Student Research Projects

Aspects of Natural History of the Arboreal Harvestman Cynorta Marginalis

Student Tatyana Zvonareva, '16
Faculty Mentor(s)
Department Biology
Course BIO 489: Research

Abstract

Relatively little is known about the natural history of the cosmetid harvestmen that inhabit the forests of Central America. The primary objective of my field research project was to investigate habitat use and social interactions among adults of the arboreal cosmetid harvestman Cynorta marginalis. My study was conducted from 11-24 August 2015 in the forests surrounding the La Selva Biological Station in Costa Rica. I established 15 different transects (40 m in length) and sampled them repeatedly in the morning (0830-1100 hrs) and after dusk (1800-2300 hrs). Over the course of two weeks, I captured and marked 258 adults, including 146 males and 112 females. Only three individuals were recaptured over the course of the study. Heavy rains occurred during several sampling periods (13 out of 80 transect samples) and appeared to reduce harvestmen surface activity (0.9 individuals per transect during heavy rain vs. 3.6 individuals per transect when dry or lightly raining). Harvestmen were most commonly observed using leaves as perches (64% of captures), but they also used tree trunks, branches and, rarely, the leaf litter (1.5%). Most individuals (85%) were found alone, however, I did observe several harvestmen in male-female pairs (8%), or in same sex pairs or heterosexual groups (7%). Of the 258 individuals captured, 18 exhibited injuries to their legs. Injured males (n = 8) used perches that were lower (mean = 125.9 cm) and narrower (mean = 163 cm) than uninjured males (means = 133.5 cm and 195 cm, respectively). Injured females (n = 10) occupied perches that were higher (mean = 138.2 cm) and narrower (mean = 158 cm) than uninjured individuals (means = 126.2 cm and 212 cm). These results indicate that there is significant intersexual variation in habitat use and that leg condition also impacts the selection of perches by adults of this species.

Conferences

Annual Meeting of the Association of Southeastern Biologists