Monday, September 27, 2010

Apple #483: Toads at Night

I like to go walking in the woods around here.  Sometimes I get so into it, I keep walking even though the sun has set and it's beginning to get dark.  Right around that time, I've been noticing toads out and about.  It's pretty tough to see by that point and I think I'm walking past dead leaves on the path and most of the time that's what they are, but then sometimes one of them moves.  Hops & skitters away.  When I lean closer, peering through the almost-darkness, I discover it's a toad.  Sometimes I can get out my camera and take a picture in time, but often the toad hops off into the grass before I can snap the shot.

What's been puzzling me is: what are the toads doing out at night?  They're cold-blooded, right?  Doesn't that mean they need sunlight to survive?  If that's true, how they heck can they be bopping around when it's dark?

These were all taken in the dark, with me aiming my camera at some dark spot on the ground, trying to zoom in and get the dark spot that's actually the toad, and then pressing the button so the flash goes off, and then I find out whether I got the frog in the photo or not. As you can see, sometimes the toads are still a bit far away to see much of them.  They're also not that big, as you can see by the comparison with the grass and little path-side plants.
(Photo by the Apple Lady)

  • First of all, I have to admit that I thought these dudes were all frogs.  Nope.  They're toads.
  • Generally speaking, toads have bumpy skin.  Frogs have sleek, smooth skin and their bodies are usually more streamlined.  Frogs spend more of their time in the water, so their bodies are better adapted for water-living.
  • Frogs are also generally slimier than toads.  Both have moist skin -- more about that later -- but again, since frogs spend more time in the water, their skin is more moist.

Frogs have smoother skin, thinner bodies, and longer legs.
(Photo from KidZone)

Toads have stockier bodies, are bumpier, and their legs tend to be more squat.
(Photo by the Apple Lady)

    • Toads are actually a type of frog, but for the purposes of this blog, we'll call them two different things and press on to the real question.  (Blog rhymes with frog, did you notice that?)
    • In order to understand what those toads were doing out at night, I had to re-learn what it means to be cold-blooded.  I had always assumed that if an animal is cold-blooded, like those alligators basking in the sun for hours and hours, they have to soak up the sun to keep warm. If they don't do that, they'll die.  Turns out, my perception was incorrect, and there is much more involved in being cold-blooded than lying around in the sun all the time.

    Alligators keeping warm by lying in the sun.  Or actually, they are skillfully regulating their total body temperature. Notice that most of them have part of their bodies in the water and part of it in the sun.
    (Photo from Go

    • Cold-blooded animals' bodies are at whatever is the temperature the air or water around them.  If the air is hot, they're hot.  If the water is cold, they're cold.
    • If they get too hot, they can't sweat to cool off like we people do. Instead, they need to change their environment -- go someplace cooler like in the shade or into cooler water.  If they're too cold, they can't shiver to warm up like we do; rather, they have to go someplace warmer such as into the sun.
    • So for cold-blooded animals, balancing their body temperature requires an ongoing change of location and environment.  They don't need sunshine all the time.  In fact, if they had only sunshine, they'd probably get too hot and blow up or something.

    It can be tough to see these little freddies.  Even though I took this picture aided by the flash, the toad is still camouflaged to look like that nearby leaf.
    (Photo by the Apple Lady)

    • Not only are toads cold-blooded, they also breathe through their skin.  This capability is the most useful for them when they're in the water. Oxygen passes directly through the skin into a network of blood vessels just below their skin's surface, and this is how they breathe underwater.  Pretty ingenious, yes?
    • But they can do this out of the water, too.  They do have lungs, but they're little sacs and very simple, not the complex network of branching things like our lungs are.  They can use the lungs to help them breathe above water, but they're better at breathing through their skin, so they'll mainly do that even in the air.
    • Breathing through their skin under water is easy for toads, piece of cake.  Out of the water, though, toads need some help. If their skin isn't moist, that magical oxygen exchange that takes place at their skin's surface won't happen.  So to keep their skin moist even when they're out of the water, their skin excretes a special type of mucus.  
    • Frogs have more of this mucus and toads have much less of it.  Sometimes they'll even feel dry to the touch when you pick them up, but according to what I read, that mucus is there even if you can't feel it.

    This toad looks pretty dry, I'd say.
    (Photo by the Apple Lady)

    • Toads don't just rely on their skin to keep things moist, they like the air around them to help out with that too.  This means they like to live in places where the air is nice and humid.  Lots of toads live in the steamy tropics for this reason.
    • But even in temperate climates, they can find humid spots to live.  Near swamps or slow-moving streams are good places.
    • Regardless of the climate, it's always more humid at night.  Think of the dew that falls at night, or the fog that sometimes rolls in.  That's sweet, delicious heaven if you're a toad.
    • When it has been warm in the daytime and it's humid at night, oh boy, that's the best time of year for a toad. They'll get out and hop around at night, looking for food like bugs, or grubs, or worms, or other little wriggly things to eat. 
    This guy's got the bumpy skin of a toad and judging by the gleam on him, he's also a bit moist to the touch, though not slimy as a frog.
    (Photo by the Apple Lady) 

      • The other thing toads do at night besides eating is to peep like mad, searching for a mate to get with.
      • That's right, all the peeping and cheeping you hear at night is toads (and frogs).  Sure, there are crickets going at it, but mostly, those are toads.  Male toads calling to the females, to be precise.
      • I knew that all that peeping was toads (actually I lumped them all together in my mind as frogs), even in my confusion about cold-bloodedness.  I guess I just thought the toads were sitting still and cheeping at each other.  But no.  The warm, humid nights are the nights when they are happiest, most active, and, frankly, getting it on.  If it's been rainy, hoo boy, look out.  Toad's delight.

      A toad on a humid evening is a happy toad.
      (Photo by the Apple Lady)

      NASA, Cool Cosmos, Infrared Zoo, Warm- and Cold-Blooded
      Journey North, Frog, FAQs Students Ask and Experts Answer
      lookd, Anatomy of the Frog
      JRank, Animal Life Resource, Getting to Know Amphibians, Frogs and Toads - Behavior and Reproduction
      Frogland, Super Skin
      Isaac Campbell, eHow, Why Do Bull Frogs Just Come Out at Night? July 8, 2010
      The Open Door Web Site, Animals which Breathe through their Skin
      Bellis, Edward D., The Influence of Humidity on Wood Frog Activity, American Midland Naturalist, July 1962
      Michigan Department of Natural Resources and Environment, Michigan's Frogs and Toads
      KidZone, Frogs Are Amphibians, Frogs vs. Toads
      Diffen, Frog vs Toad 

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