Pantex Blog

Article by Jim Ray, Pantex Wildlife Biologist/Scientist

Our pickup made its way slowly down the dusty two track pasture road. We were two miles into a 24-mile spotlight survey that we had begun once it had gotten good and dark. Our crew consisted of a spotlighter for each side of the vehicle, a Security Police Officer to provide key support and, on this night, a co-worker had come along to help us out as a data recorder. And trust me, our night had been well coordinated – assistance by Security, and notification to the Pantex Operations Center, Carson County Sherriff’s Office, Texas Parks and Wildlife Department, and Texas Tech Research Farm.

As we crept along, one million-power spotlights shown out each side of the vehicle. Its holder would watch for eye-shine, or even the outline of the animal itself if close enough to the vehicle. We stop and glass (binoculars) an animal when we need to, but otherwise we record what we have seen at the end of every mile.

We had already observed two deer and a few cottontails when Monty Schoenhals asked me to stop and identify a set of eyes that would occasionally light-up as it made eye contact with us. Through my binoculars I could tell it was a deer, but I needed it to stand-up in order to have a chance of identifying the species. A quick blow on a predator call and it did just that. An eventual glimpse of its light-colored rump and rope-like tail positively identified it as a mule deer and off we went continuing along the survey route.

Spotlight surveys are an important element of our natural resources surveillance program. We spend much time and effort trying to document and monitor our natural resources, and we utilize that information for protecting them, and making land management decisions. I initiated the spotlight surveys back in 2000, my second year at Pantex. Initially, they were aimed at trying to detect swift fox, then, a subject of much debate as to its presence or absence. I had participated in many a deer survey over the years and had also assisted with those for swift fox. Although, not a good technique to estimate numbers of swift fox in an area, you can sure detect their presence if there is a population. Although there is no hint of a swift fox at Pantex, the surveys have been continued due to the opportunity to document and monitor the other nocturnal animals that we come across.

A typical spotlight survey will take us from two to three hours to conduct depending on how many stops that we have to make to glass and identify eyes that are a considerable distance from the vehicle. Animals that we have recorded over the years on these surveys include badgers, black-tailed jackrabbits, bobcats, cottontails, coyotes, gray fox, feral cats, mule deer, raccoons, striped skunks, and white-tailed deer. In some years, it may be the only means of documenting a badger, a gray fox or, less so, a white-tailed deer.

We use the spotlight data every year to supplement other data gathered by a variety of survey methods. For the most part, I just use it for presence/absence-type data and this is included in annual reports and all-time species lists.

Whether in Palo Duro Canyon, the Canadian River bottom, or on the flat plains of Pantex, it sure is a different world out there at night in the lit-up beam of a spotlight. It is another view of our Wild Pantex, one that most will not get to see, and one that we look forward to every year.

Article by Jim Ray, Pantex Wildlife Biologist/Scientist

Recently a Pantexan couple were fortunate enough to see and photograph a strange mouse at their new home in my neighborhood north of Canyon. This mouse was “different” in that it had a very short tail. Their visitor was one of the most unique mammals in our area, and I was impressed that my neighbors had already properly identified it as a grasshopper mouse.

Our local grasshopper mouse is the northern grasshopper mouse. It is found in our prairies and I first became acquainted with them while trapping for my Mammalogy collection while a student at Texas Tech. I found them to be an easy catch in the grasslands and playa edges around my hometown of Dalhart. Evidently, they have a fondness for peanut butter, as do most mice.

The northern grasshopper mouse is found in western North America from southwestern Canada into northwestern Mexico. This is a stoutly-built mouse, with a short tail that is less than one-third of its body length. Its color is drab brown to reddish brown, with white underparts. Its short tail stands out, causing the mouse to resemble a hamster.

So, besides its short tail, what makes this animal so unique? First off, this mouse is a predatory species, subsisting off of a diet that includes insects and other invertebrates, as well as mice, reptiles, and even grassland birds. NO FOOLING! Additionally, this animal has a well-known vocalization that resembles a scream or a howl. It is believed that it is given while hunting as well as for territorial reasons. During this process, the mouse stands on its hind legs, throws its head back, and gives it all he/she has.

Here is a recording of a grasshopper mouse vocalizing, which I can attest to, is a common sound at night in the grasslands of Pantex!

Screaming Mouse

Pantex and Texas Tech University actually has some pretty good data on grasshopper mice. During two different research projects that looked at what wildlife species utilize prairie dog colonies versus prairie without prairie dogs, Texas Tech and Pantex discovered that the grasshopper mouse was more abundant, by far, in prairie dog colonies than in prairie not occupied by prairie dogs. In fact, they were the only small mammal species that showed a strong relationship to prairie dog colonies. No doubt, the burrows of prairie dogs and the preponderance of ground-dwelling insects that we also found to be highest on prairie dog colonies, make these areas attractive habitat to this species. BTW, when captured these guys smell horrible, a likely tactic used to get an occasional predator to drop him.

Here is an interesting statistic for you! The number one predator of a well-studied population of Texas horned lizards in South Texas is…you guessed it – the northern grasshopper mouse! This may explain why we find fewer than expected horned lizards in the very promising-looking habitat (for horned lizards) found in prairie dog colonies at Pantex. The question is, is this because of predation by grasshopper mice (and burrowing owls??) or are our Panhandle horned lizards programmed to avoid this predation by avoiding prairie dog colonies?

So, next time you are out on the prairie at night, listen for the howling of grasshopper mice. Perhaps, before, you assumed it was a bird. Now you know that it was one tough ole mouse!

Photo: A northern grasshopper mouse at Pantex. The gray coloration shows that this is an older individual.