Recovery Strategy for the Swift Fox (Vulpes velox) in Canada
- 1.1 Species assessment information from COSEWIC
- 1.2 Description
- 1.3 Populations and distribution
- 1.4 Needs of the swift fox
- 1.5 Threats
- 1.6 Knowledge gaps and recommended studies
1.1 Species assessment information from COSEWIC
Common Name: Swift fox
Scientific Name: Vulpes velox
COSEWIC Status: Endangered
Reason for designation: The species was previously extirpated from Canada. A small population is now established in Alberta and Saskatchewan through reintroductions. Animals are successfully breeding in the wild, although the species is potentially at risk from coyote predation and habitat loss.
Canadian Occurrence: Alberta and Saskatchewan
COSEWIC Status History: Last seen in Saskatchewan in 1928. Designated Extirpated in April 1978. Status re-examined and designated Endangered in April 1998 after successful reintroductions. Status re-examined and confirmed in May 2000. Last assessment based on an existing status report.
Swift foxes are cat-sized canids with pale yellowish-red and grey on the upperparts peppered with white and black-tipped hairs; they average 30 cm high at the shoulders and weigh 2.2-2.4 kg (James 1823, Bailey 1926, Soper 1964). Swift foxes have a characteristic black tipped tail and black patches on either side of the muzzle (Seton 1909, Rand 1948).
Long before the Europeans named the swift fox Vulpes velox (or initially Canis velox), the native people of North America had given it a variety of common names in a diversity of languages. In fact, many First Nation cultures had fox societies, such as the Kainai (Blood Tribe) Kit Fox Society. These kit, swift, or prairie fox societies had unique apparel, haircuts, ceremonies, dances, customs, and accompaniments (Laubin 1977). The status of these societies was related directly to the Tribe's image of the fox's worth and character. For example, the "kit-fox" was the name of an extinct Piegan society that was regarded as being very powerful. It was considered dangerous even to speak of it and "of all the societies of the I-kun-uh-Kah-tsi, the Sin-o-pah, or Kit-Fox Bands, had the strongest medicine" (Wissler 1995). Kainai spirituality is influenced directly or indirectly by the sacred Kit Fox Society (Francis First Charger, pers. comm., Elder, Blood Tribe). The Blood Tribe Elders in Southern Alberta recognize the Sinopaa (swift fox) as a very important part of Kainai spirituality, and considerable interest exists in continuing to reintroduce swift foxes to their lands (Francis First Charger, pers. comm., Elder, Blood Tribe).
1.3 Populations and distribution
Historically, swift foxes were widely distributed throughout the North American Great Plains but population density steadily declined throughout the late 1800’s and early 1900’s (Merriam 1902, Seton 1909). In Canada, the last recorded specimen, before extirpation, was collected in 1928 (Carbyn 1998). Although the last confirmed sighting of a swift fox in Canada occurred in Alberta in 1938 (Pied Piper 1950), they were not officially designated as extirpated until 1978.
The combined historical range in North America has been estimated at 1.6 million km2 (Scott-Brown et al. 1987) but has probably always been patchy in some areas and continuous in others (Carbyn 1996).
Canadian population and distribution
Prior to the turn of the century the distribution of swift foxes in Canada approximated the mixed prairie regions in the southern portions of Alberta, Saskatchewan, and Manitoba (Merriam 1902, Seton 1909, Rand 1948, Soper 1964, see COSEWIC 2000). Following swift fox extirpation from Canada by 1938 (Pied Piper 1950), swift foxes were reintroduced annually into southern Alberta and Saskatchewan beginning in 1983 until 1997. Additionally, in 2004, 15 swift foxes were reintroduced to Blood Tribe lands of southwestern Alberta. Numbers and distribution of foxes have been increasing since the last releases in 1997 (Moehrenschlager and Moehrenschlager 2006). Although the current population is concentrated in southeastern Alberta and southwestern Saskatchewan, occasional sightings have been documented in Suffield, AB., north of Swift Current SK., and a single sighting in Manitoba. Currently, the best estimate of extent of occurrence is 12,897 km2, based on live trapping records (Cotterill 1997, Moehrenschlager and Moehrenschlager 2001) and sightings from 1996 to 2003 that were reviewed and confirmed by the Recovery Team (Figure 1).
