Fact or Fiction: Tree frogs and drowning

[ViperJr]

I understand what you're saying. The problem is that a healthy frog isn't going to want to swim, and if it does take a dive, it will be able to get out of the water. So in essence, having water is a non-issue. Furthermore, frogs don't breathe like we do, they breathe through their skin, so even in a soaking dish they can decide to completely submerge themselves and they'll still be okay.

I'm afraid that's not totally true. There are some gas exchange through their skin, but the primary respiration is with the nostrils and lungs. If I recall correctly, there are one species of lungless frogs, but needless to say, they aren't exactlly the norm. It is very possible for them to drown when being submerged for a long peroid of time( one example is Bufo bufo, where females occasionally drown when several over-eager males all tries to mate at the same time, and the combined weight is too much for the female, so she drowns.

[SkeletalFrog]

Martin is 100% correct, and the reasoning is simple - water contains less oxygen than air. Species which respire mostly via water either have gills (which have sophisticated counter-current blood flow to maximize extraction of O2), or vastly expanded skin surfaces (as in the Lake Titicaca frog and hellbender salamanders) and live in cold, fast-flowing waters (cold water holds more O2, fast flow improves gas exchange). That's why you get fish die-offs in hot, stagnant ponds - hot water has less oxygen, still water doesn't exchange it as well with the atmosphere or mix between water layers, and it eventually reaches a point that even the highly specialized gills of fish cannot extract enough O2 to stay alive.

As far as swimming ability, I've actually never run across a healthy frog that cannot swim, and for the past 6 months I've explicitly been tossing every species I can get my hands on into a large tub of water and filming their swimming with a high-speed video camera as part of my thesis. I've not only gotten Hylid tree frogs to swim extremely well, I've gotten good swimming from spadefoot toads, fowler's toads, and even red & black walking frogs (Phrynomantis bifasicatus). The only one that doesn't swim well is Bufo asper, and that's just because they prefer to play dead, and will swim perfectly well once I turn my back. I haven't done the tests yet, but the bumblebee toads seem perfectly capable of swimming too.