Sunday, August 23, 2009

8-14-09 Bufo americanus

The american toad (B. americanus) is a good place to jump into the Fauna of the White Mountains because it's ubiquitous and probably not the most attractive of the region's animals. It's technically an amphibian meaning it spends it's juvenile life stage in water. In the juvenile form it possesses gills like a fish and is vegetarian. After it undergoes its metamorphosis and becomes a "land animal" it's exhuberantly carnivorous and eats tons of insects. It's tongue is long and sticky and legend and because of it's length B. americanus doesn't have to run around and chase it's supper. It can remain stationary and zap morsels right out of the air or from inches away on the ground.

I took these photos near Zealand Falls Hut and this summer I have seen enormous numbers of toads like the one above, a mature adult male, and small ones like the one in the photo below. On my off-trail hikes they've been constantly underfoot. This seemed to be the case two years ago as well. I've read that they hibernate by digging into the soil and the depth varies with locale so I would expect they have to dig down fairly far in the White Mountains and further north. Their northern range is to James Bay where winter temperatures are severe. They come out of hibernation at the beginning of the breeding season which is triggered by warm temperatures.

B. amerianus' range is huge from far north in Canada down through the southern US and west across the Mississippi to Northern Mexico, Oklahoma, Kansas, Nebraska and Iowa. As a species B. americanus blurs some genotypic boundaries cross breeding with other closely related species. It is versatile and a generalist. It eats a vast variety of animals, mostly insects, all non-vertebrates: snails, slugs, beetles, an assortment of worms, millipedes, centipedes, spiders, other toads, and every kind of insect you can name including mosquitoes and crickets.

The melanistic coloring, or camoflage, helps the toad defend itself from predators. They're principal predators are snakes. The eastern hognose (Heterodon platyrhinos) and garter snakes (Thamnophis sirtalis sirtalis) are their most common predators. The garter snake is plentiful in the White Mountains. I have seen a lot of those around Zealand Falls this summer and in Carter Notch. The garter snake, which like B. americanus has a huge range as well, has adapted itself to the toxins found in the two prominent glands on either side of the toad's head (visible in the above photo). There's a wonderful story that was told by Sherman Adams, a famous denizen of New Hampshire, about a foreman of a logging crew working high up on North Hancock Mountain 110 years ago who ran down the mountain in terror when he encountered a huge black snake eating a toad legs first. All that showed of the toad was it's head and to the logger it looked like a two-headed monster. He screamed, dropped his axe, and ran all the way out of the woods to Lincoln.

Toads need water to reproduce but they are found in a number of different habitats including forested mountains like the Whites. Damp habitats are important as they don't drink water but absorb it through their skin. As kids we used to have pet toads we'd keep for the summer in glass aquariums (with heavy screens on top) and we would have contests and bet on whose toad could jump the furthest. At the end of the summer we would have a contest to see whose toad grew to be the biggest.

Lastly, and one of the most intersting things about B. amerianus is it's call. Everyone has heard it, usually in the evening, and it's kind of a trilling noise, high pitched in smaller toads and deeper toned in larger individuals. It vaguely sounds like a cicada or perhaps a spring pepper, but louder. It's very distinctive. A friend in college studied neotropical and tropical toads for a summer and learned that the calls are individualized and that this method of communication probably evolved because the toads' means of locomotion is to hop, or jump, so they don't leave a consistent scent trail. To report they're location they've developed the lovely, sophisticated epiglotal sound that we hear as a way to signal they're whereabouts to other toads, particularly the males trying to connect with females (and vice-versa).

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