Threats to Reptiles and Amphibians in Ontario
Reptile populations have declined drastically in Ontario over the past century. The Ontario Endangered Species Act, 2007 considers 18 of the province’s 24 reptile species (75%!) to be at risk. Fewer amphibian species are considered to be at risk, although amphibian populations are declining in parts of the province. Three species – timber rattlesnake, spring salamander and tiger salamander – have been extirpated.
1. Habitat loss and fragmentation
Habitat loss and fragmentation are the primary causes of the decline of reptiles and amphibians, both globally and in Ontario. In southwestern Ontario, urban sprawl and clearing of land for agriculture have caused the local extinction of many populations. For example, the eastern massasauga once inhabited much of that area, but this species is now restricted to the eastern shore of Georgian Bay, the northern Bruce Peninsula and two tiny, disjunct populations (one near Windsor and the other on the Niagara Peninsula). Intense development pressure in the current range of the massasauga continues to threaten this species. Aside from habitat loss, roads are the primary cause of habitat fragmentation in Ontario.
Habitat destruction by off-road vehicles, such as ATVs, is especially problematic because the areas in which they are often used tend to be sensitive habitats, such as wetlands, shorelines and old dune habitats. People who operate off-road vehicles may not realize or care that they are destroying important habitat. This type of habitat destruction is one of the few that persists in many of our protected areas, such as national parks, provincial parks, conservation areas and privately owned nature reserves.
Ontario Road Network. Click to enlarge.
2. Road mortality
In Ontario, vehicles kill countless reptiles and amphibians on roads every year. Most of Ontario’s reptile and amphibian diversity occurs in southern Ontario, where road density is among the highest in Canada. The network of major roads in this area has grown drastically over the years, from 7,133 kilometres in 1935 to 35,637 kilometres in 1995. It is now so extensive that no location in southern Ontario is more than a kilometre or two from the nearest road. Due to the high road density in southwestern Ontario, reptiles and amphibians must cross roads as they move throughout their home range. These species are accidentally struck by vehicles and killed much more often than most people realize.
Up to 4 percent of drivers in Ontario intentionally run over snakes and turtles on the road. Many people kill snakes in this way because they are afraid of them, even though – with the exception of the massasauga, which occurs in only a few locations – all snakes in Ontario are completely harmless.
Because most roads are exposed to the sun and have gravel shoulders, they present excellent nesting conditions for turtles. In June, when turtles are looking for a place to lay their eggs, they are attracted to roads, and individuals may wander back and forth along a road for hours. Inevitably, some are killed.
On warm, rainy nights, amphibians move overland to breeding habitats in the spring and to overwintering habitats in the fall. During these mass migrations, swarms of amphibians may cover roads. The only way for drivers to avoid running these animals over is by staying off the road altogether.
The concern with road mortality is not simply that animals are being killed, but rather that the mortality rate in many places is high enough to completely wipe out populations. This is especially true of Ontario’s turtles, which have long lifespans (over 70 years in some species) and low rates of reproduction. Consequently, the death of even a few individuals a year on roads will cause populations to decline, as they have sharply in Ontario. Seven of Ontario’s eight turtle species are already on the Species at Risk in Ontario list.
Road mortality is a threat to reptiles and amphibians even in our national and provincial parks. Algonquin Provincial Park, for example, has more kilometres of roads than the city of Toronto. A recent study found that rates of road mortality in a provincial and a national park in Ontario were as high as road mortality rates outside the parks. It is ironic that the very roads we use to access these parks and “appreciate nature” are probably the primary threat to wildlife populations in the parks.
Unfortunately, a surprisingly high number of people intentionally kill reptiles and amphibians in Ontario. Snakes are most affected by human persecution, because many people fear them. To help reduce this threat, people must be made aware of the truth about Ontario’s snakes:
- The massasauga is the only venomous snake in the province. Even though its bite can harm a human, this snake uses its venom to kill mice and other small rodents, rather than for defence. The massasauga’s primary defence is to remain motionless and unseen. Its camouflage is so effective that, in a test, even experienced observers overlooked about 85 percent of the massasaugas in a search area. If the massasauga is threatened, it rattles to warn intruders of its presence or disappears into a hole or under nearby cover. Generally, this snake bites only as a last resort, for example, when people intentionally pick it up or accidently step on it.
Although the massasauga is venomous, its bite has caused only two recorded human deaths in Ontario; both occurred over 40 years ago, and neither victim received any medical treatment.
- When threatened, many other snake species, even though harmless, act aggressively in an attempt to scare away predators. The most notable example is the hog-nosed snake, which flattens out its neck (like a cobra), rears up, hisses loudly and strikes, but always with its mouth closed.
- The milksnake and eastern foxsnake vibrate their tail when something alarms them. This behaviour, combined with their blotchy coloration, fools many people into thinking they are rattlesnakes and has earned the eastern foxsnake the local name “hardwood rattler.”
- Ontario’s snakes feed on mice, other rodents and insects and are an important form of natural pest control.
4. Illegal collection for the pet trade
Some reptile and amphibian species in Ontario are illegally collected and sold in the pet trade. Unfortunately, poachers do significant damage, since the species they target generally are already very rare. Wood turtles have almost been extirpated from southwestern Ontario due to poaching. Consequently, details about the locations of rare species are closely guarded. Poachers have been known to attend naturalist club or conservation group meetings and pose as interested naturalists or photographers in order to trick well-meaning people into divulging the locations of rare species.
Pollution is a serious threat to amphibians, which have moist, absorptive skin that quickly takes up any toxins in the environment. Amphibian eggs lack the protective shell that bird and reptile eggs have, and are more susceptible to toxins in the environment. Furthermore, amphibians rely heavily on aquatic habitats, which are often polluted due to leaching, runoff or intentional dumping of chemicals into lakes and streams.