Friday, October 24, 2014

American Bullfrog

Bullfrogs are native to eastern North America but have been introduced across the country and around the world. These introductions have been accidental or on purpose—they are considered a delicacy and escape from farms, they have been used as biological control agents, or they may be escaped pets.

Where established outside of eastern North America, they are invasive species. Female Bullfrogs lay up to 25,000 eggs, and, after about two years, hop out of their ponds onto land (MN DNR). The concern is that Bullfrogs may out-compete, native amphibians and unbalance local ecosystems. Bullfrogs are voracious, opportunistic, ambush predators that capture any small animal they can overpower—rodents, small reptiles, amphibians, crayfish, birds, and bats have all been found in Bullfrog stomachs (Wikipedia).

On the other hand, Bullfrogs provide nutrition to their predators, including herons, otters, large fish and snakes. Bullfrogs may be resistant to copperhead and cottonmouth venom—an interesting hypothesis for study if one were looking for a thesis topic.

This bullfrog and many others hunted under the algae-covered pond at the Nisqually National Wildlife Refuge near Olympia, Washington. I confirmed my identification with a refuge ranger, who made an unhappy face and said, “I wish they weren’t there."

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