Population Size, Plant Occupancy and Threats to Acavus in Three Selected Homegardens in Kandy District, Sri Lanka

Abstract

Acavus is an endemic genus of arboreal land snails, widely distributed in south west wet zoneof Sri Lanka. Acavus consist of three species, Acavus haemastoma, Acavus superbus andAcavus phoenix with two subspecies Acavus phoenix phoenix and Acavus phoenix custaneus.Although Acavus is an endemic Gondwanan relict there are only few studies carried out onthese snails, especially focusing homegardens. Homegardens serve as islands of habitatsmaintaining a considerable portion of Acavus. The objectives of the study are to estimate thepopulation size of Acavus, to study the tree species commonly occupied by Acavus and toidentify the threats to Acavus in homegardens in Kandy district. Study was carried out inthree homegardens (each with about 60 perches) in Kahalla, Pilimathalawa and Gampola forsix months from February to July 2013. All the sites harboured Acavus phoenix custaneus.Each site was visited twice a month and total count of Acavus and tree species they occupiedwere recorded. Threats to Acavus also observed in the field. Sites that were studied showedbasic characters of Kandyan homegardens. According to the results, population sizes ofAcavus of the sites are as follows, Kahalla 181, Pilimathalawa 40 and Gampola 117. Of theAcavus observed highest percentages were observed associated with following tree species,Areca catechu (24.29%), Artocarpus heterophyllus (15.91%), Cocos nucifera (12.78%),Michelia champaca (7.78%), Persea Americana (5.35%), Musa spp. (3.31%), Coffea arabica(2.87%), Gliricidia sepium (2.57%), Caryota urens (2.52) and Artocarpus altilis (1.92%).Rest of the Acavus observed was distributed in a variety of other tree and shrub species. Inhomegardens Acavus is threatened mainly by greater coucal (Centropus sinensis),occasionally by toque monkey (Macaca sinica), shrinking of homegardens (as they pass fromgeneration to generation) and unawareness of public. It is clear that the presence of certaintree and shrub species supports the survival of Acavus in homegardens and sustainable use ofsuch flora will help to maintain healthy Acavus populations.