Water Quality Concerns Surrounding Feral Hogs
By: Aaron Sumrall, PhD
It is no secret that Texas is in the firm grip of a significant drought that is expected to persist into the last quarter of 2022. Anyone can travel the highways and byways of this great State and conduct their own windshield survey and quickly see the many black patches along the ditches and the large expanses of chard landscape consumed by fire. Ponds intended for water sources for livestock have dried to the point that the fish have ticks! Hay trailers did not have much of a spring reprieve before hauling hay again to feed livestock. Our wildlife managers can quickly teach students the importance of understanding carrying capacity across our wild landscapes to keep those populations healthy.
Evaluating the varying components of our landscape in this current situation is taxing and leads to a lot of head scratching. When we assess landscapes, we must always begin at the foundation – Water. We must answer the questions of quantity and quality to better understand the building block needs of landscape health. The question of water quantity in Texas is very easy to answer – there is not enough. The second pertaining to quality, then, becomes a much more serious question to answer correctly. In agriculture, water quality concerns can be addressed in many instances by managing access to water by livestock through fencing and/or rotation of the herd. The lion’s share of our native wildlife species poses little concern to water quality by loafing in the water to cool like cattle. Sure, we see some quality complications from avian rookeries but nothing like the water quality complications stemming from the ever-present feral hog (Sus scrofa).
The skills of feral hogs are seldom referred to with positive adjectives and especially in concerns surrounding water quality. With the inability of the species to sweat to regulate body temperature, we typically find daytime loafing in water sources in increasing frequency as the mercury rises. When thinking about what this means to a decreasing water quantity, we come back to the elephant in the room of water quality. Let’s take a minute to ponder the quality implications posed by feral hogs with regard to dissolved oxygen, fecal coliform units, erosion, disease, and the aftermath of when the rains come again.
Dissolved oxygen is the concentration of oxygen incorporated into the water with four primary factors affecting said level. Water temperature (most important), atmospheric pressure, salinity, and water turbulence drive the bus when discussing dissolved oxygen. Oxygen enters the water column through atmospheric pressure and turbulence influenced by temperature and salinity. Warm water holds less oxygen than cool water, and water with less turbidity hold more water than does turbid water. This simply means that warm, colored, stained, murky, or muddy water holds less than cool, clean water.
Feral hogs may not have an influence on temperature, atmospheric pressure, or salinity but they can heavily influence turbidity seeing smaller water sources more significantly impacted. Turbidity can be summed up by the particle load suspended in the water column. Direct turbidity from feral hogs comes from the rooting, wallowing, and loafing within the impoundment not allowing particles to settle and water clear. Other water turbidity injections originate from the riparian zones surrounding the water body. When feral hogs leave the water for short daytime excursions, they typically stay within the shady confines of those riparian zones. Such zones typically see an elevated level of bare ground, loss of vegetative cover, and higher erosion potential.
When I think of fecal coliform units (FCU) in the water body, I can’t help but wrinkle my face with concern. Feral hogs do not have a mom to instruct them to get out of the water to answer the call of nature in order to preserve water quality. Yep- They go right there! FCU is measured in 100mL increments by determining bacterial levels. Coliform bacteria originate in the intestines of all warm-blooded animals and are excreted through the feces. The FCU assay is utilized as an indicator of fecal contamination leading to possible pathogens that are possible in the feces. Feral hogs are listed in virtually every watershed management plan in Texas as a major contributor of FCUs in given watersheds. This opens a completely different can of worms when we start to consider disease transmission possibilities to people, livestock, food crops, and other wildlife.
Riparian zones are hugely important in the overall health of landscape-level ecology. Many species, both plant and animal, depend on riparian zones to survive and thrive. Some species exclusively depend on microclimates to exist. Feral hogs running amuck in riparian zones frequently destroy plant communities, life cycles within microclimates, nutrient cycling, and erosion potential. Oftentimes easy food such as large seeds from species like oaks and pecan is wiped out and completely eliminated over time. Combine this with the loss of native grasses and forbs and bare ground, the stage is set for the intrusion of invasive species establishment on the ground that does not erode off into the water.
Conditions spanning Texas cause feral hogs to change travel patterns with waterways as travel thoroughfares in pursuit of nutrition to stay alive until the rain falls. I often speak to land and wildlife managers that did not have feral hogs in a given area until following a drought. This makes perfect sense. The species will travel vast distances along said waterways in search of nutrition, and when the landscape recovers following a drought, feral hogs will leave the immediate confines of the watery corridors onto a new landscape of nutrition. We observed this years back when fragmented private land ownership increased on the western side of the State, and newly drilled water sources allowed feral hogs to inject themselves into harsher climates.
Texas land is in excess of 95% privately owned. The beauty of land ownership is the ability to manage the land, with wide parameters, as the owner sees fit. We need to keep in mind that every action (or the lack thereof) has a reaction. Life has value. Landscapes are intended to be productive when well managed. Some things are expected on a landscape, and others are not. Natives are just that- native. Feral hogs are not native! I was asked what is the carrying capacity of feral hogs on the landscape. The answer is simple – None! They are a proven scourge on the landscape, so as we watch the resending levels of water in our impoundments, what can we do to preserve the quality?
By: Aaron Sumrall, PhD
Director of Research and Outreach
Field Engine Wildlife Research and Management
Pig Brig Trap Systems
