a role in the persistence of ferrets. Lower density colonies could provide a buffer of replacement ferrets and may be instrumental in maintaining breeding populations over the long term.

Social behaviour may dictate a maximum black-footed ferret density regardless of prey abundance. Although more than one family group of ferrets may occasionally occupy the same area simultaneously (Paunovich & Forrest 1987; Richardson et al 1987), the solitary, territorial nature of black-footed ferrets limits their density even when prey numbers are high. Reintroduced ferret populations in South Dakota showed a minimum female territory size of approximately 30 ha even when prey density was high enough to energetically support one female per 20 ha or less (Biggins et al. 2006b). A complex of several prairie dog colonies, each with high enough density to support a female and her litter, may support more ferrets overall then would large blocks of uniform habitat by reducing the limiting effect of female territoriality (Biggins et al. 2006b).


1.4.2 Ecological role

The black-footed ferret is a highly specialized predator of prairie dogs. The tight relationship between ferrets and prairie dogs suggests a long-term association between these two species (Hillman & Clark 1980). Ferrets themselves are also prey for a range of larger mammalian and avian predators.


1.4.3 Limiting factors

The black-footed ferret is a highly specialized carnivore. The ferrets' specialization in both prey and habitat requirements makes them especially vulnerable to declines in prairie dog distribution and density. With only approximately 1000 ha of prairie dog colonies currently occurring in Canada, the availability of suitable habitat could be a significant factor limiting ferret recovery. The potential for black-footed ferrets to utilize Richardson's ground squirrels for both habitat (burrows) and prey is unknown in Canada, but the historical range of ferrets beyond prairie dog colonies suggests this is a possibility (Laing & Holroyd 1989). The significance of this limiting factor in Canada will be determined through ongoing evaluation of behaviour, survival, and population viability of both ferrets and prairie dogs.

1.5 Threats

1.5.1 Threat classification

Table 1 (1. Sylvatic Plague): Threat classification table (Local refers to Canadian populations; Range-wide refers to North American population distribution.)
 1. Sylvatic PlagueThreat Information
Threat CategoryExotic speciesExtent: Widespread
General ThreatSylvatic plagueOccurrence (Local): Anticipated
Occurrence (Range-wide): Current
Frequency (Local): Recurrent
Frequency (Range-wide): Recurrent
Specific ThreatIncreased incidence or prevalence rate of disease, reduced prey availabilityCausal Certainty (Local): High
Causal Certainty (Range-wide): High

Severity (Local): High
Severity (Range-wide): High
StressIncreased mortality, reduced population sizeLevel of Concern: High

 

Table 1 cont. (2. Natural Diseases): Threat classification table (Local refers to Canadian populations; Range-wide refers to North American population distribution.)
 2. Natural DiseasesThreat Information
Threat CategoryNatural processes or activitiesExtent: Widespread
General ThreatCanine distemper virus, rabiesOccurrence (Local): Anticipated
Occurrence (Range-wide): Current
Frequency (Local): Recurrent
Frequency (Range-wide): Recurrent
Specific ThreatIncreased incidence or prevalence rate of disease, reduced prey availabilityCausal Certainty (Local): High
Causal Certainty (Range-wide): High

Severity (Local): Moderate
Severity (Range-wide): Moderate
StressIncreased mortality, reduced population sizeLevel of Concern: Moderate

 

Table 1 cont. (3. Predation): Threat classification table (Local refers to Canadian populations; Range-wide refers to North American population distribution.)
 3. PredationThreat Information
Threat CategoryNatural processes or activitiesExtent: Widespread
General ThreatCarnivores that prey upon ferretsOccurrence (Local): Anticipated
Occurrence (Range-wide): Historic
Frequency (Local): Continuous
Frequency (Range-wide): Continuous
Specific ThreatPredation by carnivores such as individual owls that learn to specialize on ferrets during the time shortly after releaseCausal Certainty (Local): High
Causal Certainty (Range-wide): High

Severity (Local): High
Severity (Range-wide): Low
StressIncreased mortalityLevel of Concern: Moderate

 

