The Amphibians and Reptiles of Alberta: a Brief Introduction

THE HERPETOFAUNA OF ALBERTA is not extensive (Table 3.1), but there remains much to be learned about our native amphibians and rep- tiles. Even in the short time that has elapsed since the publication of the first edition of this book significant new information has been gained about the biology and conservation status of several species. Moreover, the specific and even generic allocations of several of our native forms have been changed as a result of further research on geographic variation and phylogenetic relationships.

The Albertan herpetofauna includes an interesting mixture of forms with southern and eastern affinities. The greatest concentration of amphibians and reptiles occurs in the arid southeastern corner of the province, but interesting correlations of species distributions with other biotic regions exist. Eight species of reptiles and ten of amphibians are known to occur in the province. (See colour plates for photographs of all taxa known to occur in the province.).

The salamanders of Alberta belong to the family Ambystomatidae and can be distinguished from all other western species by their teeth, which form a continuous or broken row across the roof of the mouth. Typically (Fig. 3.1), they have a broad head, small eyes, prominent costal grooves and a tail flattened from side to side. Males usually have a bulbous vent and a longer tail than that of females.

These forms are rarely seen, except during their brief breeding season. They crawl over land to ponds, lakes and streams and sometimes stumble into cellars and light wells. Migrations usually occur at night, during or after rains, and generally take the animals back to the parental pond. Breeding may start early, soon after the ice melts from lakes and ponds, but at high altitudes and in the north it may be delayed until summer. Throughout the rest of the year, except occasionally during rains, these salamanders stay inside rotting logs and animal burrows, or in other moist places underground. Larvae may be found throughout the year. At high elevations and in the north, where temperatures are low and the growing season short, they may not transform until their second season. Some larvae may fail to transform and may breed without metamorphosing. The family ranges from Alaska and Labrador in the north, south to the southern part of the Mexican plateau.

In Alberta, four families of anurans are represented—the Bufonidae, Pelobatidae, Hylidae and Ranidae. The bufonids are the true toads and are worldwide in their distribution, except for extremely cold or dry areas, remote oceanic islands and Australia (where, however, the marine or cane toad has been introduced by man). Toads are able to live under adverse conditions and range from below sea level in Death Valley, California, to above 5,000 metres in the Himalayas; and from the tropics almost to the Arctic Circle.

Typical toads of the genus Bufo are chunky, short-legged, warty and have parotoid glands that distinguish them from all other tailless amphibians. The parotoids and warts are the sites of secretion of a sticky white poison, which in some species can paralyze or kill predators. Some predators, however, can eat toads with no apparent ill effects. Distinguishing features between Alberta species are differences in size, shape and distribution of the parotoids, con- spicuousness and arrangement of the cranial crests, the extent of wartiness, form of the foot tubercles, and colour. Colour, however, may change from light to dark in response to temperature. Breeding in bufonids occurs in spring and summer, usually after rains. Adult males of most species have a dark throat. All develop brown nuptial pads on the thumb and inner fingers, which help them to cling to the slippery body of the female. Amplexus is pectoral.

The family Pelobatidae is represented by a single species in Alberta. The spadefoots are distinguished from the true toads by their cat-like eyes, single black, sharp-edged spade on the hind foot, teeth in the upper jaw, rather smooth skin, and the absence of parotoid glands. Males may have a dusky throat and dark nuptial pads on the innermost front toes; amplexus is pelvic. Spadefoots breed in pools that form after heavy rains, or in slow streams, reservoirs or irrigation ditches. The developmental stages are very rapid, as the eggs are often deposited in bodies of water that are only transient. Dry periods are spent in burrows either constructed by other animals or by themselves. When burrowing, spadefoots back into the ground.

The family Hylidae is also represented by only a single species in Alberta. The hylids are a large family of slim-waisted, long-legged frogs mostly of small size. Many are arboreal and have well- developed toe pads set off from the rest of the toe by a small, extra segment. These frogs are found on all continents but are most abundant and varied in the New World tropics.

The remaining group of amphibians that occurs in Alberta is the family Ranidae. This is composed of typically slim-waisted and long-legged frogs with a smooth skin. On land they jump, and the feet are webbed. There are dorsolateral folds which are very prominent, and these act as distinguishing features for ranids in western North America. Again there are representatives on all continents. Distinction between species is often extremely difficult as colour patterns may be quite variable.

