How the Loss of American Chestnuts Impacts Timber Rattlesnakes Today



Snake fungal disease, caused by the pathogen, Ophidiomyces ophiodiicola, is a source of great concern in the snake conservation realm. Causing blister-like lesions on the skin of snakes, especially on the face, the infections can be fatal. Timber Rattlesnakes are especially susceptible, but the harm snake fungal disease will do to their populations over time is unclear. However, this is not the first time a fungus has harmed Timber Rattlesnake populations. Nearly a century before a herpetologist ever uttered the words, “snake fungal disease”, Timber Rattlesnakes were dealt a serious blow by another fungus. Yet, this other fungus never infected a single snake. The fungus at play here is lethal, but only to a single species of tree; the American chestnut (Castanea dentata).  

One of only a handful of mature American chestnuts remaining in New England, "Berlin Jr" now stands alone after an even larger chestnut on the property succumbed to blight a few years ago. Photo by Kiley Briggs

American Chestnut Blight

Due to chestnut blight (Cryphonectria parasitica), a fungus originally from Asia, the American chestnut is on the brink of extinction. But how has the chestnut blight affected Timber Rattlesnakes? To understand this, it is important first to understand the role American chestnuts played in Appalachian forests. For millions of years, the American chestnut was a huge component of hardwood forests in the eastern United States, both in numbers and size. With trunks spanning up to nearly 10 feet in diameter, these trees could tower a hundred feet in the air. Each of these trees produced up to 6,000 highly nutritious chestnuts every year. American chestnuts numbered in the billions, perhaps accounting for up to a quarter of all trees in the Appalachian region. The chestnuts these trees produced were also a valuable source of food for both wildlife and people. This all changed drastically with the arrival of chestnut blight in the early 1900s.

American chestnuts numbered in the billions prior to the arrival of chestnut blight, and these very large trees produced upwards of 6,000 nutritious nuts every year. Photo by Gail Whistance

First noticed by staff at the Bronx Zoo in 1904, yellow cankers turned up on some of the chestnuts in New York City. Eventually the cankers girdled branches and trunks, killing the trees. Within two years the disease spread to other states, and by 1945 the American chestnut was nearly extinct. Only hundreds of mature trees remained out of billions. Many more survive in a diminished form, sprouting from the roots of fallen trees, and then dying back off before ever producing a single nut. The loss of the American chestnut as a food source sent shockwaves through forests that can still be seen today.

Chestnut blight forms orange cankers around the stems of trees and branches, killing off the vascular tissue and girdling the tree, eventually killing it. Photo by Kiley Briggs

Chestnuts aren’t the only nut-producing tree in Appalachia, but the chestnut’s ability to provide large crops every year was unique. Today, forests comprised largely of oak, beech and hickory are characterized by periodic pulses in resource (nut) availability. For example, red oaks produce minimal acorn crops most years, but some years, the trees produce large acorn crops all at once. Acorns are an important food for wildlife, but these fluctuations present challenges to long-lived animals depending on stable resources. Timber Rattlesnakes are one such species still reeling from this major shift in forest food availability.

How the Loss of American Chestnuts A Century Ago Impacts Timber Rattlesnakes Today

Timber Rattlesnakes can live for decades and give birth to live young, but not every year. Birthing is a very expensive process for Timber Rattlesnakes, and several years may pass between reproductive cycles. So, you might expect roughly a third of the females to give birth each year. Instead, what we see are years with low birth rates and occasional years with high birth rates. These birth pulses closely resemble the patterns we see in oak mast production, which is not a coincidence.

Timber Rattlesnakes are sit-and-wait predators that specialize in feeding on rodents. In the absence of the American chestnut, woodland rodent populations in Appalachia dropped, and year-to-year variations in their numbers increased, limiting the Timber Rattlesnake's food supply. Photo by Kiley Briggs.

Timber Rattlesnakes do not eat nuts themselves, but their food does. The mice and other rodents Timber Rattlesnakes feed on go through population booms in years following large acorn crops. During periods of acorn scarcity, rodent populations drop back to low levels. Pre-blight, woodland rodent populations were larger and more stable from year to year than they are now. So, in the year following large acorn crops, rodent populations increase. A year after the rodent population spike, Timber Rattlesnakes birth more and larger litters. Pre-blight, Timber Rattlesnakes might have given birth more often, and to larger litters too. That is an educated guess, though, because we don’t have the pre-blight data to be certain. 

American Chestnut Restoration

There is hope that American chestnuts may soon return to Appalachia, thanks in large part to the American Chestnut Foundation. The Chinese chestnut (Castanea mollissima), from which the blight originates, is resistant to the fungus. Efforts to breed that resistance into the American chestnut date back many decades, but it is a very slow process. More recently, innovations in gene editing technology opened other doors to creating blight-resistant chestnuts. Both approaches hit roadblocks along the way, and neither are without debate. Regardless, it appears blight-resistant American chestnuts are on the horizon, be it in a few years, or decades. Whether the American chestnut can ever reclaim its place in the ecosystem, remains much less clear. 

Test plots, where potentially blight resistant American chestnuts are being planted, their growth and health are closely monitored. Photo by Kiley Briggs

Biodiversity at Risk

Meanwhile, other trees are at risk from non-native threats. Dutch elm disease arrived in the 1920s, nearly wiping out mature elms. Butternut canker has killed up to 80% of butternut trees in some states. Emerald ash borer beetles threaten ash trees, causing massive die-offs. The woolly adelgid beetle has the potential to almost wipe out hemlock completely. Beech bark disease threatens yet another nut-producing tree. If a hypothetical pathogen threatens our oaks, how might Timber Rattlesnakes adapt? And how will the loss of these trees affect other wildlife? American black bear, for example, face declines of numerous food sources they depend on to fatten up before winter.

American chestnuts such as this one are far from the only species of tree affected by introduced threats. Butternut, American beech, American elm, and eastern hemlock are all threatened by non-native pests and pathogens. Photo by Kiley Briggs

Lessons learned from efforts to restore the American chestnut may be instrumental in the restoration of other trees as well. Ultimately, however, preserving biodiversity within our forests before the next species falls is preferred. American chestnuts were one of the first trees to fall in our region, but they weren’t the last, and we don’t know which will be next. Predicting the consequences of each loss is even harder, so preserving the health and biodiversity within our forests is something we should all care about. 

The Timber Rattlesnake is one of The Orianne Society’s priority species – learn more about Timber Rattlesnakes here.