What are Thermals?
Thermals refer to the upward movement of warm air in the atmosphere, which occurs when the sun heats the earth's surface, causing the air above it to expand and rise.
As the warm air rises, it cools and eventually reaches a point where it is no longer buoyant and begins to sink back down to the ground. In the context of hunting, thermals are important because they can carry scent molecules. By understanding the direction and strength of thermals, hunters can predict the movement of scent and use it to their advantage when scouting or hunting.
What Direction Do Thermals Go in the Morning?
In the morning, thermals tend to rise and flow uphill, as the sun heats the ground and causes the air to expand and rise. This movement of warm air is called an upslope thermal.
What Direction Do Thermals Go in the Evening?
In the evening, thermals tend to move downhill as the ground cools and the air begins to sink. This movement of cool air is called a downslope thermal.
How Do Mature Bucks Use Thermals?
Thermals can oftentimes be a mature bucks lifeline, especially in a big woods hill country setting. Bucks will use the scent carried with thermals to collect information necessary for their survival such as doe bedding area activity and human intrusion.
The information bucks collect, combined with the topography of the land helps determine how they navigate through the woods en route to staging areas, food sources, and checking up on doe beds.
Thermals also play a huge role in the selection of a buck's bedding area. This example is one of those prime hill country buck bedding locations, as this buck beds on a south side knob, collecting sunlight and getting a consistent upward thermal pull above all of his areas of interest.
Wind Mapping Buck Bedding Areas
One of my favorite things to do in the springtime is head out onto public land, locate buck beds, and pick them apart to learn exactly how and why they work through the landscape the way they do..
With similar foliage levels and prevailing wind directions, I find it to be extremely effective to slip into the beds and drop milkweed to get a sense of how the thermals move through the area.
I call this wind mapping. One of my biggest takeaways from this activity is regardless of the wind direction predicted in the forecast, subtle terrain features not easily seen on a map can cause wind shifts, altering how a deer uses an area.
This bedding area was no different. As indicated by the green arrows in the image below, you can see there are slight depressions in the topography.
These areas created a strong pull from the drainage system below, giving the buck a great sense of all the activity happening below him throughout the day.
Connecting Key Features of Buck Bedding Areas to Thermals
The features around buck bedding areas are almost as important as the buck bed itself as one doesn't exist without the other.
Once I locate the bucks bed and gather an understanding of how the thermals act, I can work my way out of the bedding area and begin to locate the areas of interest used by other deer.
Once you have these areas of interest marked, you can start drawing lines in relation to the topography to determine the bucks' access routes throughout the timber.
These areas vary depending on location, but here are some of the top things I'm looking for when out scouting.
White Oaks
In big timber, very rarely do I come across buck bedding that isn't in close proximity to a group of white oak trees. The ideal cluster is going to be within the bedding cover, even creating a wall-like structure on the exterior of buck bedrooms.
Doe Bedding
Locating doe bedding is typically no more than a stone's throw away. Oftentimes a bedded buck will position a group of deer (typically doe) between himself and the primary food source.
In this case, there is a historical clear-cut below the buck bed that is extremely thick. This overgrown clear-cut is located near multiple large oak ridges, and is loaded with doe bedding.
Edge Habitat
We've all heard that deer are edge creatures. Sometimes edges are easy to identify, like the edge of cattail marshes or fence rows. In a large stand of timber, you may have to read between the lines to find these edges.
The old clear-cut creates two well drawn-out edges, almost parallel to the main thermal pulls, giving a great sense of direction near the doe and buck bedding areas.
Hub Scrapes
Hub scrapes can be found in areas where a lot of thermals come together, also known as a thermal dump.
The majority of the mature buck activity in these areas occurs during the night time hours, but can be great locations for trail cameras when gathering inventory on buck bedding areas.
Hunting Pressure
Many hunters fail to realize how far their smell can travel through the woods with the guidance of thermals. The massive drainage system below the buck bed allows the buck to smell the presence of hunters throughout the day.
Whitetails, especially mature bucks are very instinctive. Repeat behavior such as access into a stand location the same way day in and day out is a sure way to tip-off your whereabouts.
Escape Routes
The icing on the cake for perfect buck bedding areas is a well-located escape route. The top of this ridge is made up of few trees open to the sun, creating thick cover and making it nearly impossible for anything to approach the buck from the rear without him knowing.
This back wall type feature is also the perfect spot for the buck to slip out the back if he catches a smell of something from the upward thermal pull he doesn't like. As seen here, you can typically find these escape routes within a few yards of the buck beds as a faint trail.
Connecting Scouting to Habitat Design
It's hard to beat a day of scouting when everything comes together. Finding buck bedding areas like this and figuring out why whitetails do the things they do allows me to continuously develop my skills personally and professionally.
The beauty of learning how a mature buck uses thermals to operate in an unmanaged area with unregulated human intrusion gives valuable insight when putting together habitat plans where I am in full control of the design and desired outcome.
Whether further developing existing buck beds or putting together a new bedding area, I can jump back into my notes from previous experience to help create a perfect template for the task at hand.
Key Takeaways & Notes
The chase of a mature buck starts long before the hunting season begins. Understanding how thermals work and the impact they have on whitetails has been one of the most influential lessons in my journey as a hunter and habitat manager.
Here is a high-level overview of some of the most important things to take away from this article:
Learning how thermals work through the landscape can often lead you to prime bedding locations.
A buck will frequently position himself in a way that the majority of the deer herd is bedded between him and the primary food sources.
Dissecting buck beds from the inside out can show you how the thermals in a specific area work and how you can use them to your advantage.