exotic species

Managing Exotic Species and Whitetails | Hall and Hall Resources

Managing Exotic Species and Whitetails in Texas

By: Justin Bryan

 

Where’s Waldo…in the Texas Edwards Plateau?

My wife and I have three kids, one girl and two boys. Yes, we have a healthy herd with a very good recruitment rate and the potential to spread highly desirable genetics…upon maturation and matrimony of course. Our kids thoroughly enjoy spending time working through the “Where’s Waldo?” books. Each book contains illustrated pages where Waldo is strategically hidden among a plethora of characters that are performing a wide variety of activities. Waldo is always sporting a red/white striped shirt with blue jeans, therefore one would think he would be easy to find. The task is to find where Waldo is hidden among the other characters.  He is “lost” in the great diversity of associates that surround him.

As I thought about writing this article I couldn’t help but think that at times this must be the same dilemma and thought process that white-tailed deer face in Texas. Where is their kindred “Waldo”? I am specifically speaking of the white-tailed deer population that resides in the Texas Hill Country, part of the Edwards Plateau ecoregion. This sub-region ranges from the state capital of Texas, Austin, then west to the cities of Kerrville and Del Rio and returning back east through Uvalde and San Antonio.

As a wildlife biologist and consultant I’ve been fortunate to spend time on quite a few interesting ranches that fall within this region. A typical property is 1,000 acres or less in size that has historically been overused by cattle, sheep, and goats, leading to dominance of less than ideal plant quality and quantity. Topographically, this area is characterized by hills that suffer from less-than-fertile, shallow soils which easily expose the heavy limestone and granite structures that define the Texas Hill Country. Genetically, white-tailed deer in this area are small with mature bucks only sporting an average live weight of 125 pounds and measuring at 115” to 125” Boone and Crockett. What I find to be interesting in this area and the native deer likely find to be puzzling is the “plethora of characters” (a.k.a exotic species) that now calls these rangeland sites home, thus keeping the white-tailed deer wondering – where’s their kinsfolk and who are these other guys?

exotic-species-managing-whitetails-texas_1Texas is no stranger to the introduction of non-native, exotic species and exotic hunting. Historical documentation shows exotics were likely to have begun being brought to Texas as early as the 1940s in the south Texas, King Ranch area. Since then, the introduction areas have greatly increased and expanded. I have had the opportunity to step foot on ranches that were home to eland, wildebeest, ibex, zebra, red sheep, elk, hog deer, nyala, red stag, oryx, waterbuck, Pierre David’s deer, and amazingly enough a few that had giraffes and a wart hog or two among an abundance of other non-native species. The facts around exotics in this area of Texas are well documented in literature.

Roughly 68 percent of the total confined exotics in Texas occur within this Edwards Plateau region. It is estimated that Texas is home to an excess of 200,000 exotic animals that are made up of just over 70 species. The dominant players or most common exotic species are axis deer, fallow deer, sika deer, blackbuck antelope, nilgai antelope and aoudad sheep which represent 99 percent of the free-ranging exotics in Texas and they predominantly occur in this Hill Country area. You are correct if you hypothesized that Texas has the most plentiful and largest dispersed populations of hoofed animals in the United States.

The obvious question from a white-tailed deer management standpoint should be, “what is the influence of these contained and more often than not free-ranging exotic species, if any, on the white-tailed deer population?”

Exotic Species and Whitetails

Probably the most common detail that those of us who have spent quite a bit of time in the field have witnessed is the social interactions between these species. I believe that research supports much of what we assumed from these observations. The scientific term is interference competition; in other words, when on animal interferes with another animal’s ability to obtain its required resources (food, water, and cover). The most common area for this type of interaction to occur is in localized optimum habitat areas, water sites, and supplemental feeding locations. As noted earlier, this area of the Edwards Plateau is often nutritionally poor due to past land management practices, recurring bouts with drought conditions, and shallow soils. Therefore, supplemental feed offers the only real opportunity for a land manager to attempt to increase the level of the nutritional plane for the existing deer population.

exotic-species-managing-whitetails-texas_2

We already know from research that a level of intimidation/interference exists among whitetails themselves, especially in regards to interactions around supplemental feed locations. Mature males tend to dominate over younger males and females, the latter being those within the population who need the supplement the most. When it comes to intermingling with exotic species, white-tailed deer tend to be like 15-year-old boys at their first school dance, quite the wall-flowers and always minimizing direct eye contact with likely dance partners. Not that the “likely dance partners” are another species (some may argue that) but you get my point. Understandably, this type of avoidance behavior is most easily and commonly observed at feeder locations and prime habitat locations. Research directly related to this topic showed that in fact, axis deer are dominant to white-tailed deer at feed locations, each species spending more time alone than dancing together.

