Abstract:
Achatina fulica, which is found in all homegardens in many parts of Sri Lanka is an
invasive, alien molluscan species. This snail is considered as a destructive pest in crop
lands and homegardens as it feeds on live and dead plant matter. It is also important as
an intermediate host in transmission of parasites and its empty shells is important as
mosquito breeding sites. The size of the snail population will greatly influence the
amount of damage and it is determined by factors such as the availability of food,
moisture, CaCC>3 and temperature extremes. The present study was designed to
investigate whether there is any relationship between density and abundance of A. fulica
and available food sources and to identify the effects of rainfall and soil moisture
content on A. fulica abundance and density in study sites. Four abandoned lands
(Sl;150m2, S2:400m2, S3;250m2, S4: 400m2) at Walgama in Matara district were
selected as study sites. At each study site, the data on temperature, soil moisture content
and percentages of available food souces and number of snails were collected in twelve
months period from February, 2010 to January, 2011. The population size of snails was
estimated by placing ten random replicate quadrates (50cmX 50cm) at each site at 6.00
a.m. in each month and, by counting the numbers in-situ. Abundance and density of A.
fulica in four study sites were estimated. Soil moisture content was determined in
percentage by comparing the weight of the soil samples at the time of collection with
their weight in oven-dry condition at 105°.-110° C. SPSS-16 statistical software package
was used to analyse the data. According to the results, density and abundance of A.
fulica in all study sites were significantly different (P<0.05) and the highest mean
density and thehighest mean abundance were recorded in Site 3(0.92/m2&«2.0
rspectively). The soil of Sitel had the highest moisture content. But the mean density
and mean abundance values were 0.85/m2 and 1.91 respectively. The lowest mean
density and lowest mean abundance values were found in Site 4. The types available
food sources for A. fulica were herbs and wines, large trees and dry leaves eventhough
the available amounts were diferent in all four sites. About 90% of area in Site 3, where
the highest mean density and abundance were recorded, was covered with herbs and
wines. It is concluded that A. fulica may prefer green herbs and wines than dry leaves
or large trees. Therefore, this invasive, alien snail species can be controlled by clearing
abandoned lands.
