New research reveals that traditional management efforts for New England cottontail, which relied on the best available science, may actually be thwarting their recovery Wildlife conservation is frequently limited by an incomplete understanding of how animals interact and respond to native ecosystems--a limitation that is only further challenged by the many novel factors, like invasive species or habitat fragmentation, that alter the way in which species interact with their environment. Although it is in the best interests of threatened species for us to thoroughly investigate these relationships, obtaining specific information is often difficult due to cost, low population size, lack of technology, or the evasiveness of the species in question. In these circumstances, we rely heavily on what information we do have; though it may be incomplete, applicable across only a narrow environmental niche, or unable to account for critical changes to the environment from, for example, the introduction of new competitor or spread of invasive plants. When information is lacking, scientists are forced to rely on the “best available science.” For many species, the best available science may be studies conducted across only a narrow portion of a species’ niche, research from closely related species, or based on ecological theory. Because there isn’t more relevant research, this best available science is then used to inform policy decisions, like whether to list a species as Threatened or Endangered under the U.S. Endangered Species Act. This information is also used to decide how to conserve species and spend conservation dollars. But nature is messy. Species often react to their environment in unexpected and complicated ways –a situation that is particularly common when there have been changes to their environment. Unfortunately, when this happens, applying the best available science can result in policies that are ineffective, or worse have unintended negative consequences. Such unintended effects seem to have arisen in the case of the imperiled New England Cottontail, as suggested by new research by Amanda Cheeseman and her colleagues, published this month in Ecology and Evolution. A decade of conservation efforts relied on best available science, targeting the creation of early successional shrublands to recover New England cottontails. While these shrublands provide a lot of shrub cover, known to be important for New England cottontails, they are often dominated by invasive plants and may not mimic the natural habitat of New England cottontails. Further, recent studies have shown that New England cottontail are excluded from these restored patches by the eastern cottontail, an introduced competitor. These issues raised the question of whether early successional shrublands are providing habitat for New England cottontails or just supporting eastern cottontails. Cheeseman and colleagues sought to address these questions using half a decade of trapping and radio tracking data on New England cottontails and eastern cottontails, looking at how habitat affects their survival and population density. This new research reveals that we’ve missed the mark on managing landscapes for New England cottontail recovery. The studies on which we have based our conservation actions were conducted largely in the absence of eastern cottontails and invasive plants; however, where they are present New England cottontails fare poorly, having both low survival and low population density in the early successional shrublands that have been a conservation focus. Meanwhile, these targets have been generally beneficial to eastern cottontails that proliferate under these conditions. It turns out that where eastern cottontails and invasive shrubs are present, later successional and persistent shrublands, such as those found in forested heathlands or shrubby wetlands, are strongholds for New England cottontails. Eastern cottontails not only appear to avoid these shrublands, but they also do not thrive in these conditions when they are present suggesting management for these shrublands is a promising way forward in recovering New England cottontail populations without promoting their non-native competitor. In addition to identifying changes to what habitat is managed for NEC recovery, the authors pointed to the need to conserve areas between habitat patches. The study underscored that habitat fragmentation is an important barrier to New England cottontail dispersal. They found that when New England cottontails were forced to travel long distances between habitat patches, they were far more likely to die, most likely due to a predator. And if that weren’t hard enough, juvenile New England cottontails have parasites to contend with. Tick infestations dramatically lowered the survival of certain juvenile rabbits. By necessity, conservation actions must be enacted with incomplete knowledge. Collecting more data is not always possible and often conservation interventions are needed immediately to try to save an imperiled species. However, this means that managers risk making well-intended decisions that are ineffective or even detrimental to the species they’re trying to protect. In the case of the New England cottontail, management based on “best available science” --which has been enacted at considerable expense to state and federal agencies over the past decade--has not reversed the alarming pace of population decline. This new research suggests that for New England cottontails, in many areas, the enacted conservation actions were unlikely to be beneficial over short time frames and may have even had detrimental impacts on populations since they reduced survival and density of New England cottontails while helping their competitor, the eastern cottontail. These findings are a cautionary tale for conservation--we must strive for a thorough understanding of the systems we manage and evaluate species’ responses to our actions. In a world where conservation funding is limited but uncertainty is high, taking actions in an experimental manner rather than putting all of one’s eggs in one basket built on incomplete knowledge is prudent.
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AuthorAmanda is an Assistant Professor at South Dakota Sate University. Her research focuses on conservation and management of wildlife and their habitats Archives
October 2023
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