Dim Lights and Bright Lightning
Beetles, dark nights, and drives of terror
In the early 1970s, my summer research was mostly in the Chiracahua Mountains in southeastern Arizona on darkling ground beetles, aka tenebrionid beetles, which is kind of a translation of the Latin name meaning dark, which is more or less the color of most of the 10,000 or so species in the world. The trouble with tenebrionids is that most of them are nocturnal or at best crepuscular (bet you don't know what that means! And it has nothing to do with blood), so studying them in the wild is a nocturnal activity. Because there was very scant information on populations of tenebrionids, we planned to do a population estimate of species of tenebrionids using the mark-release-recapture method. Our initial target was the large and common beetle, Eleodes armata. In the desert flats, you can even spot them easily in the headlights, puttering slowly on dirt roads (we, not the beetles were puttering. On second thought, maybe both). Being large, it was easy to number each beetle with our dot code, then release it again.
The trouble was that, for mark-release-recapture to work, you must not only complete the first two acts (i.e. mark and release), but also the third, and that was not happening. The method assumes that emigration and immigration from your study plot is small, but almost every marked beetle we put back on the ground seemed to make a beeline for the horizon, never to set foot in our plots again. Maybe some ended in Mexico, others in Animas, and surely some in Rodeo, only six miles away.
So, without recaptures, there was no way to estimate the population. Or to put it another way, the home range of the population was enormous, perhaps the size of the wide-open desert in which these beetles trundled about. Therefore, John and I reasoned that habitats in which travel was more physically constrained would be better for estimating population size, and finally settled on working way up in the pine forests at 8000 feet elevation.
Every evening, as the sun dropped behind the mountains, we drove our VW Squareback up the dirt road winding through the pleasant, mid-elevation Gambel Oak forests (see drawing at the top), up into the Chiracahua pine forests, turned left at Onion Saddle and parked opposite our 40 by 40 meter research plot as the last sunlight reddened the distant Peloncillo Range across the valley. Until 1 o'clock in the morning, we searched by the light of headlamps, marked each beetle we found with an individual dot code and released it again, noting which of the 400 plot grids it was found in, while John's wife and mine recorded the data. Then it was back down the mountain by the dim lights of the Squareback to eat a late-night snack of Velveeta and crackers before going to bed for a well-deserved night's sleep.
The excitement of this routine came in the form of the thunderstorms that bring the August monsoons to southeastern Arizona. We could see the storms forming as towers over the distant mountains, the clouds briefly illuminated bright against the dark sky as lightning jerked. But storms are not anchored to the mountains of their birth, so we kept a cautious eye on their drift, judging when to leave our sitting-duck location near the mountaintop to head back down to safety.
But there are three elements to judging a storm--- its center of location, its drift, and its rate of increase in coverage, and occasionally we misjudged one or the other. Starting down the winding mountain road too late meant a terrifying drive as the road turned into a river in the pouring, whipping rain, occasional rocks rolled into the road from the embankment, and sizzling lightning splintered trees within a stone's throw of our car. The storms seemed to be equal parts electricity and rain, delivering a brilliant flash and shocking thunder every few seconds. The headlights of the VW, powered as they were by a mere 6 volts were no match for the blinding two-million volts that repeatedly bleached the entire landscape into pale, ghostly white, before going back to deep black, leaving a static afterimage burned on my retina. The best I could do was grip the steering wheel and hope that the wheels would still be on the road when my vision recovered. The chatter from the back seat that had been such a pleasant backdrop on the drive up was now a tense silence, not a word for 6 of the 7 miles. One time we drove back up after the storm had passed and found hail drifts a foot deep scattered throughout our plots. Imagining what it would have been like to add dense hail to the rain and lightning gave me a sort of pathetic feeling of luck.
We learned a lot about six species of tenebrionid beetles through this study--- their population size, their habitat preference, and their vagility (tendency to travel). Two species were very local, traveling very little during the two-month study, while others walked with determination, moving long distances in and out of our plot. These tenebrionid beetles are generally long-lived, so that searching the plot a year later discovered quite a few of our marked beetles. John and I published our results in a paper full of sophisticated statistics and educated judgements. It had been a fun, though intense summer project, but we never followed up with another similar project. As in so much of what we biologists do, the summer was an act of exploration and learning, acts that sometimes lead to long term research, and sometimes not, depending on opportunity, personal preference, difficulty, and prospects for enlightening outcomes.
Gambel Oak, a medium-sized, pleasant tree with pretty leaves, brings back memories of that summer project. Perhaps it is not fair, because the tree was in no way responsible, but to me, Gambel Oak will forever be associated with those scary drives down the mountain wondering with every flash and white-out whether we would get back down alive.
It was not my intention to impugn your vocabulary (wink wink smile).
What a harrowing experience! I might be called crapuscular!