How Excellent Whitetail Hunting Can Exist in Mexico

The controversy continues regarding climate change, but no matter which side of the issue you support, I think we all can agree that the white-tailed deer has faced and survived some pretty dramatic climate changes during its existence. I have a jawbone on my desk that was found in Florida, and it dates back to about 1.3 million years ago. Whether then or today, climate remains the number one limiting factor to whitetail populations, especially on the outer limits of the species’ range!

Much of the popular literature on deer habitat management includes activities like planting food plots, trees and manipulating forest stands to improve natural forages and cover. On the surface, it seems pretty simple, right? Yet, I have spent the bulk of my career studying and managing whitetails in the places where climatic challenges throw a big wrench into this machine.

My work in the northern Lower Peninsula of Michigan routinely is challenged by excessively low temperatures, poor soils and infrequent droughts. This has greatly influenced research topics here at the Institute for White-tailed Deer Management & Research, but even as great as these challenges are, they pale in comparison to those I’ve faced in the driest and hottest whitetail habitats in the southwestern U.S. and northern Mexico. My goal for this article is to educate you about what it takes to successfully manage these deer in dry, desert climates.

A HARSH HABITAT

I have done work in Mexico since the 1960s, and I’ve grown to love the northern desert country and its incredibly beautiful landscape! It is home to some of the largest antlered bucks on the continent, and in spite of the climate, body sizes reach 200-plus pounds. However, in the absence of management, northern Mexico is a “boom or bust” environment where rainfall is fickle, and temperatures reach over 110 °F.

I like to point out that northern Mexico is a drought interrupted infrequently by rain! The landscape can be scattered brush species with bare earth around them one year, and lush green browse amidst a wonderous variety of weeds and grasses the next. The mainstay of food lies with the browse plants that, unlike their northern counterparts, drop their leaves during hot, dry periods; not during winter like northern climates! We call them “drought deciduous.”

Even the soil is unfriendly, often consisting of fine silt deposited when the area was under a vast sea. The soil is so tightly compacted that water does not infiltrate the ground. Water sources also are sparse and short-lived, requiring deer to migrate during prolonged dry periods. So, you can see why I was attracted to the challenging deer management this country provides!

Most American hunters either are unaware of or poorly informed about Mexican whitetails. There are thought to be 38-40 subspecies of whitetails in North, Central and South America, with about a dozen living in Mexico. Mexico also shares the range of the Texas, Coues and Carmin Mountain Whitetails. I have been blessed to have worked with and hunted all three of these subspecies, but I wish to focus this article on what I have learned about managing the subspecies called “Texan” north of the Rio Grande River and “Mexican” south of the Rio Bravo River (same river).

My experience goes back to the late 1960s, when I worked throughout the northern Chihuahuan Desert and Tamaulipas Province, studying mostly reptiles and amphibians in those days. I quickly gained an interest in deer and their habitats, and to my surprise, there were many landowners already managing them for sport hunting!

My first hunt was along the Rio San Rodrigo river flowing into the Rio Bravo. I was amazed by how big the bucks were in that area, both in antler size and body weight, which perhaps was due to low population densities. Years later, I would have the privilege of returning to help manage one of the area’s many large ranches. I gladly accepted the challenge for the same reason I had accepted a similar challenge in managing Turtle Lake in the northern Lower Peninsula of Michigan — I was told emphatically it was not possible!

CLIMATE AND VEGETATION

In northern Mexico, the “hot” season lasts four months, from May to September, with highs averaging 93 °F and lows at 75 °F. The “cool” season is from November to February, averaging 72 °F high and 45 °F low. The dry season lasts seven months and the “wetter” season only five months; with a total annual rainfall of 15.1 inches. Most of which (2.2 inches) falls in May, and the least accumulates in December (0.5 inches).

Areas lucky enough to have a river flowing through them enjoy riparian habitats consisting of diverse tree species; these include native pecan, Mexican walnut, sycamore, willow, cedar elm, huisache and mesquite. These areas are frequented by large flocks of Rio Grande wild turkeys and even a black bear or two! Mountain lions and coyotes are the principal predators, and they certainly have an impact on deer herds. There is a huge array of shrubs that provide the backbone of the forage system for whitetails. Average protein content often is around 15 percent, almost twice what I find in the southern U.S. The non-woody plant community is highly dynamic, springing up only days after a rain.

