USGS Science Supporting 50 Years of the Endangered Species Act Active

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Black-footed Ferrets 

To increase populations of endangered black-footed ferrets and conserve the prairie dogs they rely on for survival, it is essential for land managers to control disease outbreaks. The USGS National Wildlife Health Center (NWHC) develops various disease management tools, including vaccines.  

The SARS-CoV-2 virus, the cause of the COVID-19 pandemic, is known to infect and cause severe disease, such as respiratory distress and death, in mustelids, including farm-raised mink and domestic ferrets. This raised concern that the virus may also pose a threat to endangered black-footed ferrets managed in captivity for breeding and recovery purposes. 

A preliminary vaccination trial against SARS-CoV-2 was completed in captive black-footed ferrets to assess safety, immunogenicity, and anti-viral efficacy.  Scientists saw a significant rise in mean antibody titers against the virus, about 150-fold that of pre-vaccination titers.  

Scientists with the NWHC and the University of Wisconsin - Madison developed a sylvatic plague vaccine to help control outbreaks of plague in prairie dog communities. Sylvatic plague can decimate prairie dog populations, which in turn affects the recovery of endangered black-footed ferrets that depend on prairie dogs for food. Protecting wildlife from plague and reducing spread of the disease can also help people and pets that are susceptible to infection. 

Whitebark Pine 

Whitebark pine is an ecologically and culturally important high-elevation conifer. It has been recognized as a foundation species in high-elevation montane ecosystems in the Pacific Northwest and Rocky Mountain due to its importance in promoting snowpack accumulation and retention, facilitating vegetative establishment, and providing a critical food source for a variety of wildlife. 

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However, there is great concern about the future viability of whitebark pine forests due to extensive tree mortality associated with a highly aggressive exotic pathogen, white pine blister rust, and extensive outbreaks of the native mountain pine beetle linked to a warming climate.  

Managers tasked with supporting and maintaining the viability of whitebark pine into the future need information on how whitebark pine forests respond to climate and other disturbances throughout its geographic range. 

Tree growth and resin-based defenses play a crucial role in defending whitebark pine against conifer bark beetle interactions. The relationship between resin ducts and climate in higher-elevation, energy-limited ecosystems is currently poorly understood. 

USGS scientists evaluated the relationship between biological trends in tree growth, resin duct anatomy, and climatic variability to determine if tree growth and resin duct morphology of whitebark pine is constrained by climate and/or regional drought conditions. 

Their results suggest that whitebark pine growth and defense was historically limited by short growing seasons in high-elevation environments; however, this relationship may change in the future with prolonged warming conditions. 

Hawaiian Honeycreepers 

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The iconic forest birds of Hawai‘i are facing a conservation crisis. Across the Hawaiian Islands, native forest birds have been experiencing population declines that have accelerated in the last one to two decades.  

While habitat loss, invasive species, and non-native predators have negatively affected forest bird species for hundreds of years, and continue to do so, introduced diseases, particularly avian malaria, are the greatest threat to forest birds today. Further, climate change has increased temperatures in the high-elevation forests, facilitating the spread of disease into areas that were once largely disease-free.  

Rapid population declines have pushed four Hawaiian honeycreeper species to the brink of extinction: the endangered ‘akikiki and ‘akeke‘e on Kaua‘i Island, and kiwikiu and ‘ākohekohe on Maui Island.  

To help evaluate alternative conservation strategies for minimizing the risk of extinction, the USGS gathered experts with broad experience in Hawai‘i forest birds and ecosystems, as well as the management approaches being considered, to assess the probability of success of alternative management actions. In addition to assessing this crisis from a biological perspective, we convened a group of Native Hawaiian participants that have a strong connection to the forest birds, forests, and the integration of their culture in natural and biocultural resource management. They gave voice to the significance of forest birds to Native Hawaiians and provide their perspectives on alternative management actions.   

The expert evaluations were summarized in a report and provide a broad assessment of conservation strategies that could be undertaken to prevent the extinction of the four Hawaiian honeycreepers.  

Colorado Pikeminnow 

Native fish within the Upper Colorado River Basin, like the endangered Colorado Pikeminnow, encounter many threats, including invasive species, habitat degradation, and streamflow alterations.  

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Mercury and selenium contamination is known to be elevated in some fish species of the Upper Colorado River Basin. To understand the potential threats that these contaminants may have on the long-term viability of managed fish populations, USGS scientists compiled 50 years (1962–2011) of mercury and selenium tissue concentrations for native and nonnative fish collected during previous studies within the Upper Colorado River Basin.  

Mercury and selenium concentrations varied by species and by location within the watershed. Concentrations of mercury and selenium were above health benchmarks in 13 and 48 percent of individual fish, respectively, and some species of management concern, such as the federally endangered Colorado pikeminnow and the candidate roundtail chub, accumulated mercury above health benchmarks. The Colorado pikeminnow and the razorback sucker had selenium concentrations that exceeded the selenium benchmarks.  

The data and knowledge gaps identified in the study can be used to guide research and monitoring to address the effects of mercury and selenium on endangered species populations and recovery. 

California Tiger Salamanders 

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Endangered California tiger salamanders must cross roads to reach essential breeding and foraging habitat and are slow moving or are too small for drivers to see and avoid. These behaviors put them at high risk of vehicle collisions 

USGS researchers investigated how the salamanders interacted with different types of barrier fencing while migrating to their annual breeding site and whether they were able to find and use an under-road tunnel passage system. 

They found that the probability of a salamander reaching a passageway decreased rapidly as distance from the tunnel increased. They estimate that with a maximum of 12.5 meters between passages, approximately 90% of adult salamanders are likely to encounter road crossings. The materials that the barrier fences were made of also made a difference: the salamanders moved more efficiently along solid fencing than along mesh fencing without a visual barrier. 

These considerations can assist those seeking to design effective road mitigation for California tiger salamander and other migratory amphibians and reptiles. 

The research was conducted in collaboration with Caltrans, the Western Transportation Institute, Herpetofauna Consultants International Ltd, Stanford University, the US Forest Service, and the California Department of Fish and Wildlife.