21: Boreal Chorus Frog
Sorry for the hiatus (I did promise a new animal every day) – work was particularly busy this weekend/week. But I am back and I missed learning about Colorado wildlife while I was gone!
I write to you from Arapahoe, Ute, and Cheyenne land. I am interested in learning about the different animals that live in the place where I was born. I want to mention that biological classification as taught by western science has its roots in racism, sexism, and transphobia – here’s a good explainer about why.
It’s night time in Colorado in the summer and if you’re anywhere near a body of water, you’ll be hearing this. It’s the Boreal Chorus Frog (Pseudacris maculate)! Actually it is the males of the species, as the females do not make a sound. You’ll be happy to know that they are designated as a “non-game species” here in Colorado, so please do not shoot at them!
The frog is found throughout most of the state except the southeast corner, and can live up to altitudes of 12,000 feet! Learning that led me to ask how they survive the cold. Most frogs survive winter by burrowing into mud or, like the American Bullfrog we talked about a few weeks ago, getting underwater. But these frogs live throughout the Rockies at high altitude – I was doubtful that even those methods could withstand -40 C, a temperature that they are sure to experience every winter. Turns out that they have the ability to FREEZE THEMSELVES. From this article,
“The tricky thing about freezing is that when water freezes, it expands. When water inside animal cells freezes, they expand to the point they rupture, resulting in the death of the animal. A few species, including the boreal chorus frog, have evolved the ability to control their freezing by producing protein ice nucleators. Ice nucleators are shaped much like ice crystals and therefore act as a location for ice to freeze. The boreal chorus frog’s ice nucleators are located in the intercellular areas of the frog, not in cells, so ice forms outside their cells. The nucleators also control the growth and size of ice crystals to prevent cell damage. Molecules which act as antifreeze are inside their cells and prevent the cells from freezing. Their antifreeze chemicals include glucose and sugar alcohols. Freezing inside their cells would destroy them. As winter begins, the frogs slow their metabolism down until their heart stops and they no longer breathe, all while their extracellular fluids freeze and their cells remain unfrozen.”
One other extremely cool thing about this literally cool species: they exhibit individual, cultural learning! From the abstract of “Cultural learning of predator recognition in mixed-species assemblages of frogs: the effect of tutor-to-observer ratio” (2008):
“Animals that live in social groups have the opportunity to acquire information about foraging opportunities, mates and predators. Traditionally, social learning has been studied in birds and mammals, but few tests have been conducted on less social taxa such as amphibians. Moreover, few studies have considered cross-species learning among members of mixed-species assemblages. We examined social learning in tadpoles of the boreal chorus frog, Pseudacris maculata, and found that they do not display a fright response to the odour of predacious tiger salamanders, Ambystoma tigrinum, without prior experience with salamanders, but they can learn to recognize the salamanders when they are paired with predator-experienced woodfrog, Rana sylvatica, tadpoles. Moreover, the efficacy of learning is enhanced when the ratio of tutors-to-observers increases. Social learning has far-reaching implications for survival of individuals in mixed-species assemblages.”
Wow! I had no idea that tadpoles could learn like that. Amazing!