The Saskatchewan - Alberta border area and Grasslands National Park region, which are loosely connected through the contiguous habitat in northern Montana, have an estimated 513 and 134 individuals respectively (Moehrenschlager and Moehrenschlager 2006) but it is unknown how many of these foxes are mature, reproducing individuals. (Please see IUCN Red List Criteria (http://www.redlist.org/info/categories_criteria2001.html#definitions) for a discussion on defining “mature”). Additionally, consecutive surveys are needed to confirm population increases and or stability. The Montana area is thought to support 515 foxes for a total of 1162 foxes in the Canadian/Montana area (Moehrenschlager and Moehrenschlager 2006).
Percent of global distribution in Canada
The estimated current U.S. distribution of swift foxes is between 505 149 km2 and 607 767 km2, based on an approximation of 39-42% of the historical range remaining (Sovada and Scheick 1999). Two percent of the current global distribution is found in Canada, calculated from the Canadian occurrence estimate of 12 897 km2 and the midpoint of the U.S. distribution estimates.
United States distribution
Estimates of swift fox abundance in the United States and the ability of management agencies to accurately assess these numbers are difficult to determine (Carbyn 1996). Based on vegetation mapping, Kahn et al. (1997) estimated the current geographical distribution of swift foxes in the United States as being about 40% (approximately 600 000 km2) of its original range which is consistent with estimates by Sovada and Scheick (1999) (see COSEWIC 2000).
Figure 1. Area of occupancy and extent of occurrence in Canada
Current area of occupancy and extent of occurrence (IUCN 2001 - http://www.redlist.org/info/categories_criteria2001IUCN) are based on live trapping records (Cotterill 1997, Moehrenschlager and Moehrenschlager 2001) and sightings from 1996 to 2003 that were reviewed and confirmed by the Recovery Team. Circular areas of occupancy assume a 31.9 km2 home range size and were calculated from a re-analysis of telemetry data from Moehrenschalger (2000). Exent of occurrence was calculated using a 99% minimum convex polygon.
Description of Figure 1
Figure 1 consists of a main map and an inset map. The main map displays the area of occupancy, 5 901.5 km2 and the extent of occurence, 12 897.3 km2 for the swift fox. It also displays cities and towns, roads and Provincial Parks. The inset map displays the location of lands directly managed by the Federal or Provincial government.
1.4 Needs of the swift fox
1.4.1 Biological needs
Swift foxes are among the most den dependent of the canids and use burrows throughout the year. Availability of suitable den sites is thought to be an important factor affecting the maintenance of viable swift fox populations (Egoscue 1979, Russell 1983, Pruss 1999, Harrison and Whittaker-Hoagland 2003). Swift foxes often modify burrows such as badger (Taxidea taxus) holes and use them as natal and rearing den sites and as escape refugia from predators throughout the year (Herrero et al. 1986, Pruss 1999). Swift foxes opportunistically use a variety of foods (Pruss 1994) and a list of identified items from scats collected in Oklahoma included 13 species of mammals, four species of birds, one species each of amphibians and reptiles and 30 species of invertebrates (Kilgore 1969). On a seasonal basis, ground squirrels (Spermophilus spp.) and grasshoppers (Melanoplus spp.) are important food resources while white-tailed jack rabbits (Lepus townsendii) are probably the largest prey species for swift foxes in Canada (COSEWIC 2000).
1.4.2 Habitat needs
In Canada, the availability of mixed-grass prairie in Alberta and Saskatchewan is important for swift fox reintroduction and survival (Carbyn 1998, COSEWIC 2000, Smeeton et al. 2003). Swift foxes are especially well adapted to the prairies as evidenced by their opportunistic foraging strategy and use of dens for shelter and protection from predators (Pruss 1999, see reviews Allardyce and Sovada 2003, Harrison and Whitaker-Hoagland 2003, Tannerfeldt et al. 2003). Swift foxes do not appear to rely on open water sources (Golightly and Ohmart 1984, Pruss 1999). Swift foxes have demonstrated that they can coexist amicably with humans within a native landscape where the primary land use is extensive livestock production on native prairie.
1.5.1 Threat classification
|1||Habitat loss or degradation due to unsuitable agricultural practices or industrial development||1|
|2||Habitat fragmentation due to unsuitable agricultural practices and oil & gas development||2|
|3||Predation and competitive exclusion by coyotes and red fox||2|
|4||Direct mortality due to collisions with vehicles||3|
|5||Indirect mortality due to disease, poisoning or trapping||3|
Identification and ranking of the current (2006) threats to the survival and habitat of the swift fox (Vulpes velox) on the Canadian prairie (1= severe/widespread, 2= moderate/potentially widespread, 3= limited threat in scope and severity, 4= unknown).
