Field notes on deer and scent

Your walk in is the longest scent trail of the day.

You sit still for hours, but you walk in and out every time, and walking gives off about twice what sitting does. Most hunters do it in the dark, while every slope is still draining. Where that trail goes decides what knows you're there before shooting light.

By Gavan. 26 October 2026, a 6-minute read.

What a walk gives off

• About twice a sitter's. On an easy walk, people gave off 2.4 times the carbon dioxide and 1.9 times the skin ammonia they did sitting. After they sat down, the skin kept giving off more for about 15 minutes and was near normal by 30 (Yang 2024). That was indoors in a T-shirt at 24 °C, so a cool morning in hunting clothes gives off less, but the first half hour on stand is still your strongest.
• Laid along a line. A 1 km walk (just over half a mile) at an easy 4 km/h takes 15 minutes. At twice a sitter's rate, that's half an hour of sitting's worth of scent, spread along everything you walked past (our sums). Pennsylvania public-land hunters carrying GPS got 0.84 km from the road on average and walked about 5.5 km a day (Luloff 2004; Stedman 2004).
• It stays on the ground. Search dogs following 1- to 3-hour-old walking trails kept mostly within 10 m of them (Jinn 2020). Your route is a corridor a nose can follow for hours.

What deer do about it

Nobody has measured how deer react to a trail of human scent alone. What's measured is people, with sight, sound and scent together.

• Bucks move off and come back. In Maryland, collared bucks came within 100 m of a hunter's stand 23 times over two seasons. Nine times they turned or ran, and the seven that bolted went about 257 m on average. They came back to the same places later. Morning trucks taking hunters to stands along the field roads pulled deer off the feeding fields early (Karns 2012).
• They learn where you go. In hunting season, deer moved farther from the roads hunters used: from 367 to 420 m in Florida (Kilgo 1998). On Anticosti Island, where 477 hunters carried GPS, deer were shot where access routes were sparser than where hunters spent the day travelling (Lebel 2012).
• A hunted stand stays hunted. GPS-collared does used a stand's surroundings less at midday after it was hunted, coming back a little each day, and each hunt made it worse (Sullivan 2018).
• A steady line costs less than a wander. Mule deer noticed a walker off the trail sooner, at 67 m against 46 m, and moved more than twice as far (Miller 2001). Those deer weren't hunted, but it argues for one planned way in, used every time.

Walk in while the air drains

Before first light nearly every slope is draining, and a slope the sun hasn't reached keeps draining after sunrise (Whiteman 2000; Farina 2023). Every step of your route is a source, and its scent slides downhill. A route along the slope above where deer bed or feed lays a line of scent that drains straight onto them. Coming in from below sends it down behind you.

You'll read "enter from above for morning hunts," on the idea that thermals rise in the morning. Before the sun reaches your slope, they don't. It's the same rule as the sit in hunting thermals, applied to the whole walk: while the air drains, stay below the deer or level with them, never above.

The walk out after dark is the same. The air is draining toward the bottoms and fields where deer feed at night, so a careless exit puts your scent on tomorrow's deer (Honeycutt, Bowhunter).

Route mode

Groundwind's Route finds three ways in on foot over the LiDAR ground. Easiest is the quickest walk. Hunt keeps your scent off the best ground for the animal you've picked: it checks where the head-height wind carries your scent off each step, out to about 200 m, skirts the best ground rather than walking into it, and comes into your spot with the wind in your face or across it. It uses one moment's wind for the whole walk, so it doesn't yet time the walk against the morning switch, and it hasn't been checked on the ground yet. Puff your powder as you walk: each check is tied to its minute and still helps your sit hours later.