Swift Fox Life History

There has been very little work done on the behaviour and requirements of swift fox in the wild. This has come about in part because, following the European conquest of North America and the settlement of the great Plains, the swift fox vanished from its range almost as soon as it was identified as a species. Also, the swift fox was of little commercial interest to settlers and trappers as the main demand for its pelt was from China, which wasn't as big trading a partner as Europe. Being of small commercial interest, the species was little studied.

In Canada, research into the species was undertaken only after it had been declared extinct over its Canadian range (Carlington 1980, Reynolds 1983). In the United States more studies of swift fox in the wild have been conducted over a longer period.

JANUARY & FEBRUARY: The mating season begins in late January when the swift foxes start scentmarking at the confluence of trails and on small (swift fox sized) landmarks, like large rocks. In  February, there is increased excavation of existing den sites, and by mid February the animals have begun calling.  This mating calling behaviour will continue until March, and later for un-mated animals. During the mating season the swift foxes, both male and female, attract mates using a distinctive cry, known as the lubricious bay. This call is composed of a series of short barks clear enough to distinguish the voice of each individual swift fox. The lubricious bay sounds more like the sound made by a startled pheasant than by a fox, but the sound has tremendous carrying capacity and can be heard for 2.5 Km on a still night.

Swift fox are extremely fastidious in mate selection, and the preliminaries of courting are very prolonged for newly paired animals. Established pairs mate earlier in the season than newly paired couples, and after successful mating the calling stops.

The gestation period for swift fox is believed to be between 50 and 53 days. The birth of the kits in dens and the sensitivity of the vixens to disturbance hinder the firm establishment of the gestation period. Schroeder's observations on copulation dates (5 February to 5 April) confirm a fairly extended breeding season.  No observations could be found on the breeding season or gestation period for Swift fox in the wild

It is possible that vixens past breeding age cease to call during the breeding season (Weagle and Smeeton, 1995).

APRIL & MAY:  At the CEI whelping generally occurs in the artificial den boxes or, in some cases, in underground dens dug by the pair. For approximately two weeks after whelping the dog fox provides the vixen and their cubs with food.  During this period when the cub's eyes are still shut and they are completely helpless, the vixen rarely leaves the den.

  During this two week period the male  spends more time outside the den (Weagle and Smeeton, 1995). 

Pruss (1994) has made observations on the activity patterns of reintroduced Swift fox in southern Alberta. She assumed that the cubs were all born on May 1 and that they first emerged from the den at four weeks. In the captive colony, the kits were observed to emerge from the den for the first time, in mid to late April, at approximately 15 days old (Weagle and Smeeton, 1995). In the captive colony, the four week old cubs get their first health check and set of prophylactic inoculations, (many thanks to the Canadian Department of Agriculture Veterinarians).

In May, Pruss’ study of swift fox in the wild found that the adults spend more time above ground during daylight hours once the kits emerged from the den. This activity pattern was also observed in the captive population. Teeling (1996) made similar observations in the captive population at CEI.

JUNE & JULY: For the captive colony, the veterinarians come again and the eight week old cubs get their second health check and set of prophylactic inoculations.  In June the swift fox cubs become much more active throughout the 24 hours of the day, so their parents have to spell each other off throughout the day and have to forgo their normal rest hours underground.  During these months the social structure of the swift fox community becomes very apparent, warning barks at the sight of a predator will be taken up and repeated by all pairs within earshot.  The cubs are more vociferous, and parental influence over them more obvious.  The cubs , although still begging food from any adult ( swift fox will feed any cubs which ask, they do not have to be parents of the cubs to feed them) will also be practicing hunting, caching, interacting with other animals.  Summer is the time that they learn the life skills which will help them to survive while still remaining with-in the protective circle provided by their parents and other adults.

Weagle and Smeeton (1995) reported that when captive born kits were first introduced to the 9 hectare enclosure they were observed hunting immediately. This indicated that kits born and reared in the single pen enclosures quickly developed hunting skills. Subsequent studies on the food habits of the Swift fox in the 9 hectare enclosure showed that they appeared to hunt in preference to the food provided and that prey species made up over 67% of their diet.

Limited observations are available on Swift fox life cycles in wild populations. What data is available indicates that the wild population and captive breeding colony showed similar characteristics. The difference between the captive colony and the wild populations appears to be in the age of the animals. In the captive breeding facility males have produced progeny up to the age of 14 years. Death, in the captive colony, was as result of old age, not predation as would happen in the wild. Unpublished data on the age of Swift fox in the wild (Swift fox Stud Book, maintained by CEI) indicates that the oldest known male in the wild was 8 years, the oldest known female in the wild was aged 6 years. The observation in the captive colony of Swift fox becoming deaf after 8 years has significant implications for survival in the wild.

AUGUST: A critical period in the captive breeding cycle is August. By this time the kits have entered full adolescence and most of them are ready to disperse. Vocal aggression, high pitched hums and chittering between the kits is more common. Digging in the single pair enclosures increases markedly.   The veterinarians come out for the cubs' final health check. In a wild environment this is a period of range expansion when feed (grasshoppers) is readily available, and the kits begin to disperse from the family unit.   The area surrounding the natal den and den sites closest to it, will have been heavily hunted over while the cubs are small and the family group will need to look elsewhere for food.  The family will travel over a greater part of its range and cubs will overnight in more distant dens, while the parents (and less adventurous siblings), will stay in another den (Jon Sharps, pers. com). The family will continue to  split up and rejoin over the next months.  In the captive breeding situation, this is the time when the kits are best released to the wild (Weagle and Smeeton, 1995). Juvenile Swift fox mature in their first year and can breed at less than one year old, although studies show that they only have an 11% chance of doing so.

For release methods see the Montana Release

SEPTEMBER TO NOVEMBER:  In the captive colony, this is a time of "make and mend", the cubs are released and the adult established pairs are relaxing, while the newly paired animals are getting to know each other.  There is a lot of densite excavation, while the ground is still unfrozen.

DECEMBER: December finds the swift foxes in the Captive colony lazing around on the snow in the sun for a couple of hours in the middle of the day,if the weather is still and cold and clear, while spending the rest of the day underground.  Blizzards and high winds, will keep them underground all day and a greater part of the night.
 

You can help support these animals by becoming a member of Cochrane Ecological Institute, by Adopting an enclosure, or naming a fox.
Contact us at: cei@nucleus.com