1.5.2 Description of threats
Habitat loss, degradation, and fragmentation due to unsuitable agricultural practices or industrial development
Fragmentation and destruction of habitat are the sources of many conservation problems and are some of the primary reasons many canid populations are rare or endangered (Debinski and Holt 2000, Crooks 2002, Swihart et al. 2003). With habitat destruction and degradation, demographic and environmental stochasticities make small populations more vulnerable to extinction (Hill et al. 2002). Of the endemic Great Plains species, over 74% are listed by government agencies as species of concern (Erickson et al. 2004). Since swift foxes are primarily prairie specialists, grassland conversion to cropland has been one of the most important factors for the loss of swift fox habitat (Soper 1964, Hillman and Sharps 1978, Carbyn 1998). In Canada, estimates suggest that 80% or more of the native prairie landscape has been converted into agricultural use (Gauthier and Patino 1993), while about 70% of the North American Great Plains has been lost. Fragmentation continues to occur with roads, service trails, towns, and the expansion of oil and gas industry into previously isolated prairie areas (Carbyn 1998, Moehrenschlager 2000, Forrest et al. 2003, Samson et al. 2004). In the transboundary area of Saskatchewan, Alberta and Montana, the grasslands at risk of cultivation (i.e., potentially arable, that are publicly or privately owned and do not have restrictions on cultivation) total 8247 km2, which is 45% of the native grassland remaining in this area (Erickson et al. 2004).
Predation and competitive interference/exclusion by coyotes and red foxes
For swift foxes, competition with and predation by coyotes (Canis latrans), as well as expansion of red fox (Vulpes vulpes) populations may be two of the most important limiting factors to swift fox movement into suitable habitat (Scott-Brown et al. 1986, Carbyn et al. 1994, Brechtel et al. 1996, Carbyn 1998). In the case of coyotes, expansion has been facilitated by the extirpation of the wolf from the prairie (Riley et al. 2004). Changes in faunal and floral species composition, ungulate grazing patterns, fire suppression, and use of pesticides and insecticides all alter the ecosystem in ways that probably influence local and seasonal prey availability (Voigt and Berg 1987, Linnell and Strand 2000). This may increase risk of interference intraguild interactions between swift foxes and other predators such as the coyote and red fox (Voigt and Berg 1987, Carbyn 1998, Linnell and Strand 2000). Killing of swift foxes by coyotes has consistently been identified as the principal cause of swift fox mortality in many studies (Covell 1992, Carbyn et al. 1994, Sovada et al. 1998, Kitchen et al. 1999, Moehrenschlager 2000, Smeeton and Weagle 2000, Schauster et al. 2002, Andersen et al. 2003). Additionally, avian predators are also a cause of swift fox mortality (COSEWIC 2000).
The dietary overlap between Canadian sympatric (i.e., occurring in the same area) swift and red foxes is greater than that of sympatric coyotes and swift foxes (Moehrenschlager and Sovada 2004). Consequently, the potential for exploitative competition is highest between the former. Moreover, in sympatric populations there is greater chance of a red fox – swift fox encounters than coyote - swift fox encounters because, when compared to coyotes, red foxes tend to be found in higher densities, with smaller home ranges, and they move as individuals rather than as pairs or groups (Henry 1996). Work by M. A. Sovada (unpublished data) suggests that red foxes may actually limit the expansion of swift fox populations into suitable uninhabited areas. In Canada, red fox dens were significantly closer to human habitation than coyote dens, while swift fox dens were spaced randomly (Moehrenschlager 2000). Anthropogenic change such as greater urbanization and fragmentation (e.g., oil and gas development) of native prairie may facilitate the expansion of red foxes with potentially devastating effects on swift foxes, particularly in the core areas of the population (Carbyn 1998).
In rural areas, coyotes typically avoid areas of high human activity (Roy and Dorrance 1985, Pruss 1994, Pruss 2002). This trend, coupled with coyote control, could lead to interference and exploitative competitive exclusion (i.e., situations where competition can influence species distribution) of established swift foxes by red foxes in prairie areas (Carbyn 1998, Linnell and Strand 2000, Allardyce and Sovada 2003). This effect could potentially be more damaging to swift fox recovery efforts than the direct, density dependent killing of swift foxes by coyotes. This competitive exclusion has been documented for kit foxes (Vulpes macrotis) (White et al. 1994) with their apparent displacement by red foxes (Allardyce and Sovada 2003). The fact that coyotes may be necessary to exclude red foxes suggests that scenarios exist where too many or too few coyotes could lead to the exclusion of swift foxes; determining where these equilibria fall and how they are affected by changing environmental conditions or human disturbance needs to be examined (Moehrenschalger et al. 2004). Currently, the extent and severity of this problem remains unknown and research into this problem should be initiated within the next five years.
Direct and indirect human induced mortality
Vehicle collisions: Swift foxes are often observed near roadways and swift fox dens are often located relatively close to roads (Hillman and Sharps 1978, Hines 1980, Hines and Case 1991, Pruss 1999, Moehrenschlager 2000, Kintigh and Anderson 2005). Collisions with vehicles can be a major source of mortality particularly for juvenile foxes (Pruss 1994, Sovada et al. 1998, Herrero 2003). Oil and gas development includes the creation of new roads, as well as increased traffic along existing roads, which contributes to an increased risk of collisions.
Poisoning and trapping: Several factors are thought to have contributed to the reduction in population size and distribution of swift foxes. Bailey (1926) states that swift foxes were very easily trapped, poisoned, or caught by dogs and that they became increasingly rare after the country was settled. Widespread poison campaigns for wolves, prairie dogs, and coyotes are thought to have contributed significantly to the decline in swift fox numbers around the turn of the last century (Scott-Brown et al. 1987).
In both Alberta and Saskatchewan, poison bait, including strychnine, is available to producers for controlling Richardson’s ground squirrels (Spermophilus richardsonii). Swift foxes may inadvertently consume the poison bait, directly or indirectly (i.e., secondary poisoning by eating poisoned ground squirrels). In Alberta, trained municipal staff investigates complaints of predation and can provide landowners with poison and/or snares to control predators (Joel Nicholson pers. comm. Species at Risk Biologist, Alberta Sustainable Resource Development). In both cases, although swift foxes are not the target species, accidental mortality can occur as a result of these practices. Saskatchewan has a swift fox exclusion zone (Twp 1 to 7 W of 3rd) where no predator poisoning is allowed. Power snares and free hanging snares can be used in the exclusion zone but the bottom of the snare must be at least 30 cm high and a special snaring permit is required (Sue McAdam pers. comm. Ecological Specialist, Saskatchewan Environment).
In the United States, the 1972 presidential ban on predator toxicant use (e.g., strychnine, compound 1080) on Federal lands may have contributed to recovery of swift foxes. Compound 1080 is currently being legalized in prairie areas of Saskatchewan, which will likely limit reintroduced swift fox populations. Moreover, some landowners who are attempting to protect their livestock from predation illegally use poison baits and swift foxes readily consume such baits (Moehrenschlager 2000). Current rodent and predator control activities, legal and illegal, and their effects on swift fox population viability are unknown. Best management practices and/or policy should also be developed for addressing potential increased insecticide use during grasshopper outbreaks. The Alternative Strategies and Regulatory Affairs Division of the Pest Management Regulatory Agency has reevaluated regulations regarding the use of sodium cyanide in an effort to protect swift foxes from poisoning and has proposed changes to the label to indicate: 1) a website for a swift fox range map; and 2) users must consult with the Alberta Fish and Wildlife Office in Medicine Hat or Lethbridge for approval to use this poison (Pest Management Regulatory Agency 2006).
Disease: Small populations are particularly vulnerable to disease outbreaks that could threaten or defeat recovery efforts (Thorne and Williams 1988). Exposure of swift foxes to canid diseases and the prevalence in different age classes and regions has not been determined in Canada (Moehrenschager and Sovada 2004). The effects and likelihood of disease transfer between swift foxes and sympatric coyotes, red fox, and domestic dogs should be evaluated (Pybus and Williams 2003). This is critical as disease can have devastating effects on endangered canid populations (Woodroffe et al. 1999, Laurenson et al. 1998).
The long period of extirpation from the Canadian prairies is a testament to the presence of dispersal barriers and the inability of swift fox populations in Wyoming, South Dakota, and Nebraska to disperse northward and “rescue” the Canadian population. The rate and extent of disease flow is unknown but there is potential for transmission from and reservoirs in other canid species.
Currently, conservation strategies typically do not take into account the future effects of climate change and the challenges associated with changes in species distribution and abundance as well as geographic variation in the scale of responses to climate change (Huntley and Webb 1989, Hannah et al. 2002a). Although it is difficult to predict with certainty, general circulation model (GCM) simulations indicate that the trend throughout the northern Great Plains will be decreased precipitation and increased mean annual temperatures (Karl and Heim 1991, Lemmen et al. 1997). Globally, predictions suggest species distributional shifts to both higher elevations and latitudes (Hughes 2000). Climate vegetation modeling by Rizzo and Wiken (1992) proposes that southern Alberta and Saskatchewan may become a semi-desert. Some obvious conservation planning implications are shifts in species ranges in terms of protected area boundaries as well as maintaining populations of rare and endangered species in cases where climatic conditions for them may be deteriorating (Peters and Darling 1985, Hannah et al. 2002a, 2000b). These climatic changes could result in current swift fox habitats becoming unsuitable; whether any new habitat would be appropriate is unknown. Modelling of these potential effects of climate change can provide important insight into strategies for future conservation and recovery planning.
1.6 Knowledge gaps and recommended studies
- A quantitative evaluation of recovery habitat has not been completed at this time. The utilisation of different habitats by swift foxes is not well understood, particularly those habitat types that are considered atypical. Research is needed to assess the limited dispersal of swift foxes to seemingly suitable habitats, and to identify the barriers (physical and ecological) for more effective management and conservation (Moehrenschlager and Sovada 2004). What levels of habitat loss, degradation, and fragmentation limit the viability of swift foxes? While individual foxes occasionally utilize human-modified habitats, there is a need to understand appropriate ratios of modified to native habitat, degrees of connectivity, and the changes in habitat quality that would still allow swift fox populations to recover. In Canada, the oil and gas industry is rapidly expanding and undeveloped prairie areas are now targeted for exploration and development. The effects of disturbance and associated road and infrastructure development needs to be investigated. These activities have the potential to decrease habitat carrying capacity, alter canid interspecific interactions, and increase vehicular swift fox mortalities. Guidelines for mitigating these impacts need to be developed.
- Currently, conservation strategies typically do not take into account the future effects of climate change and the challenges associated with changes in species distribution and abundance as well as geographic variation in the scale of responses (including habitat alteration in quality, type, and distribution) to climate change. Further modeling will be required to address the potential effects of climate change on swift foxes.
- Swift fox exposure to canid diseases and the prevalence in different age classes and regions has not been assessed in Canada. The effects and likelihood of disease transfer between swift foxes and sympatric coyotes, red foxes, and domestic dogs should be evaluated (Pybus and Williams 2003). Antibodies to numerous disease agents have been found and canine distemper and rabies antibodies have been noted among swift foxes (Miller et al. 2000, Olson 2000), but it remains unclear under what conditions diseases will be expressed and what the effects might be.
- Interspecific competition with and predation by coyotes as well as expansion of red fox populations may be two of the most important limiting factors to the movement of swift foxes into suitable habitat (Scott-Brown et al. 1986, Carbyn et al. 1994, Brechtel et al. 1996, Carbyn 1998). One of the strongest examples of intraguild pressure among carnivores is the killing of swift foxes by coyotes. The fact that coyotes may be necessary to exclude red foxes suggests that scenarios exist where too many or too few coyotes could lead to swift fox exclusion. Determining where these equilibria fall and how they are affected by changing environmental conditions or human disturbance should be an area for future investigation (Moehrenschlager et al. 2004).
- Data on swift fox demography, disease prevalence, genetics, habitat use, and population trends should be incorporated into Population Viability Models to guide conservation planning on a provincial and/or federal basis.
- Genetic analyses should be conducted to examine bottlenecks, genetic variability, connectivity, and dispersal distances in Canada and within isolated population fragments of the United States. It is necessary to understand the genetic viability of small populations and the genetic barriers that habitat fragmentation might pose over time. It would be important to estimate effective population size of introduced swift fox populations to determine the rates of effective to census population size (Ne/N).
- This recovery strategy identifies many studies that, once completed, can be used to identify whether further reintroductions will be required to achieve the population goal. Currently it is unknown if further reintroductions are required.
- Work on small mammal biomass in winter by Klausz (1997) suggests that there are differential concentrations of prey availability within various habitats of the swift fox release areas. Because little is known about the effects of land management practices and large scale grazing management on prey availability, experiments are underway in Grasslands National Park (Henderson 2005).
- Some behavioural research has been done on swift foxes in Canada (Pruss 1994, 1999), however further research into swift fox behavioural ecology would be valuable.
- There is a need for collaborative research approaches that address similar problems of prairie species. Unified conservation planning for these species might be the most effective way to achieve financial, political, and ecological means that will sustain grassland communities into the future.
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