It's that time of year. I'm switching out of the bird mode and into the snake mode. They're starting out of their brumation (hibernation). I generally catch, measure, and release 300 to 500 snakes each summer above my house. I'm looking at population numbers, trying to get an idea of what's happening. Interestingly, terrestrial garter snakes have declined about 90% since 2011. All other species have maintained about the same population levels. What's happening?

The rubber boa (Charina bottae) is the only boa constrictor this far north.



The prairie rattlesnake (Crotalus viridis) is our only true viper around that's dangerously venomous.



Racer youngsters (Coluber constrictor) don't look anything like the adults. This is our only snake that looks different as a juvenile.



Here's a photo of an adult.(Coluber constrictor). Note the huge eyes. It hunts by sight.



The western terrestrial garter snake (Thamnophis elegans) is actually venomous, but mild enough venom that it is not a threat to humans or pets.



The common garter snake (Thamnophis sirtalis) is pretty rare here.



The gophersnake/bullsnake (Pituophis catenifer) can get 5 feet long, our longest snake hereabouts.

have any thoughts on the terrestrial garter snake decline?

hickoryridge - No. I don't have a clue. Apparently, they're not overly sensitive to environmental poisons (herbicides, pesticides, etc.). Could be that it has something to do with extreme dryness lately. We normally get 12 inches annually, but lately, it's been about half of that. Technically, we're in a desert.

Garter snakes are doing fine here. If I ever leave a bunch of tarps or black plastic in a pile somewhere on the farm they can always be found underneath wet it gets moved.

hickoryridge and beaverpeeler -

Back in 2011 when I started this, found 31.54 garter snakes per 100 miles of survey. In 2021 (11 years later) found 3.13 garters per 100 miles. Really, not much scientific literature about garter snakes. I'm not too worried, perhaps a normal cycle? Interesting though.

Fixin to have an eye peeled for finding a Boa ...nice shots, Jack. As always.

Cool pics Jack, thanks for the info

Hhmm . . interesting

Sharon that first snake is beautiful, great job........jk

Prairie Rattlesnake

Could it be that one of the other snakes are eating them or maybe a bird of prey?

The dryness is probably the reason for the decline in garter snake numbers. Here in Ohio, garter snakes typically give birth in late Summer sometimes as late as the end of September. The babies seem to prefer earthworms over all other prey. I used to have large numbers of garter snakes born from my captive snakes. My largest female, that I had for close to 20 years, had 74 live and 2 dead babies born one year. Most of my females had 20 some. In wet years, I could still find enough worms to feed them. They were always hit or miss on whether they would consume insects. In dry years, I only kept garter snakes that would consume fish. Small creek chub and stonerollers were abundant and concentrated in pools. Their size was perfect for the gape of the snake. I let the snakes that would not eat fish go.

Keith

Manitoba has some large garter snake dens at Narcisse just north of Winnipeg
https://www.bing.com/ck/a?!&&p=17080e463d5dd9c8JmltdHM9MTcxNTI5OTIwMCZpZ3VpZD0xYmQ5OWJlOS0wMDNkLTY3NWYtMmFlMy04OTc5MDFhOTY2NDEmaW5zaWQ9NTIzNQ&ptn=3&ver=2&hsh=3&fclid=1bd99be9-003d-675f-2ae3-897901a96641&psq=narcis+snake+dens&u=a1aHR0cDovL3d3dy5uYXR1cmVub3J0aC5jb20vc3ByaW5nL2NyZWF0dXJlL2dhcnRlci9OYXJjaXNzZV9TbmFrZV9EZW5zLmh0bWw&ntb=1
They are coming out in full force now.
Limestone caves/ cracks is where they travel to. Floods in the fall can be bad.
It is not unusual to see upwards a 1000 in a day.
The last 3 years of drought has effected their numbers as many wet areas are dry with no frog production happening

Bob Iowa-Good possibility sir. Over the years, I've found two roadkill racers with terrestrial garter snakes in them (as prey). I think it's pretty common, but not to the extent that it's causing declines. Kestrels, sharp-shinned, northern harriers, and red-tailed hawks, I've seen with snakes here, but their numbers haven't changed appreciably, so I doubt their responsible. I still think it may be drought-related, but why just the single-species declines?

Bob Iowa -

I've also put out trail cameras at roadkill snakes. Red foxes, coyotes, and especially striped skunks seem to search these snakes out, but these scavenger/predator densities are minor. I doubt they're responsible.