Sunday 14 August 2016

The snakes of Ontario - Part 5

Part 1 - Eastern Gartersnake, Dekay's Brownsnake, Northern Redbelly Snake, Northern Ribbonsnake
Part 2 - Northern Watersnake, Lake Erie Watersnake, Queensnake
Part 3 - Eastern Milksnake, Eastern Foxsnake, Eastern Hog-nosed Snake
Part 4 - Northern Ring-necked Snake, Smooth Greensnake
Part 5 - Gray Ratsnake, Butler's Gartersnake
Part 6 - Blue Racer, Eastern Massasauga

Back when I started this blog in the middle of 2011 one of the first series of posts that I made was about the snakes native to Ontario. I covered nine of the fifteen species, plus one additional sub-species of snakes that can be found in this province. I posted the fourth installment (covering Northern Ring-necked Snake and Smooth Greensnake) in 2013. After a hiatus that was much longer than anticipated I thought that I would finish the series of the remaining four species. This post will cover two species that are range-restricted in Ontario - the Gray Ratsnake and Butler's Gartersnake, while the final installment will include Blue Racer and Eastern Massasauga.

Gray Ratsnake (Pantherophis spiloides)

The Gray Ratsnake is a well-known and widespread species found throughout the forests of central and eastern North America, though it reaches the northern edge of is range in southern Ontario. The taxonomy of this and the other ratsnakes in North America is in flux, and different taxonomists have opinions on how many species constitute the species throughout North America. Until recently the form found in Ontario had been known as Black Ratsnake (Elaphe obsoleta obsoleta).

Gray Ratsnake - Leeds and Grenville United Counties

Gray Ratsnakes are an impressive snake and it is not unusual to find individuals close to 1.5 meters in length, though the record length is over 2.5 meters.Their closest relatives in Ontario are the Eastern Foxsnake and Eastern Milksnake, and like these two species they dine predominately on warm-blooded prey, such as birds and small mammals.

Gray Ratsnake - Leeds and Grenville United Counties

This individual was one of only two Gray Ratsnakes that I have encountered in Ontario. Unfortunately the lack of forest cover and abundance of roads transecting suitable habitat has reduced the numbers of Gray Ratsnakes throughout southern Ontario. A few small populations are hanging on in Elgin, Norfolk, Haldimand and Niagara in southwestern Ontario, but fortunately the species still has a relative stronghold in deciduous forests and pastures in several counties in eastern Ontario.

Gray Ratsnake - Leeds and Grenville United Counties

Education and increased awareness has no doubt had a positive impact on this federally and provincially Endangered species, though road mortality still remains a big issue over its range here in Ontario.

Gray Ratsnake - Leeds and Grenville United Counties

Gray Ratsnakes are well-known for their ability in scaling trees, a technique which allows them easy access to eggs and nestlings in bird nests, one of their main prey items. The second individual that I encountered in Ontario was scaling a tree beside a boardwalk passing through the edge of a marsh in eastern Ontario. Along with Laura and my brother Isaac, we had gone for a walk specifically to look for Gray Ratsnakes. I was mentioning to them how sometimes they can be seen climbing trees, and gestured towards one of the nearby maples as an example - a maple that happened to have a large black snake slowly ascending the trunk!

Gray Ratsnake - Leeds and Grenville United Counties

I have yet to cross paths with an individual from the southwestern Ontario population of Gray Ratsnake, but hopefully that will change eventually.

Butler's Gartersnake (Thamnophis butleri)

The Butler's Gartersnake is a diminutive species with a small global range. Preferred habitat includes wet prairies and other open grassy habitats in eastern Michigan, northern Indiana and Ohio, and southwestern Ontario, while a disjunct population also occurs in southeastern Wisconsin. In Ontario, the Butler's Gartersnake is associated with tallgrass prairie in Essex and Lambton counties, while a small population also can be found in the Luther Marsh area. This is the smallest of the three Thamnophis species found in Ontario, rarely growing larger than 50 cm in length.

