The poison-dart frog, Dendrobates pumilio, highly mysticised but rarely studied, exhibits complex parental behaviors. Prior to Maura Maple’s work, there has been no documented research done on the predation upon D. pumilio (Maple, pers. comm.). Donnelly (1989a, 1989b) has done several studies on D. pumilio with emphasis on reproduction and feeding patterns. According to Donnelly, the female exhibits "nurse-like" behaviors and transports her tadpoles to water filled leaf axils. Maple expanded upon Donnelly’s studies, which found that females deposit their eggs in bromeliads (Donnelly, 1989a) to find that they were also present in Dieffenbachia ssp.

Donnelly (1989a) suggested that further studies focusing on parental care need to be conducted. Maple began her study five years ago, emphasizing parental care and selection of placement of tadpoles to best ensure survival. As a portion of this parental care study, Maple examined predation factors.

In assisting Maple with her research, we hypothesized that female frogs would deposit their tadpoles in the larger bromeliad species. We felt the larger water capacity would be beneficial for movement and defense.

Methodology

Assisting in a Ph. D. dissertation, our group helped measure and consolidate gathered data, for researcher Maura Maple. Beginning with bromeliads that had been previously gathered we removed debris from the petals and axils using spatulas and running water. The leaves of the bromeliads were marked and the plants were identified in regards to their activity. If there were ctenid spiders or tadpoles in a leaf axil, that axil was automatically selected. Random axils were also chosen for a minimum of six axils per plant. The volumes of water were collected for each of the marked leaves. The liquid was pipetted into shallow bowls and measured in cubic centimeters.

After drying the bromeliads we prepared the plants for the molding process. The molds were made in the leaves that had been previously marked. The markings were made because the axils of the plants had once held ctenids and/or tadpoles. Random axils were also chosen; we used six leaves on each of the plants. Wax was heated and pipetted into the axils and allowed to cool and dry for further lab process.

We cored the bromeliads and removed the leaves that had not been used in the molds, the leaves were totaled and recorded. The mold pattern was traced on the six leaves and removed. The leaf was then measured for length, width (at the top of the mold and the bottom), and length of the tracing (at the top of the mold and the bottom).

The length of the mold was measured at the front and back, and the measurement was taken from the center of each mold. The top of the mold was also measured. Tracing the top of the mold, cutting it out, and running it through a leaf area meter derived the surface area in square centimeters.

A count, as well as a few samples of ctenids was conducted on diffenbachia in a transect measuring 1500 square meters, to determine if the ctenids frequented areas where tadpoles are typically found.

Gathering more information by going to the field, we measured the volume of water capacity from plants that had been previously studied and mapped out. Our group pipetted and measured the liquid from the leaves. The leaves were chosen from those that had been previously marked and additional leaves were also randomly chosen. Because Maple had marked priority plants, we focused on them first. After the volume was gathered from the critical plants, two random plants were chosen and the volume collecting process was repeated. The bromeliads were categorized according to size: small, medium, and large and alpha-species.

Several spiders that represented each type that been seen to prey on tadpoles were gathered, identified, and measured. The spiders were measured at their cephalothorax and abdomen.

 Due to the limited nature of the participation of our assistance in this continuing investigation, the results identify only a portion of the actual study being conducted. The graphs below depict some of the data we researched:

Maple chose two species of Bromeliads in her research, Bromeliad A and Bromeliad 6; Bromediad A being the smaller of the species. They were then classified according to size within their species (small, medium and large). Additional results yielded the correlation between spider presence and tadpole presence in the two species. Finally, a survey to determine preference between bromeliad and diffenbachia plants by tadpoles and ctenids was also conducted.

Discussion

During the brief observations conducted throughout this investigation, we found that the female frogs chose to place her tadpoles in the smaller species of bromeliads. Additionally, the assumed predator, (as predicted by Maura Maple) the ctenid spider, was more prevalent in the larger species of bromeliad. The data proved to not be conclusive towards our hypothesis and therefore is rejected. Further exploration of the relationship between ctenid and tadpole placement needs to be completed.

The significance of size and shape of bromeliad axils and the correlation to parental care choice will be determined by the calculations of the compiled data. Maura will be analyzing the data as part of the final step of her doctoral dissertation.

Applications for the classroom

Math and science kinesthetic as well as cognitive skills could be transferred from this project to the classroom. For math, measuring skills could be incorporated such as: caliper manipulation, volume calculation, data table construction, and graphing creation. For science, inquiry methodologies could be utilized to explore the interrelationships and interactions among local plants and animals, or animals and animals. This could help in the understanding of the concepts of biodiversity and the importance of species conservation.

Literature Cited

Donnelly, Maureen A. 1989. Effects of reproductive resource supplementation on space use patterns in Dendrobates pumilio. Oecologia 81:212-218.

Donnelly, Maureen A. 1989. Reproductive phrenology and age structure of Dendrobates pumilio in Northeastern Costa Rica. Journal of Herpetology 23(4):

Maple, Maura. 1999. Personal communication