With respect to Alberta's reptiles, there is but one species of turtle, six species of snake and one species of lizard. The turtle is Chrysemys picta, the western painted turtle. It has been found in the Milk River of southeastern Alberta and is an aquatic form which frequents ponds, marshes, small lakes, ditches and streams where the water is quiet or sluggish and the bottom muddy and overgrown with aquatic plants.

The lizard is Phrynosoma hernandesi, one of the horned lizards. These lizards are armed with head spines and sharp, projecting scales on the dorsal surface of the body. They are usually solitary in habits and when approached often crouch low, their markings and spiny skin blending with the ground. They feed chiefly on ants. This food resource and fine soil for burrowing appear to be essential environmental features for these lizards. When picked up, they may inflate themselves by gulping air, may jab with the horns, or, rarely, spurt blood from the eyes. The Alberta species is not known to employ the latter tactic. This blood comes from a sinus at the base of the nictitating membrane and is thought to repel predators.

There are three species of garter snake in Alberta, and these are all moderately slender snakes with a head slightly wider than the neck. The dorsal scales are keeled, and the anal scale is usually single. Dorsal scale counts are important in identification. Most species have a conspicuous pale yellow or orange vertebral (mid-dorsal) stripe and a pale stripe low on each side. Garter snakes occupy a great variety of habitats from sea level to high in the mountains. Many are aquatic or semi-aquatic, but some are completely terrestrial. When caught, they often void feces and expel musk from their anal scent glands. They are viviparous.

One species of Pituophis occurs in Alberta. This is the gopher snake or bullsnake (P. catenifer), a large yellow or cream-coloured snake with black, brown, or reddish brown dorsal blotches. This species lives in a variety of habitats throughout North America, from the lowlands high into the mountains and from coast to coast. It frequents desert, prairie, brushland, woodland, coniferous forests, and farmland. It is a good climber and burrower and is active chiefly by day, except in hot weather. When aroused, it hisses loudly and sometimes flattens its head and vibrates its tail. This behaviour, along with the diamond-shaped markings, causes these snakes to be mistaken for rattlesnakes.

The western hog-nosed snake, Heterodon nasicus, is a heavy bodied, blotched snake with a broad neck and upturned snout, which it uses in digging. This species frequents sandy or gravelly prairies, farmlands, and flood plains of rivers. In the extreme western part of its range, it occurs in semi-desert habitats and occasion- ally in mountain canyon bottoms.

The prairie rattlesnake, Crotalus viridis, is the only venomous snake found in Alberta. It belongs to the family Viperidae and the subfamily Crotalinae. This family has the most highly developed venom injection mechanism among snakes. Large, hollow, moveable fangs are located at the front of the upper jaw. In biting, they are swung forward from their folded resting position, and the victim is stabbed and poisoned in a rapid thrust. The crotalids are known as pit vipers because they bear pits in the facial region that act as temperature sensitive structures, by means of which they can sense the location of their prey by detecting infra-red radiation.

Significant references: Alberta Recreation and Parks 1986; Anon 1964a, b, 1971, 1972; Beck and Beck 1988; Black 1967,1969,1970a, b, 1971; Black and Brunson 1971; Blair 1963, 1972; Boulenger 1920; Bow Valley Naturalists 1978; Breitenback et al. 1984; Burns (no date); Butler 1980; Campbell, et al. 1982; Carl 1959, 1960; Cook, F.R. 1965, 1966, 1983a, b, c, d; Corkran and Thorns 1996; Corn et al. 1984; Fowler 1934; Green and Campbell 1984; Greene 1997; Gregory and Campbell 1984; Griffiths 1979; Hardy, W.G. 1967; Harper 1931a; Hodge 1971, 1972, 1976; Holman 1972; Lewin 1963; Logier and Toner 1955, 1961; Mills 1948; Mosimann and Rabb 1952; Nelson 1979; Nelson and Paetz 1972; Nussbaum et al. 1983; Preble 1908; Roberts 1982a, b; Russell and Bauer 1991; Salt 1977,1979; Smith, H.C. 1972; Smith, H.C. et al. 1970; Smith, W.W. 1972,1975; Soper 1949; Spalding 1971,1973,1980; Tebby and Smith 1977; Watt, 1971; Weller and Green 1997; Williams 1946.