Delta Journal
by Bob Thomas

My first herp (reptiles and amphibians) collecting consisted of walking about searching for animals on the move. I spent many wonderful hours stalking water snakes sunning on limbs extending over the water. How many times did I get soaked and come oh, so close! As I recall, the most difficult to catch on a sunny day was the Graham’s Crawfish Snake.

Next I discovered night collecting. What a thrill! I can still feel the excitement of finding a five foot Diamondback Water Snake, that soon gave birth to 75 babies! And the large Mud Snake lying at the base of a cypress, or the Buttermilk Racer coiled on the side of a sunny hill on a cool spring morning! (I could go on, but I’m getting too excited.)

Those were the days of abundant snakes and turtles, with a few frogs mixed in for fun. Though I always looked under sheets of metal and assorted trash, my interests took a new turn when I read about turning logs and rocks. This was when I began to find the more secretive species and a whole new world of herpetology unfolded for me.

I remember imagining that herps congregated only under certain objects. Why would they want to live underground in the forest when there are these perfectly great logs to live in and under? The answer is, of course, that they are distributed more widely, but there is a reason that they are often found under objects.

The reason is discussed in one of the neatest biology books, Biomechanics - an Approach to Vertebrate Biology by Dr. Carl Gans.

A rock or log lying on the surface represents a break in the homogeniety of the soil. When a burrowing critter bumps into one, it must change direction of movement. When one flips a rock or log, one often sees a myriad of tunnels exposed. The reason: the object served as the top of each tunnel and was quite beneficial to the critter in that it would not collapse as soil roofs might.

Other reasons why objects lying on the surface are beneficial to burrowing critters include:
-they prevent tunnel erosion from wind, rain, or flood.
-their uneven margins allow for protected entrances to the tunnel system.
-they provide a protected place for tunnels to intersect and for larger chambers to be form where critters can gather for a variety of purposes
-in sunny areas, critters may rest in a tunnel and absorb heat form the object while being protected from predators on the surface
-for some objects, such as logs, humidity in the tunnel system may be maintained, thus contributing nutrients as it decays
-buffering the microenvironment so that it minimizes temperature changes and keeps it from drying too quickly
-their somewhat constant set of environmental conditions and stable tunnels and chambers become attractive sites for nesting for the herps and other critters, with some of the latter being herp food.

All of these add up to the tunnels under rocks and logs being places that have microenvironmental qualities that attract the critters, their prey, and, consequently, their predators (including commercial and unrestrained collectors). Since they hold moisture from recent rains and heat during the day, they are attractive locations for burrowing critters to take advantage of surface conditions without exposing themselves to terrestrial predation.

Isn’t it neat that Mother Nature’s complexities of the microenvironment provide us with these windows into the fossorial habitat?