Wild species 2010: chapter 23

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Reptiles

Reptilia - Class of vertebrates regrouping any cold-blooded scaly animals including snakes, lizards, crocodiles, turtles, tortoises, etc.

Quick facts

• There are more than 8000 species of reptiles worldwide, of which 48 species have been found in Canada. Of these, four species are found in marine habitats (sea turtles) and 44 species are found in freshwater and terrestrial habitats.
• When excluding species ranked as Extinct, Extirpated, Undetermined, Not Assessed, Exotic or Accidental, only 33% of reptiles in Canada have Canada General Status Ranks (Canada ranks) of Secure, while 42% have Canada ranks of At Risk and 25% have Canada ranks of Sensitive.
• Three species of reptiles are extirpated from Canada.
• Compared to Wild Species 2005, the Canada ranks of six reptile species have been altered. Of these, the ranks of four species moved into higher level of risk following new COSEWIC assessments, the rank of one species moved into a lower level of risk, and one species was added due to a taxonomic change.
• Since the report Wild Species 2000, the category At Risk had the highest increase in the number of species, while the Secure category had the highest decrease in the number of reptile species.

Background

A total of 48 species of reptiles has been found in Canada, including 26 snakes, seven lizards, 11 freshwater turtles and four marine turtles (over the past decade, there has been much scientific debate about the evolutionary relationships between turtles, lizards, snakes, crocodiles and birds leading to the suggestion that turtles should be considered in their own class, separate from the other reptiles. While some organizations have already adopted this approach, the general status program is currently taking the more conservative approach of keeping all turtles, snakes and lizards in their traditional class of Reptilia, until the scientific debate is clarified). This relatively small group is diverse, and contains species that live in habitats extending from belowground to the treetops, and from the depths of the oceans to the arid badlands. Reptiles can be most easily recognized by their dry scaly skin or, in the case of turtles, their hard, bony shell. Reptile scales are a continuous part of the skin and in some species are modified into unique forms, such as the spines and spikes of the Greater Short-horned Lizard (Phrynosoma hernandesi), and the nose scales that give the Eastern Hog-nosed Snake (Heterodon platirhinos) its name. All reptiles are cold-blooded, or ectothermic, meaning that instead of using food energy to generate body warmth (as mammals and birds do) they rely on external heat sources, such as the sun. In order to maintain a suitable internal temperature, many reptiles alternate between basking in the sun and hiding in the shade.

Reptiles are descended from amphibians, but unlike amphibians, reptiles have a waterproof skin and are not reliant on water or moist conditions for reproduction. This allowed reptiles to become the first completely terrestrial vertebrates, approximately 300 million years ago. One of the key adaptations that enabled reptiles to reproduce on dry land was the development of a complex egg with a leathery shell. The shell protects the embryo and prevents it from drying out, but is soft enough to expand as the embryo develops. Today, the majority of reptile species still lay eggs, but a few, such as the Northern Alligator Lizard (Elgaria coerulea), give birth to live young. This allows the mother to protect the developing young from extreme conditions of heat or cold, and from predators.

All of Canada’s terrestrial and freshwater reptiles hibernate to escape the long, cold winter, but different species have unique methods of surviving hibernation. Greater Short-horned Lizards simply bury themselves a few centimetres into the ground, often on a south-facing slope to take advantage of the sun’s warmth. Freshwater turtles, such as the Painted Turtle (Chrysemys picta) and the Blanding’s Turtle (Emydoidea blandingii), spend their winters deep underwater, where they are protected from the worst of the cold weather. In order to survive for several months without air, these turtles suck water into and out of their mouths, where specialized tissue in the throat exchanges oxygen and carbon dioxide with the water.

Reptiles sense the world very differently from humans and some even have additional sense organs to provide extra information about their environment. For example, many snakes and lizards use their tongue to detect chemicals in the air (equivalent to our sense of smell). As a snake’s tongue flickers in and out of its mouth, tiny airborne particles are collected and analysed by the Jacobson organ in the roof of the mouth. This system can be incredibly sensitive; a male Common Gartersnake (Thamnophis sirtalis) can tell the size and likely productivity of a female with a single flicker of his tongue, by detecting the pheromones she releases. Pit vipers, such as the Western Rattlesnake (Crotalus oreganus), have heat sensors concentrated in small pits between the nostril and the eye. These can detect temperature changes of less than 0.1°C, allowing the snake to detect warm-blooded prey, even in the dark. Marine turtles undergo vast migrations each year, and have a remarkable ability to return to specific locations such as nesting beaches or feeding grounds. To accomplish this navigational feat, marine turtles probably use a range of senses including sight and an ability to sense the earth’s magnetic field.

