Tap dancing tamales

Last week, I encountered a mystery that was best solved with a tamale. (I wish I could say that every day.)

One of my research projects this summer involves using game cameras to capture candid videos of small rodents eating seed bait using infrared flash. I had placed a ten of them in the field for nearly a week, and while the seed bait was gone, no videos recorded the culprits.  Well, we did have two videos of a ground squirrel one afternoon. But that left a lot seeds unaccounted for. And I did have a lot of video of wind blowing branches around, so the cameras were clearly functioning.

The seeds in question were large enough that I was skeptical of ants being responsible for their theft. And there was one more key piece of the puzzle: despite the fact that most of the small granivorous (seed eating) mammals in this area are nocturnal, I had no night time videos.

I had previously captured regular videos of wood rats, deer mice, and pocket mice in these environments eating such seed bait. What was the difference this time?

I realized it might have to do with the orientation of the cameras. While the distance to the bait was the same as before, I had secured the cameras above the bait to record downward, having read about a study from Australia in which downward orientation improved the reliability of triggering, increased the researchers’ ability to identify animals, and also provided more rigorously defined study areas and rates of animal movement.

However, these rocks are much hotter than body temperature, and take a long time to cool down.  Heat absorbed by dark volcanic rock throughout the course of a hot, arid foresummer day is familiar to me and to my field assistants. On some of our epic experimental set-up days, we laugh about how by 11am we stop sitting on rocks because they burn our backsides through our pants, by 1pm we can no long pick up small rocks to use as tools, and by 3pm they burn our feet through the soles of our shoes.

These game cameras are built generally with spotting deer at forty feet, not mice at three feet. Some of the issues with this off-label use are cheaply remedied by, for example, placing masking tape over the panel of LED flash to reduce the blow-out of close objects. It seemed likely to me that the heat-sensing motion trigger used by the camera after dark cannot “see” the rodents moving against such a hot background.

A series of tests were in order to confirm this hypothesis, but we needed some rodent stand-ins. Being Tucson, I had a dozen frozen tamales in the freezer, which seemed about the right size.

We commenced a series of trials of triggering the game camera using a microwaved tamale moving across the field of view, varying the tamale temperature and distance from the camera. These tests were conducted at first in the darkened back closet of the secret underground laboratory in the corner of the sub-basement of Biological Sciences West. I later repeated some trials with the tamale dancing before the camera in varying orientations that night in the field.

I am still looking for a journal in which to publish these groundbreaking results. In the meantime, for your entertainment, I give you a sample of my tap dancing tamales recorded in infrared.

Physiological tolerance (or lack thereof) as a tool

The Park Service ranger called my cell phone three times in ten minutes. He was concerned about my safety of myself and that of my field assistants, noting that my car was still at the trailhead to my research site at 4pm, and temperatures were well into the triple digits.

Blazing hot volcanic rock on a south facing slope on a clear June day
Blazing hot volcanic rock on a south facing slope on a clear June day

In fact, we had knocked off earlier than I had planned and were already hiking back, because despite setting up a tarp as a scenic shade ramada, and my constant encouragement to drink more water and more Gatorade, we were overheating.

This was a far cry from my last week, when I attempted to climb Mr. Rainier. With a peak at 14,411 feet and sporting the largest glaciers in the lower 48 states, this mountain tested some very different physiological tolerances. Certainly the 1:30am start was cold, and I wore a layer of wool covered by 1-2 layers of fleece, covered by a wind-proof shell over virtually all part of my body. Plus during breaks I added a down jacket over it all.

Our lack of ability to withstand heat may have to do with a trade-off for performance in a wide range of temperatures, including environments with year-round snow.
Our lack of ability to withstand heat may have to do with a trade-off for performance in a wide range of temperatures, including environments with year-round snow. Photo by Neill Prohaska

But cold was not the only physiological challenge on the mountain. Ultraviolet radiation is more intense because it has less atmosphere to pass through, and is reflected off the snow in every direction. The first day I only put on sunscreen once, and my face was badly burned.

All bundled up to withstand the radiation and cold
All bundled up to withstand the radiation and cold. Photo by Neill Prohaska
Bundled up on a 3am break. Maybe we should start research in the Sonoran Desert at that time, too? Photo by Neill Prohaska

Additionally, the low air pressure and corresponding low oxygen levels present physical challenges in acclimatization and physical exertion. One member of our party started coughing up bloody sputum, which may or may not have been indicative of his having high altitude pulmonary edema (HAPE), a potentially fatal condition. HAPE is, interestingly enough, may stem from the body’s evolved response to fungal infections.

So what a relief to return to the balmy lower latitudes and altitudes, right? Highs are well over 100 degrees Fahrenheit in Tucson, though, and my research revolves around low-elevation (hot), south-facing (hotter) slopes covered in dark volcanic rock.

But the problem of my field crew’s physiological tolerance not withstanding the Sonoran Desert summer is also a solution for an experimental annoyance. Bruchid beetles lay their eggs inside paloverde seeds. Last year, I had gathered a number of paloverde seeds to use in germination and seed removal experiments. Beetles decimated my stores, emerging from up to 75% of the seeds and attacking the rest inside my insect-proof bags.

In the last year, an accomplished naturalist mentioned the observation that those seeds falling outside the shady crown of a parent tree survive better, perhaps because the direct sun kills the beetle larvae. Their lack of physiological tolerance to the direct sun can be used against them. So I am drying the first gathered seeds on my roof:

Drying paloverde (Parkinsonia microphylla) seeds on my roof to kill bruchid beetles lurking inside
Drying paloverde (Parkinsonia microphylla) seeds on my roof to kill bruchid beetles lurking inside

Wildlife safaris of Arizona

It’s June 1, and a panther stares down at me from my National Wildlife Federation 2013 calendar on my desk. One of my field sites is on the south slope of Panther Peak, but I have yet to see my own mountain lion out there – although a friend accompanying me last week did point out that the fur-filled scat along the trail was far too large for a wildcat, and it tapers on the end in a distinctly feline way.

I think about the panthers at my field site like a Chuck Norris joke:

“How do you see a mountain lion?” Answer: You don’t. The lion sees you.

Indeed, the site is ringed by rocky outcroppings perfect for dens and ambushes by the cats. I’m sure they see me bent over my plots, nose to the ground. Which is why I try not to spend too much time out there alone, although I am far more concerned about heat and people as dangers than I am wildlife like panthers and snakes.

A dead saguaro at one of my field sites, Tumamoc Hill, overlooking central Tucson

Speaking of which, field work has started in earnest for me for the summer. Highs are creeping up over 100 degrees Fahrenheit as of today! During this hot and dry month preceding the start of the monsoon season, many animals are either just becoming active (like desert tortoises and ants and monsoon field biologists) or are hunkered down, awaiting cooler weather (like my housemate’s husky mix and the rest of Tucson).

Some  folks from Tucson Audubon, however, had a really great field day recently. You can read about that here. It’s definitely worth checking out, if only for the video of a badger waddling away!