Status: 

Completed

Title

Frog population plots (El Verde and Bisley)
Summary

DOI: 

10.6073/pasta/ca064a3573e75f4b688d89a5392d2df5

Short name: 

LUQMetadata44

Data set ID: 

44

Abstract: 

Population records were compiled for the tropical frog, Eleutherodactylus coqui, by conducting four-night censuses of four 20 X 20 m long-term study plots in the Luquillo Experimental Forest of Puerto Rico between 1987 and 2017.

Dates
Date Range: 
1987-01-02 00:00:00 to 2007-12-30 00:00:00
People

Additional Project roles: 

Name: Eda Melendez-Colom Role: Data Manager
Methodology

Methods: 

Mark-multiple-recapture during four-night census of four 20 X 20 m plots. Frogs were located visually between 2000 - 2400 h using headlamps. Adults (≥25 mm) were captured and measured to 0.5 mm with dial calipers. Each was permanently marked by clipping a unique combination of toes. Sex and reproduction condition were noted. Detailed information on methodology can be found in Woolbright 2005 Herpetological Review 36:139-142.

Additional information: 

From a written communication of the owner:

Study plots were established in the El Verde study area in 1987 and in the Bisley study area in 1988. Four-night census of the plots were conducted through 2011 at the Bisley site and through 2017 at the El Verde site. Basic methods remained constant throughout the study: time-constrained one hour searches of each plot, not counting handling time for marking and measuring frogs. The goal was to restrict all searches to the peak activity hours of 2000 – 2400 h. For most of the study that allowed the two plots at a study area to be censused on the same night. However, with peak frog numbers during the period after Hurricane Hugo, it was necessary to search only one plot per night and sometimes that took longer than four hours because of handling time. Census was generally done twice a year, but the frequency increased after Hurricane Hugo to detect the nature of the response, and also during some sabbatical years. Likewise, frequency was lower during periods with other time conflicts.

Information content collected on individual frogs increased during the early years of the study. At first I made no attempt to determine the gender of small frogs (less than about 32 mm SVL). Those frogs are labelled “s” for subadult until about 1993 at which time I started guessing at their gender (M or F) based on body type. I also denoted with a “?” frogs that were too big to be labelled “s” but for which I could not detect either vocal sac or eggs. I noted calling males and gravid females from early on and denoted them with a number 3 in their capture record. By 1993 I had developed a system of recording each capture as a 1, 2, or 3. Status 1 indicates that I was uncertain of the gender and could be wrong. Status 2 indicated good evidence of gender (visible small eggs in females and discernable vocal sacs in males). Status 3 continued to indicate active participation in the breeding population (large eggs judged ready to be laid in females and active calling by males). Thus a mature male might be a 3 one night and a 2 the next, depending on whether he was observed calling. Likewise a female with small eggs might be a 1 on a night when they were not visible through the body wall and a 2 on a night when they were. Data were not retroactively adjusted for frogs that were captured in subsequent field seasons: if I judged a frog to be a female 1 one season and then saw it calling the next (male 3), I did not go back and change the prior record.

A note is needed on the comparability of body size measurements. In field seasons that include Woolbright as one of the data collectors, I did all marking and measuring myself, and those body sizes should be directly comparable for such purposes as calculating growth rates of individuals. Care should be taken not to use body sizes taken by others for such purposes. Although I did train all field assistants who collected data in my absence, and thus their measurements should give at least a reasonable approximate of adult size patterns for that season, I have discovered that it is nearly impossible to train people well enough to ensure that they will get the exact same measurements that I do.

Throughout most of the study, populations were low enough that there were no surviving frogs left with low numbers by the time I had used all the numbers up and needed to start over. Therefore the same number system (0001-4444) was used many times over the 30-year study with no concern about confusing the current frog with the same toe clip from the previous cycle. However, after Hurricane Hugo with an increase in both the frog population density and the frequency of census, that was not the case. So in those years I added two additional series of numbers in which I clipped a thumb (the medial 5th toe on the rear foot). The frogs with the thumb clipped on the fourth (“ones”) foot were designated o (e.g., 2321o) and those with the thumb clipped on the 3rd (“tens”) foot were designated t (e.g., 4223t). When a clipping error or natural mark (such as the result of a predation attempt) resulted in two toes being shortened on the same foot, I put those two digits in parentheses such as 21(23)2. For other natural marks like deformities or missing limbs, I typically just used an abbreviated description of the feature. “Old mark” in the comments column indicates that the frog in question was marked in a previous field season. Those frogs are listed in numerical order at the end of the list of new marks for that season.

Status: 

Completed

Time Period: 

Long-Term