That fall the biologist and I lived in casitas next door to each other on former ranch land snarled with paloverde trees, overlooking a low city skyline and the orange mountains beyond. Some nights we would load his black pickup with a cooler and skeins of netting and a fold-up table and boxes of collapsible traps, and, along with two virologists from the university, we would drive into the desert in search of bats.

A science writer and wilderness guide, I followed my curiosity, giddy to be invited. These were strange and intoxicating expeditions. At the cliff-lined ends of forest-service roads or the edges of muddy cattle tanks, or in the cricket-loud groves where saguaros gave way to oaks, I would help stretch nets on moonless evenings. Bats fluttered into the thin weave and were trapped, toothy and screaming. The thick-gloved scientists would untwine them, place them in paper lunch bags, and catalog them like library cards in a small Tupperware bin. The biologist would weigh the bags one by one on a hanging scale. He’d blow belly fur aside to sex the bats. He’d spread their filmy wings against the glare of a headlamp to evaluate the fine joints and bones. He’d press their squirming bodies flat against the table while a virologist would hole-punch papery sections of wing skin, then pierce a vein and suction blood in careful crimson pulls.