However, the duration of time that individuals of each species at feeders did not differ. In other words, they wanted to dance and hang-out and did so, just not together.  Aoudad, generally disliked by landowners for their negative impacts on fencing infrastructure, also have no problem intimidating whitetails. I’ve seen the same response in regard to aoudad/mule deer contact at supplemental feeder locations in far west Texas; in addition, cattle and feral hogs do their share of “pushing” whitetails around as well, often leading to the white-tailed deer leaving the feeding area altogether. Therefore, from a whitetail’s perspective, there is a small timeframe to access a supplement and it is highly likely that only a very small percentage of the whitetail population as a whole has access at all; once again most likely coming from mature males.  As a result, a loss of opportunity occurs for a large percentage of does and fawns to feed on a supplement that was meant to provide much needed nutritional resources to maintain a does body health, facilitate quality milk production, and meet the nutritional requirements of a growing fawn’s body.

exotic-species-managing-whitetails-texas_3

Further research evaluated in-the-field interactions, away from feeder locations. This data, specifically examining the interaction between axis and white-tailed deer, showed a common consistent preference for separation, further documenting that not only is there an impact on the ability for native deer to have access to quality feeder locations as desired, but also likely intimidation and subsequent dispersal from preferred habitat locations in the field which likely include foraging areas and fawning cover. The loser here is the whitetail.

Where habitats are in good condition, providing consistent average to above-average food, water, and cover and populations are kept “in-check” these species are likely able to adequately coexist, but this is far from the norm. As one would expect, when the nutritional levels of the habitat begin to falter due to events such as drought or when carrying capacity is exceeded and a higher level of competition for all resources kicks in, problems begin to occur.  Historically it is a combination of drought conditions, poor soils, and populations that are not kept in-check. Once again, it is generally exotics that win when it comes to excelling as the conditions persist.

Unfortunately for whitetails, the majority of exotic species are intermediate feeders, thus able to physiologically make positive use of all forage classes available…grass, forbs, and browse. Whitetails on the other hand are concentrate select feeders, “selecting” for more nutritious and easily digestible actively growing portions of plants, typically browse and forbs. When the competition for nutrition heats up, exotics – most notably axis deer and sika deer – can and will outcompete and even displace whitetails due to the ability to be a successful intermediate feeder making more complete use of all forage available.

exotic-species-managing-whitetails-texas_4

An additional competitive advantage that these common exotic species have over whitetails is the timing of birth and numbers born per female. Typically exotics such as axis and sika deer give birth to only one offspring which is born in the timeframe occurring from December to March. This date range, more times than not, provides cool to warm temperatures with few instances below freezing occurring. In perspective, whitetail does generally give birth during late spring to mid-summer, to two fawns. Comparing the two, in general these common exotics are only required to allocate energy into developing one offspring that is also born at an optimal time (early spring) to take advantage of the quality and quantity of spring forage production. In contrast, whitetail does are typically placing developmental energy into the production of two offspring and give birth later into the summer. This late spring/summer fawning time period will often result in a decreased opportunity for nutritional requirements to be met for both the doe and fawn thereby decreasing doe physiological recovery, fawn development and/or leading to fawn death.

Considering the large numbers of free-ranging exotic species in combination with the native white-tailed deer populations, this can be a challenging situation for a property manager, to say the least. It is well understood that more times than not, due to their genetic personalities, whitetails prefer to stay hidden within the diversity of ungulates instead of at the forefront. With Texas being 98 percent privately owned, and these being relatively small properties at 1,000 acres or less, adjacent property owners can have corresponding or conflicting goals. One may want to maximize the opportunity to increase the quality of the habitat and focus specifically on the quality of the deer population, while another may prefer or enjoy the diversity of ungulate species as they are. To each is their own, understanding and working with the positives and negatives and understanding the potential reality of a given goal on a given property is the art of being a successful property manager.

0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *