I arrived a day later than the rest of the 2013 expedition to Baja Sur, in order to save myself $250 on the plane ticket. Consequently, I missed out on the first day’s catch, including a large calling congress of Spotted Toads (Bufo punctatus), and several Cape Aquatic Garter Snakes (Thamnophis valida celaeno), found along a rocky mountain stream that first day.
I deeply regret the toads. Is a lifer garter snake worth $250? Probably, but that’s another blog post. Fortunately, mis amigos held back the snakes for a day and I was able to examine and photograph an adult and a juvenile. A nice consolation prize, but of course, I wanted to see one for myself. Who wouldn’t?
Flash forward to September 2015, when I returned with a group to Baja, flying into San Juan del Cabo and, money-be-damned, all on the same day. A short drive north got us up into the Sierra Lagunas and back to the same mountain stream. It happened to be Sunday, and hotter than the hinges of Hades, and so a crowd of local people were down at the water, grillin’ and chillin’, splashing and swimming and even getting baptized in some cases. We trooped through the throng in full herping kit (“¿qué pasa con los gringos locos?”), heading for a quieter part of the stream. And the garter snakes were there, a hundred feet from a hundred people. Within minutes we had spotted a handful of juveniles, probably young of the year, as they foraged in the shallow water along the banks.
The juveniles were interesting to watch; they tended to come up for air alongside a rock or up the stem of a plant. There they would rest with just their heads breaking the surface, their bodies angling down to the bottom, always ready to duck under and swim away. Get too close, and some of the little snakes would wiggle-swim to the other side of the stream. After watching several escape in this manner, I began to take a closer look. Rather than swimming to some random spot on the other side, they would swim directly to a large rock and either duck under it, or anchor themselves on one side. Some of the little snakes swam back (we had herpers on both sides of the stream) and again, they would pick out a rock on the other side and swim to it. Anyone who thinks reptiles are stupid animals, blindly responding to instinctual triggers, needs to think again. They know stuff. They know how to move through their world.
We found no adult celaeno on that visit, and a few days later Jim Scharosch and I went back for another try on a weekday, when the large crowds were absent. Climbing up on a promontory above the stream, Jim looked over the edge and spotted an adult female, which swam off towards me, and then ducked under a partially submerged boulder. This was a mistake on the snake’s part – air breathers have to come up some time! Jim closed in on the snake’s location and I took off my shoes and socks and waded in to complete the pincer movement. The snake was in a crack with only two exits, so I perched by the front door, while Jim watched the back. In just a few minutes the snake emerged, close to my waiting hand, and made a break for the oxygen above. I grabbed her up and hauled her out and we had a nice adult to examine and photograph.
Once upon a time, these snakes were classified as Nerodia valida, and indeed, they look more like water snakes than garter snakes, with their large, broad heads set upon a narrower neck, and their bulky bodies. They make a diet mainly of fish and frogs, although I’m sure the adults are eating rodents and nestling birds as well. The stocky female we grabbed up was a little over two feet in length, and to me it looked similar to Thamnophis couchii, another stream-dwelling garter, found about a thousand miles due north. I don’t need to sell Thamnophis to thamnophiles, but take another look at your back yard garter or ribbon snake – they’re part of an adaptable, incredibly successful genus that ranges from the Arctic Circle to Central America.