Monday, March 3, 2014

Are feral hogs contributing to quail decline?

Feral hog populations have exploded across Texas in recent years – the current average estimated population is 2.6 million (Timmons et al. 2012;  http://feralhogs.tamu.edu/files/2010/04/FeralHogPopulationGrwothDensityandHervestin Texasedited.pdf). During the same period of time quail have gone through a drastic decline and are now at all-time lows (Figure 1). For some hunters and concerned citizens Texas, those two facts alone are enough to say that feral hogs are the cause of quail decline, but there is still that nagging issue of “correlation not implying causation.” In other words, just because both quail decline and hog explosion are occurring at the same time does not necessarily mean that one is causing the other.  Even on ranches where there is not an overabundance hogs, quail are still in decline. However, there is evidence, both circumstantial and direct, that feral hogs can be detrimental to quail. Given the currently depressed state of quail populations in Texas, any extra non-natural factor contributing to quail mortality is worth a serious look. That is why Texas A&M AgriLife Extension Service elected to fund research into feral hogs and quail as part of the Quail Decline Initiative. 


Figure 1. Texas Parks and Wildlife quail forecast for bobwhite quail in the Rolling Plains. Every year TPWD conducts roadside quail counts across the state to index quail abundance.  


Background
Feral hogs have been documented as nest predators (Figure 2). Several researchers from Texas A&M AgriLife Research and the Natural Resources Conservation Service (NRCS) used simulated quail nests to answer the question: just how many failed quail nests are attributable to feral hogs? Feral hogs contributed to roughly 10 to 30% of the nest depredations (Tolleson et al. 1992; http://agrilife.org/texnatwildlife/feral-hogs/impact-of-feral-hogs-on-ground-nesting-gamebirds).  That study was conducted in the early 1990s and feral hog populations have only increased since then. Feral hogs have an acute sense of smell; the one feature any proficient nest predator needs (think raccoons and skunks; After all, how else would you locate a well concealed nest at night?). They are also opportunistic omnivores, meaning that they eat both plant and animal material in proportion to what is available in the environment. As a result, the majority of a feral hog’s diet consists of plant material, but given the opportunity it would certainly consume such a nutritiously dense and easy to catch meal as a quail nest (Figure 3).
While feral hog foraging may seem random it is actually highly focused. They typically seek out specific areas that are utilized seasonally in response to an increase in the availability of a specific food item (i.e. nutritious vegetation during spring green up). As some landowners have suspected, it may not be far-fetched that an individual hog could hone in on and seek out quail nests causing not just random depredation, but systematic destruction. Many nest predators have been shown to develop what is termed “search images,” whereby as the nest season goes on predators get better and better at finding nests as they are rewarded by each successful meal (Ishii and Shamada 2010; http://izt.ciens.ucv.ve/ecologia/Archivos/ECO_POB%202010/ECOPO5_2010/Ishii%20y%20Shimada%202010.pdf).


 Figure 2. Feral hog consuming wild turkey eggs (Trail camera photo by Dr. Brett Collier).


Figure 3.  Feral hog sounder consuming chicken eggs. Photo by Susan Cooper.

Research
Dr. Susan Cooper of the Texas A&M AgriLife Research Center in Uvalde is using data on the spatial distribution of feral hogs and quail to determine what habitat types these two species overlap the most.  She is taking advantage of previously recorded GPS location data on 40 feral hogs and 10 years of spring call count data for quail. By making comparisons of habitat usage between the species, she intends to be able to make recommendations on the rangeland sites where control of feral hogs could have the most positive impact on breeding quail populations.
Figure 4. Researchers attach a GPS collar to a feral hog. Photo by James Cathey.

Conclusions Thus Far
The jury is out on whether or not feral hogs are the cause of quail decline in Texas. We would argue that they are likely not the sole cause of decline, but that their potential for negative impacts is undeniable and tangible.  Feral hog control is another piece of the puzzle for healthy land management that all species, quail and humans included, can benefit from. Under the current circumstances, your quail need all the help they can get and in the future we hope to be able to provide you with recommendations on how the get the most “quail bang” for your “feral-hog-control buck.”
 
The hyper-linked resource document below will provide you with quick access to many of our online feral hog resources including publications, fact sheets and videos.