Ontario
is home to 19 species of snakes, but many of these species are either of
special concern, threatened or endangered (Rowell, 2012). The Committee on the Status
of Endangered Wildlife in Canada (CSEWIC) has determined that 7 Ontario snake
species are endangered, meaning they face immediate extirpation/extinction, and
that 2 species are threatened, meaning that unless actions are taken the
species is very likely to become endangered. Three of these at risk Ontario
species are the eastern hog-nosed snake, gray ratsnake and queensnake.
Fig. 2. A gray ratsnake. Photo credit: Nick Caims (Argue, 2015).
Fig.
3. A queensnake. Photo credit: Scott Gillingwater (Crowley, “Queensnake” 2015).
Eastern
Hog-Nosed Snake (Heterodon platirhinos)
Fig. 1. An eastern hog-nosed snake, notice the characteristic upturned nose. Photo Credit: Joe Crowley (Crowley, “Eastern Hog-Nosed Snake” 2015).
As indicated by its common name, the
eastern hog-nosed snake has a unique upturned snout, but other than this,
appearance tends to vary between individuals (Crowley, “Eastern Hog-Nosed Snake” 2015).
Fig. 4.
The current and historic Ontario range of the eastern hog-nosed snake (Crowley,
“Eastern Hog-Nosed Snake” 2015).
There are two regional populations
of the eastern hog-nosed snake in Ontario, the southwestern population and the
north-central population (Rowell, 2012). Figure 4 outlines the current and
historic ranges of these two populations. Note that while the ranges appear
quite large, in reality there are only a few locations that have viable
population sizes, that is, populations of an adequate size to support survival
(Rowell, 2012). As is demonstrated in the range map, the eastern hog-nosed
snake is experiencing range reductions and population declines, mostly as a
result of human activity (Rowell, 2012).
The eastern hog-nosed snake faces a
number of human-caused threats, including habitat disturbance, persecution, and
road mortality.
·
Habitat
Disturbance: The preferred habitats, specifically soil types, of the eastern
hog-nosed snake tend to also be ideal sites for agriculture and waterfront
development (Crowley, “Eastern Hog-Nosed Snake” 2015). Subsequently, human land
use has lead to large-scale destruction of suitable area for this snake, and
any remaining habitat is at threat of being developed and disturbed (Crowley,
“Eastern Hog-Nosed Snake” 2015).
·
Persecution:
While the eastern hog-nosed snake is harmless, under threat it sometimes
carries out a frightening, cobra-like defensive display (Rowell, 2012). As a result,
individuals are often killed by humans who mistake these snakes as being
dangerous (Crowley, “Eastern Hog-Nosed Snake” 2015).
·
Road
Mortality: Death due to vehicle collision is an increasing threat to eastern
hog-nosed snakes, especially as road construction increases with the range of
this species (Government of Ontario, “Eastern Hog-Nosed Snake” 2015).
These
negative impacts that humans have on the eastern hog-nosed snake have lead to
the species becoming threatened (Government of Ontario, “Eastern Hog-Nosed
Snake” 2015). Unless action is taken to mitigate the threats human activates pose
to these snakes, the species is likely to become endangered, even extinct.
Gray
Ratsnake (Pantherophis spiloides)
The gray ratsnake is the largest
snake species in Ontario with individuals growing up to 2 m long (Government of
Ontario, “Gray Ratsnake” 2015)! Considering its large size you may be surprised
to learn that these snakes are excellent climbers and can often be found in
trees, hunting for prey such as birds (Government of Ontario, “Gray Ratsnake”
2015).
Fig. 5. The current and historic Ontario range of the gray ratsnake (Argue, 2015).
As shown in Figure 5, two
populations of gray ratsnakes occur in Ontario, the Carolinian population and
the Frontenac Axis population. While both are experiencing population declines
they are at different levels of risk. The Carolinian population is endangered
as a result of isolation caused by severe habitat disturbance, persecution and
road mortality (Argue, 2015). This area is now densely inhabited by humans who
have cut down much of the snake’s preferred forest habitat and often kill the harmless
species out of unprecedented fear (Rowell, 2012). The same human activities
have lead to the Frontenac Axis population, near Kingston ON, becoming
threatened (Rowell, 2012). It is interesting to note that this population does
benefit from the fragmenting of its habitat for agriculture as it increases the
incidence of prey, but any benefit is offset by mortality caused by persecution
and road kill as well as habitat disruption for cottage and urban development (Rowell,
2012).
Queensnake (Regina septemvittata)
The queen snake is a semi-aquatic
species and an excellent swimmer (Crowley, “Queensnake” 2015). These snakes never
venture far from their very specialized habitats; clear water bodies with rocky
bottoms like streams, rivers and lakes, where it preys predominantly on
crayfish (Government of Ontario, “Queensnake” 2015). Due to their need for
specific habitat and small home ranges, queensnakes are very poor
dispersers (Government of Ontario,
“Queensnake” 2015). The inability to move to new habitats combined with
multiple human-induced threats has lead to range and population declines of
this species (as can be seen in figure 6), which have ultimately caused the
queensnake to become endangered (Rowell, 2012).
Fig. 6. The current and historic Ontario range of the queensnake (Crowley, “Queensnake” 2015).
The
extensive development that has occurred in southwest Ontario, particularly near
waterways where queensnake are most common, pose many threats to the species (Rowell,
2012). Water control via dams, wetland draining, and shoreline development
cause changes in water flow and turbidity, making habitats unsuitable for queensnakes
(Rowell, 2012). In addition, queensnakes are more sensitive to water pollution
than other reptiles as pollutants can easily penetrate their skin (Rowell,
2012). Aside from their direct negative impacts on queensnakes, all of these
factors also indirectly harm this species as the resulting poor water quality
leads to extreme population declines in crayfish, the queensnake’s main food
source (Rowell, 2012). Recreational use of queensnake habitat also contributes
to population declines. These snakes hide in shoreline rocks and so are often
unintentionally trampled, in addition to being killed on purpose out of fear,
even though queensnakes are harmless to humans (Crowley, “Queensnake” 2015).
You may have noticed that these
three Ontario snake species are threatened or endangered as a result of a
common set of threats, all of which are founded in human activity. Indeed these
threats (habitat disruption, persecution, and road mortality) in addition to
climate change and the dangers of resulting small populations are putting
snakes at risk all across Ontario.
References:
Rowell, J. (2012). The
Snakes of Ontario: Natural History, Distribution and Status. Toronto, ON.
