It was already dark when my family and I climbed into the big white pickup truck with Marcelo Jorge. A drizzly May night in the Ozarks; everything seemed soggy and muted. Jorge was upbeat, though. It was the peak of fawning season, and so far this year, his team had captured and collared a dozen fawns. The more deer they could collar, the more data they could collect about a disease threatening deer and their relatives. Jorge is leading a multiyear study at the University of Georgia on chronic wasting disease, an always-fatal neurological illness. Ubiquitous deer may be, but in CWD, they face a serious threat. From its first appearance in Colorado in the late 1960s, CWD has crawled steadily across the country. It is now found in more than 30 states and multiple Canadian provinces. Deer are all over the United States, trampling suburban lawns, running across highways, nibbling at crops. But, though seemingly counterintuitive, American deer might be on the decline. The trend is uncertain, but an estimate from G. Kent Webb, …