by Clio Smeeton
A new method of release assayed in Grassland's
National Park
may increase the survival rate of reintroduced swift foxes in
Canada.
The swift fox (Vulpes velox/V. v. hebes), unique to the great plains of North America, was declared extinct in Canada in 1978. This small canid shared its historic great plains range with a wide variety of now extirpated or remnant species, including the prairie dog (Cynomys ludovicianus, C. leucurus, C. gunnisoni and C. parvidens). Unfortunately the swift fox vanished from the greater part of its range before possible links within the ecosystem provided by the colonial prairie dog and the swift fox could be investigated.
The swift fox, because of its small size, is preyed upon by both aerial and terrestrial carnivores. The country which comprises its range is extremely exposed and escape opportunities provided by badger (Taxidea taxus) diggings and abandoned prairie dog burrows probably have a significant effect on swift fox survival.
The mixed grass prairie is a brutal region far from the ameliorating influences of the seacoast. Dry winds roll unhindered across the flat lands or eddy around the butts at speeds of up to 129 km/hr. A clear sky arcs over plants and animals adapted to temperature extremes swinging through 80°C. This is the shortgrass prairie setting of Grassland's National Park which, once completed, will contain over 900 km² of short and mixed grass prairie, the last substantial representation of that habitat left in North America.
Swift fox have been bred at the Cochrane Wildlife Reserve (CWR), a non-government organization, since 1971. The Canadian attempt to reintroduce this species has been in operation since 1983. The reintroduction of an extirpated species always involves the cooperation of many agencies, and the swift fox re-introduction project is no exception to that rule. The participants in the programme have been four non-government breeding facilities which are responsible for producing the foxes for reintroduction, genetic management, quarantine, tattooing, necropsies and pathology. The Government agencies involved are both federal: Canadian Wildlife Service, and provincial: Alberta Forestry Lands and Wildlife and Saskatchewan Environment and Renewable Resources. Government agencies are responsible for the importation of swift fox and for the animals after release.
The attempt to reintroduce any extirpated species is a venture into uncharted territory and naturally the agencies involved arranged the varied aspects of reintroduction in order of priority. From the winter of 1991-92 onwards, the monitoring of released swift foxes was not considered a priority activity by the federal and provincial governments. Behavioural observations, habitat utilization, and prey-base studies (which had ceased in the mid 1980's) were also considered of low priority by the government agencies.
Sample sizes for projects such as the swift fox reintroduction programme must necessarily be small. Between 1989 and the spring release of 1991, government agencies radio-collared 10% of the autumn-released cubs and 100% of the spring-released animals. The first part (1983-1991) of the Canadian swift fox reintroduction took place in southern Alberta and Saskatchewan in shortgrass prairie from which the prairie dog had been extirpated (a total of 561 swift foxes). The animals were released into privately held land or Crown lands with grazing rights held by the farming community.
129 swift foxes were released in the autumn's of 1992 and 1993. At the instigation of the CWR and with the agreement of Parks Canada some were concentrated in Grassland's National Park (GNP) and its environs, the last area in Canada to contain populations of the black-tailed prairie dog (Cynomys ludovicianus). No radio-collaring or monitoring by the government agencies was undertaken for the autumn 1992 and 1993 releases.
The greatest concentration of government effort was expended on the spring releases of 1990 (27 foxes) and 1991 (28 foxes) in an effort to establish (a) the best time for release and (b) the most suitable animals for release; wild-caught, quarantined translocated animals or yearling captive-born cubs. Considerations of release methods were not part of the spring release experiment or of the post-1988 autumn releases.
A team from the Cochrane Wildlife Reserve spent 13 days in the South Dakota Badlands National Park and Ardmore (August 4-16th, 1993) live-trapping swift fox as part of the U.S. federal government's selenium research, and to gather blood samples for exciting new genetic research on the species. The taxonomic status of the Northern swift fox (Vulpes velox hebes) is currently unresolved, but blood was collected from the last remaining swift foxes (15 left from an estimated population of 40 in 1992) of the Ardmore population in South Dakota. Merriam described the South Dakota swift fox as the Northern race, so it is hoped that DNA analysis on the blood of these foxes, carried out by Dr. Robert Wayne (London Institute of Zoology/UCLA), will shed light on the taxonomic uncertainties.
If this subspecies designation proves valid, the South Dakota swift foxes belong to the same race as the now extinct Canadian population. It was thought that it would be beneficial to apply as far as possible the den site criteria of the wild, established South Dakota swift fox population to the proposed reintroduction sites in Saskatchewan's GNP. Therefore the research incorporated the gathering of information concerning the typical characteristics and den site requirements chosen by wild swift foxes in this area.
In 1993, prior to the releases (16th August-7th September) a team of four from the CWR surveyed the Western Block of GNP for signs of predator and swift fox activity and to research suitable release sites. All observations, combined with the South Dakota research were used to establish the selection criteria for the 1993 reintroduction sites.
In an attempt to enhance survival, a new method of release was introduced. Each released fox was provided with a portable protective shelter (PPS), closely resembling the fox housing used at the CWR. It was believed that the released foxes would recognize the PPS as one familiar thing in an alien world. The shelters were designed to provide immediate protection from predators for the foxes at the release site, giving them a safe bolthole while they established the bounds of their new ranges.
Each PPS comprises a central foxbox and a folding A-frame cover. The foxbox, 45 cm long, 23 cm high and 23 cm wide, is divided into two chambers with entrance holes 15 cm in diameter at opposite ends of each long side. Foxboxes for breeding pairs in the CWR have the same construction, but are 60cm long with an additional chamber.
