Study Claims Feral Hogs Really Aren't All That Bad

Study Claims Feral Hogs Really Aren't All That Bad

You may have seen the news: “Feral hogs are no worse for Texas’ plant life than native animals, study finds.” The Houston Chronicle article cites a new study published on February 2 in the journal Science, arguing that feral hogs aren’t having a detrimental effect on native grasses—any more so than native herbivores are.

The article, however, is misleading. The scientific study referenced is actually a meta-study (a large review of already-published data from around the world) conducted by researchers at Aarhus University in Germany. The researchers use feral hogs as one data point in an otherwise wide-ranging study, covering everything from cape buffalo to oceanic island plant communities. The main takeaway? In the words of the authors:

Empirical claims used to argue for the eradication of introduced megafauna could be used for any megafauna, except for a key normative difference: native megafauna are considered to “belong,” while introduced ones are not. As such, the effects of introduced megafauna can be described as “harmful,” regardless of what those effects are. We argue that the effects of introduced megafauna should be studied as any other wildlife would be studied…with the normative dimensions of their “belonging” considered separately and with transparency.

In essence, the authors are arguing that we should ignore “native” and “non-native” distinctions when looking at the ecology of large herbivores and instead view the data from a strictly scientific standpoint.

With regards to hogs specifically, the researchers conclude that feral pigs often increase plant diversity by eating the dominant vegetation in an area, allowing for lesser vegetation species to increase in number to fill in the gaps. The authors then argue that diversity, from a scientific perspective, is inherently a good thing, leading to more resilient ecosystems in the long run. While that might be an accurate assessment in the broad-scale picture, it wildly overlooks the intense, localized effects that feral hogs have on the US landscape.

Take a more localized study, for example, conducted in 2022 by researchers at the University of Massachusetts, Duke, and the Virginia Institute of Marine Sciences. In their field-based study, the researchers set up 260-square-foot, fenced exclusion areas on coastal marshes in Georgia. Then, every four to six months for three years, the researchers revisited the plots (alongside unfenced control sites) and recorded the changes in vegetation species and abundances.

Over the three years of data, the researchers found that hogs suppressed and trampled dominant plant species, allowing competitively inferior species to take hold. The overall effect created a plant community that was 33% more diverse but less productive. The negative effects were especially pronounced on the edges of dunes and marsh grass monocultures, where the hogs traveled, bedded, and wallowed.

In terms of the bigger picture, however, the researchers on the Georgia study note that historically, Pleistocene-epoch consumers like mammoths, wild horses, and bison were on the landscape having a similar effect as the feral hogs are currently. That’s to say, native plant species pulsate in abundance and density over time, so who’s to say what “normal” is?

But from the more pragmatic standpoint of local farmers and ranchers whose land is being impacted by hogs, the changes are not necessarily for the better. Hogs are notorious for rooting in farm fields—sometimes up to three feet in depth—in search of grubs and tubers. The resulting hummocks and holes left behind can damage farm equipment or at least make it more challenging to tend fields.

On top of that, they’ll eat just about any crop, including wheat, corn, soybeans, and oats—big cash crops across much of the feral pigs’ range throughout the southern half of the country. They also destroy pine and hardwood seedlings, changing forest compositions.

In Texas especially, the hog problem has become particularly acute in recent years, with reports of hogs destroying farm fields overnight and videos surfacing of pigs running through the streets of downtown Houston. On the whole, the USDA estimates that feral swine cause $2.5 billion in damage annually.

In other words, claiming feral hogs aren’t all that damaging may be cherry-picking the facts. In the large-scale perspective of global landscapes, there have always been, and always will be, large herbivores and omnivores present. And while ignoring “native” and “non-native” distinctions might make sense in some empirically-based scientific applications, wildlife management is a whole different ball game—one that must account for numerous other social and economic factors. A species that has seen such rapid range expansion in the last 40 years will undoubtedly have significant impacts beyond native grasses, and those impacts must be taken into account.

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