Butler's Gartersnake - Essex County

One first glance, the Butler's Gartersnake can be mistaken for the widespread and abundant Eastern Gartersnake, a species that can be encountered in virtually every habitat type in the southern half of the province. Some of the key ID features for Butler's Gartersnake include a small, narrow head (often the same width as the neck),  chocolate brown coloration along the sides below the yellow lateral stripe, an olive head, and a pale yellow preocular scale (the scale in front of the eye), somewhat reminiscing of the white preocular scale seen in Northern Ribbonsnakes. On closer inspection, Butler's Gartersnakes often show an orange or reddish iris, though this is just something that I have noticed anecdotally. Additionally, the lateral stripe covers the third scale row, as well as half of the scales in the second row and fourth row. The location of this stripe differs from Eastern Gartersnake and Northern Ribbonsnake.

Butler's Gartersnake - Essex County

In 2010 and 2011 I was involved with a long-term study of Butler's Gartersnake near Ojibway Prairie in Windsor, Ontario as part of a massive project called the Windsor-Essex Parkway. Our research was critical to determine information on abundance, diet, habitat preferences, birthing areas and more, with the ultimate goal of influencing the highway footprint to minimize harm to this species and other species at risk found in the area.

Butler's Gartersnake - Essex County

I was involved with coverboard surveys and daily radio telemetry, apparently the first time that radio transmitters had been implanted in this species. We were able to find out some pretty interesting information about Butler's Gartersnakes, such as home range size, seasonal movements, and micro-habitat preferences for where they feed and give birth. This image below is of a healed scar resulting from the surgical procedure to implant a radio transmitter. After providing us with useful data, the snakes were recaptured and taken back to the veterinarian to have the radio transmitter removed.

Butler's Gartersnake - Essex County

Unlike Eastern Gartersnakes which dine on a wide variety of vertebrates and invertebrates, Butler's Gartersnakes are rather specialized in their habitat preferences. Part of our study was determining the stomach contents of the snakes, something that the snakes were more than willing to help us with. It turns out that Butler's Gartersnakes have a relatively short lifespan but grow quite quickly, especially when they live in wet fields with an abundance of earthworms to eat. It was astounding how quickly the babies would pack on weight throughout the summer, and it wasn't an uncommon occurrence for one to regurgitate upon capture. Often I was able to identify the earthworms down to species, if they had been recently consumed. Combined with an earthworm collection study I undertook on the study site, we were able to determine crucial parts of the site where those particular species of earthworms could be found. It turns out that the snakes were not picky as far as what species of earthworms they "hunted", and often the earthworms they regurgitated were the larger, more common species. 

Butler's Gartersnake - Essex County

This image below is of a gravid female, a week or two before she would likely give birth to ten or fifteen babies, each weighing under a gram. Often the babies would weigh over ten grams by early autumn.

Butler's Gartersnake - Essex County

The main threat to this species is habitat loss; particularly the tallgrass prairie where they are most common in southern Ontario, though also fallow fields and other grassy habitats which they may use as habitat. Butler's Gartersnakes can be someone tolerant of human disturbance, and we found quite a few individuals in patches of grass surrounded by development, or in ditches alongside the highway. Often they outnumber the Eastern Gartersnakes in certain habitats. Road mortality plays an impact as well, though Butler's Gartersnake is likely less affected than other species because they simply do not have large home ranges and are quite content staying put in a small patch of suitable habitat. That being said, we still found occasional road-killed individuals, including gravid females likely traveling a relatively large distance towards a suitable birthing area.

The Butler's Gartersnake is a unique little snake that holds a special place in my heart. Hopefully they will continued to survive in southern Ontario for many years to come.

Butler's Gartersnake - Essex County


Anonymous said...

Great pictures! Thanks so much for continuing this series :)


Lev Frid said...

Your herp pictures are amazing, Josh

Josh Vandermeulen said...

Thanks, Lev!