Status of knowledge

The status of knowledge of Canadian reptiles is highly variable between species. Although some reptile species have been well studied, many have not, and the distribution, population trends and life history of some Canadian reptiles remain poorly known. This is partly due to lack of baseline data and partly due to the difficulties of detecting reptiles, which are often solitary and secretive by nature.

Volunteer initiatives such as Nova Scotia Herpetofaunal Atlas and the Ontario Herpetofaunal Summary Atlas are collecting valuable information about the distribution and abundance of reptiles, as well as raising public awareness of this group. To date, COSEWIC has also assessed many species, subspecies and populations of reptiles, consolidating knowledge of species that are already suspected of being at risk.

Canada is home to one of the best studied snake populations in the world, the Red-sided Gartersnakes (Thamnophis sirtalis parietalis) of the Narcisse Wildlife Management Area in southern Manitoba. These snakes, a subspecies of the Common Gartersnake, hibernate in communal dens, called hibernacula. In southern Manitoba, good hibernacula sites are rare, so snakes crowd into the few available sites, where as many as 10 000 snakes spend the winter together. This large concentration of snakes has allowed researchers to study mating strategies, mating success, thermoregulatory behaviour and migration with relative ease.

In recent years, some Canadian reptile research has focused on species that are known to be declining. As well as providing information on reasons for declines, these studies can provide valuable information on the life history and distribution of Canadian reptiles. For example, recent studies on the Wood Turtle (Glyptemys insculpta, Canada General Status Rank (Canada rank): At Risk), have investigated life history and population size, impacts of agriculture on population recruitment and survival, habitat selection and genetics of isolated populations.

Most reptiles are represented in Canada by populations at the edge of the species’ geographic range. This offers opportunities to study factors that limit a species’ range and compare peripheral populations with those in the center of a species’ range. Another hot topic in Canadian reptile research is the thermal ecology of reptiles; how reptiles use different habitats to control their body temperature and the importance of this to their life history and fitness.

Richness and diversity in Canada

Terrestrial and freshwater reptiles are concentrated in southern Canada, with the highest species richness in Ontario (27 species), Quebec (19 species) and British Columbia (16 species) (figure 23). British Columbia has the highest number of species (nine) that have been found nowhere else in Canada. Two regions of Canada (Yukon, Newfoundland and Labrador) report no reptile species. All of Canada’s reptiles are also found in the US, but several species, such as the Eastern Foxsnake (Pantherophis gloydi) and the Northern Alligator Lizard, have a large portion of their range in Canada.

Canada’s four marine turtles are all found in the Atlantic or Pacific Oceanic regions; none have been found in Arctic waters, where conditions may be too extreme for reptiles to survive (figure 23).

Species spotlight - Leatherback Seaturtle

The Leatherback Seaturtle (Dermochelys coriacea), is the world’s largest living reptile, reaching a length of 2 m and a weight of up to 900 kg! Leatherback Seaturtles live in the Atlantic, Pacific and Indian Oceans and nest on sandy beaches in warm tropical waters. Between breeding seasons, they migrate north and can be found off the east and west coasts of Canada in the Atlantic Ocean Region and the Pacific Ocean Region. The Leatherback Seaturtle is the only marine turtle without a hard shell. Instead its back is covered with a semi-flexible substance made of connective tissue and numerous tiny bones, allowing Leatherback Seaturtles to dive to much greater depths than other marine turtles. The favourite food of Leatherback Seaturtles is jellyfish and they have special backward pointing spines in their throat to help them swallow this slippery food. Global populations of Leatherback Seaturtles declined by approximately 70% between 1980 and 1995 and this species has a Canada rank of At Risk.

These amazing turtles are difficult to study because they spend very little time on land. After they have hatched, the females return to shore only to lay eggs and males never return to shore, making it difficult to study the distribution or migration patterns of these turtles. However, Canadian researchers, working off the coast of Nova Scotia, have pioneered a new method for studying Leatherback Seaturtles. Turtles are captured at sea, and a small satellite transmitter is attached to their shell, before they are released. This does not harm the turtles, and allows researchers to track their movements via satellite. Adult males, adult females and juveniles have been tracked in this manner, the first time that researchers have been able to follow the movements of male or juvenile Leatherback Seaturtles. The results of the study are quite incredible; adults and juveniles completed migrations of approximately 10 000 km from the cold waters off Nova Scotia, to the Caribbean Sea and adjacent areas of the Atlantic Ocean and back again, within a 12 month period. This study, and others like it, provides us with the information necessary to help conserve these giant reptiles.