The vast majority of the land is dominated by the ever-present mesquite (and its “friend” huisache), which depending on your personal biases, can be the boon or the bane of a deer management program! The first thing I learned about them was that you do not want to “make them mad!” By that, I mean if you try to destroy them (especially by mechanical means), they will come back with a vengeance. I learned the best management strategy is if they have been left alone, then leave them alone.

As trees, they provide valuable shade and seem to always produce a bumper crop of mesquite beans during a drought. Mesquite beans contain as much as 38 percent protein (twice as high as other beans), eight percent fiber and are rich in calcium, magnesium, potassium and iron. More than once our management program has been saved by a heavy bean crop during a drought year.

Mesquite is not the only producer of high-protein seeds for deer and other wildlife. Species such as catclaw acacia and guajillo produce periodic crops of beans, too. All in all, northern Mexico has dynamic deer habitat that can go from being lush and rich in deer and wildlife forage, to a barren desert with little to eat in just weeks. If you are not careful, it can beat you nine ways to Sunday! Ultimately, that’s why I love this landscape.

Now, let’s talk about how we have successfully managed this wild, challenging place to produce greater numbers of trophy bucks.

THE MANAGEMENT UNIT

Long ago, we determined there is a minimum management unit size for most deer habitats. In the vast majority of the range, that minimum unit size is about 80 to 100 acres, meaning that everything a deer needs should be supplied in an area of this size. The life requisites are forage, water and cover (escape, travel corridors, summer and winter), all arranged in the proper order and abundance.

However, in the desert country of northern Mexico, the minimum management unit size increases to between 300 and 400 acres, due to climatic limitations. Whatever the management unit size, the proportions for the life requisites are 30 percent cover and 70 percent forages, with a small amount devoted to water.

Regarding forage, a deer’s world is the 4.5-feet zone above the ground, known as the “deer zone.” A forage management scheme should be designed to keep forage within the reach of your deer, so that means the 70 percent forage element has to be subdivided to provide a sustained supply of food. For example, you cannot cut an entire forest and expect it to produce forage within the deer zone for the next decades. It has to be treated in a staged manner to accomplish that goal.

ALL ABOUT WATER

The single limiting factor for dry climate deer habitat is availability of water. Every place on earth has what we call a “site index” for plant growth. By definition, site index is a measure of the amount of vegetation that a certain area will grow during a set period of time. It has been applied mostly to forestry to predict the expected height trees will grow during a specified period.

I have expanded the term to include the expected amount of vegetation a specific site will grow on an annual basis. We call this vegetation “forage.” Forage can be any type of palatable vegetation that can be eaten by animals, such as deer. It is normally divided into browse (leaves and twigs of woody plants), forbs (weeds) and grasses. So, in simple terms, site index in whitetail management is the amount of forage produced annually that can be eaten by deer.

The primary factor determining this amount is totally based on the characteristics of the soil. The most critical of these is available soil moisture and minerals. Soil organic matter has the greatest impact on moisture holding capacity, along with the soil texture (sand, silt or clay), subsoil type, fertility, internal drainage and presence of layers that limit water infiltration. Since site index also predicts the height the woody vegetation will grow in a period of time, site index can tell you something about how fast the woody plants will shade out the understory plants. Later, I will discuss how we ensure that this does not happen.

There has to be at least one source of free water somewhere within the management unit (in the center is best). We use a waterline connected to what the Mexicans call a “pila” (water tank), which is filled using a windmill well. The waterlines are buried along access roads for convenience, both in construction and maintenance. They’re also connected to an innovative system of water troughs designed for water conservation in a hot climate. These devices support an impressive array of wildlife species in addition to deer.

A SUSTAINABLE SUPPLY OF DIVERSE FORAGE

The ideal vegetative community for deer is 1/3 browse, 1/3 weeds and 1/3 grasses. This distribution assures a diverse plant community that not only provides a diverse food source, but also a more stable ecological community.

