Mexican Spadefoot
Spea multiplicata
Another One off the List!

Mexican Spadefoot (Spea multiplicata)
Schleicher County, Texas
When I started recording anurans four or five years ago, I didn't really have a plan.  I just liked recording and documenting frogs and toads.   After a year or two, as I amassed more and more recordings it suddenly seemed worthwhile to try and get every species in my home state of Texas.  I did pretty well for a few years, but adding these last few Texas species to my "recording" lifelist has been harder than I thought.  Some of the species I need have restricted ranges or are rare in the state so their absence on the list is not unexpected.  But the Mexican Spadefoot doesn't fit in either category, I have seen lots of them, I have just whiffed on getting a recording of it calling multiple times.

Although it ranges widely across the desert Southwest of the US and down into the Central Plateau of Mexico, the Mexican Spadefoot (Spea multiplicata) is not a real "desert" dweller per se.   It is a grassland species that is found in the dry grassy desert grasslands.

A few days ago, I saw that it had rained 2 inches in the grasslands of far western Texas (Hudspeth County) and I decided that it was time to make another quick trip to west Texas to get this species.  While two inches of rain isn't enough to get frogs breeding in many areas, in the heart of the Chihuahuan desert where they might only get 5 inches of rain in a year, a two inch rainfall is a deluge.   Desert amphibians have to take advantage of that or not breed at all.  So I piled my gear into the car and headed out in to the high grassy desert of northern Hudspeth County.   

When I arrived I drove up to the area that had received the rain and spotted a  few anurans on the road.  That is always a good sign for me to stop and listen at that spot.   When I got out of the car all I could hear was the wind blowing across the grassland at 20mph from the east.....but then I heard it....I weak drumming sound from across the grasslands - Mexican Spadefoot calls!

I pointed my shotgun mic out into the darkness of the desert and managed to get a few weak recordings.  Here's what I heard in the distance -



The call of the Mexican Spadefoot is often described as a drumming or a dry trill sound.  It is like a short drum roll on a toy drum lasting about 3/4 of a second.  It reminds me of the sound made by a ball bearing dropped onto a hard surface from a few millimeters.   The ball bearing bounces with each bounce making a sound.  The bouches get a bit faster each time as the ball bearing bounces a little lower with each bounce and the pitch of the sounds goes up a bit toward the end. (Maybe that doesn't work for you, but that's the image I get?)

After I got back to my hotel that night, I was trying to decide where my next hunting ground would be.  Yes, the species was on "the list" but I wasn't very satisfied because it wasn't a great recording, I didn't have a recording of a single individual and I didn't have a photo of one calling.  I looked online and saw that central Schleicher County (central TX) had received heavy rainfall that night and I decided my next night would be there.  After all, I already had my spadefoot and it wasn't supposed to rain where I was so I might as well move on to wetter pastures.
  
When I got to Schleicher County, I was delighted to find the flooded fields held huge choruses of Mexican Spadefeet (Spadefoots?) that were easily approached, recorded and photographed.   Here's a single individual from Schleicher County -




Here's the sound of one of the Schleicher County choruses.  The nasal groans are Couch's Spadefoot and the higher pitched "crick, crick, crick" are Spotted Chorus Frogs. -



Here's a spectrogram of their call.  You can see how the later drum beats increase in pitch slightly -




And here is a short sequence of one of the little spadefeet in action.  As he called, the motion of expanding and collapsing his vocal sac seemed to propel him forward so he was hard to follow with the tripod-mounted camera!


So that's another species off the list, and more importantly my last panhandle/west Texas species.  This means I can focus my searches on the areas with missing species and not have to make the 6-10 hour drive up to those areas again!

© Chris Harrison 2016

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