The first step of any research project is a hypothesis, so in that light let us hypothesize.  I suspect that the reason for the inability of Rio Grande wild turkeys to establish populations in the Eastern United States is a combination of factors and the testing of various hypothesizes will be necessary.

Hypothesis 1, The Instinctive Behavior Hypothesis:

Wild turkeys are known to be very instinctive animals.  The rituals involved in turkey reproduction exemplify this, leading me to infer that the behavioral contrast between rios and Easterns may be the product of instincts having evolved to suit the different environments each subspecies inhabits.  One such behavior is different travel habits of each sub species.  The Rio Grande travels longs distances from summer nesting grounds to winter roosting habitat.  This is necessary for rios to find the type of nesting habitat that is preferable to wild turkeys, which is of course large trees next to water.  After running up to 60 miles the sight of a mature live oak grove bordering the Pecos River must look extremely welcome to a Rio Grande turkey.  If you take that same turkey and drop him in the middle of the Big Thicket National Forest he is going to have to run a lot longer than 60 miles to find that familiar grove he has been conditioned by years of evolution to recognize as a suitable roosting site.  Rio Grandes are also in the habit of forming flocks of several hundred birds for winter roosting season.  In the midst of the dense understory of the East Texas woods how is a group of 200 turkeys going to navigate?  By the only clearings that typically exist, pipelines and logging trails.  Being forced into such narrow and predictable traveling corridors will make them extremely susceptible to predation, leaving little chance for survival.

This hypothesis states that wild turkeys are extremely instinctive thus incapable of altering their instinctive behaviors to suit environments other than the environment each subspecies’ behaviors or instincts evolved to suit.

Hypothesis 2, The Dominant Gobbler Hypothesis:

Young gobblers very seldom get the chance to mate even if they are sexually mature.  During and prior to the mating season gobblers compete to establish dominance.  Only the more dominant gobblers of a flock are allowed to participate in reproduction.  Being physically smaller than Easterns and thus less dominant, released Rio Grande gobblers would rarely get the chance to sire hens in East Texas if any Eastern gobblers were present.  This would result in F-1 hybrid turkeys that historically do not fare any better in the wild than misplaced subspecies.  Even if hybrid wild turkeys would survive, Eastern gobblers would dominate breeding competitions causing the eventual minimization of Rio Grande wild turkey presence in the gene pool.

This hypothesis states that due to the larger size of Eastern wild turkeys they would dominate breeding competion eventually reducing the presence of introduced Rio Grande wild turkey genes in the East Texas turkey gene pool.

Hypothesis 3, Disease and Parasite Hypothesis:

This hypothesis states that Eastern wild turkeys are more immune to the higher number of bacteria and parasites typically found in moist areas such as East Texas and therefore have an advantage over Rio Grande turkeys.  While there are plenty of disease-causing agents in Central Texas, they often differ from those found in East Texas, possibly making the Rio Grande subspecies adapted to fend off only those pathogens and parasites occurring in their natural range.  While I consider the first two hypotheses to be more plausible explanations, susceptibility to specific disease-causing agents may play a minor role in wild turkey subspecies distribution and should be investigated.

Analyzing the facts and formulating testable hypothesis will lead to a more specific explanation of turkey subspecies distribution.  However, I believe the answer we are looking for will be some variation of this more general hypothesis.  The different subspecies of wild turkeys became isolated (either geographically or otherwise) and evolved habits, instincts, and physical characteristics that reflect the various habitat components of their historic home ranges.  This variation of habitat components is largely a result of the different average rainfall totals specific to the native range of each subspecies, explaining why these subspecies ranges can be defined by precipitation totals.

We now know that the area in which the Eastern and Rio Grande wild turkey subspecies has the potential to establish a viable population can be defined by that area's average precipitation, but the difference is obviously not the availability of moisture alone.  More research is needed to examine exactly what it is about these regions that make them inhabitable by a specific wild turkey subspecies, so that we may be able to recreate these subspecies-specific desirable conditions through our wildlife management efforts.  I will continue to research this topic and formulate possible methods of experimentation testing these and various other hypotheses so that we may increase our knowledge and understanding of wild turkey management.  If you have a special interest in this subject, or would like to contribute, please contact me. Until then-

This is John Schwarzlose for The Texas Hunting and Fishing Network wishing you safety and success in all your outdoor adventures.

John Schwarzlose
TEXLA Wildlife
(409) 658 7261
texla@texlawildlife.com