Threatened & Endangered Species

Science Center Objects

Science on threatened and endangered species often includes challenges in counting rare animals or in resolving human-wildlife conflicts.  Our research is focused on measuring populations and managing species in spite of these challenges, and working with agency biologists who must manage populations under competing priorities for habitat use.


Lower Keys marsh rabbit (Sylvilagus palustris hefneri - LKMR)

Lower Keys marsh rabbit (Sylvilagus palustris hefneri) (Public domain.)

Assessing Endangered Marsh Rabbit and Woodrat Habitat use and Predator Population Dynamics

 Feral and free-ranging domestic cats (Felis catus) have strong negative effects on wildlife, particularly in island ecosystems such as the Florida Keys. We deployed camera traps to study free-ranging cats in National Wildlife Refuges and state parks on Big Pine Key and Key Largo and used spatial models to estimate cat population dynamics and stable isotope analyses to examine cat diets. Top models separated cats based on movements and activity patterns and represent feral, semi-feral, and indoor/outdoor house cats. We provide evidence that cat groups within a population move different distances, exhibit different activity patterns, and that individuals consume wildlife at different rates - all of which have implications for managing this invasive predator. 


West Indian manatees, Trichechus manatus

(Public domain.)


Modeling, Estimation, and Adaptive Management of Florida Manatees

Florida manatees are threatened by watercraft-related mortality, the potential loss of warmwater habitat, red tide events, and other anthropogenic factors. The USFWS and the Florida Fish and Wildlife Conservation Commission have regulatory authorities under the Endangered Species Act (ESA), the Marine Mammal Protection Act (MMPA), and state statutes to recover manatees. To support management decision-making, these agencies need quantitative assessments of population status.



Polar Bear, Ursus maritimus

(Public domain.)


Adaptive Management for Threatened and Endangered Species

Threatened and endangered species have to be managed in the face of uncertainty, but traditionally, there has been reluctance to think about adaptive management of listed species. Management agencies with responsibility for threatened and endangered species need tools to help manage in the face of uncertainty, with the hope of reducing that uncertainty..









Banded whooping crane and mate observed during fall migration in central Kansas.

Banded whooping crane and mate observed during fall migration in central Kansas. (Public domain.)

Whooping Crane Restoration

At more than five feet tall with brilliant white plumage, black primary feathers, a red cap, and yellow eyes, the highly endangered Whooping Crane (Grus americana) is one of the most spectacular birds native to North America. In 1942 there were fewer than 20 birds in the flock that migrates from Wood Buffalo National Park in Canada to Aransas National Wildlife Refuge in Texas. An additional six cranes were alive in Louisiana, bringing the total global population to only 22 individuals. The non-migratory Louisiana flock died out a few years later; hence all Whooping Cranes now alive derive from a core flock of only 16 birds. Whooping Cranes were likely uncommon even before hunting and habitat loss reduced them to dangerously low numbers. The vanishingly small population of 16 in 1942 represents an extreme genetic and demographic bottleneck that few species survive.



Colorbanded Roseate Tern, Sterna dougallii

Colobanded Roseate Terns that can be identified repeatedly at distances up to 50 meters or more are providing a wealth of new information about the movements, behavior, and population dynamics of this endangered species. (Public domain.)

Modeling Sex-specific Demographic Rates in Metapopulations

Research that integrates population dynamics and ecological studies is needed to identify the causal factors involved in population declines and viability. For highly mobile organisms such as birds, “between-patch” movements and the use of different geographic sites and habitats at various stages of the annual cycle can make it difficult to measure the effectiveness of “within-patch” site-specific management activities. These local restoration activities must be evaluated within the context of overall population changes on a regional or metapopulation scale. The major objective of this study is to develop new multistate capture-recapture/resighting and ultrastructural models to examine sex- and age- specific regional survival, movement, and recruitment rates. Once developed and tested with data collected from a long-term regional metapopulation study of a suitable species, these general types of models can be adapted for widespread use on a variety of other species.


Staging HY ROSTs still need parental care

Roseate Terns (Public domain.)



Evaluation of Potential Offshore Wind Projects in the Northeastern U.S. on Endangered Roseate Terns: Who is at Risk and When?

