***This is in my experiences in hilly topography... Yours may vary.*** --First the definition of a thermal- Thermals are currents of air that fall or rise based on the air temperature. Cool air falls and warm air rises. Thermals can be brisk from rapid heating and cooling or soft from gentle heating or cooling. --Sunny to partly sunny days as the sun rises it slowly heats the ground and the cold night time air causing it to lift and rise up following the contour of the land toward the sky. These warm air thermals will rise all day long until the air begins to cool in the evening. Once the air has started to cool it begins to retreat back down toward the ground. The cold air thermals will follow the contour of the land back down just as it raised. --Overcast days thermals are mostly stagnant. They may gently rise and fall based on warmer daytime or cooler evening temperatures but they are very gentle and do not move much without day time sun or much cooler evening temps. --Rain days thermals do not move much at all either. They stay mostly in the lower lying areas as the air is to heavy to rise much even with warmer daytime temperatures. They will stay low until the humidity in the air is decreased enough to allow the air to desaturate and rise. In the hilly areas I hunt deer seem to base their bedding areas more on thermal activity than the wind. In some instances you will see where they are taking advantage of both thermals and predominate wind currents but it seems if they have to pick one or the other they choose thermals. I believe this is because thermals are steady and reliable and the air currents from the wind can be variable and change from one minute to the next. Especially in hilly areas where swirling wind is the norm. From my experiences and subsequent thoughts.... Deer bed higher on sunny days because of the thermals rising up the slopes to them all day. On most days during daylight hours they can bed with the thermals rising to them from the bottom and the predominate wind current to their back. They can then also drop into the bottoms in the evening with the cold air thermals to their back with their eyes looking ahead. With out a predominate wind on variable wind days, they can bed with the warm air thermals rising to them and they can face the other direction to scan for danger where they are unable to scent check. On cloudy or rain days is where I get confused the most from my past sightings. I see deer bedded in the lower areas often in these weather patterns but also still see most good bucks bedding high. I believe the older bucks are not willing in most cases to give up the high ground vantage points even if there is an inconsistent wind up high to bed low and use the sinking thermals on rain or overcast days. I believe the bucks who are bedded high on these days are bedding high strictly based off of their view from the high ground vantage points and secondly the wind current (even if they aren't consistent wind currents) even though they are unable to take advantage of any rising daytime thermals because of the cloud cover or rain.
Although I am aware of thermals I don't ussually give them a lot of thought since the land I hunt is not very hilly. I do pay extra attenion to wind directions in the evenings though with the thermals staying lower to the ground. The deer seem to pick up scent easier late in the day vs. in the morning like you mentioned.
Good stuff Scott. I've just started concentrating on thermals the last couple of years. I find that most of the deer in my area will bed out on the points about 1/4th from the top to take advantage of the thermals and use their eyes. In MS, our predominate wind direction is southerly coming in from the Gulf. I find the most active beds on North side of the ridges as would be expected, allowing them to use the thermal tunnel to their advantage. The area that gives me the most trouble is what are they doing on the few days we have a west or north wind... Are they moving to new beds or are they staying put and simply relying on the thermals and their eyes... That is the puzzle I am still trying to put together.
You and me both.... This is something we would probably never be able to answer. I am sure pressure and the individual deers temperament / personality would have a lot to do with where they would bed down. I am sure there isn't a 100% clear cut answer for this question. I bet they do both, depending on a host of influences (time of year, pressure, weather etc.)
I work in HVAC.. so thermals and pressures and anything to do with air flow come easily to myself. I would have to agree with most of your insight Buckeye. But I will warn to not take cloudy conditions to lightly.. overcast skies can produce very odd wind currents and thermals.. especially throughout October as the air is cooling very quickly and the earth is usually still warm. Lots of things are happening in October which contribute to this.. and of course.. it depends where you live in the country for all this. As far as buck bedrooms.. I totally agree that they love to sit on-top hills and watch over the ground like generals (although not necessarily the tallest hill).. but when hunting much of the swamp regions I do.. this general rule holds little water (pun intended). Good post.
Jim Roy book on whitetail behavior. EDIT: I left this to open ended. Some good stuff in this book on what Scott mentioned.
Good post bud. Just this past season I started to really notice thermals, mainly due to a new piece of property that is all on a downhill in some fashion. It will affect my stand placement for this coming season. There were days last season that I set out to hunt a stand and there was a slighty dominant wind from the North, but as prime time hit, the wind would always settle down the hill possibly busting my location. I quickly learned to take heed to this thermals and hang accordingly. I never really hunted land like that, the wind was the wind to me. Good topic. I hope more chime in.
