lag

The time elapsed since a track or sign was made — minutes, hours, or days, estimated by reading the condition of the impression. Fresh tracks have sharp edges, moist soil, and undisturbed detail. Aged tracks have crumbled edges, dried surfaces, windblown debris, and may be overlaid by other prints or crossed by insect trails. Rain, sun, wind, temperature, and substrate all affect how quickly sign degrades. Estimating lag is the most difficult and most consequential skill in tracking — it tells you whether you are following a memory or closing on something alive.