For at least 100 years, ranchers in Mexico and South Texas have unfortunately tried several vegetation management schemes that produce a single-use landscape tailored to livestock, particularly cattle. To do so, they have used mechanical practices such as chaining and root plowing to remove woody vegetation, primarily to favor grasses and weeds. Given the slow rate of ecological succession after such disturbance, it takes decades to return to the original state!

We discourage using these methods in lieu of one that is much more ecologically sound — roller-chopping.

Roller-chopping involves pulling a large drum filled with water (for weight) that is armed with offset blades across the landscape using a bulldozer. The chopper breaks down the woody plants, but does not kill the roots, allowing them to resprout into nutritious browse. By breaking them down, the shade that kept grasses and weeds from growing is reduced. The result, in most cases, can be the perfect 1/3 mix of vegetation types. However, there is an even more important benefit.

Many of the soils, especially the silt soils, are packed so tightly that they do not allow rainfall to infiltrate beneath the surface. It just runs off! The roller chopper blades shatter the soil surface, providing an avenue for water infiltration. At the same time, you can position a seeder above the roller to distribute grass and weed seeds to replace those lost through years of over-grazing.

The chopping pattern is important and should follow the topographic lines of the land. We seldom roller-chop on hill tops, because of low site index and rocky soils. We like to roller-chop on shallow slopes and terraces to improve water infiltration and take advantage of more nutritious soils. Bottoms often are left vegetated as bedding areas and travel corridors. We try to never knock down large trees, such as mesquites or huisache, as this would cause resprouting in a manner we do not prefer. They also provide shade areas for deer bedding and game bird loafing.

The normal cycle for re-chopping these areas is five to seven years; however, in the much wetter eastern U.S., we re-chop every three to five years.

We try to leave un-chopped strips and drainages for bedding cover and travel corridors. Since the area has a large population of coyotes and even mountain lions, we also plant areas to switchgrass or a non-native grass such as buffelgrass. These areas serve well as fawn bedding cover, especially when interspersed with large trees or small groups of shrubs. Yes, there are purist biologists who just “hate” buffelgrass, but we have found it to be strikingly effective as cover. And it even serves as some food value.

FOOD PLOTS

With just 15 inches of rainfall annually, why on earth would I even bring up food plots? We construct as many ponds as possible on each property. They are not always filled with water for the entire year, but during some years, we can use them as a source for a simple irrigation system for food plots strategically located on the upper drainage of the ponds. We plant primarily cool season crops such as forage oats, or grain sorghum for cover, gamebird food and deer forage. The system commonly involves simple landscape sprinklers arranged in a grid pattern to cover a small area. In addition, we also use “natural” food plots developed from our roller-chopped areas by fertilizing them. Most of the soils in northern Mexico and South Texas are phosphorus deficient, so we apply 50 pounds per acre of triple-super-phosphate right after chopping. Phosphorus will remain in the soil for three to five years, making it very economical.

FEEDING

In managing any habitat for whitetails, it is important to be adaptable in case growing conditions deteriorate from drought. That is where supplemental feeding can prevent losing the fruits of your labor. Where legal, a free-choice supplement with a pelleted ration can prevent losing your fawn crop or antler growth.

We supply one free-choice feeder per 400 acres in most dry climate areas. Each one contains a pelleted ration of no more than 18 percent protein. Do not fall prey to the “more protein is better” syndrome of deer feeding! The feeders are placed near a watering station.

Feeding is the most expensive management practice we use! You can expect our deer to eat about two pounds of feed per day under most conditions. That does not sound like much, but if you multiply that number by the estimated number of deer, you will be surprised.

When managing whitetail habitat in dry climates, you must be adaptable – be ready for anything nature can throw at you! You also should be ready to take advantage of any opportunity that comes your way. That may mean planting food plots on the upper end of your ponds in years with adequate rainfall, or adding supplemental feed to take up some of the slack when things go dry. Remember, the deserts of Mexico are not the only places where dry conditions limit management; they also happen in 14 percent of North America each year through drought!

Hopefully this article gets you thinking about applying some of my dry-climate strategies to your situation. Even if you aren’t based in Mexico or South Texas, drought can happen to you. If it does, you’ll find that preparing for it will make things easier on you and your deer herd!

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