The A-frame cover is made from 12 mm plywood, 60 cm long, 90 cm high and 45 cm wide at the base. Hinges along the top allow the sides to fold flat against each other, and hinges along the upright side of each end allow the triangular end pieces to be folded flat against the sides. The whole A-frame can thus be lashed to a backpack frame. Entrance and exit holes on either side of the frame are placed at opposite ends from each other so that the wind does not whistle through the frame. A-frame covers used for breeding pairs in the CWR are built in the same way, but are bigger and do not fold up, and the empty space above the foxbox is filled with insulation in order to regulate the temperature inside the foxbox.
The 1993 releases consisted of 54 cubs of the year released without radio-collars. CWR released 16 foxes (5 litters) in 5 sites within GNP. All foxes were released using PPS (one per litter), and post-release monitoring was carried out at all 5 sites. Saskatchewan Environment and Renewable Resources staff undertook 2 releases, 15 animals to Wood Mountain, where foxes have been released yearly since 1989, and 8 animals released on the periphery of GNP. PPS were not used, and no monitoring was done for either release. Canadian Wildlife Service personnel undertook the release of 15 animals into the Southern Alberta Release sites, the core release area for the swift fox re-introduction programme since 1983. Foxes were released at the side of the road, without PPS, and no monitoring was done.
After release, the 5 sites where PPS were used were monitored constantly by CWR staff for 24-48 hrs (using night-lighting techniques and binoculars). Once the foxes had established themselves in their own dens (12-24 hrs after release), the observers patrolled each site frequently, both by day and night, over a 10 day period. Information was gathered on behaviour and spoor, and scat samples collected. This patrolling was repeated for a further 10 days, 34 days after the initial monitoring.
Of the 5 litters released using PPS, 3 were still using the shelters the following day, and for the next 48 hours, even though natural dens had also been excavated and were in use. The remaining two litters established dens very close to the PPS, and continued to use the PPS as a focal point. Only one litter ceased to use the PPS during the first 12 hours after release. The PPS for this litter of two was placed in a lower, more brushy, less exposed area, and the foxes disappeared into the bush on release. However, they subsequently returned to the release site and were observed there 48 hours later. With the exception of this litter, all the cubs released spent their first 12 hours of freedom within 200 m of the PPS. During the next 24 hours they moved a little further away and established dens. After this, the focal point of their territories became the new dens, with the PPS of more peripheral importance to home range establishment. Hunting during daylight hours occurred in close proximity to PPS and natural den site, although nocturnal activity was more widespread.
The home ranges used by the swift fox using PPS made it possible for the CWR and GNP staff to follow up on the released animals four and a half weeks later. The follow up on the reintroduced animals in Grassland's (20-28th October) confirmed sightings of 6 of the 16 animals released, fresh spoor, scat and in-use den sites.
CWR staff researched the 1993 southern Alberta release sites 4 weeks after release but had no confirmed sightings of swift fox. No spoor, scat or in-use den sites were found. A hunting party visiting the area gave a good description of seeing what they believed to be a single swift fox.
At present, the data available are too few to establish whether the use of PPS has an appreciable effect on the survival of reintroduced swift foxes. Field observations seem to indicate that the use of PPS and the application of release site criteria to the reintroduction sites reduces the rapid dispersal of released animals and encourages the establishment of home ranges in the areas where the animals are set free. Research is needed on the post-release behaviour and the further refinement of the release methodologies.
1992 and 1993 have seen a bloom in the coyote population. The wet spring and summer of 1993 have also adversely affected the populations of the normally abundant Richardson's ground squirrel (Spermophilius richardsonii). Coyote are a significant predator of Richardson's ground squirrel and of swift fox. The relationship between the swift fox predators and prey needs to be researched so that target sustainable population levels can be estimated.
The present methods of monitoring the released foxes for mortality estimates do not adequately estimate survival rates. Future programmes will have to incorporate cost- effective monitoring, so that range size, dispersion, movement patterns, and mortality can be better determined.
The CWR has developed a research programme that will address: (1) Habitat utilization, (2) Population and behavioural dynamics, (3) Food habits, (4) Sub-species definition, and (5) Contaminant impacts. This research programme is presently under way. It will be supported by post-graduate research, charitable foundations and corporate sponsorship and private donations. Government support has also been requested.
Six yearling swift foxes (3 litters: 3 males, 3 females) were recently released into an 8.3 ha enclosure containing artificial dens. These widely separated dens consisted of foxboxes covered by A-frame shells, and one artificial mound (foxbox covered by chickenwire and polystyrene insulation).
When the cubs were released in the area, their behaviour was monitored in the same way as for the litters released into GNP. Although the area was smaller, and the release not preceded by 48 hrs of travel, the behaviour of the six cubs was very similar to that of the litters in GNP. They too used the artificial dens, and are in fact still using them. This is probably due to the fact that the weather is extremely cold, making the ground too hard to dig, and there are no naturally occurring holes for them to use.
Swift foxes have not been kept in this way before, and it is hoped that observations of their behaviour, particularly during the breeding season, can provide much needed information on how swift foxes behave in groups.
Staff from CWR, just returned from GNP, reported that by 13th January swift foxes released using PPS had established dens and were still resident in the areas where they were freed.
(Photos by Bill Rackstraw) [coming soon]
* Clio Smeeton and her parents founded the Cochrane Wildlife Reserve, a Registered Charity which is devoted to the breeding and re-introduction of endangered species. The CWR has been breeding swift fox for re-introduction and release since 1971, and currently holds the worldµs largest breeding colony of this species. CWS is very grateful for the generous support of the FFPS and Whitley Wild Animal Protection Fund in 1993.
© 1994 International Union for the Conservation of Nature and Natural Resources
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