USGS - science for a changing world

Amphibian Research and Monitoring Initiative

ARMI » Topics » Monitoring and Population Ecology

Monitoring and Population Ecology

K. Cecala (ARMI) sampling a stream in Shenandoah NP for salamanders. Photo by: E. Grant.

Advances in technology (e.g., PIT tags) have allowed scientists to individually mark more types of species than ever before, and concurrent developments in biometrics have allowed scientists to ask more types of questions about animal populations under more circumstances. Some of these developments have been particularly useful when estimating parameters about amphibians, a group that can be difficult to sample (e.g., multiple life stages, small size, difficult to mark, high juvenile mortality).

These developments in marking and estimation have allowed scientists to ask specific questions about the effects of potential stressors or beneficial management actions on amphibian populations, and quantify these responses.

ARMI Products on Monitoring and Population Ecology

* USGS neither sponsors nor endorses non-USGS web sites; per requirement "3.4.1 Prohibition of Commercial Endorsement."
* PDF documents require Adobe Reader or Google Chrome Browser for viewing.

This is an ARMI Product. Declines revisited: long-term recovery and spatial population dynamics of tailed frog larvae after wildfire
Authors: Hossack BR, Honeycutt RK | Outlet: Biological Conservation
Drought has fueled an increased frequency and severity of large wildfires in many ecosystems. Despite an increase in research on wildfire effects on vertebrates, the vast majority of it has focused on short-term (<5 yrs) effects and there is still little information on the time scale of population recovery for species that decline in abundance after fire. In 2003, a large wildfire in Montana (USA) burned the watersheds of four of eight streams that we sampled for larval Rocky Mountain tailed frogs (Ascaphus montanus) in 2001. Surveys during 2004?2005 revealed reduced abundance of larvae in burned streams relative to unburned streams, with greater declines associated with increased fire extent. Rocky Mountain tailed frogs have low vagility and have several unusual life-history traits that could slow population recovery, including an extended larval period (4 yrs), delayed sexual maturity (6?8 yrs), and low fecundity (<50 eggs/yr). To determine if abundance remained depressed since the 2003 wildfire, we repeated surveys during 2014?2015 and found relative abundance of larvae in burned and unburned streams had nearly converged to pre-fire conditions within two generations. The negative effects of burn extent on larval abundance weakened >58% within 12 yrs after the fire. We also found moderate synchrony among populations in unburned streams and negative spatial autocorrelation among populations in burned streams. We suspect negative spatial autocorrelation among spatially-clustered burned streams reflected increased post-fire patchiness in resources and different rates of local recovery. Our results add to a growing body of work that suggests populations in intact ecosystems tend to be resilient to habitat changes caused by wildfire. Our results also provide important insights into recovery times of populations that have been negatively affected by severe wildfire.

This is an ARMI Product. Amphibian dynamics in constructed ponds on a wildlife refuge: developing expected responses to hydrological restoration
Author: Hossack BR | Date: 2016 | Outlet: Hydrobiologia
Management actions are based upon predictable responses. To form expected responses to restoration actions, I estimated habitat relationships and trends (2002‒2015) for four pond-breeding amphibians on a wildlife refuge (Montana, USA) where changes to restore historical hydrology to the system greatly expanded (≥8 times) the flooded area of the primary breeding site for western toads (Anaxyrus boreas). Additional restoration actions are planned for the near future, including removing ponds that provide amphibian habitat. Multi-season occupancy models based on data from 15 ponds sampled during 7 years revealed that the number of breeding subpopulations increased modestly for Columbia spotted frogs (Rana luteiventris) and was stationary for long-toed salamanders (Ambystoma macrodactylum) and Pacific treefrogs (Pseudacris regilla). For these three species, pond depth was the characteristic that was associated most frequently with occupancy or changes in colonization and extinction. In contrast, a large decrease in colonization by western toads explained the decline from eight occupied ponds in 2002 to two ponds in 2015. This decline occurred despite an increase in wetland area and the colonization of a newly-created pond. These changes highlight the challenges of managing for multiple species and how management responses can be unpredictable, possibly reducing the efficacy of targeted actions.

Content image.
S Dykman  
This is an ARMI Product. Large-scale recovery of an endangered amphibian despite ongoing exposure to multiple stressors
Authors: Knapp RA, Fellers GM, Kleeman PM, Miller DAW, Vredenburg VT, Rosenblum EB, Briggs CJ | Date: 2016-10-03 | Outlet: Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.1600983113 | Format: .PDF
Amphibians are one of the most threatened animal groups, with 32% of species at risk of extinction. Given this, is the disappearance of a large fraction of the Earth’s amphibians inevitable, or are some declining species more resilient than is generally assumed? We address this question in a species that is emblematic of many declining amphibians, the endangered Sierra Nevada yellow-legged frog (Rana sierrae). Based on >7,000 frog surveys conducted across Yosemite National Park over a 20-year period, we show that after decades of decline and despite ongoing exposure to multiple stressors including introduced fish, the recently emerged disease chytridiomycosis, and pesticides, R. sierrae abundance increased 7-fold during the study and at a rate of 11% per year. These increases occurred in hundreds of populations throughout Yosemite, providing a rare example of amphibian recovery at an ecologically relevant spatial scale. Results from a laboratory experiment indicate that these increases may be due in part to reduced frog susceptibility to chytridiomycosis. The disappearance of nonnative fish from numerous water bodies following cessation of stocking also contributed to the recovery. The large-scale increases in R. sierrae abundance we document suggest that when habitats are relatively intact and stressors are reduced in their importance by active management or species’ adaptive responses declines of some amphibian may be partially reversible, at least at a regional scale. Other studies conducted over similarly large temporal and spatial scales are critically needed to provide insight and generality about the reversibility of amphibian declines at a global scale.

Accessibility FOIA Privacy Policies and Notices logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: ARMI Webmaster
Page Last Modified: Tuesday, June 27, 2017