Terns in coastal areas of the Northeastern US likely will be impacted by construction and operation of offshore wind turbines. The “Cape Cod & Islands” (CCMA) area of Massachusetts is a particularly important area for the endangered Northwest Atlantic Roseate Tern (ROST) population as most ROSTs from throughout the breeding range (Nova Scotia to Long Island, New York) congregate there in large numbers for several months during the postbreeding staging period prior to fall migration to South America. To properly evaluate the risk to this species we need to learn more about the timing of use of the staging sites by ROSTs of different ages/breeding status.


Banding a Least Common Tern Chick

A member of the field crew holds a recently banded least tern chick, displaying both its metal permanent band and its plastic field readable band. (Public domain.)




Productivity of Species of Concern – Least Tern and Common Tern on Poplar Island Restoration Site

Concern has been raised over productivity of two important tern species that have colonized Poplar Island Environmental Restoration Project (PIERP): the Maryland state-listed Least Tern (Sternula antillarum) and Common Tern (Sterna hirundo). Over the 14 year monitoring period at PIERP (beginning 2002), hatching and fledging success of these species has been variable, believed to be linked with natural stressors including avian and mammalian predators and severe weather events.

Ducks eating brine flies

(Credit: Ian Thomas, US Fish and Wildlife Service. Public domain.)




Survival and Reintroduction of the Laysan Teal

The Laysan Teal is an endangered, endemic, Hawaiian dabbling duck that has been pushed to the brink of extinction numerous times. The previous range includes the Main and Northwestern Hawaiian Islands, and its current range is less than 10 sq. km within the National Wildlife Refuges of Papahānaumokuākea Marine National Monument. This non-migratory waterfowl was eliminated from all the Hawaiian Islands except for Laysan by the 1860’s through anthropogenic effects (i.e., introduced rats, shipwrecked mariners, etc.). The Laysan Island population was threatened when guano miners inhabited the island, hunted the duck, and introduced rabbits, devastating the native habitat until they were removed in 1923. Presently, extreme events (e.g., tsunamis, hurricanes, drought, or flooding), disease (e.g., Avian Botulism), sea-level rise, accidental predator or competitor introductions, are ongoing threats to this duck’s survival.





Shenandoah Salamander (Plethodon shenandoah)

(Public domain.)


Managing the Extinction Risk of the Shenandoah Salamander

In many National Parks organisms at high elevation are severely threatened and may be sensitive to changes in temperature and moisture gradients in the Appalachians, which may result in species extirpation in high elevation habitats. Many species are specifically adapted to the unusual conditions typical of high elevation sites; risks of extirpation increase as conditions change. Compounding the risk is the extraordinarily small range of many high elevation species; such is the case with the endangered Shenandoah salamander.







Endangered Karner blue butterfly, Lycaeides melissa samuelis

(Public domain.)


Estimation of Density and Abundance of Biological Populations on National Parks and Wildlife Refuges Through Distance Sampling

Assessing the status and trends of populations of biological organisms is an important management goal and a recurrent theme in USGS research. Often, the most basic question of “how many are there?” remains elusive, thus making management decisions more difficult. This study continues a long-term commitment of technical support for the use of distance sampling for wildlife population abundance estimation in our National Parks and Wildlife Refuges.








Researchers on cliff face investigating the effects of climbing on rare cliff plants.

Researchers on cliff face investigating the effects of climbing on rare plants (Public domain.)


Assessing Recreational Impact to Cliff Habitats and Rare Plants

The Potomac River Gorge, managed by the National Park Service in Virginia and Maryland, is a highly accessible protected natural area bordered by the intensively developed Washington metro region. The Gorge is biologically rich, with more than 400 occurrences of over 200 rare species. Potomac Gorge receives exceptionally heavy visitation, with nearly two million visitors recorded in 2000. This research assesses visitor impacts to its numerous and extensive cliffs, which include several miles of cliff-associated hiking trails and over 410 climbing routes (over 17,210 lineal feet) along a 4-mile stretch of the Potomac River. The Great Falls Park and Carderock crags are the premier climbing areas in the DC Metro region.




American Holly Forest

(Public domain.)


Conservation of Rare Vegetation Communities of the Atlantic Coastal Barrier Islands

A synthesis of the role of disturbance, in all of its manifestations, on the establishment and development of the American Holly forest is required to guide future conservation measures. Because many forest fragments have already endured >30 years of chronic deer herbivory, a legitimate question of how much more impact by deer can be tolerated and still conserve the essential type and character of the maritime forest remains unanswered.