Telltale bits of DNA help track past and elusive wildlife

Animals lose hair, scales and feathers as they move. They also discard skin cells and waste. All of these leave traces of genetic material that can be detected hours, weeks or even millennia later.
Scientists say analyzing the DNA floating in waterways or hiding in soil, which they call environmental DNA or eDNA, promises to help in managing and protecting biodiversity. The tactic has become increasingly popular within the past few years and has already provided clues of ancient mammoths in Siberia, early warnings of frog die-offs in California and evidence of elusive sawfish in Mexico.