This entry I'll explain more about the frog counting (as I promised in my first entry), one of the activities I'll be doing on the expedition to Puerto Rico.
You might remember that I will be a volunteer on this expedition. That means the Researchers who will be leading the expedition have all the knowledge and technical expertise, the volunteers will just be following orders and learning as we go. :-) But we have been given a good briefing pack as an introduction, and I've been doing my own research on the topics, so what I write is my understanding on what I have learnt so far.
There are 7 objectives of this expedition. Since the frog counting seems to be the most intriguing, lets start with Objective 5 & 6:
Continued monitoring of the frog population
and Complete a Herpetological* Survey the forest area and collect a baseline data set
* Any guesses what Herpetological means?? Its not that hard I promise!
Frogs are very important and special animals when it comes to monitoring the stability of an ecosystem. They are considered 'bioindicators' as they have complex life cycles and their skin is permeable to gases and liquids. A decline in the frog population will tell if the ecosystem is out of balance and give a signal of general environmental problems. Also it will have an impact on other insects and plants populations.
The frog population in the forest follows the 80/20 rule, meaning the amphibian diversity tends to be high in species, but low in genus, ie many of one type of frog. For example, of the 170 species of frogs found in the Caribbean islands, 80% of them are the Coqui frog, Eleutherodactylus.
Out of interest, the species that have been observed at Las Casas de la Selva:
- Leptodactylus albilabris Common Name: White Frog, White Lipped Frog
- Elutherodactylus coqui Common Name: Coqui frog, Common Coqui
- Elutherodactylus wittmanae Common Name: Coqui, Coqui Wittmanae
- Anolis pulchellus Common Name: Grass Anole
- Anolis christatellus christatellus Common Name: Puerto Rican Crested Anole, Garden Lizard
- Anolis krugi Common Name: Krug’s Anole, Olive Bush Anole
- Anolis gundlachi Common Name: Yellow Chinned Anole
- Anolis evermanni Common Name: Emerald Anole
- Anolis stratulus Common Name: St. Thomas Anole
- Arrhyton exiguum Common Name: Puerto Rican Racer
- Sphaerodactylus nicholsi Common Name: N/A (gecko)
The picture above is of the white frog, their croak sounds like this.
A picture of the coqui frog and its croak can be found in my previous blog entry.
The questions I received about the frog counting is: We would like to know how you are going to find and count all the frogs, they are tiny and jump around so much?
Good question! Well the method that we will do is the following:
Step 1: Preparation of plot
10 areas will be selected for the study. In each area six 10m x 10m (100m2) quadrants (plots) will be established. Plots will be marked off using PVC piping for plot corners and florescent plastic flagging tape for plot borders.
Step 2: Observing the environment
Before the study begins, the following information will be collected for each plot:
- Elevation
- General Habitat description (What kind of forest, open, with or without streams, topography, etc)
- All species of trees in each plot
- All species of undergrowth shrubs in each plot
- Start/End time
- Start/End temperature
- Start/End humidity
Step 3: Moving through the forest and counting
The volunteer team will be divided into two groups.
a) The first group will advance through the plot, focusing on the ground level and inspecting all leaf litter on the floor in order to observe the species (Coqui, Sphereodactylus, etc). So literally we will be on our hands and knees, crawling through the forest during the night.
b) The second group will advance behind the first, focusing on the understory and canopy trees in order to observe arboreal species (anoles).
For each observation the following will be noted:
- Species that has been seen
- Gender (for reptiles)
- Total Length Snout to vent (SV) length (for reptiles)
- Phenotypes (observable characteristics)
- Behavior
- Microhabitat (must be descriptive enough to include the species of tree/plant, if applicable)
- Insolation
- Interaction with other species (if applicable)
- Position
Some of the frogs will be as small as the one above!
Step 4: Estimating Totals
Using the data collected the population sizes and densities will be estimated using scientific methods, specifically those of Heckel, and Roughgarden & Schnabel.
The sites are not closed population size (ie the frogs can jump around!!) and density may be high so it will no doubt be challenging to count them all. :-) But the research methods will be applied consistently so the resultant data will be valid for comparative purposes.
The research methods can generate reasonably accurate estimates based on data collected in short periods of time, and the Heckel and Roughgarden method was designed explicitly for this purpose.
Step 5: Finally, calculating the Biodiversity Levels
The total biodiversity of each plot, ie the range and variation with regards to reptile and amphibian populations, will be determined using a special formula called the Simpson’s Diversity Index.
The Simpson’s index uses the number of species present, as well as the relative abundance of each species, to quantify the level of biodiversity of a given area. The final number ranges from 0 to 1, where 0 means no diversity and 1 means infinite diversity.
So there we have it, a little insight into how Frog Counting will be done!
