Case Study #2: Monitoring amphibian (anuran) species abundance in Western Belize
Question: Does local site management succeed in protecting Red-eyed Tree frogs (Agalychnis callidryas)?
(i.e., are the conservation benefits of this monitoring site considered to be increasing or decreasing over time or are they stable?)
Background: As part of the MAYAMON Anuran monitoring protocol, a site at the Green Hills Butterfly Ranch is being monitored for frog species.
One of these sites, designated 'Mayamon CD1', is a small artificial pond shaded by trees of secondary growth.
This site is monitored by a member of BERDS who enters the annual monitoring data into the BERDS online monitoring database.
Solution: Compare total number of observed Red-eyed Tree Frogs for each year at 'Mayamon CD1' site. Since every year may not have the same amount of monitoring events, but each event follows the same protocol,
one needs to divide the annual specimen count by the number of monitoring events for that year.
Time: 10 minutes
Method: Monitoring results are only accessible to the data's owner and other members of the BERDS system.
- Login to the BERDS system
- Click on the 'Data Manager' link in the Toolbar
- Select the Monitoring section on the Data Manager page. [Only available to Members, not Data Providers]
- Select the 'Temporal Distribution' link in the 'Query & Report Generation' section of the page
- Select a Monitoring Site (in this example, 'Mayamon CD1') and click [Go]
- On the following page, select a species (in this example, Agalychnis callidryas) and click [Go]
- On the following page, enter the data range in the Long Time Frame section and click [Go] (in this example, 1997-01-01 to 2004-12-31)
- View your results
Images: See the figure below.
Results: The system presents 2 graphs, one displays annual data showing number of specimens recorded per year (not shown here). Lines connect annual data, points indicate months with data.
More useful for this case study is the second graph (shown below) which displays annual data indicating number of specimens recorded per year divided by the monitoring effort undertaken to record those specimens (events per year). This provides a relative measurement of annual change in species occurrence at this locality.
The graph shows an increase from 1997 through 2000. After year 2000, species abundance appears to drop.
Conclusions:
This result appears to indicate that initially, local conservation management benefited the Red-eyed Tree frog, but since 2000, the abundance of Agalychnis callidryas appears to decline, possibly indicating negative changes in site conservation management.
The site is surrounded by trees of secondary growth (see 'Monitoring Site' description for details) and the fluctuations in species abundance could also be the consequence of ongoing regeneration of the habitat. Perhaps, this species is less inclined to use this site for breeding purposes as the habitat matures. If the Red-eyed Tree Frog was an important conservation element (e.g., an indicator species) however, this trend could be reason for alarm.
Other actions needed:
Validate these data by incorporating rainfall data. Tree frog reproductive activity is strongly dependant on rainfall and dry/wet years could be expected to affect counted individuals for any given year.
Amphibian decline can also be the result of disease: Check to see if the the database mentions illness or dead specimens associated with Site Visit Reports for the Mayamon CD1 site? If so, this could be a reason for the decline.
Compare results for other anuran species at the same monitoring site. Do they follow the same pattern or are they different? If they follow the same pattern, a general decline in the overall quality of the site may be suspected. As well, there could be a drying trend leading to the decline in abundance numbers.
Amphibians are notorious species for their strong population fluctuations. Continuous monitoring will be required to monitor the progress of this population.
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