DESERT-MOUNTAIN TIMES (Alpine, Texas)

DESERT-MOUNTAIN TIMES (Alpine, Texas) 23 June 05 A secretive turtle and a search for understanding (Dennie Miller)
Photo: Once captured, each Big Bend Mud Turtle is marked in sequence by notching the marginal scales with a three-sided file. The marks will remain visible for the life of the turtle.( Dennie Miller)
When the good Lord gathered the turtles together to pass out grace and elegance, the mud turtles must have been at an all-night kegger hosted by the snapping turtles. Grace and elegance are simply not words in their vocabulary. With drab shells and markings, a snotty temperament and an odor that would make a polecat proud, only a herpetologist could love them. Like the late Rodney Dangerfield, mud turtles get no respect.
In 1985, my friend and mentor, Dr. Jim Scudday, then a zoologist at Sul Ross State University, was awarded a contract to produce a report on the natural history of the Big Bend Mud Turtle in the United States and Mexico. Jim asked me to assist him with the project, and I eagerly agreed to do so. For me, it was to be the start of a personal interest in Big Bend Mud Turtles that continues to this day.
Prior to this study, little was known about the Big Bend Mud Turtle. In fact, neither Jim nor myself had ever seen a living specimen.
And so it was that we found ourselves in a loaded pickup, searching for Jack Brown Springs (the site of the collection of the first specimens) and enduring the discomfort of a dusty limestone road on a hot summer day near Presidio. The anticipation, a conversation between old friends and a cool drink all contributed to legitimize the torturous journey. As we negotiated the twists and turns of the road, the talk turned to what we had learned from the literature.
The Big Bend Mud Turtle, the largest of two members of the mud turtle family found in West Texas, was first described in 1951 by Baylor University biologists, Bryan Glass and Norman Hartweg from specimens found along the Alamito Creek drainage south of Marfa. A number of common names have been given to this turtle since its discovery including Big Bend Mud Turtle, Mexican Mud Turtle and Mexican Rough-footed Mud Turtle. We inadvertently added to the confusion by referring to them as Chihuahuan Mud Turtles, a more appropriate designation. The name Big Bend Mud Turtle has withstood the test of time and is most frequently cited today.
In the United States, this mud turtle is restricted to spring-fed pools near Presidio, in the Alamito Creek drainage. In Mexico, it’s a common inhabitant of the major river drainages of the western Chihuahuan Desert, the Rio Conchos, the Rio Papigochic and the Rio Santa Maria, where they are conversationally referred to as “pedoras,” an uncomplimentary term alluding to the smell produced by the animal when excited or threatened.
The Big Bend Mud Turtle is much larger than its cousin, the Yellow Mud Turtle, a common resident of stock tanks, streams and rivers of the Southwestern desert regions. The shell of a large male can exceed 8 inches in length, while the Yellow Mud Turtle rarely exceeds 5 inches in length.
To capture turtles, low cost funnel traps were fashioned from hardware cloth and baited with canned sardines that had been packed in oil. A funnel at each end allowed turtles to easily enter the trap, but made it difficult for them to exit. The oil from the sardines used as bait produced a “chum slick” irresistible to any self-respecting mud turtle.
Once captured, each turtle was carefully weighed, measured and identified as to its sex. Once the observational data was recorded, each turtle was permanently marked by creating small notches in the marginal scales with a three-cornered file. These notches remain visible throughout the life of the turtles and are sequenced to allow future identification.
Over the next few years, recaptures revealed growth rates. In addition, a ratio of marked turtles to unmarked turtles trapped at each site allowed us to make educated assumptions about the number of turtles inhabiting each site.
In 1986, our data revealed the presence of healthy populations of Big Bend Mud Turtles in at least seven spring-fed pools in the Alamito Creek drainage. Since that time, a half-dozen additional sites have been documented.
At many of these sites, the ratio of turtles to habitat is very high. How the habitat can sustain such formidable populations is curious. The answer seems to lie with a lack of important predators and an abundant
We also learned that female Big Bend Mud Turtles lay one to six eggs at a time. Studies of Mexican populations indicate that egg-laying may take place at multiple intervals during the year. As yet, we know little of the preferred nesting sites.
The Big Bend Mud Turtle is protected in Texas as a threatened species. At this time, it appears the primary threat to their populations in the United States is associated with the health of the spring-fed pools they inhabit. If a pool becomes contaminated or the source of water interrupted, the turtle will almost certainly disappear from that site.
For the past two years, I have been collecting data at a single site, searching for understanding. There are still many mysteries about the lives of these secretive creatures. Like the nature of the turtle itself, progress is slow. The answers are out there, somewhere, still waiting to be discovered. Let’s not forget, the tortoise beat that silly rabbit by perseverance and patience.
http://www.dmtimes.net/blog/Outdoor/_archives/2005/6/23/968182.html