Duels in the Dark

GOING NATURE’S WAY

By Kate Crowley

There are duels in the dark and the adversaries are trying to out sing one another; a much more civilized form of settling differences than that practiced by human males in times past.  The players in this night time confrontation are amphibians.  These vocal antagonists have been going at it for weeks now, although the list of entrants has changed and expanded.

The site for these assignations is a couple of small ponds in our front yard.  One is only a couple feet in diameter and the other is three times that size.  Both need cleaning out, as algae left over from last summer has bloomed and mostly filled the water.  But I can’t empty them out when they are obviously being used for the important purpose of courtship and territorial defense.  So, for the time being they will look unkempt to human eyes, but continue to be havens for frogs and toads.  Of course, if their pursuits are successful there will be eggs and then tadpoles to consider, so it could be July or later before I can really clean them up.  I just hope that the adults and juveniles will consume all the mosquito larvae that are sharing the water with them.

The duels began several weeks ago with the small, nearly invisible Western chorus frogs.  They are Minnesota’s smallest frog, measuring just ¾ to 1 ½ inches in length and are found throughout the state in almost any small body of water, including temporary wetlands and ditches. While their body color can vary – they all have three dark lines running from their head down their back, a dark line through the eye and a white line above their upper lip.  Their call is a high pitched, vibrating sound.  It is not musical at all and has been compared to the sound made when you run your thumb down the tines of a comb.

This can be heard in the daytime as well as at night, but I have never been able to sneak up on the little creatures and catch them in the act of singing. They must have extremely good eyesight and can pick up the slightest peripheral motion or shadow.  The females can lay as many as 100 eggs, which they attach to vegetation; 90 days later they become frogs.  That fact will cause even more delays in my pond cleaning. The good news is that the tadpoles eat algae.  Now I’m hoping for thousands of tadpoles, which may be possible. 

The second amphibious song that has arrived belongs to the American Toad.  Slightly larger than the chorus frog it reaches 2 to 3 ½ inches in length.  I found one of these little warty brown amphibians last week in the backyard near the outside faucet.  These toads are great assets to our gardens as they eat all manner of insects, worms and even snails.  Some people even create little ‘houses’ for toads to find shelter in among their flowers or vegetables, but at night, it is in the pond where the toads gather.  The male’s long (up to 30 seconds), loud, high pitched trill blasts out in all directions. The volume seems impossibly loud for such a small critter, but they are equipped with an amplifier in the form of a globular pouch in the throat which acts as a resonator, after air passes over the vocal chords.  When you listen closely you can hear the echo of other males returning the volley of calls.  Their passionate pleas will go on as long as the females are in breeding condition. 

When a female is coaxed into range the male hugs her from behind  (called amplexus) and fertilizes the thousands of eggs that she lays in strings. Like the chorus frog these eggs are attached to plants. The tadpoles will eat vegetation.  Each summer I have seen black tadpoles in the pond, but I am not sure if they are all one species or a mix of  the two.  Either way, I am happy to be host to these important members of the ecosystem. 

You have probably heard about the trouble many amphibians are facing because of changes in the environment and toxins that have gotten into their watery world.  Whenever and wherever we can help them survive, we should.  They are an ancient thread in the fabric of life on this earth, a part of the weave that sustains the entire garment. 

We are still astounded by the fact that this little, algae filled oasis we created in our sandy yard a decade or more ago has become a haven for such life.  We still can’t figure out how they found it and us, but we celebrate every spring when we hear them dueling in the dark.