DFW Urban Wildlife

When I first discovered these crayfish I had no idea what species they were. As it turns out, positively identifying invertebrates is often very challenging, and these crayfish were no exception.

I visited the crayfish colony one evening after a summer rain storm had passed through. The temperature was relatively low, and the humidity was high. It was my hope that these conditions would encourage the crayfish to come out of their dens. I found this crayfish walking through the grass near his burrow, and managed to collect it easily. My plan was to use this live specimen to help with the identification process.

There are over 350 species of crayfish in North America, and at least 36 of them live in Texas. In general, crayfish species are under-studied, and poorly documented. Figuring out which species I had was going to be a challenge.

I started my investigation by searching the internet. The information I found there was scarce and incomplete. Eventually, I got some help with the identification on a crayfish enthusiasts message board. I posted a couple of my pictures, and received the suggestion that what I had was either a Procambarus gracilis, or a Procambarus steigmani; both of which had been found in Texas, but neither of which were documented as living in Denton County where I collected my specimen.

To further complicate the matter, both of these crayfish species are very similar in appearance and behavior.

Procambarus gracilis is a well known species from Oklahoma up through the Midwest, but it has only been found in Texas in one county near the Oklahoma border.

The Procambarus steigmani, on the otherhand, is a relatively new species, only first identified scientifically in 1991. According to the Texas Parks and Wildlife Department website, the Procambarus steigmani is only found in two Texas counties: Collin and Hunt.

As Collin county is adjacent to and directly east of Denton County, the Procambarus steigmani became the most likely candidate.

Procambarus gracilis and Procambarus steigmani have nearly identical coloration. With deep red color over the dorsal surfaces, and cool gray color on the sides of the carapace, light pink appendage undersides, and dark blue pincherss.

Behaviorally, both species are what is know as Primary Burrowers. Primary Burrowers are unique in that they spend the majority of their lives in dens or burrows that they construct themselves. These burrows can be well away from bodies of standing water. Burrows of both species can be up to 6 feet deep, and terminate in a water-filled hollow.

The only reliable differentiator between the two species is a subtle difference in the shape of the Form I (reproductive) Male’s gonopods. The gonopods are a pair of appendages used for reproduction. They are located at the base of the crayfish’s tail, and are held close to the body, tucked neatly between the last two pair of walking legs.

Careful examination of the gonopods on this specimen revealed that I had discovered a colony of Procambarus steigmani, otherwise known as the Parkhill Prairie Crayfish.

Procambarus steigmani, or the Parkhill Prairie Crayfish, is an interesting find for a number of reasons. First, they were only just recently described as a new species, with the publication of the required scientific literature occurring in 1991. Further, they are only documented as having a very limited range, covering only areas in Collin and Hunt counties. Because of this exceedingly limited range these crayfish are considered rare, threatened, or endangered by the Texas Parks and Wildlife Department.

The specimens I have discovered were found in Denton County just to the west of Collin County in an area where they are not documented to exist.

Observation Details

County	–	Denton
City	–	Carrollton
Date	–	August 3, 2007
Time of Day	–	Afternoon
Temperature	–	Hot (greater than 89°F/32°C)
Weather	–	Partly Cloudy
Habitat	–	Recreation-Park
Type of Behavior	–	Other
Gender	–	Male
Maturity	–	Adult
Observer	–	Chris Jackson