Living and Dying, Reptiles and Amphibians, Wildlife

Cryptic Croakers

Northern leopard frog among fallen maple leaves.
Northern leopard frog spot on with a fallen maple leaf
Hiding in plain sight
Hiding in plain sight

By Gabe Andrews –

Imagine that you are the size of a Reese’s cup and, to many animals, equally delicious. You occupy a precarious position in the food chain; you are a danger to many, and safe from few. You dine on insects, slugs, snails and even the occasional small bird. Predators that hover above include herons, hawks, and waterfowl. Raccoons, foxes and snakes lurk behind stumps on the ground, awaiting your misstep. Water, your true home, swarms with otter, mink and bullfrogs, each hungry for their main course delicacy. How do you, a northern leopard frog (Lithobates pipiens), survive such an onslaught?

Many of us may think that we witness a frog’s primary defense as it jumps away. But this erratic hopping demonstrates a last-ditch effort to stay alive. Before he leaps for his life, stillness keeps him hidden among the leaves; camouflage is his best friend. Numerous amphibians employ camouflage to protect themselves from potential predators, but few excel in this department as well as the northern leopard frog. Under the cloak of camo, this frog gains the opportunity to find dinner without always becoming it.

The waning months of summer in Vermont bring about new dangers for these cryptic croakers, as they venture from the water’s edge into meadows to forage for food. Luckily, hues of green and brown underlie rounded black spots that decorate the skin in a pattern that serves function over fashion. These colors blend in inconspicuously to the fields of forbs, grasses, and goldenrods in a cloak of camouflage. This crypsis is termed background matching.

The use of background matching is not uncommon elsewhere in the animal kingdom. A white-tailed deer fawn (Odocoileus virginianus) resting on the forest floor, an eastern screech owl (Megascops asio) waiting motionless in the hollow of a tree, or a spring peeper (Pseudacris crucifer) hiding amongst the autumn leaves are all able to avoid detection with their special camouflage. Whether feather, fur or frog, these animals are a rare treat if your eye can pick them out of the patchwork.

With the warmer portion of fall still upon us, spend a Saturday in the meadows of the Champlain Valley and try to catch a glimpse of a leopard frog during its feeding forays. Vermont winters hit hard for these amphibians. Soon, they’ll head for the trenches with the northern map turtles (Graptemys geographica). Both of these cold-blooded critters move to well-oxygenated waters to escape the brutal winter winds and hunker down into hibernation. They begin to tuck themselves in by late October to early November, and won’t fully emerge until February or March. By then, it will be time to fatten up, find a mate, and blend into their surroundings once more.

Gabe is a first-year Field Naturalist student at UVM

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