Sinkholes are just as they sound—places where soluble bedrock dissolves, creating cavities or holes in the surface. Groundwater then often fills the hole. The process is typically slow, but local legend has it that one of the refuge’s sinkholes formed overnight beneath a parked bulldozer. Some sinkholes here are but a few feet across, though one is large enough—about an acre—to be called (with a bit of exaggeration) Lake St. Francis, 70 feet deep with beautiful blue and Caribbean-green water. These sinkholes have become aquatic "islands" in this arid desert habitat.
Sinkhole conditions differ a great deal. Some have steep, naked gypsum sides; others have reeds and grasses that grow right up to the water’s edge. In some sinkholes, the water is so saline that it supports red and green algae blooms. Other sinkholes are saltier than seawater and invite species of dragonflies and damselflies usually found in estuaries, although the nearest seashore is a thousand miles away. The unique blend of conditions in each sinkhole creates entirely different ecosystems, even though one sinkhole may be only ten feet from another. As a result, each sinkhole, Gaines explained, seems to have its own special array of Odonata, and some species breed only in a single sinkhole. (Sinkholes also host the only known populations of certain other animal species, such as the last genetically pure species of the extraordinarily salt-tolerant Pecos pupfish and certain springsnails and amphipods.) "It’s a natural outdoor laboratory," Gaines said.
She keeps track of this confusing and colorful aerial menagerie with a little biological sleuthing. Gaines regularly places little ladders of wire mesh leading from the edge of sinkholes into the water. Because Odonata leave their larval casing on the ladder as they crawl out, she can identify which species breed in the Bitter Lake sinkholes and which migrate here after breeding elsewhere.
Nearby Roswell may be a mecca for UFOs, but the dedicated scientists here at Bitter Lake have a pretty good handle on what’s flying around. Already, I can spot the fluttering flight of the desert whitetail (Libellula subornata) and the bright red body of the flame skimmer (L. saturata). I was struck by how much these Odonata folk sounded like bird-watchers, singing out the name of a dragonfly they see whizzing by for but an instant. Indeed, the common names of these creatures are just as exciting as bird names—or more so.
After all, where’s the poetry in spotting a crow or a snipe? But imagine spotting an Eastern amberwing, a seaside dragonlet or a Halloween pennant during a single outing at your neighborhood pond. And if your life list included the Comanche skimmer, the desert forktail and the black saddle bags, wouldn’t your chest swell with pride?
by Jake Page