What the Amphibians are Telling Us and Why We Should Listen.
We’ve all heard the news – worldwide, amphibians including frogs, toads and salamanders, are in decline. In fact, research from a 2004 report documents that 33 percent of amphibian species across the globe were threatened and approximately 43 percent were declining. In addition, amphibians on U.S public lands disappeared from 3.7 percent of the places where they lived each year between 2000 and 2010. If that annual decline continues, it would result in amphibians disappearing from half the places they live in about 30 years.
Why do amphibians matter?
Amphibians are a very old group of animals, existing before and alongside the dinosaurs. As a group, amphibians are fairly resilient to environmental changes. Thus, recent declines raise serious concerns for amphibians, but also for the environment we share with them. Most amphibians use aquatic habitat for part of their life cycle, with eggs and tadpoles that develop in water. Both amphibian eggs and skin are highly permeable, allowing water and oxygen to pass directly and be absorbed internally. The combination of these two biological characteristics makes them especially vulnerable to changes in habitat quality and pollutants.
Here at the U.S. Fish and Wildlife Service, we are very concerned about these declines in amphibians. Current research shows us that competition with other species, pollution, disease, habitat loss, parasitism, predation, UV radiation, climate change, and combinations of these stressors, are all factors contributing to the worldwide decline of amphibians.
Amphibians play essential roles, both as predators and prey, in their ecosystems. Adult amphibians eat pest insects, including those pests that damage crops or spread disease. Amphibians also have important functions in the food webs of both aquatic and terrestrial systems. Amphibians consume aquatic vegetation, as well as invertebrates and other vertebrates. In the absence of fish, amphibians are usually the top predators in freshwater systems. However, amphibians are also an important food source to numerous predators, including snakes, fish, birds, mammals, and other insects and amphibians. Consequently, amphibians influence the populations of other species in their ecosystems.
So what is the Service doing to conserve amphibians? We have numerous research and conservation initiatives across the country, and even internationally, to help identify the causes of decline for amphibians and implement conservation actions to help them recover.
Researching amphibian abnormalities
In 2013, the Service announced the results of an unprecedented 10-year-study, published in PLOS ONE, on amphibian abnormalities on national wildlife refuges. The Service found that on average, less than 2 percent of frogs and toads sampled on 152 National Wildlife Refuges had physical abnormalities involving the skeleton and eyes—a lower rate than experts feared based on earlier reports. This indicated that the severe malformations such as missing or extra limbs repeatedly reported in the media during the mid-1990s were actually rare on national wildlife refuges. However, there were a few hot-spot clusters that had higher rates of abnormalities. One of these hot spots was at Kenai National Wildlife Refuge in Alaska.
As part of the follow-up research on this hot spot cluster, the Service worked with researchers from Alaska Pacific University and the University of California at Davis to understand how and why there were higher rates of abnormalities. They found that wood frog tadpoles were attacked by dragonfly larvae 30 minutes sooner and three times more often in warm, slightly polluted water treatments, than in cooler, pollution free treatments. The experiments simulated the effects of degraded water quality due to road runoff and climate change. The researchers videotaped the interactions of the tadpoles and dragonfly larvae under various water temperature and copper exposure treatments to watch how the animals’ behavior affected their interactions. The tadpoles in the experiment spent more time at the surface of the water making it easier for dragonfly larvae to see and attack them. The dragonfly larvae exerted the least amount of energy to capture more tadpoles in the warm, polluted water treatment. The increased predation observed in this study supports previous research and could also help explain the prevalence of malformed frogs in some National Wildlife Refuge hotspots.
Chiricahua leopard frog conservation
The Chiricahua leopard frog is a threatened species that can be found in streams, ciénegas, cattle ponds and other wetlands in the high valleys and mountains of southeastern Arizona, southwestern New Mexico, eastern Sonora and western Chihuahua, Mexico.
The Service’s Arizona and New Mexico Field Offices have been working with a wide variety of private and public partners and stakeholders to implement recovery actions for Chiricahua leopard frog conservation. Great strides have been made through captive head starting and breeding programs, including the Phoenix Zoo, which has been hatching wild egg masses and rearing tadpoles for release since 1995; the “Ranarium”, which is an outdoor breeding and head start facility operated by Turner Endangered Species Fund; and several other small-scale breeding and rearing facilities run by BLM, Forest Service, Western NM University, Fort Worth Zoo, and the New Mexico Field Office.
