Snake Diameter Info for Hibernacula Construction

[elspru]

Hi,

In bird-houses to exclude non-target species the entrance hole is of limited size.
Similar to a species-specific bird-house, I'd like to make a snake hibernacula,

Do you know where can get information about diameters of snakes?
In particular I'd like to know the diameter of smooth green snake, eastern garter snake, and massassauga rattler.

Even if you don't have a source, perhaps you have handled these species before and thus can give an approximation.

I'm planning on making it out of a plastic bucket,
it will be mostly underground, with drainage at bottom, and rocks inside and on top.
the lid and some of the protruding sides will have entrance/exit holes drilled.

I'd like to make it a hibernacula exclusively for smooth green snake adults, and so it is ideally too narrow for both garter snakes and massassauga rattlers. Though at a minimum so it is too narrow for rattler adults (don't want rattlers in my backyard).

If there is interest I can upload blueprints and eventually photos/videos of construction and results.

[pet_snake_78]

I see you're in Canada. The frost line in Canada is probably 5' deep so I don't think a bucket would work. You also have to think about drainage. There have been artificial constructions in Canada (I think for Garter snakes) but you'd need heavy equipment.

[eminart]

This sort of depends on how big the snake is. Most birds are full size as soon as they leave the nest and, within the species, very similarly sized. That's not how reptiles work. A snake of the same species could be anywhere from smaller than a pencil to a few inches in diameter.

[elspru]

eminart thanks, that explains why so little information is available about that.
I guess since this is in a backyard, and there are neighbours, politically I'd probably be safest with the narrowest adult diameter possible.

I know from bat-house construction that anything over 2cm or 3/4" would invite wasps, so it would have to be less than that. Politically, since this is going to be in my backyard, with neighbours nearby, it would be best to go for pinky width size or smaller (~1cm). Also I think the biggest drill bit that fits in my hand-drill is 3/8 around 1cm.

I guess once a snake gets too big they'll have to find somewhere else, though hopefully there are enough egg-laying adult smooth green snakes that would fit, to sustain the species.

pet_snake_78 thanks "frost line" that helps a lot in terms of understanding the depth I should be going for.

Based on my research, for worst-case scenario the frost-line should be about 130cm or 51inch. Can attain that with a stack of with two 200litre (55 gallon) plastic drum barrels which have heights of 85cm or 33.5inches each, or 170cm/66inch total.

Even with drainage it should be less than 6ft of digging, especially since can mound the soil somewhat. since people dig graves of 6ft, presumably I wouldn't need any special equipment unless I hit bedrock.

However according to this Dow-Chemical report if the surrounding soil is clay or silt, then at the 600 frost index where I am located, the depth of penetration would be a less than 2 feet. so one barrel would be enough. If there is turf (yes) and snow-cover (definitely) then penetration should be under 1foot, so even a 40cm (15inch) high bucket might be good enough. from-source 12668dw FrostDepth pdf
msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_01f6/0901b803801f6296.pdf?filepath=styrofoam/pdfs/noreg/178-00754.pdf&fromPage=GetDoc

I can also paint both the bucket and rocks carbon black with non-toxic waterproof paint, also can have some rocks on top for additional protection. I think first year I'll try the bucket, and if that doesn't work then I can try a drum barrel.
Considering that clay is better than sand, then it is likely thermal mass that makes the biggest difference, so could try to stock the barrel with dolomite or quartzite or other high thermal-mass rocks.