Water: The Most Limiting Factor to Deer Herd Health

Nestled some 93 million miles from our sun is the “Blue Planet,” called that because it is the only celestial body for billions, or even trillions, more miles covered with water! It has been estimated that water covers as much as 70 percent of Earth, and water remains the most important factor in sustaining life on Earth. It becomes an even more special place when we realize that the old sailor’s lament, “water, water everywhere, nor any drop to drink” is quite true!

You see, the vast majority (96.5 percent) of that 71 percent is composed of salt water, which few, if any, terrestrial animals can drink! Only about 3 percent of the Earth’s water is fresh! Yet, even with this tiny amount, an incredibly diverse assortment of terrestrial animals (including 8 billion humans) and plants flourish. Each individual depends totally on water for bodily functions, including regulating body temperature, lubricating movable body parts, protecting organs, carrying nutrients and transporting oxygen to cells and waste out of the body, digestion and other chemical processes.

For most animals, water can be obtained from a variety of sources, including free water, metabolic water, and water from what they consume (preformed water). Free water is the water that is readily accessible after being captured in lakes, ponds, streams, and temporary catchments in shallow rock basins, pools and puddles. Yet there are other sources of water, such as that found inside food, especially plants, which can be as much as 90 percent water. Lastly, in dry climates, water often is recovered during chemical processes in the body such as digestion and chemical synthesis.

The amount of water each species regularly needs depends on its adaptations for using and conserving water. Some desert dwelling animals hibernate during dry times, in order to conserve moisture. Ruminant animals on a high fiber diet need larger quantities of water for digestion. Reproductive functions, such as lactation in female mammals, have much higher water needs than males or non-lactating females. Animals restricted from water do not just die from lack of water; those that survive also can develop weakened immune systems and become more susceptible to parasites and disease. Drought causes decline in forage growth, which forms the foundation for food chains, and affects all species, whether herbivore or carnivore!

During my five decades of work on white-tailed deer, I have come to the strong opinion that water often is the No. 1 limiting factor to deer herd health and growth. Yet, only recently, have we seen increased interest in managing water for deer. There are a lot of misconceptions about the water needs of deer and management strategies to improve times when water is limiting.

IS WATER LIMITING ON YOUR LAND?

We often post materials and information on the Dr. Deer Facebook page about need for providing water to deer on your land. You would be surprised how many people post challenging comments that water is not a limiting factor on their land. Unfortunately, many deer managers look at water management as something for people in dry, desert climates to worry about, not the fertile fields of the Midwest. So, let’s talk about this!

Drought is a phenomenon that has or will affect every acre of land in North America, sooner or later. The USDA has a drought monitoring program and posts their Drought Monitor Maps weekly on their website (https://droughtmonitor.unl.edu/).

Attached is a drought map posted as I write this article, July 25, 2024. I will bet you there is someone right now in northern Virginia who will argue with you about providing supplemental water to his/her deer! That area has 43.6 inches of rain annually. Yet, the USDA clearly shows that area today is classified as “D3, Extreme Drought. If we go back a year ago (July 25, 2023) to check on the same area, it was only listed as “Abnormally Dry;” and the year before as not droughty!

But wait! In 2023, an area in southern Wisconsin was, “D3, Extreme Drought,” yet showed no drought in July 2024. That area normally has 37.1 inches annually. My point is, drought can happen anywhere, and no matter where you live, management of water resources for your deer and crops, is part of your management plan.

DEER DROUGHT RESPONSE

What do deer do when there is a drought? My research over five decades has shown that white-tailed deer rarely migrate, but there is an exception — and that’s during drought!

In 2011, much of Texas had what was called a “Millennial Drought,” one that had not been recorded in 1,000 years. During the drought, my emails and phone calls buzzed with people wanting to know: “What happened to my deer?” I asked them where was the nearest existing water? Then I told them to go to that area and look. They were amazed that large numbers of deer had relocated to where there was dependable water.

WHAT CAN YOU DO ABOUT IT?