The main threat to the Chiricahua leopard frog is the predation by non-native, introduced bullfrogs, fish and crayfish. As more southern Arizonans build homes closer to natural wetlands and mountain canyons, these non-native pests are escaping from garden ponds and golf course lakes and spreading to wild areas. Once these animals are established, it is very difficult and expensive to remove them from natural wetlands. To combat the nearly overwhelming impacts from non-native species on Chiricahua leopard frogs, biologists with our Arizona Field Office are working with numerous partners to inform and educate the public about these non-native species and how to create habitat that protects the native frog.
Columbia spotted frog conservation
The Great Basin population of Columbia spotted frogs, currently a candidate species for Endangered Species Act protection, is found in eastern Oregon, southwestern Idaho, and the northern drainages of Nevada. Spotted frogs live in spring seeps, meadows, marshes, ponds and streams, and other areas where there is abundant vegetation flooded throughout the year. The largest known threat to the Columbia spotted frog is habitat alteration and loss, specifically the loss of wetlands used for feeding, breeding, hibernating, and migrating. Habitat loss and degradation is mostly due to recent drought conditions, diversion of natural spring flows, wetland degradation, water diversions, road construction, dam construction, fire, and loss of native beavers.
Service biologists are working with our partners to monitor current spotted frog populations to assess population trends and distribution, and also improve and create habitat throughout the Great Basin to prevent the frog’s further decline.
For example, our Reno Field Office in Nevada had a 10 year Conservation Agreement and Strategy for the Toiyabe Mountains and Northeast populations of Columbia spotted frogs, to coordinate monitoring and implement conservation measures to alleviate stressors to the species. Through implementation of the Conservation Agreement and Strategy, 36 ponds were created in central Nevada and all ponds have documented occupancy with 77 percent having breeding activity. And in Idaho, a Candidate Conservation Agreement with Assurances was completed to improve breeding, foraging, dispersal, hibernating habitat, and migration corridors for Columbia spotted frogs at Sam Noble Springs while allowing continued livestock use on these state lands. In addition, 41 ponds were constructed or enhanced on private lands in Idaho to increase breeding habitat and connectivity between existing populations. The Malheur National Wildlife Refuge recently completed a Comprehensive Conservation Plan which includes numerous activities aimed at improving aquatic health on the refuge, including 6 goals that will directly benefit Columbia spotted frogs.
Active monitoring, research, and habitat improvement projects are occurring or are planned throughout the entire range of the Great Basin population of Columbia spotted frogs, which are increasing our knowledge of life history characteristics, population fluctuations, effectiveness of habitat improvement projects, genetics, and stressors to the species.
Research on Ozark hellbender reproductive health
The federally endangered Ozark hellbender is a large salamander that spends its life in clear, cool spring-fed streams, under large rocks or in crevices. Drastic declines have occurred in populations of the Ozark hellbender since the 1970s, and experts are still working to understand reasons for the salamander’s decline. One of the tools we are working on with our partners to increase the population of hellbenders in a captive breeding program at the St. Louis Zoo.
One factor potentially contributing to hellbender population decline is the sperm health of male hellbenders. Endocrine disrupting compounds, which have been shown to alter normal reproductive development in various aquatic species, have been detected in streams occupied by Ozark hellbenders. Although concentrations of these compounds were lower than EPA standards to protect aquatic life, biologists questioned whether the presence of these or other undetected compounds might be interfering with successful fertilization of eggs.
To address this question, our Columbia Missouri Ecological Services Field Office collaborated with the Missouri Department of Conservation to assess the sperm health of wild Ozark hellbenders. Since 2010, Service biologists have captured Ozark hellbenders during the breeding season and assessed the rates of motility (percentage of moving cells), viability (percentage of live cells), and concentration of sperm samples.
