Naturespeak A naturalist's view of the world

June 19, 2007

In Cold Blood

Filed under: Uncategorized — wykes @ 9:51 pm

     The Rana girls are pretty much in the same place every day. They’re not much in the small talk department and can bore you into a stupor with their inactivity.  In fact, on the “exciting to be around meter,” they come in just after drying paint and growing corn observation.

  As bullfrogs, they certainly have a lot of “wow” potential.  Weighting in at 1 lb. or more and measuring up to an excess of 8 inches from snout to tail bone, they represent the largest frog in North America.  They have the singular ability to eat just about anything that fits in their mouth (see this video on the Natl. Geographic site) and are the stuff of story (as in Mr. Twain’s Celebrated Jumping Frog) and cuisine (frog legs).  The rolling bellow of the male frogs (listen hear- scroll down to the bullfrog recording) is one of the more impressive sounds of nature, but the sisters are excused from this singular male duty.

  With all this going for them, you’d think that watching them in their natural habitat would be exciting, but such is not the case. Except for the occasional blink or foot readjustment, their role as space saver could just as easily be performed by ornamental lawn frogs. To be fair about it, these frogs have no responsibility to entertain me.  They are cold-blooded creatures whose energy level is maintained at a very low idling speed. It is their duty to conserve energy until they absolutely need to use it, unlike our warm-blooded passion to burn it up.

  With this thought in mind, I was surprised when the sisters exhibited a veritable flurry of activity the other day. At one point, sister two actually nabbed a passing damselfly. She launched into a short leap, flung out her thick pink tongue, plastered the insect and squeaked with satisfaction before resuming her usual repose.  Sister one continued to stare blankly into space with her tremendous marble-like eyes and registered no reaction to the nearby excitement. (This is the same individual that was nearly overturned by a passing muskrat last week but maintained her place with an equally stone faced response.)

  You can imagine my shock,then, when I saw sister one begin to twitch.  Not believing my eyes, I was astounded to see her repeat the dramatic performance and then follow it up with an encore.  What could make her display such youthful vigor, I wondered? Upon closer examination, I saw that her actions were inspired by the pesky attentions of a mosquito. Every time the skeeter landed on her back, it evoked a localized twitch like that of a horse. 

  As warm bloods, we humans believe that mosquitoes are strictly our burden to bear.  Deadly malaria virus transmitting mosquitoes certainly have altered the course of human history, but the fact is that not all mosquitoes feed on humans.  Some species restrict themselves to birds, while others specialize in cold-bloods like snakes, turtles, and frogs.

  The females of the clan do all the blood sucking – the males stick to a diet of plant juice. Whether derived from bullfrog blood or Timmy’s left arm, a blood donation is digested over the course of several days.  During that time she is uses the blood proteins to nurture several hundred eggs.

  As if my column wasn’t enough to convince you that everything you read isn’t true, I am reminded of a statement from a frog site that states that “amphibians (like the bullfrog) are protected by pathogens, mosquitoes, ticks, and leeches by special components that the skin secretes.”  No, bullfrogs serve as blood donors just like the rest of us. It took a silent still frog to teach me that not every mosquito on earth likes people.

  As far as I know, there is no one particular mosquito species that prefers Bullfrog blood, but one – called Culex pecator – hits on bullfrogs more often than not. When Culex makes a strike, it probably seeks a location where the skin is sun dried and the slime coating at a minimum, such as Ms. Rana’s back.  They also seek out the delicate area behind the eye as a likely drilling site.

  A well placed eyeball bite will frequently elicit a raised white bump similar to our reaction to a mosquito attack. The thought being bit on the back of my eyeball is a sobering thought, one that almost makes me appreciate the bite I just got on my arm…almost.

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