Managing forests and understanding social intolerance for Ohio’s declining timber rattlesnakes
Andrew Stewart Hoffman, PhD
William E. Peterman, Advisor
Reptiles and amphibians are in rapid, global decline but these declines are regionally and taxonomically disproportionate. North American pit vipers have low fecundity and rely on high adult survivorship, making them particularly vulnerable to anthropogenic threats. The rare, but potentially fatal consequences of human-viper interactions further compound this threat by increasing persecution and decreasing human tolerance for snake populations. The timber rattlesnake (Crotalus horridus) is the most broadly distributed venomous snake in North America, but has declined dramatically, especially at the periphery of its range in states like Ohio. Remaining populations in Ohio are largely found on relatively remote and expansive tracts of public land in the southeastern part of the state. These forests are managed for recreation, ecological diversity, and resource extraction (timber harvest), but the effects of silvicultural practices employed here are generally unknown for rattlesnakes.
From 2016–2020, we captured and tracked timber rattlesnakes using VHF radiotelemetry to measure their habitat use in the context of disturbance-mediated changes to forest structure from past silviculture treatments and timber harvest. We also extensively monitored snakes during spring egress and fall ingress with radiotelemetry and game cameras to better understand spring and fall phenology and quantify their risk of exposure to prescribed fire. Finally, we surveyed Ohio residents during 2020 to measure their tolerance for rattlesnakes in Ohio and test psychological models of tolerance commonly used to better understand tolerance and risk acceptance of large, predatory mammals.
We tracked 43 timber rattlesnakes multiple times per week for time periods ranging from a month to up to three years. Snakes at our study site disproportionally used warmer parts of the landscape with greater solar radiation, higher mean tree basal area (larger trees), and more disturbance (lower canopy height). However, behavior and physiological state strongly mediated this trend with snakes selecting warmer and more heavily disturbed sites when thermoregulation was a priority (e.g., gestation, ecdysis) and more moderate temperatures when foraging. We also evaluated forest structure and composition metrics commonly used in the silvicultural decision support system SILVAH, but most (tree diversity, oak dominance, total DBH, total basal area) were not good predictors of site use. However, snakes were more likely to use sites with relatively low tree density, along upper slopes and on ridges making both relative tree density and ELTP (Ecological Land Type Phase) good predictors of snake site use.
We were also able to model rattlesnake ingress and egress at our site using meteorological variables, but day of year was the most important variable in the model with temperature also having a modest effect on fall and spring phenology. Though the beginning of the state’s fall burning season (October 15th) overlapped aboveground activity, on average, for about half of our telemetered snakes, there was relatively little aboveground snake activity prior to the end of the spring burning season (April 15th). Additionally, we used our model to retrospectively predict the risk of exposure for rattlesnakes in southern Ohio during 12 previous prescribed burns and found that risk of exposure, on average, was low (< 30%) for a snake located within a burn unit.
Finally, we collected 447 responses from our survey of Ohio residents’ attitudes toward rattlesnakes and were able to predictively model tolerance for rattlesnakes in Ohio using a psychological model of wildlife tolerance. However, our model only predicted the acceptable population level for rattlesnakes in Ohio (wildlife stakeholder acceptance capacity) but did not effectively predict acceptance or stewardship. Respondents were more likely to tolerate larger rattlesnake populations if they perceived more benefits and fewer risks from the presence of rattlesnakes. Their perceptions of risks were negatively affected by their attitude toward rattlesnakes and positively affected by their domination-
oriented wildlife values and their perceptions of benefits were positively associated with their attitude toward rattlesnakes.
This research has generated the largest and most detailed dataset on any Ohio rattlesnake population and provides insight into their management. Timber rattlesnakes had relatively broad habitat associations and seemed to be minimally affected by past and present land use practices. In fact, we found that snakes were more likely to use sites with a recent history of canopy disturbance, likely due to thermoregulatory benefits. Our observations indicate most snakes do not emerge from hibernacula until after the close of Ohio’s burn season (April 15th) and snakes out before this date are more likely to be sheltered and at lower risk from fire. Ongoing forest management activities are therefore unlikely to negatively impact rattlesnake populations.
However, intolerance of rattlesnakes in Ohio and resistance to their conservation may present a more substantial barrier to recovering the species in the future. Although sound land management should ensure the stability of remaining populations, broader population recovery in Ohio will be difficult without outreach efforts aimed at reducing intolerance for these now rare snakes.