I know there are a lot of factors that will influence the answer to this question — dog breed, environmental conditions, etc — but as a generalized thing, how long after a trail is laid down can a dog follow it by scent?
I don’t know for sure, but I would guess a few days to a week or so, depending on the weather and other environmental factors. The scent that dogs track is made by clusters of epithelial traces that people constantly shed as they move, so a dog’s ability to catch and track an old scent would be based on how long those skin flakes can last in the specific environment– which gets to your qualifier about the environment. Water obviously washes away the flakes, and I’d bet that wind could disperse them eventually, but in a dry, still environment? Who knows?
Would other things (blood, vomit, etc) leave a trace that identifiably carries the same scent as the skin flake?
I couldn’t say with certainty, to be honest. I know I’ve seen such things used as literary and cinematic devices, but I don’t know for sure how accurate the concept is. That said, I wouldn’t be surprised if they could, but I actually doubt it would be relevant. I’d think that those things would be consumed by wildlife (insect, scavengers, etc) long before skin particulates (which don’t have any nourishment value to any animal I know of) would fade or be dispersed. If bodily fluids are still present, epithelials almost certainly would be as well.
According to this internet person, “no one knows for sure. . . . The majority of successful scent trails that have been worked reveal that the oldest successful trails are about ten to twelve days old. In general, most search-and-rescue trailing dogs are unable to do accurate work on scent trails that are older than seven days.”
That’s useful, thanks — as long as I can justifiably say three days or so, I should be fine.
As an aside, it’s more about training than about breed capability. Yes, bloodhounds are great for following human trails… but that’s because they’re so rare that practically every one gets snatched up and trained from puppyhood. I’ll take a well-trained terrier or Dachshund over an untrained bloodhound.
And the training is even more important is the spoor is not human-scent, but artificial-thingy-scent (which includes drugs, explosives, etc.). This reference (which appears reputable) might help:
http://www.militaryworkingdog.com/history/
Thanks!
