Seed handling by three prosimian primates in southeastern Madagascar: implications for seed dispersal

In this paper, we studied three species of prosimian primate (Propithecus diadema edwardsi, Eulemur fulvus rufus, and Eulemur rubriventer) from June-July 1995 at the Ranomafana National Park to answer three questions: 1) how they handle and process seeds, 2) how the physical properties of seeds influence seed handling and seed fate, and 3) whether handling and processing patterns influence seed dispersal. Seeds from five plant species were collected from feces and examined for external damage (punctures and scrapes), weighed, measured, and checked daily for germination. P. d. edwardsi masticated seeds into two or more pieces while feeding. Seed fragments were either dropped under the parent tree or chewed and swallowed; seeds never emerged as recognizable units in feces. In contrast, both Eulemur species either dropped or swallowed seeds whole while feeding. E. rubriventer passed seeds that were longer, wider, and heavier than seeds passed by E.f. rufus. Although seeds emerged as separate units when passed by both Eulemur species, 65 Protorhus sp. seeds were scraped and/or punctured prior to being swallowed. Based on physical property tests, Protorhus seeds were more susceptible to mastication than undamaged seeds from Eugenia sp., Cissus sp., and Chrysophyllum madagascariensis. H. madagascariensis seeds also were undamaged but had physical properties comparable to Protorhus and may avoid being masticated due to their small size (2-3 mm). All damaged seeds were moldy or rotten within 6 days, and only 15% of the undamaged seeds passed by E. rubriventer germinated. None of the seeds passed by E.f. rufus germinated. Eulemur species also rested in the same tree after feeding and defecated prior to a new feeding bout or before moving, so seeds were most likely to be dispersed under the parent tree. Consequently, we concluded that these primate species do not appear to serve as effective seed dispersers for these plant species at this time of year.