07 September 2007

Laboring on Labor Day – Site Visit to Inscription and Pig Pen Caves, Northern Arizona

Both Inscription and Pig Pen Caves are synonyms used to protect the actual name of the cave. What’s in a name? You may ask; it can often times be enough to have people start a search to actually find the cave. Caves are incredibly sensitive resources. As a cave researcher, I do everything I can to protect these resources.

My mission on Labor Day was to retrieve data from temperature sensors I had placed at these two northern Arizona caves. My team and I been monitoring thermal behavior of these caves for almost two years now. To my knowledge, this is becoming the largest long term dataset monitoring cave thermal behavior, which incorporates monitoring at both surface and subterranean sites.

HoboPro U-12 Four-Channel data logger. We are using these instruments for logging hourly temperature data at the cave's entrance, dark zone and surface.

I arrived at the caves at late morning. I met an archaeologist and a cave steward there. The two were collecting archaeological data at Pig Pen Cave. Pig Pen Cave was heavily used by Native Americans and evidence of their occupation occurs throughout the cave. The archaeologist was conducting a study at this cave to support her Master’s research. We chatted briefly and then I was off to pull data from my temperature sensors, relaunch them and then head back to Flagstaff.

But before I do this, I always look around and document what I see. In addition to collecting data on cave thermal behavior (this work is part of the Earth-Mars Cave Detection Program), I’m also most interested in the ecology of this cave.

Through my exploring of Inscription Cave, I encountered one tiger salamander (Ambystoma tigrinum) at, what I call, the soda straw forest. I’ve seen as many as four salamanders in this area, and was rather surprised to see only one this time of year. The soda straw forest is located along a wall just below the cave entrance. I’ve always wondered, if there was water on the other side of the wall. However, while observing this salamander, I noticed he appeared to be covered in a layer of dust. I know they do they have enough water to survive in this cave because I’ve observed them here over the past two years.

As I was searching for additional salamanders, I found four dead bats below the entrance – all apparently Townsends. I last visited this cave in the end of June and I didn’t observe any dead bats. This apparently happened in the past two months. It made me wonder. There is a maternity colony of

Townsend’s big eared bats (Plecotus townsendii)

in Pig Pen Cave, which is about 10 meters away, and I observed non-vagile pups in this cave in late June. I’m also aware the bats in Pig Pen fly into Inscription in early evening before they leave to forage (and perhaps they do this throughout the evening, I just haven’t been there to observe it). I wonder if the dead bats were new pups who were not aware of the cave gate, and flew into it. This may be something we’ll need to investigate further because the cave owners are interested in protecting the cave fauna (which is why they installed the gate). So, if this is problematic for the new pups, the gate design may have to be overhauled.

Also, in this cave I noticed two dead tarantulas in Inscription. Both were

Arizona blond tarantula (Aphonopelma chalcodes)

. This is the only tarantula that occurs in Arizona. One was recently deceased and was being consumed by other invertebrates in the cave.

I had photographed a live tarantula back in September 2006. I’m wondering if one of the dead tarantulas was the one that I photographed.

After investigating Inscription cave, I went to the back of the cave to pull data from my data loggers. Thereafter, it was time to retrieve data from Pig Pen Cave.

Pig Pen is a transient home to

javalinas (Tayassu tajacu)

. I have observed them using this cave throughout late fall and through the winter. However, while I was in this cave on Monday, I noticed fresh javalina scat.

These native pigs occur throughout mid-elevations to low elevations in Arizona, and range from the southwestern United States, south into South America. Evidence of peccary activity is throughout this cave and includes rooting, fresh scat and peccary hair. Here are four of the peccaries I observed in September 2007.

Millipedes from Inscription Cave.

Another great discovery at Pig Pen is I’ve learned this cave also contains the cave limited millipede that was discovered in Inscription cave. The cave steward indicated he had observed a millipede while conducting the archaeological survey. He flipped over a rock in the twilight zone of the cave, and found a millipede crawling on it. I must admit I’m not surprised because the millipede is not cave adapted per sey, it is cave limited.

Refer the Washington Post article on the new millipede genus discovery


As I mentioned earlier, there is an active maternity colony of Townsend’s Big Eared Bats in Pig Pen Cave. Visiting this cave late in the maternity season is best because the pups are now able to fly, and although entering the cave does disturb them, you’re not at risk of having the stressed adult female bats dislodge pups from the ceiling. When this happens, the pups often die. This photo is of the current maternity colony. These bats will be leaving in the next few weeks. Where they go remains a mystery. Townsend’s bats do what is called “roost switching,” and they do this throughout the year. They will find another cave to roost in during winter, and then they may roost switch half a dozen times before they return to Pig Pen. We do know these bats typically maintain a 60 mile home range. So, chances are these bats will be roosting somewhat nearby in the winter months in an undiscovered cave!

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