If you asked me what the “coolest animal alive” was, I probably couldn’t give you an answer. I could give you a list, and that list would probably never end, but I can tell you without a doubt that frogs and toads would be in the top ten. Not everyone loves every frog but, just like pet lovers with cats and dogs, there is a species of frog for pretty well every person to connect with. Personally, I always loved red-eyed tree frogs, but some people are fonder of pebble toads or poison dart frogs, and a few people out there even love the Suriname toad that births its babies out of its back. For anyone who has not seen the Suriname toad give birth be warned it's not for everyone and you will probably want to check it before showing your children.
I understand not everyone has been instructed in Frog 101, so I will give a quick overview to catch everyone up. Frogs are amphibians, meaning they don’t create their own body heat (ectothermic), lay clutches of soft eggs, and need to be around water to survive. Amphibians don’t have scales, feathers, or fur. Instead, they simply have a very thin layer of skin covering their body which is the exact reason they need to live near water. Since their eggs have no hard coatings and their skin is so thin, amphibians and their eggs dry out very quickly and require water to stay hydrated. This thin skin comes in handy when amphibians go underwater as many are able to breathe through the skin on their backs.
Most amphibians undergo metamorphosis, meaning they change from one form to another as they become adults. All frogs undergo metamorphosis, with tadpoles being the famous larval stage, where they transition from aquatic and legless swimmers with gills, to four-legged jumping animals with lungs. Metamorphosis is a truly astounding stage to consider for a vertebrate animal since it must rearrange its respiratory, skeletal, and digestive systems to do this. A fun note on frog digestion: frogs have to squish their eyeballs down on top of their food to help swallow.
Now that you have graduated Frog 101, let's step into Frog 102! First and foremost, toads are part of the frog family tree. There really aren’t any things that separate toads from frogs scientifically, but often toads are referred to as the leathery-skinned frogs that have some growths on their skin, often mistaken for warts. Second, not all frogs jump and swim. Some frogs run, others burrow through the ground, some climb, and even a few glide from tree to tree with specially adapted webbing on their feet. The last thing I will add is that some frogs can live out of water for long periods of time. Species such as Australia’s burrowing frogs are able to live for months or even years underground waiting for rains to make ideal breeding conditions.
While frogs are ectothermic, and therefore can’t generate their own body heat, some frogs are able to survive in climates with cold winters by freezing solid. Yes, some species like Rana sylvatica can freeze their body with the surrounding environment until the spring thaw. They can achieve this due to very special adaptations that use glucose (a common sugar in the body) to essentially wrap around the cells in a protective blanket to prevent damage during the freeze. It is also key that the freeze happens slowly and only to about -3⁰C as freezing too quickly means the body can’t disperse the glucose fast enough and they don’t tend to have enough glucose stored on hand to handle even cooler temperatures. These frogs also have special proteins and other systems in place to help with protecting their cells and getting their cells back in working order after thawing.
I think this is a good place to stop and appreciate everything we’ve learned about our amphibious friends, from their breathable skin to their amazing strategies to deal with droughts and freezes. Frogs truly cover a broad spectrum of adaptation and survival strategies but, unfortunately, are not amazing at adapting to their quickly changing environments… but let's leave that for next time. For now, let's just enjoy everything that makes our jumping/swimming/running/burrowing/gliding friends amazing and tell someone, or even us, your favourite thing about frogs in preparation for World Frog Day on March 20th!
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