For the nose of a fox:
I shot two Roe deer in a flat stubble field on Monday at 6pm, both dropped on the spot, each at around 175 yards. The landowner did not want any dogs on his land so headshot or low neck shot for every deer, and I carried high-res thermals + night vision binos for locating the deer. This field was flat, with no bushes or anything. Sounds easy?
Took note of distance and bearing of each deer before each shot, but as darkness fell at 6:30pm, I was seriously struggling to find them.
The thermals could pick out every living deer, every rabbit, stoat, and even mice right across the field, but not a freshly dead deer.
After a further half an hour of walking a search pattern in the field as dusk fell, centred around my distance and bearing, with thermals glued to my eye, hands being shredded by the odd strand of blackberry thorn, I found the first one, laying in a slight rut with low vegetation on both sides, just enough to hide it from thermals unless one is aligned with the rut. Head shot had removed half the skull and sent an ear and section of skull several feet, so it definitely had dropped on the spot.
Perhaps a rut was why I could not find the other deer so walked backwards and forwards in search patterns for two more hours across that part of the field for the second deer, again thermals to my eye, nothing to be seen.
Lamenting that the deer tracker dog service has nobody anywhere near Edinburgh.
Then a fox came out, clear as day vis on the thermals allowed me to watch him out of interest. The fox did a beeline for a spot, then wandered off and returned 5 minutes later to the same spot. Sure enough at 8:30pm, the spot was a deeper rut containing my second Roe, 22kg gralloched.
So dumb human with thermals versus dogs / foxes, the animal wins hands down in ability to find the deer.
The fox also wins on the pain index: After dragging the deer and loading them, I wiped my hands on some grass in the dark, which tingled as I rubbed harder, before I realised the grass was 6" high stinging nettles. This added to the pleasure of a fair few thorn cuts from wandering around a field at night with thermals stuck to one's eye. So not only do the foxes win in ability, they also win on the lower pain index compared to thermals: if I had just watched the fox, I would not have run into as many thorns.