Table 1 cont. (4. Richardson's ground squirrel poisoning): Threat classification table (Local refers to Canadian populations; Range-wide refers to North American population distribution.)
 4. Richardson's ground squirrel poisoningThreat Information
Threat CategoryChanges in ecological dynamics or natural processesExtent: Widespread
General ThreatRichardson's ground squirrel suppressionOccurrence (Local): Current
Occurrence (Range-wide): Current
Frequency (Local): Unknown
Frequency (Range-wide): Continuous
Specific ThreatReduced prey availability, consumption of poisoned preyCausal Certainty (Local): Low
Causal Certainty (Range-wide): Low

Severity (Local): Unknown
Severity (Range-wide): Unknown
StressReduced population size, increased mortalityLevel of Concern: Unknown

 

Table 1 cont. (5. Black-tailed prairie dog poisoning): Threat classification table (Local refers to Canadian populations; Range-wide refers to North American population distribution.)
 5. Black-tailed prairie dog poisoningThreat Information
Threat CategoryChanges in ecological dynamics or natural processesExtent: Widespread
General ThreatPrairie dog suppressionOccurrence (Local): Historic
Occurrence (Range-wide): Current
Frequency (Local): Unknown
Frequency (Range-wide): Recurrent
Specific ThreatReduced prey availability, consumption of poisoned preyCausal Certainty (Local): High
Causal Certainty (Range-wide): High

Severity (Local): High
Severity (Range-wide): High
StressReduced population size, increased mortalityLevel of Concern: Low

 

Table 1 cont. (6. Climate change): Threat classification table (Local refers to Canadian populations; Range-wide refers to North American population distribution.)
 6. Climate changeThreat Information
Threat CategoryClimate and natural disastersExtent: Widespread
General ThreatChanges in weather patternsOccurrence (Local): Anticipated
Occurrence (Range-wide): Anticipated
Frequency (Local): Unknown
Frequency (Range-wide): Unknown
Specific ThreatIncreased frequency and/or duration of droughtsCausal Certainty (Local): Low
Causal Certainty (Range-wide): Low

Severity (Local): Unknown
Severity (Range-wide): Unknown
StressReduced prey availability, reduced reproduction rateLevel of Concern: Low

 

Table 1 cont. (7. Reduced genetic diversity): Threat classification table (Local refers to Canadian populations; Range-wide refers to North American population distribution.)
 7. Reduced genetic diversityThreat Information
Threat CategoryNatural processes or activitiesExtent: Widespread
General ThreatInbreeding depressionOccurrence (Local): Unknown
Occurrence (Range-wide): Unknown
Frequency (Local): Continuous
Frequency (Range-wide): Continuous
Specific ThreatReduced genetic diversityCausal Certainty (Local): Low
Causal Certainty (Range-wide): Low

Severity (Local): Moderate
Severity (Range-wide): Moderate
StressReduced reproduction and survivalLevel of Concern: Low

 


1.5.2 Description of threats

Threat 1 - Sylvatic plague

Sylvatic plague, caused by the bacterium Yersinia pestis, is one of the primary factors limiting black-footed ferret recovery in the U.S. Effective prevention or control strategies for plague are not currently available. Black-footed ferrets are highly susceptible to plague and may suffer high mortality rates on infection (Williams et al. 1994). Plague also dramatically impacts the black-footed ferret's main prey, prairie dogs. Prairie dogs have exhibited 90 to 100 percent mortality upon infection (Antolin et al. 2002; Cully & Williams 2001; Lorange et al. 2005; Stapp et al. 2004). Although it was thought that prairie dogs cannot survive in the presence of even low levels of plague, recent evidence suggests that the disease can exist in prairie dog colonies without causing widespread mortality (Hanson et al. 2007).

The main plague transmission route for prairie dogs is via the bites of infected fleas and, for ferrets, through both flea bites and direct consumption of infected prey or carrion (Butler et al. 1982; Castle et al. 2001; Rocke et al. 2004; Thomas et al. 1989). Plague-resistant mammals, such as coyotes and other rodents, may serve as reservoir hosts. Disease modeling suggests that fleas are important in the initial introduction and establishment of plague in prairie dog towns, but that transmission from a different short-term reservoir, such as a plague-resistant rodent species, may also serve a role in the dynamics of plague outbreaks (Webb et al. 2006).