Species spotlight - Greater Short-horned Lizard

Many Canadians are surprised to learn that seven different species of lizards have been found in Canada! One of the better known Canadian lizards is the Greater Short-horned Lizard, Phrynosoma hernandesi. Within Canada, these lizards are patchily distributed in mixed-grass prairie habitat in south-eastern Alberta and south-western Saskatchewan, where they favour sheltered, south-facing slopes. This slow-moving lizard has many potential predators, including hawks and other birds, snakes and mammals. When approached by a predator, the lizard freezes, and relies on its cryptic colouration to escape capture. Greater Short-horned Lizards eat ants, grasshoppers and other small invertebrates, using their excellent eyesight to locate their prey.

Greater Short-horned Lizards are at the very northern edge of their range in Canada. To escape from the cold winter, they hibernate under shallow soil on south-facing slopes. During the summer, these lizards conserve energy and heat by moving slowly, and spending much of their time on south-facing slopes. In addition, the females give birth to live young, allowing the mother to keep the eggs warm and safe from predators.

Greater Short-horned Lizards are patchily distributed in Canada, and most populations are small. Distribution and population size are greatly restricted by environmental variables, and increased grazing and development threaten their habitat. Greater Short-horned Lizards have a Canada rank of At Risk.

Results of general status assessment

Of Canada’s 48 species of reptiles, only 28% (13 species) have a Canada rank of Secure, while a total of 35% have Canada ranks of At Risk (17 species, figure 23 and table 32). A further 21% have Canada ranks of Sensitive (10 species), 4% have Canada ranks of Exotic (two species), 4% have Canada ranks of Accidental (two species) and 2% have Canada ranks of Undetermined (one species). Finally, three terrestrial reptiles have Canada ranks of Extirpated (6%), none of which have been reported in Canada for at least 40 years.

Comparison with previous Wild Species reports

Since the report Wild Species 2000, the category At Risk had the highest increase in the number of species, while the Secure category and the highest decrease in the number of reptile species (table 32).

With the revision of the ranks provided in this report, the Canada ranks of six reptile species have been altered compared to Wild Species 2005. Of these, the ranks of four species moved into higher level of risk following new COSEWIC assessments, the rank of one species moved into a lower level of risk, and one species was added due to a taxonomic change (table 33).

One species, the Prairie Rattlesnake (Crotalus viridis, Canada rank: Sensitive), has been added to the national species list since the report Wild Species 2005, bringing the total number of reptile species in Canada to 48. This addition was due a taxonomic change (split from the species Western Rattlesnake, Crotalus oreganus).

Threats to Canadian reptiles

The major threat to terrestrial and freshwater reptiles is habitat fragmentation and destruction. For example, populations of Prairie Skink (Eumeces septentrionalis) are thought to have declined as prairie habitat has been converted to agriculture and as habitat within protected areas has become fragmented by succession.

Road mortality is a serious threat to some reptile populations, especially for species that are long-lived and rely on high survival rates of adults to sustain their population. Reptiles may be attracted to roads as suitable basking spots, or as suitable nesting substrate, putting then in danger of being killed by passing cars. In addition, roads can create barriers that reptiles must cross to reach breeding or hibernating habitat. Finally, roads can fragment populations by preventing or reducing the number of individuals that move between populations.

Reptiles are popular pets around the world, and although ethical suppliers only sell animals bred and reared in captivity, reptiles are still taken from the wild to be sold as pets. Collecting animals in an unsustainable manner can lead to population declines, and adds an additional pressure to populations that may already be contending with habitat loss or other threats. Both the Exotic reptiles found in Canada were introduced into the wild by release of captive animals, and both species have the potential to compete with native reptiles. Other important threats to freshwater and terrestrial reptiles include exotic predators, pollution, disease, exploitation and human fear of reptiles.

Threats to marine reptiles include pollution and injuries and mortalities through contact with fishing equipment. In addition, some marine reptiles face habitat loss and over-exploitation through illegal harvest or poaching on their nesting beaches. Habitat restoration on nesting beaches can be hampered by sand removal.

Conclusion

This report shows that a total of 35% of reptile species have Canada ranks of At Risk in Canada, the highest proportion of any group covered in this report. Wild Species 2010 presents a more accurate report on the status of reptiles in Canada, than was available in 2000 and 2005 due to an increase in the amount and detail of information available about Canadian reptiles.

Further information

Bider, J. R. and Matte, S. 1996. The atlas of amphibians and reptiles of Quebec. St. Lawrence Valley Natural History Society, Sainte-Anne-de-Bellevue, Quebec: 106 pp.

