“I’m Freezing!”–Literally

by Barbara Walvoord

(From Lathrop Lamp Post Feb. 9, 2017)

Sharon and I found this wood frog on November 16, on the east campus wide woods path. near two of Lathrop’s vernal pools (see trail maps of both campuses at https://lathropland.wordpress.com/trail-map-easthampton/) .

Yikes!  What is this tender little creature doing now that its world is all frozen?

It’s hunkered down in the leaf litter–frozen.  Its heartbeat and breathing have stopped. A special antifreeze keeps its cells from freezing, but  ice has formed between its cells.

In early spring,  our wood frog will thaw out, emerge from the leaf litter, start eating slugs, worms, bugs, and snails, and, if it’s not picked off by some snake, turtle, raccoon, coyote, fox, or bird, go find the vernal pool it was born in.  Though a vernal pool, by definition, has no streams running into and out of it, it fills up in spring with snow melt, rain, and ground water, just in time for frogs to mate.

The males will begin a song that must sound sexy to a female, but which the Minnesota Park Service characterizes as “racket, racket, racket.” Hear them at https://www.bing.com/videos/search?q=wood+frog+sounds+audio&&view=detail&mid=2A4EA8DBBA2D4861380C2A4EA8DBBA2D4861380C&rvsmid=0408C65668FCB54E96D70408C65668FCB54E96D7&fsscr=0&FORM=VDQVAP

A fairy-tale princess had to kiss a lot of frogs, but a male wood frog has to hug a lot of frogs, because clasping them is the only way he can tell whether another frog is a male, a female ready to mate, or a female who has already  mated and released her 1,000 – 3,000 eggs, and she’s done for the spring, thank you very much.

Tadpoles hatch after about 3 weeks.  They have to grow legs and lungs before the vernal pool dries up, which it does, by definition, at least every few summers.  The drying eliminates the fish that would eat this frog’s eggs and tadpoles, though the little ones may be gobbled by beetles, salamanders, wood turtles, and, sadly, other wood frogs.

Because the survival of the wood frog depends on vernal pools, it is an “obligate species.”  That means a recording of its mating song (constant and overlapping), or photos of all that hugging (at least 5 pairs), or of egg masses or tadpoles, can be used to certify  a vernal pool with the National Heritage and Endangered Species program, thus giving special protection to these unique, precious, and increasingly rare environments.


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