At the landscape level it appears that roads, streams and lakes may serve as barriers to plague in black-tailed prairie dog colonies by affecting the movement of, or habitat quality for, either plague hosts or fleas that serve as the vector (Collinge et al. 2005). While sylvatic plague has not been documented in prairie dogs in Canada, antibodies for plague have been found in 4.2 % of rural domestic dogs and cats in southern Saskatchewan including areas near Grasslands National Park (Leighton et al. 2001).

Ultimately, control of plague in black-footed ferrets would require the control of this disease in prairie dogs. The effectiveness of several insecticides to control flea populations on prairie dogs and in prairie dog burrow systems has been investigated (Hoogland et al. 2004; Karhu & Anderson 2000; Seery et al. 2003). These studies show that insecticidal dusting during the early stages of an outbreak can stop the spread of plague, while application during later stages does not. Work is also underway to develop a vaccine against plague for use in black-footed ferrets. A small-scale clinical study found that a vaccine that has been developed offers black-footed ferrets some protection from Y. pestis (Rocke et al. 2006), but the duration of the protection as well as the effectiveness of the vaccine against different routes of exposure and different levels of Y. pestis remain unknown. The effectiveness of this vaccine over time in protecting wild black-footed ferrets against infection is currently being assessed in the U.S. While the likelihood of a sylvatic plague outbreak in the ferret reintroduction area is unknown, the impacts on the ferret population could be dramatic if it occurred.

Threat 2 - Natural diseases

Canine distemper virus (CDV) is a globally distributed Morbillivirus virus species affecting many terrestrial carnivores and aquatic carnivores. Members of the weasel family are among the most susceptible to CDV disease (Deem et al. 2000). Blood testing shows CDV is present in wild dog populations on the Canadian prairie, including southern Saskatchewan. Eleven of 21 swift foxes that were tested contained antibodies indicative of CDV infection (A. Moehrenschlager, unpublished data). Black-footed ferrets are extremely susceptible to CDV exhibiting nearly 100 percent morbidity and mortality when exposed experimentally and naturally (Liu & Coffin 1957; Williams et al. 1988).

Rabies, a viral disease affecting the central nervous system, has been documented in Saskatchewan (Canadian Food Inspection Agency (CFIA) 2006). The implementation of an effective ferret vaccination protocol for rabies, such as has been done in the U.S., effectively addresses this threat.

A range of other diseases may pose a low risk level to wild black-footed ferrets in Canada, but are not a deterrent to the reintroduction of ferrets. These diseases include:

  • Tularemia (Francisella tularensis)
  • Parvovirus
  • Toxoplasmosis (Toxoplasma gondhii) - seen in captive black-footed ferret populations
  • Coccidiosis - higher morbidity and mortality in captive black-footed ferret populations
  • Cryptosporidiosis (Cryptosporidium parvum) - seen in captive black-footed ferret populations
  • Influenza
  • Blastomycosis (Blastomyces dermatidis).
Threat 3 - Predation

Numerous mammalian and avian predators, such as coyotes and Great Horned Owls, occur in southwestern Saskatchewan and may prey on black-footed ferrets. Predation has been a problem at reintroduction sites, causing up to 95% of the documented mortality of ferrets (Breck et al. 2006). Review of data from South Dakota and Montana indicates that removal of individual Great Horned Owls causing significant ferret mortality can be beneficial but that lethal control of coyotes and the use of electric fencing does not enhance short- or long-term survival of reintroduced ferrets (Breck et al. 2006). This review also indicates that the data are confounded by a variety of factors and that further studies are needed to properly address the effectiveness of predator management for enhancing ferret survival.

In the Grasslands National Park area the Great Horned Owl (Bubo virginianus) population is currently artificially high. Great Horned Owls typically occur in woodlands that contain some open habitat (Houston et al 1998) not in prairie grassland ecosystems. However, abandoned buildings and shelter belts have altered the mixed-grass prairie of southwestern Saskatchewan to the extent that Great Horned Owls are now one of the most common raptors nesting in Grasslands National Park (Sissons pers. comm.). This could lead to significant mortality of ferrets by Great-Horned Owls and the need for removal of individual owls.