There were parts of his book I enjoyed when I read it a year or two ago, but a lot that I thought was way over the top and outdated (it is an older book though). I went back and reread his chapter about thermals this morning. Things where my experiences don't match his. Him claiming deer only bed with thermals - That they bed low with sinking thermals and high with rising thermals... That deer only travel with the wind or thermals to their back where ever they go... The way he claims deer bed in a formation with the dominate buck centered and the rest of the herd bedded in a formation around him to protect him... I also thought he went over the top with his explanation of thermal reversals... I am not saying he is wrong (far from saying that), I am just saying the deer I hunt do not behave the same way. Very well could be differences in location.
He mentioned that his hunting was in no pressure areas far from what me and you hunt that is for sure.
Interesting post Scott, good info. Hunting in the mountains has provided a life long education in thermals and how big bucks use them to their advantage. Often I can only hunt a specific spot the last hour of the day because I have to wait for the thermals to change. I can't tell you how many times I have reached a point in my hike into an area only to sit down and wait patiently for the thermals to change before I preceded. Big bucks here use elevation and thermals to survive predators like wolves and mountain lions. They will almost always lay up 2/3 to 3/4s of the way up on a thickly timbered mountainside all day long. Most big buck bedding areas, great shed hunting spots are found at these levels of elevations. The big boys learn over time that they can use the wind coming up the mountains to detect anything approaching from below through most of the day, not to mention all of the noise they will pick up from thick dense timber and blowdowns when something is approaching them. They almost always position themselves in blowed down timber, very thick bedding areas that have so much debris in it that nothing can approach them without the danger making noise to their backside. Big bucks also really like high benches positioned in the crotches of intersecting ridgelines because they get a swirling wind affect from the daily thermals banking against prevailing winds that are banking off of mountain structure like ridgeline tops, through saddles etc. So in essence they have a consistent swirl of wind from all directions all day long. They can pick up anything approaching them from any direction. No diffent than a mountain campfire constantly changing directions blowing scent periodically in every direction. A big buck will almost always leave his bed very close to dark, much later than the does and fawns down slope and he allows all the other deer below him on the mountains to warn him of any danger they encounter. If the does blow; hes immediatly on alert! He has the thermals change right before dark, about 1 hour or so... so it blows over his back now as he makes his way downslope... but he is still picking up occasional swirls and banking winds from the prevailing winds that are diverting off of ridges and mountain slopes..."Sound" also carrys great distances in the mountains. I can hear my boys on a normal low wind speed day talking in the yard from a mile away up on a mountain when I am in my stands. Thermals and banking winds are a bucks best friend.
Good stuff, bro. I hunt quite hilly terrain so I always consider thermals in my equations, but what is obvious to me (after reading your post and chewing on it some) is that I need to consider it more in terms of how deer relate to it. I pay very close attention to them in terms of scent control, and I love nothing more than a ridge top on a high pressure morning.
I'm with you on that rybo!!! X2 Last year I really started to get into using the wind to my advantage and since have gained more knowledge from sites like these. It's great that the "SIRES" from theses web sites can help me/you/us to capitalize on any advantages in the forests...
This is good stuff......... This is a topic I started look at when I started hunting hill country. In this hill country most hills or ridges have a trail at the top, middle, and bottom. I have observed many bucks running all the trails with out rime or reason. I have seen bucks on two of the trails at the same time going opposed ways and this was not during the rut but the early season. How do you think the thermals will dictate which trail the bucks will travel on a hillside???
Great post and great information placed throughout. This is one of those posts that gets placed in my hunting notes for later learning/re-reading.
Scott, I'm not sure how I missed this thread even after we talked about it on the phone. I've always wondered if it makes more sense to hunt lower (treestand height) during hours of the day that the thermals are falling. If you hunt lower wouldn't it make sense that the wind would have a smaller opportunity to blow your scent as it falls with the thermals?
The same amount of scent would be falling from you and your equipment with the thermal and that scent would still be pushed along with the wind. In my mind I cannot see much of a difference with how high you are and how far the predominate winds would blow your scent. But, really I don't know?
I have a question for you Scott. I was watching a hunting video the other day and in so many words they described this scenario. Imagine hunting on a giant rectangle of a hillside. The cover in this scenario is on top of the hillside, and in a small patch where the guys were set up about halfway up the hillside. They said that bucks were cruising the south side of the cover scent checking with a north wind. He said the thermals were rising as the day grew hotter in the morning. They said that bucks were cruising using the north wind to scentcheck/smell for danger to north, while using the rising thermals from the south to detect danger from below. They did not come right out and say those exact words but that is what I took. If that type of scenario sounds logical let me know. And if so, how much wind do you think would be necessary to counteract the thermals if a buck were trying to use it to smell for danger from below? Thanks.
Deer live and die by thermals - absolutely! If you want to learn a TON about this topic, you should check out the new Blood Brothers video "Hill Country Bucks". It has EXCELLENT descriptions and examples of how mature deer use wind in all ways shapes and forms. It's a MUST see for any whitetail fanatic!
