Research Training Program

Robert Anderson
Kansas State University
Manhatten, Kansas

Charles O. Handley, Jr., Ph.D.
Project Advisor
Department of Vertebrate Zoology
Division of Mammals

"The RTP is a great chance to see a big group of dynamic scientists in action. In addition, the research is tremendously stimulating. I learned many skills and ways to apply theories to go about conducting a research project."

Taxonomy of the Sloths of Bocas del Toro, Panama

The islands of the Panamanian province of Bocas del Toro are landbridge islands in shallow coastal waters formed by rising sea level over the last 10,000 years. The fauna of the islands includes relict species as well as species which have differentiated from the mainland stock during their time of isolation. This study examined pelage and cranial characteristics of three-toed sloths, Bradypus, collected on the islands and mainland of Bocas del Toro. The discrete pelage and cranial characters were examined and a morphometrical study of cranial anatomy was conducted employing both bivariate and multivariate statistical analyses of the measurements taken. The data show that no relicts exist, but that the sloths of five of the islands have differentiated from the minland stock, primarily by becoming smaller. Discrete cranial characters also serve to separate some island populations from the mainland Bradypus. Through similarities in pelage characteristics it appears that these populations have differentiated separately, under similar changes in selection pressurers, which may include a poorer diet or the absence of predators found on the mainland, an example of parallel evolution. At this point all three-toed sloths from Bocas del Toro are classified as Bradypus variegatus Schniz.

This research was supported by a grant from the National Science Foundation Research Experiences for Undergraduates (Award: BIR-9300225).