Long-term Amphibian Monitoring Project at Huntington Wildlife Forest

Debora Endriss

Background
Amphibian species have been monitored for several years at Huntington Wildlife Forest, a research station in the central Adirondack Mountains operated by the State University of New York College of Environmental Science and Forestry. In order to prevent their skin from drying out, amphibians prefer wet places and are constantly interacting with water. Since amphibians exchange gases and water through their skin, they are extremely sensitive to pollution and may be the first group to show signs of stress due to degrading environmental conditions. Therefore, the status of amphibian populations in an area is a good indicator of the environmental condition of that region.
Amphibians are particularly sensitive to acidic precipitation. Many amphibians breed and lay eggs in water, often in vernal pools or beaver ponds, and therefore the crucial stages of development of tadpoles and larvae occur in the water. Vernal pools are small, temporary bodies of water that form in early spring due to snowmelt, heavy rainfall, and/or upwelling of ground water and dry up by the middle or end of summer. Because they are seasonal bodies of water, vernal pools do not contain fish and are therefore an ideal location for tadpoles and larvae to develop free of fish predation. Vernal pools are of specific interest because they often have higher acidity than other permanent bodies of water in the same area because snowmelt and rain entering pools in early spring serve as an "acid shock." Wood frogs and spotted salamanders are two species that breed in vernal pools.
Amphibians are also sensitive to climatic fluctuations and increased solar ultraviolet radiation. Some effects of these environmental problems on amphibian populations are decreased mobility, abnormal embryonic and larval development, and changes in the timing of reproduction, development, or hibernation. The objectives of our study were to gather information on the 1) relative abundance of species and distribution at HWF, 2) reproductive success of wood frogs and 3) amount of effort needed to gather this information. The three methods we used to monitor amphibians were egg mass searches with drift fences, cover objects, and visual encounter transects.

Methods

Egg Mass Searches/Drift Fences
In early spring, we searched vernal pools in HWF for wood frog and spotted salamander egg masses. Data was also collected on the physical characteristics of the pools. The first time a pool was visited the percent canopy cover was measured, the type of bottom substrate was recorded (i.e., mud/silt, vegetation, dry leaves), and the percent of emergent vegetation and cyanobacteria were estimated. Every time a pool was visited the length and width was measured, the 4 deepest depths were recorded, and pH and temperature was taken at the edge and the center of the pool. Finally, the time and the species, number, and if possible sex of any adult amphibians at the pool was noted.
We drift fenced pools to measure reproductive success. Each drift fence was 4 meters long and consisted of 3, 0.5 m tall, PVC pipes, nylon rope, 4 mil clear plastic, 3, 15 by 15 cm., buckets, and plastic funnels. We covered 20% of the perimeter of each pool with drift fences and the total number of metamorphs captured at each pool was multiplied by 5. The buckets were checked daily before noon and the number and species of any amphibians found in the buckets was recorded.

Cover Objects
There are 32 sets of cover objects at HWF. At each site there are 4 arrays, each consisting of 6 bricks, placed 2-3 meters away from a center pole in each cardinal direction. All salamander species found under the bricks and in the leaf litter above the bricks were recorded. The number of prey species (spiders/mites, centipedes, millipedes, snails, springtails,isopods, beetles), and presence of ants, fungus, and holes was noted. The first time the bricks were checked, each salamander was weighed with a hand held spring scale and body length was measured.

Visual Encounter Transects
There are 21, 76.2 meter long, visual encounter lines on lakes, ponds, and streams at HWF. Two people walked each line parallel to the shore or stream, the first person about 2 meters below the edge of the water and the other person 2 meters above the edge of the water. If possible, frogs were caught and identified; otherwise frogs were identified by sight. Time start, time end, and the percentage of cloud cover was recorded for each transect line.

Results

Egg Mass Searches/Drift Fences
In 2001, we mapped 87 vernal pools and beaver ponds on the southern half of HWF. Of 55 pools, 22 contained wood frog egg masses and 31 contained spotted salamander egg masses. The maximum number of wood frog egg masses found was 69 and the maximum number of spotted salamander egg masses found was 270.
Physical characteristics were consistently measured at 23 vernal pools. The average maximum area for these pools was 213 + 42 m2 and ranged from 6 m2 to 1135 m2. The average pH for these pools at the initial measurement was 5.5 + 0.1 and ranged from 4.9 to 6.1. The average temperature for these pools at the initial measurement was 55.1 + 0.9 F and ranged from 49.5 to 67.0 F. The average percent canopy cover was 72 + 5% and ranged from 17 to 100%. The average maximum depth was 51 + 5 cm. and ranged from 31 to 162 cm. We drift fenced 7 pools. The estimated total number of wood frog metamorphs emerging from each pool was 0, 90, 100, 105, 725, 2675, and 3445.

Cover Objects
Cover objects were visited 5 times in 2001. We found an average of 0.34redbacked salamanders, 0.35 dusky salamanders, 0.03 two-lined salamanders, and 0.04 red efts per site .
Visual encounter transects were visited 3 times in 2001. The average number of frogs per transect ranged from 0.5 to 13.7 (n=20). A total of 262 frogs were found. Forty-one percent of the frogs found were green frogs, 9% were pickerel frogs, 6% were bullfrogs, 3% were mink frogs, and 40% were unidentified frogs.

Implications
The egg mass counts, physical characteristic measurements, and drift fences provided substantial data. However, since they required a lot of effort, it may not be feasible to continue these methods every year. If possible, these methods will be repeated every few years.
The cover objects provided significant data and required little effort. If possible this method will be continuously used. In the future, data may be collected on the vegetation, soil, and proximity of water around the cover object sites.
The visual encounter transects required a lot of effort and yielded little significant data because of the high percentage of unidentified frogs. This was due to the difficulty of catching for identification all frogs encountered on the transect lines. This method may not be used in future years.

Contact Information
Adirondack Ecological Center- aechwf@esf.edu
Debora Endriss- daendris@syr.edu

About The Author: Debora Endriss
I am currently a B.S. student at SUNY-ESF studying Wildlife Biology. I am interested in the effects of fragmentation and pollution on amphibian populations. In the future, I hope to become involved with wildlife conservation issues in foreign countries.