Amphibian drama: prey and predator in a pond
May 3, 2012 —
Along the Delaware River, there are many small ponds fed by springs or streams, or left over from floods. Also present are remnants of the D&H Canal, with many sections still holding some water. All these ponds play a role in the diversity of the riparian habitat along the shore of the river. A variety of fauna and flora are present in or near these ponds that would not otherwise be present on the river shore.
It was the courtship call of the American toad (Bufo americanus) that led me to one particular pond on the flood plain one late April day. This cricket-like call could be heard from a few hundred yards away, and several toads were calling. When I got to the edge of the pond, I watched some toads and checked to see what other frog or other species I could spot. Almost right away, I spotted the Northern water snake (Nerodia sipedon).
After spotting the first one, I spotted at least four other of the same species in the pond. Most of the snakes appeared to be actively hunting, slithering across the pond and along the shore in search of prey. Water snakes are fish eaters, but frogs and other amphibians are also on the menu.
After watching for a bit, I saw a near-miss; a snake came close to a hidden frog or toad, and two quick hops later, the lucky amphibian evaded the snake with only a wet “frog print” on an otherwise dry rock to bear witness to the event. I then saw and heard an American toad next to a rock, singing away. On the other side of this rock was a water snake, stealthily approaching with just its head visible. How would this drama play out? Would the toad meet its demise singing its last song?
The toad disappeared behind the rock, and shortly reappeared on the snake’s side. Surely, they see each other by now. The snake closed the distance until only a few inches away and then: nothing! The snake continued on its original heading and the toad kept singing.
American toads are a prey item of water snakes, even though these toads have paratoid glands (large glands behind the eyes) that exude a toxin as a defense against predators. Maybe the snake was hunting for green frogs, which were also present in the pond. Whatever reason for the passed meal, the toad gets to sing another day.