Threat 4 - Richardson's ground squirrel poisoning

Poisoning of Richardson's ground squirrels is widespread outside Grasslands National Park. Though ferrets prey almost exclusively on prairie dogs throughout their range in the U.S., the historic range of ferrets suggests that they may have utilized alternate prey sources in Canada (Clark et al. 1985; Laing & Holroyd 1989). As a result, the consumption of poisoned Richardson's ground squirrels may result in ferret mortality outside Grasslands National Park.

Threat 5 - Black-tailed prairie dog poisoning

Prairie dogs are protected against unlicensed killing on provincial and private lands and are fully protected on lands managed by Parks Canada (Government of Canada 2000; Government of Saskatchewan 1998; Government of Saskatchewan 1981). No permits have been issued for prairie dog poisoning; however, it is possible that illegal poisoning of prairie dogs could occur outside Grasslands National Park. Indirect poisoning via the consumption of contaminated prey could cause ferret mortalities outside Grasslands National Park.

Threat 6 - Climate change

Conservation strategies must consider the effects of climate change, the challenges associated with changes in species distribution and abundance, and geographical variation in the scale of responses to climate change (Hannah et al. 2002; Huntley & Webb 1989). Many studies suggest that the northern plains will experience decreased precipitation and increased mean annual temperature (Karl & Heim 1991; Lemmen et al. 1997; Rizzo & Wiken 1992). Such climatic changes will undoubtedly affect primary productivity in the prairie ecosystem impacting prairie dogs and, in turn, black-footed ferrets. While the extent of this impact is unclear, prairie dog densities have been observed to decline by 80 percent in response to drought (Sissons pers. comm.). Drought is believed to impact ferret reproduction more than adult survivorship with fewer kits produced in association with drought (Miller et al. 2005). The predicted climate change could exacerbate multi-year droughts which may result in the inability of ferret populations to recruit breeding females, as their life expectancy is less than three years.

Threat 7 - Reduced genetic diversity

Loss of genetic variation can reduce individual fitness (fecundity and survival) including the ability to resist disease and the potential for populations to adapt to environmental change (Altizer et al. 2003; Lacy 1997). The loss of the Great Plains populations of black-footed ferrets and the population bottleneck associated with the establishment of the conservation breeding program greatly diminished the species' genetic diversity (Wisely et al. 2002). Due to habitat limitations, the Canadian black-footed ferret population will likely always be small. Preliminary modeling suggests that inbreeding depression has the potential to reduce population viability and that these effects will be greater and experienced sooner in smaller populations (Miller et al. 2005).

1.6. Actions already completed or underway

A successful conservation breeding program has been providing black-footed ferrets for reintroduction in the U.S. and Mexico since 1991. Sufficient animals are being produced from this program to facilitate reintroductions in Canada as well. BFFRIT will apply their in-depth knowledge and experience in the reintroduction and management of black-footed ferrets to assist with ferret recovery in Canada. Extensive analyses and planning have already been completed in an effort to prepare for this reintroduction and will be detailed in an action plan that will follow this recovery strategy.

A number of initiatives have been completed or are underway to consolidate knowledge gained through black-footed ferret recovery efforts in the U.S. and Mexico and to develop a ferret recovery strategy and action plan for Canada. These include:

Workshops and meetings

  • Potential of Black-footed Ferret Recovery in Canada (May 24-25, 2003, Val Marie, Saskatchewan)
    Representatives from government agencies and potential partners investigated the feasibility of initiating black-footed ferret recovery efforts in Canada, leading to the formation of formal workshops.
  • Towards a Management Strategy for Black-tailed Prairie Dogs and Black-footed Ferrets in Southwestern Saskatchewan (June 8-9, 2004, Val Marie, Saskatchewan)
    This workshop brought together 27 scientists and managers from the U.S. and Canada specializing in biological, ecological and management aspects of black-footed ferrets, black-tailed prairie dogs and associated species. The main goal was to share information and advice in order to inform decisions regarding black-footed ferret recovery and black-tailed prairie dog conservation in Canada. This workshop led to the formation of Canada's Black-footed Ferret / Black-tailed Prairie Dog Recovery Team.
  • International Black-footed Ferret Recovery Workshop (April 1-4, 2005, Calgary Alberta)
    Facilitated by the IUCN Conservation Breeding Specialist Group, this population viability analysis workshop brought together 29 black-footed ferret and black-tailed prairie dog scientists and managers from Canada, the U.S. and Mexico to form ferret population goals and recovery strategies for Canada and Mexico. Management and research recommendations were also developed.
  • Black-footed Ferret Recovery Strategy Workshop (September 8-10, 2005, Val Marie, Saskatchewan)
    Utilizing the expertise of those involved in black-footed ferret recovery in the U.S. and input from affected local stakeholders, key elements of the Black-footed Ferret Recovery Strategy, USFWS Ferret Allocation Request and Black-tailed Prairie Dog Management Plan were outlined by the recovery team.
  • Community Focus Groups (November 14-17, 2006, Val Marie, Saskatchewan)
    Seven focus group sessions, moderated by a social science specialist from Parks Canada's Western and Northern Service Centre, were conducted with various stakeholders from the Val Marie area to assess the current knowledge about black-footed ferrets, the level of support for ferret reintroduction and to identify potential concerns around ferret recovery.
  • Black-footed Ferret and Black-tailed Prairie Dog Recovery Team meeting (December 5-6 2006, Val Marie Saskatchewan)
    Team members and invited Parks Canada Agency staff gathered for two days to discuss components of the draft black-footed ferret recovery strategy and to provide input and edits for the final draft.
  • Black-footed Ferret and Black-tailed Prairie Dog Recovery Team meeting (September 5-7 2007, Toronto Zoo, Toronto, Ontario)
    Team members and key U.S. ferret recovery specialists gathered for three days to discuss components of the draft black-footed ferret recovery strategy and action plan and prairie-dog management plan.

Knowledge consolidation

  • Black-footed Ferret and Black-tailed Prairie Dog Communication Plan - Draft 1.0
    (G. Holroyd & M. Franke 2005)
  • An ecological review of the black-footed ferret with special reference to prairie dog habitat in southwestern Saskatchewan (C.J. Knowles 2005)
  • A plague response plan - currently under development by Parks Canada and Claire Jardine (University of Guelph) in conjuction with Saskatchewan Environment, Saskatchewan Health and Health Canada

Research and monitoring

  • Black-tailed prairie dog colony mapping and density counts in Grasslands National Park (Parks Canada - ongoing)
  • Assessment of disease risk for black-footed ferret reintroductions in Grasslands National Park (C. Jardine, G. Crawshaw and T. Shury)
  • Evaluation of the viability of the black-tailed prairie dog metapopulation in Canada (T. Stephens, D. Gummer, and D. Bender - ongoing)
  • Baseline monitoring of Burrowing Owl populations, productivity and distribution in Grasslands National Park and adjacent black-tailed prairie dog colonies (G. Holroyd and H. Trefry - ongoing)

1.7 Knowledge gaps

Many knowledge gaps exist because no scientific studies have been conducted on black-footed ferrets in Canada. With the last confirmed record of a black-footed ferret in Canada occurring in 1937, existing knowledge is based on research in the U.S. and Mexico. This leaves many unknowns around the behaviour of ferrets at the northern edge of their range, their biological and ecological characteristics, and the way they interact with co-existing species. Monitoring the ferrets and the effects of the ferret reintroduction on other species will allow adaptive management of the reintroduced ferret population, reveal any unique considerations regarding ferret recovery in the Canadian Great Plains, and allow threats to be evaluated and mitigated when necessary. Working closely with black-footed ferret recovery committees in the U.S. and Mexico and coordinating recovery efforts on a continental level will benefit recovery of black-footed ferrets across North America. Unifying conservation planning for related prairie species may also create the political, financial and ecological means needed to sustain grassland communities into the future.

  1. The extent to which ferrets in Canada will use alternative prey sources (e.g., Richardson's ground squirrels) is unknown.