Preliminary results indicate that Ozark hellbenders are producing healthy sperm, with viability and motility rates approaching 100 percent in some instances. In addition, males used in the breeding program at the Saint Louis Zoo have been assessed and also appear to have healthy sperm. Although exact causes behind Ozark hellbender declines continue to remain unclear, these results certainly bode well for captive breeding efforts and for natural reproduction in the wild.
Crawfish frog research and restoration
Big Oaks National Wildlife Refuge in southeastern Indiana and its partners are working to understand the habitat requirements and breeding preference of crawfish frogs, a species that is rapidly declining throughout much of its range. While not federally listed as endangered or threatened, this species is susceptible to drastic population declines due habitat loss and habitat alterations. This frog requires a combination of grassland habitat, ephemeral breeding wetlands, and crayfish burrows, which limit the number and location of reestablishment sites.
It is believed that historically, crawfish frogs were associated with grassland and savannah habitats; specifically, the flooded bison wallows as breeding wetlands. In southern Indiana, it is probable that crawfish frog populations persisted along the buffalo trace where millions of bison migrated from the Midwest prairies to Tennessee. This highly disturbed environment suited the crawfish frog’s ability to quickly colonize newly created wetlands. Since then, much of the frog’s habitat has been converted to row crop agriculture and its ephemeral wetlands drained or their hydrology drastically altered. We have even documented historical breeding areas where their ephemeral breeding wetlands were converted to permanent marshes for waterfowl or their burrow retreats destroyed by agricultural practices, especially plowing practices that destroy the crawfish burrows.
In an effort to increase population levels at Big Oaks National Wildlife Refuge, refuge staff initiated a number of research projects during the 2004-2015 field seasons. Crawfish frogs can lay approximately 5000 eggs per pair of breeding adults, so the opportunity to help crawfish frogs make a comeback on the landscape is tremendous. Initial modeling identified focus areas for breeding pond construction where quality grassland habitat existed but populations were absent. Combining this with the results from an early pilot project investigating how experimentally drained ponds increased crawfish frog use and reduced their predator and competitor communities, enables staff to better design and construct breeding wetlands to improve the management of this species. To date, we have restored and installed water level management devices in 16 new crawfish frog breeding wetlands in grassland focus areas. Initial monitoring of these breeding wetlands has shown newly established populations, increased breeding adult use, and increased numbers of juvenile frogs on the landscape. The success of this management regime could be replicated to restore populations in appropriate habitat to stabilize population declines throughout their range.
North Atlantic LCC is mapping sites that offer the best chance of conserving amphibians
There is a strong relationship between climate and the distribution of species that depend upon external sources of heat for survival, like amphibians. So it is reasonable to believe that climate change may have especially strong effects on these animals. The best defense against this threat is to pinpoint and manage sites that can offer the best habitat for the most vulnerable species even as temperature changes. By combining climate change projections with information on the natural history and distribution of a number of priority reptiles and amphibian species, the North Atlantic Landscape Conservation Cooperative funded Priority Amphibian and Reptile Conservation Areas project is identifying geographic areas that offer the best opportunity to sustain these species now and in the future. The resulting maps will help guide long-term ecological planning and management to ensure that the North Atlantic region continues to offer a home for these species, and others, even if our climate changes.
International Amphibian Conservation
The Service also administers Amphibians in Decline, the only federal government program dedicated to funding research and conservation of amphibians around the world. Through this fund and other programs, the Service is actively involved in a number of projects specifically targeting amphibians. This includes research in the United States and overseas into the chytrid fungus, widely recognized as one of the most serious and widespread threats to frogs globally; protection of key habitat for threatened frog species such as the golden matilla in Madagascar; invasive species control for species such as the rough moss frog in South Africa; and community education programs. In 2012, the fund distributed $121,000 in grants, leveraging an additional $263,000 in matching partner contributions.
So as you can see, the Service is very concerned about the issues and stressors affecting amphibians across the country, and the globe. As competition with other species, pollution, disease, habitat loss, parasitism, predation, climate change, and combinations of these stressors, are contributing to precipitous declines in amphibians, we are working to position our agency to help address these complex issues into the future. Conserving amphibians not only helps frogs, toads and salamanders, but conserves clean water and healthy ecosystems for other plants, animals and humans.