There’s always so much anticipation leading up to spring. My heart flutters just thinking about all those firsts, first robins singing in the morning, first flowers to emerge, first earthworms out crinkling up leaves, and one of my favorites: the first movement of amphibians.
Conditions for movement
If an amphibian could call in for the ideal weather to help them along the way as they take that annual trip from their upland wintering grounds down to their spring breeding territory, this is what they’d order up:
- A week of warm temperatures to melt all the snow and thaw out ice cover in wetlands
- A solid afternoon and evening of rain to wet the woods and roads
- A warm evening (above 37 will do for temp, but they’re poikilothermic heterotherms so the warmer the temperatures, the faster they can move)
- A new moon or cloudy sky to make it harder for predators to detect them
- High humidity (which goes hand in hand with clouds, warmer temperatures, and all that rain)
Movement last night
There’s some debate about the effect of atmospheric pressure on amphibian movement (article on toads), but the previous conditions will be enough to get amphibians out waddling and hopping. With temperatures last night around 40 and a light rain, I was hoping that last night would be good for some early movement. Last week saw a huge flush of amphibians in warmer areas to the south, but Shelburne Pond is usually just a bit behind. With a hopeful heart, I headed down to Pond Rd along the southern edge of Shelburne Pond to see what I could see. At 8:30pm, it wasn’t raining all that hard but the roads were still wet. On my drive down I had seen a couple of dead frogs on the road so it seemed like there was a good chance that there’d be some movement. I walked the road for a disappointing hour without seeing anything. The pond was totally quiet (other than some goose honks, mallard quacks, and beaver splashes), and there was still ice cover in some sections of the cattails and road side pools.
And then, just as I got back to my car a lone male wood frog appeared! I snapped a couple pictures before ushering it across the road. ID for wood frogs is pretty easy. They have a striking dark mask that covers their eyes and dorsolateral ridges on their back (unlike the similar spring peeper which is both ridgeless and maskless). Male wood frogs tend to be smaller and darker in color than females (females are redder). The males have engorged thumbs during the breeding season, which they use to clasp onto the female (see below). He’s a link to an undergrad’s research on color dimorphism in wood frogs: link. Additionally, there are about 10 males to every female, so there was a good chance on probability alone it was a male.