  2. Sylvatic plague is severely restricting the recovery of black-footed ferrets in the U.S. and Mexico. Plague has been detected in rural domestic dogs and cats in southwestern Saskatchewan (Leighton et al. 2001), but plague levels are unknown in wild dog and rodent populations. The species that act as reservoirs and/or vectors for this disease are also unknown in Canada.

  3. Insecticidal dusting of prairie dog burrows has been used in many areas in the U.S. to reduce the risk of sylvatic plague outbreaks. Dusting burrows with deltamethrin and/or vaccinating ferrets against plague has increased ferret survival two-fold (Rocke et al. 2006). The long-term impact of dusting on invertebrate populations and other species inhabiting prairie dog colonies, such as Burrowing Owls (Athene cunicularia hypugaea) is unknown.

  4. The extent of predation on reintroduced ferrets is not well known and makes it difficult to predict for the Canadian reintroduction. The effectiveness of predator management for enhancing ferret survival is also unknown.

  5. The carrying capacity of Grasslands National Park and surrounding areas to support black-footed ferrets is unknown. As black-footed ferrets prey primarily on prairie dogs throughout their range, a better understanding of black-tailed prairie dog population dynamics is needed to refine the carrying capacity for ferrets. Evaluating the viability of black-tailed prairie dogs based on demography, spatial distribution, disease risk, habitat characteristics/requirements, predation, weather and climate is necessary to facilitate recovery actions for ferrets. Canadian prairie dog populations may also behave differently from those in the U.S. or Mexico due to their location at the extreme northern edge of the species' distribution. For example, prairie dogs in Grasslands National Park hibernate for approximately four months per year in dense family groups, appear larger in mass and do not experience the same level of human disturbance and population control measures as those in the U.S. (Miller et al. 2005; Rodger et al. 2004). Factors such as these may impact the habitat requirements of ferrets. Once our understanding of carrying capacity is improved, short-term and long-term goals for population size can be formulated.

  6. Climate change may alter species population levels and distribution. Evidence suggests that drought decreases prairie dog populations in Grasslands National Park (Miller et al. 2005), underlining the importance of understanding the impacts of climate on black-footed ferret prey species and predator/prey interactions. Understanding the impacts of climate change may become increasingly important to the recovery of black-footed ferrets.

  7. Little is known about either black-footed ferret behaviour or the demographic characteristics of ferret populations at the northern edge of the species' range. This includes, but is not limited to, ferret sociality, survivorship, productivity, movement and dispersal patterns, prey selection and how these are affected by a ferret's age, sex, reproductive state and history (captive or wild born).

  8. The effects of black-footed ferret recovery on other species at risk in Canada are unknown. Black-tailed prairie dogs, the ferrets' primary prey, are themselves listed as Special Concern (COSEWIC 2006). Ferret releases in the U.S. do not appear to have resulted in declines of prairie dog populations (Rodger et al. 2004). In Canada, however, black-tailed prairie dogs are already susceptible to declines because they occur in a small area with a relatively small population size, are threatened by plague, and are geographically isolated at the edge of the species range (COSEWIC 2000b). Unlike southern prairie dog species, Canadian black-tailed prairie dogs use extensive hibernation to facilitate over-winter survival (Gummer 2005). White-tailed prairie dogs in the U.S. hibernate and sustain predation by ferrets, but they are much more dispersed and solitary during the winter whereas Canadian black-tailed prairie dogs hibernate in large family groups (Gummer 2005). This behaviour may predispose black-tailed prairie dogs in Canada to particularly intensive predation by ferrets.

    Burrowing Owls (Endangered) live on prairie dog colonies (COSEWIC 2006). While the impact of ferret predation on Burrowing Owl populations is unknown, expert opinion suggests it is likely to be minimal (Rodger et al. 2004). Burrowing Owls occur on almost every current ferret reintroduction site in the U.S. and there appears to be no impact of ferret predation at the population level (Livieri pers. comm.). The direct impact of ferrets on Greater Sage-Grouse is also unknown, but thought to be minimal (Rodger et al. 2004).

    Black-footed ferret recovery may impact other species through ferret habitat expansion. While increasing ferret habitat may be beneficial for some species such as the Burrowing Owl, it could be detrimental to others, such as the Greater Sage-Grouse.

Introduction