|Amphibian Biomonitoring||Creating the Context: Research Methodology|
Results of Study
Results of Study
Training in Identification
It is very important that data collectors be familiar with the calls of local frogs and toads. Calls that are available on this website and commercially available tapes should be used to teach data collectors what calls to listen for. Information necessary for local anurans should include the range for each species as well as basic information on their natural history. Successful completion of a listening test given to each data collector to verify the observer's abilities should occur before going into the field.
Sampling Area Selection
We recommend that a stratified, randomized method be employed to determine sampling locations. Differentiate between a large "area" of similar habitat (e.g., a large bog several hectares in size) and a large area with several discrete but similar habitat types or "basins" (e.g., many farm dugouts - water-filled pits used as watering holes - across a large agricultural landscape) that are to be surveyed. To better sample rare or highly specialized anurans in some regions, further stratification beyond a general approach to placing points at wetlands may be needed. The easiest way to accomplish this would be to identify section roads. Section roads are the roads that occur every mile and were (are) laid out in a grid. Stopping every .5 mile along this road would be a good sampling technique. Recorded with a directional microphone and a tape recorder all calling species at each stopping point. Each data collecting group should follow a different road.
Wetland breeding sites for amphibians come and go. It is to be expected that some sites will be better over time (for example, beaver activity may form a new pond), and others will disappear (for example, under a new shopping center parking lot). The stops should not be changed to incorporate new sites or eliminate sites that are no longer available. This is important because even if the main wetland is destroyed, other water sources, such as water control pits and drainage ponds, may still provide suitable frog habitat. Under unusual circumstances it may be possible that new forms of wetland may be developed where none formerly existed. If these new wetlands occur in places that were not initially determined to be within the realm of possible wetland locations (for example, the creation of new cattle tanks in upland areas that previously did not support anuran populations), then it should not be incorporated until the survey has been statistically adjusted to account for this new habitat. A review of wetland trends every 5 years should catch any such changes.
Data Gathering and Timing:
The number of detection's of new species rapidly falls off after the first minute of listening time (Shirose et al. 1995). Time for an individual survey stop along a route has been set at three minutes. Observers can listen for up to two minutes longer than the initial three minutes if noise from traffic, etc., is interfering with the ability to hear calls. We also advise volunteers to wait (quietly) one minute after arriving at the point and then begin the three-minute survey. This will reduce the effect any disturbance made by the volunteers' approach may have had on anuran calling.
The frequency of surveys must be tailored to capture the seasonal differences in calling rates of anurans in the observers particular region. Some rare species, species that call very late in the evening, species that call underwater, or species that don't call at all would not be expected to be adequately monitored in an extensive survey conducted within two hours after sunset. Driving surveys should be conducted at a minimum of once every two weeks during the breeding season. These should be begin in February and continue to June 1.
The current approach is:
On each survey, the observer must record:
Habitat Data should include:
Data to be kept as Local Data may include:
Sample Analysis for Species Richness and Diversity
The following examples will guide your work in calculating Species Richness and Diversity.
Blanchards Cricket Frog - 15
Gray Treefrog- 5
American Toad - 8
Northern Spring Peeper -3
Southern Leopard Frog - 6
Mean = (15 + 5 + 8 + 3 + 6)/5 = 7.4
Species Richness = total number of species found = 5
Calculating Diversity using the Simpson Diversity Index
Calculate the proportion of the total number of amphibians of each species (Pi).
To calculate the Simpson Diversity Index = 1 - sum(Pi)2
Using the example above, you have 15 cricket frogs, 5 gray treefrogs, 8 american toads, 3 spring peepers, and 6 leopard frogs. You would calculate:
Diversity Index = 1- ((15/37)2 + (5/37)2 + (8/37)2 + (3/37)2 + (6/37)2)
This index ranges from zero to one and is literally a measure of the probability that two amphibians taken at random from the sample are different species. A number close to zero means low diversity and it is likely you will get the same species of amphibian and a number close to one means high diversity.
|1999, KanCRN Collaborative Research Network|