The study was presented as part of the Discover Life in America 2023 Colloquium, a virtual conference in which researchers in different fields presented. A video of the talk is available on YouTube. Hellbender Press previously reported on the colloquium.
“I think that our results are important for conservation. I think that they could potentially drive conservation in the park via selective management of hogs at high elevations,” Funk told his virtual audience.
Feral hogs, the ancestors of which escaped from hunting preserves in the early 20th century, are invasive and widespread across the Southeastern United States. Great Smoky Mountains National Park has long targeted the hogs with traps and contract hunters.
The study looked at the salamanders at a “patch-scale,” meaning in small areas, but the hogs root “extensively” at higher elevations across the Smokies, Funk said.
“They actually root about 80 percent of all hardwood forest in the park each year when they come up to high elevations to forage,” he said. He said this rooting tends to disrupt the upper soil layer, understory plant cover and leaf litter. Plethodontids use the leaf litter and understory plants as shelter. So the hog disruptions are likely to affect these salamanders.
He also said he’d been analyzing hog stomachs to see if the hogs ate the salamanders directly rather than just affecting their habitats.
“They eat salamanders, but not that frequently,” he said. He said salamander mortality was more likely due to environmental conditions caused by the disruption of habitat.
Overall, Funk said, his studies seemed to show that the hogs’ foraging lowered plethodontids’ abundance and diversity. He said there were at times positive effects for the salamanders, but these positive effects were either short term or likely associated with how easy the salamanders were to see rather than whether they were present.
He said that the visible hog disturbance did not seem to affect the abundance of plethodontid salamanders in the spring “which is not surprising given that rooting really becomes intense in the late spring into the summer.” He said it affects them more strongly in the summer.
In the fall he said, hog foraging seemed to have a positive effect on the abundance of plethodontids observed. He said he suspected that this effect might not actually mean there were more of the salamanders, however.
“Hogs increase soil moisture, which increases the probability that you see a salamander on a plot and not the probability of a salamander actually being on a plot,” he said regarding this fall effect.
His studies also looked at the diversity of plethodontid species.
In the spring the areas the hogs disturbed had less diversity of plethodontids, which seemed to be related to the loss of understory plants. In the summer, however, uprooted plots seemed to have more plethodontid diversity. Still, the patches that were undisturbed last year had more diversity than areas that were not. He said the temporary increase in diversity could be associated with the salamanders using the disturbed areas as a route through which to walk rather than a place to live. His chart showed little effect in the fall on diversity.
He concluded overall that the trends across seasons might mask variation between seasons, but the inverse might also be true that seasonal variation could also obscure cross-seasonal trends.
He said long-term effects over decades was something that his study had not covered.
