Abstract
The distribution, abundance, size distribution and diurnal activity patterns of invasive land snails, Theba pisana, in the West Coast National Park (WCNP), South Africa, were investigated. The park was divided into 1 km2 grids, within each of which five 1 m2 quadrat counts of live snails were recorded. Of 106 grids sampled, 19% contained live snails. The average density of snails was 4.04 m-2 ± 24.9, significantly lower than in disturbed habitats adjacent to the park (57 m-2 ± 96.25), but very high densities were recorded at two sites. Snails were most abundant along roadsides and densities decreased dramatically with distance from roads. T. pisana in the WCNP appear to have an annual lifecycle, breeding in autumn to winter and growing to adult size of about 14 mm diameter by the end of the following summer. Snails were observed on a wide variety of endemic and introduced plant species and appeared to have a catholic diet. They are active mostly at night and especially during periods of high humidity, irrespective of temperature. Given the very high densities that T. pisana can attain at some sites, plus their apparently catholic feeding habits, their potential impact on the vegetation of the park is cause for concern and should be further investigated. Control of the main colonies should also be considered.
Highlights
The distribution, abundance, size distribution and diurnal activity patterns of invasive land snails, Theba pisana, in the West Coast National Park (WCNP), South Africa, were investigated
Theba pisana (Müller, 1774), a land snail native to the Mediterranean region (Baker 1986), was introduced into South Africa prior to 1881 (Durr 1946), yet has received little attention from researchers, despite the fact that the extent of its invasion in the fynbos biome has been known for some time (MacDonald & Jarman 1984)
This study aims to determine the distribution, abundance and size distribution of T. pisana in the West Coast National Park (WCNP), a reserve largely dedicated to the conservation of coastal fynbos
Summary
The distribution, abundance, size distribution and diurnal activity patterns of invasive land snails, Theba pisana, in the West Coast National Park (WCNP), South Africa, were investigated. The Cape Floristic Region (CFR), the smallest of the six recognised floral kingdoms of the world, is an area of extraordinarily high diversity and endemism (Cowling et al 1996), and is home to more than 9 000 vascular plant species, of which 69% are endemic (Goldblatt & Manning 2002) Much of this diversity is associated with the fynbos biome (Turpie et al 2003), a Mediterranean-type, fire-prone shrubland (Turpie et al 2003; Van Wilgen et al 2001). Theba pisana (Müller, 1774), a land snail native to the Mediterranean region (Baker 1986), was introduced into South Africa prior to 1881 (Durr 1946), yet has received little attention from researchers, despite the fact that the extent of its invasion in the fynbos biome has been known for some time (MacDonald & Jarman 1984). The collection of reliable data on T. pisana is urgently
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