10 



NORTH AMERICAN FAUNA 75 



in 1978 as an OTS student and has continued to work at the station and to bring 

 students from his classes there. 



T. H. Fleming studied the rodent fauna in 1970 and 1971. The number of 

 small mammals, including marsupials, known from La Selva increased greatly dur- 

 ing this period (Fleming 1973). At the same time, large mammals were observed 

 more frequently as the number of trained observers increased. 



During 1973 and 1974, LaVal sampled the bat fauna intensively using both 

 mist nets and harp traps. His efforts dramatically increased the number of species 

 known to occur at La Selva, several of which were new to the country (LaVal 

 1977; LaVal and Fitch 1977). 



Information on all mammals has continued to accumulate with OTS's continued 

 sponsorship of courses at the site and with the increased number of resident and 

 visiting researchers. A log book is maintained to record mammal sightings, and 

 considerable information has accumulated over the years. Likewise, our knowledge 

 of the entire mammalian fauna of Costa Rica has increased tremendously since 

 Goodwin's (1946) faunal study. Our estimate of the country's terrestrial mammalian 

 fauna is more than 200 species. With 114 species, La Selva contains more than 

 half the mammalian species known to occur in Costa Rica. 



A 12-day scientific expedition to the Zona Protectora in 1983 made a pre- 

 liminary evaluation of the resources there and estimated 800 species of trees and 

 400 species of birds. The expedition recorded 17 species of frogs and toads, 



27 species of reptiles, and 18 species of mammals. Expedition members found 



28 new plant species and 12 others not previously known from Costa Rica (Pringle 

 et al. 1984). 



With this information in hand, a more extensive expedition organized by the 

 Organization for Tropical Studies began on 25 March 1986 and covered a transect 

 from the La Selva Biological Station to the top of Volcan Barva (Fig. 1). The team 

 of researchers included mammalogists, botanists, entomologists, herpetologists, 

 invertebrate zoologists, and ornithologists, who studied various aspects of the 

 biological richness and uniqueness of this area. This report covers only the mam- 

 mal survey, the objectives of which were to determine general distributions and 

 relative abundances of mammal species along the altitudinal transect between La 

 Selva (30-137 m) and Volcan Barva (2,906 m). 



We have not addressed the biogeographic affinities of this mammalian fauna 

 since several recent reviews treat the biogeography of Costa Rican mammals from 

 a variety of perspectives. Timm (in press) and Wilson (in press) treat the biogeo- 

 graphic relations of the mammalian fauna of La Selva, McPherson (1985, 1986) dis- 

 cusses the biogeography of Costa Rican rodents, and Savage (1974) provides an 

 interesting review of the Isthmian Link and the evolution of Neotropical mammals. 