Canadian Amphibian and Reptile Conservation Network [PDF, 302 KB]. (Accessed February 16, 2010).

Cannings, S. G., Ramsay, L. R., Fraser, D. F. and Fraker, M. A. 1999. Rare amphibians, reptiles, and mammals of British Columbia. Wildlife Branch and Resource Inventory Branch, B.C. Ministry of Environment, Lands, and Parks, Victoria: 400 pp.
Cook, F. R. 1984. Introduction to Canadian amphibians and reptiles. National Museum of Natural Sciences, Ottawa, Ontario: 200 pp.

EMAN. 2004. Status of amphibian and reptile populations in Canada. (Accessed February 16, 2010).

Laurin, M. and Gauthier, J. A. 2000. Diapsida. The tree of life web project. (Accessed February 16, 2010).

Oldham, M. J. and Weller, W. F. 2000. Ontario herpetofaunal atlas. Natural Heritage Information Centre, Ontario Ministry of Natural Resources and Forestry. (Accessed September 13, 2005).

Partners in Amphibian and Reptile Conservation. (Accessed February 16, 2010).

The Centre for North American Herpetology. (Accessed February 16, 2010).

Reptiles and Amphibians of Ontario. (Accessed February 16, 2010).

The Reptiles of British Columbia. (Accessed February 16, 2010).

References

Alberta Sustainable Resource Development. 2004. Status of the short-horned lizard (Phrynosoma hernandesi) in Alberta: update 2004. Alberta Sustainable Resource Development, Fish and Wildlife Division and Alberta Conservation Association Wildlife, Status Report No. 5, Edmonton: 27 pp.

Arvisais, M., Levesque, E., Bourgeois, J.-C., Daigle, C., Masse, D. and Jutras, J. 2004. Habitat selection by the wood turtle (Clemmys insculpta) at the northern limit of its range. Canadian Journal of Zoology 82: 391-398.

Barber, K. (editor). 1998. The Canadian Oxford Dictionary. Oxford University Press. Toronto, Oxford, New York: 1707 pp.

COSEWIC. 2001. COSEWIC assessment and update status report on the leatherback turtle Dermochelys coriacea in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa, Ontario: 25 pp.

Gibbons, J. W., Scott, D. E., Ryan, T. J., Buhlmann, K. A., Tuberville, T. D. Metts, B. S., Greene, J. L., Mills, T., Leiden, Y., Poppy, S. and Winne, C. T. 2000. The global decline of reptiles, déjà vu amphibians. BioScience 50: 653-666.

James, J. D. 2002. A survey of short-horned lizard (Phrynosoma hernandesi hernandesi) populations in Alberta. Alberta Sustainable Resource Development, Fish and Wildlife Division, Alberta Species at Risk Report No. 29, Edmonton: 25 pp.

James, M. C., Ottensmeyer, A. and Myers, R. A. 2005. Identification of high-use habitat and threats to leatherback sea turtles in northern waters: new directions for conservation. Ecology Letters 8: 195-201.

Lohmann, K. J., Lohmann, C. M. F., Ehrhart, L. M., Bagley, D. A. and Swing, T. 2004. Geomagnetic map used in sea-turtle navigation. Nature 428: 909-910.

Oldham, M. J. 1996. Amphibians and reptiles. In Assessment of species diversity in the mixedwood plains ecozone (I. M. Smith, editor). Ecological Monitoring and Assessment Network, Environment Canada. (Accessed April 11, 2010).

Pough, F. H., Andrews, R. M., Cadle, J. E., Crump, M. L., Savitzky, A. H. and Wells, K. D. 2001. Herpetology, second edition. Prentice Hall, Upper Saddle River: 612 pp.

Seburn, D. and Seburn, C. 2000. Conservation priorities for the amphibians and reptiles of Canada. World Wildlife Fund Canada and the Canadian Amphibian and Reptile Conservation Network, Toronto: 92 pp.

Shine, R., Phillips, B., Waye, H., LeMaster, M. and Mason, R. T. 2003. Chemosensory cues allow courting male garter snakes to assess body length and body condition of potential mates. Behavioral Ecology and Sociobiology 54: 162-166.

Uetz, P., Chenna, R., Etzold, T. and Hallermann, J. 2005. EMBL reptile database. (Accessed September 13, 2005).

Walde, A. D., Bider, J. R., Daigle, C., Masse, D., Bourgeois, J.-C., Jutras, J. and Titman, R. D. 2003. Ecological aspects of a wood turtle, Glyptemys insculpta, population at the northern limit of its range in Quebec. Canadian Field-Naturalist 117: 377-388.