For some time now, I have been publishing articles and distributing materials on how to supply supplemental water to your deer in an economical way. Before I dig into the best ways to do this, I offer a short primer on watering preferences of white-tailed deer.

Believe it or not, when given the choice between running water and a still puddle, deer will select the puddle every time! Why? Deer are always on the lookout for predators. For a deer to lower its head to a bubbling brook to drink, places them in a vulnerable position. When they drink from fast running streams, it most often is from small eddies and pools adjacent to the running water. A good friend and colleague once said: “The white-tailed deer would rather drink from a cow track than a stream!”

We recommend supplying supplemental water in one of two ways. First, you can simply place a polypropylene trough, about one foot deep, in a shady area near deer trails. I created a controversy some years ago, when I advised against burying the trough in the ground. There is a danger of fawns drowning by slipping and falling into the trough. I also advise placing a large stick in the trough (whether buried or not), so that small animals that fall in can get out. It saves their lives and keeps the water from being contaminated.

The white-tailed deer’s rumen holds 1-2 gallons of liquid; but we have found that the average deer does not drink more than a half-gallon at a time. Visitation is usually once a day but may be twice in very hot weather. Remember to keep the trough in a shady spot, because deer will not drink water that is over 90 °F.

That given, each deer will remove from a half to one gallon per day. If you use a standard 35-gallon trough, that means it will provide water for 35-70 “deer-days.” If you place a trail camera on your trough, you can get a good idea of how many deer are watering there. Then you can time your trips to re-fill the troughs.

Remember, we recommend placing an 80-acre grid over your land map, then check to see if each grid has a permanent and reliable water supply is. In the last few years, we have reduced the grid size to 40 acres, to allow for intensive management. We have many troughs on our research facility, one that is no more than 100 yards from a 3 1/2-acre lake. Believe it or not, our deer prefer to use a water trough than go to the lake’s edge. I feel like it is more secluded, and they feel safer.

For those of you who own or control land that is too far away to make regular trips to fill troughs, we use a storage tank positioned uphill from the trough. The trough is outfitted with a float valve, that keeps the trough filled. We use a 450-gallon storage tank and fill it from totes in the back of a UTV or pick. We use a good quality garden hose or PVC pipe to connect the tank to the trough. I have a small trailer with a larger container and a gasoline pump for filling my storage tanks.

One last method is being used by two of our cooperators near Fort Worth, Texas. They designed a water collection system that captures rainfall, then funnels it into a standard tote, mounted up on a stand. Again, the setup is connected to water troughs with a hose and float valve. This is not unlike the famous “Gallinaceous Guzzlers” used for game birds in desert environments.

I often am asked: “If I have $500 to spend on my deer, what should I do to get the most for my money?” I never hesitate, and reply “supplemental water!” A simple polypropylene 50-gallon trough costs about $90; a float valve is $25, and a 100-foot heavy duty hose is $90, totaling $205. That’s enough to construct two and have change left over! If you opt for a 350-gallon storage tank, that adds about $1,000.

We have discovered that providing a reliable water supply to every 40-80 acres will significantly increase fawn crop and recruitment for you deer herd. But here is one last piece of information about supplemental water.

The number one killer of deer is a viral disease called, Epizootic Hemorrhagic Disease (EHD), which is spread by biting midges (gnats) when they feed on a sick deer, then fly to a healthy deer. The midges lay their eggs in the mud adjacent to water, where the maggots pupate, emerge at sundown and seek a blood meal. If you have deer coming to a water trough, instead of “natural water,” there is no mud!

We are convinced we have significantly reduced EHD on properties we manage using water troughs! So, supplemental water spreads your deer out (reducing social stress), increases fawn survival and recruitment, and can reduce disease. With all that, coupled with combating sporadic drought issues, please explain to me why your land does not need supplemental water.

About the Author: Dr. Kroll is founder and director of the Institute for White-tailed Deer Management & Research in Nacogdoches, Texas.

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