Conservation: Lake Erie water snakes were once endangered in Ontario due to human persecution, having a low genetic diversity, road mortality and habitat loss from developed shoreline. Eutrophication also causes issues as agricultural run off depletes the fish populations these snakes depended on for food. It was not until the round goby was introduced from Eastern Europe that their numbers started to improve. The round goby is considered invasive as it aggressively competes with, and feeds upon native fish species. They also feed on the eggs of game fish and are linked to type E botulism which effects both native fish and birds. Despite being invasive, they are easy for water snakes to catch, plentiful and the perfect size to swallow. This has caused large dietary changes in the Lake Erie water snake with the round goby now making up 92% of their diet. As the round goby population rose so did the Lake Erie water snakes, greatly improving their numbers by increasing size and growth rate due to the surplus of food.
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Colour and Pattern: Lake Erie water snakes originated roughly 4000 years ago when the Lake Erie islands were formed. Transient water snakes became separated on these islands and in their isolation, they adapted a paler colouration and a reduced pattern. This helped them to camouflage on the rocky limestone and dolomite coastline of the islands. This change in colour mainly aided neonates and juveniles who are better able to hide from the prying eyes of hungry birds. Adults do not have this luxury as their larger body makes them conspicuous against the rocks. There is some diversity amongst the snakes on the islands with many individuals displaying no pattern at all while others display somewhat evident banding. There are also some with a very clear banded pattern and dark colour that would be characteristic of northern water snakes on the mainland. Between the years 1980 and 2003 there has been a noticeable increase in individuals with clear bands on Pelee Island, an increase of roughly 15%. This is believed to be caused by gene flow as every 3-4 years, roughly 9.2 northern water snakes become transient, finding their way to Pelee Island from mainland Ontario. Once on the island, northern water snakes end up hybridizing with the Lake Erie water snakes. These hybrids are able to breed further with Lake Erie water snakes creating an increase in banded hybridized individuals throughout the island.
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Development: For young snakes, being able to grow larger quickly is a beneficial trait, reducing the amount of potential predators during the early stage of their life. Lake Erie water snakes do not seem to do this, instead neonate water snakes will go without eating until after their first hibernation, growing slower than other species. To allow for this, the mother spends a greater amount of her own energy ensuring her young have a larger yolk and more fat reserves, allowing them to subsist without food for longer. The reason for this is unclear though it may be a method of reducing foraging behaviour as water snakes hunt in open water and wetlands where they can easily become prey to larger fish, frogs and birds. Reducing the time spent hunting in the open, reduces the chances of juveniles becoming prey themselves.
Sources:
"Lake Erie Water Snake." Ontario Nature, 2021, ontarionature.org/programs/community-science/reptile-amphibian-atlas/lake-erie-watersnake/. Accessed 18 Nov. 2021. Mack, Elizabeth W., et al. "Maternal Investment and Delayed Feeding in Neonatal Lake Erie Water Snakes: a Life-History Strategy." Zoological Society of London Publications, Journal of Zoology, 22 Oct. 2016, zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/jzo.12404. Accessed 18 Nov. 2021. Rowell, Jeffrey C. The Snakes of Ontario: Natural History, Distribution and Status. Winnipeg, Art Bookbindery, 2012. |