THE LAND SNAIL FAUNA
The Madagascar pioneer work was summarized in 1993 and 1994 by the publication of the Fauna of Madagascar by Fischer-Piette& Blanc & Blanc & Salvat. Since then Emberton in 1994 described an additional 30 species and in 1999 an additional 10 Ampelita, 2 Clavator, and 1 Helicophanta. In 1999 he revised Edentulina adding 8 new species and synonymizing five.
Madagascar has a very rich and a highly endemic land snail fauna. The present fauna (Fiecher-Piette et al 1993 and 1994; Emberton 1994, 1996a and 1996b) consists of 627 taxa of which 572 were endemic. This means that 91% of the land snail fauna does not occur outside of Madagascar. The operculates consist of 243 taxa with 96% endemic and the pulmonates of 384 with 88% endemic.
Madagascar snail fauna has 11 endemic genera with 258 taxa. These are:
Acroptychia (13 taxa in Madagascar, 1 in Ranomafana, and 1 in the Guide)
Ampelita (89, 9, 9)
Bathia (1, 0, 0)
Boucardius (33, 6, 0)
Clavator (13, 1, 1)
Helicophanta (18, 7, 7)
Kalidos (72, 4, 4)
Leucotaenius (7, 1, 1)
Madecataulus (6, 0, 0)
Malarinia (2, 1, 0)
Malagarion (5, 1, 0)
and the almost endemic genus Tropidophora is also found in Comoros, Seychelles, and southeast Africa. It has 144 Madagascar taxa of which 141 or 98% are endemic.
The species I’ve included in Ranomafana National Park fauna are those which have been found in the (2 x 70 x 65) 9,100 square mile area between latitude 20 to 22 degrees South and longitude 47 to 48 degrees East AND greater than 10 mm in longest dimension. The park is located at approximately latitude 21 degrees 16' South and 47 degrees 25' East in the northern center of the lower sector. Included is the area with a minimum radius of 50 km (30 miles) and a maximum of 135 km (80 miles).
The park has 67 taxa of which 57 or 85% are endemic. There are 43 taxa over 10 mm in dimension (which are included in the Guide) of which 36 or 84% are endemic. If the 7 introduced species are excluded, the endemic ratio is 97%.
The introduced species are the “tropical tramps” Lamellaxis gracilis, Subulina octona and Bradybaena similaris along with Subulina mamillata and Edentulina ovideus. The Giant African land snail Achatina fulica is widespread and Euglandina rosea can be expected. Of the total 43 taxa 7 or 16% are introduced.
There are four carnivore species in the following families:
Spiraxidae – Euglandina rosea & Streptostele manumbensis
Streptaxidae – Edentulina ovoidea
Charopidae – “Rhytida” covani
THE GUIDE AND ITS USE
This guide has its limitations. Only the snails over 10 mm in size have been included. These are the ones most likely encountered. Since there is no “official” list of the snails present at Ranomafana, I have included the snails seen during my month visit in 1998 and those reported from the region surrounding the park.
Euglandina rosea, not presently found at Ranomafana, has been included because it may be found in the region in the future. It is a carnivore that was introduced to Madagascar to control the devastation caused by the introduced Giant African Snail, Achatina fulica. Rather than living on a diet of Achatina, Euglandina prefers to feed on the native species and in some areas like the South Pacific has exterminated the native species. It is presently (1994) found in the vicinity of Antananarivo and near Tamatave on the East Coast. You should be on the lookout for it and report any sightings to the park authorities.
LAND SNAIL IDENTIFICATION
"If land snail classification were based on the shape of the shell, there would only be ten species." The identification of land snails is a challenge. Land snail taxonomy is based on the soft anatomy, consequently the shell is only of secondary taxonomic importance. Thus, many similar appearing shells are in distant or non-related families. You soon learn that snails were never meant to be classified. Thumbing through pictures looking for your specimen can be very discouraging. But what is more important, you don't learn anything about the features which make your specimen distinct. A key is needed to highlight the specific characteristics which make this specimen different.
HOW TO USE THE KEYS
The keys are presented in the form of questions. You are to answer based on your observations of your specimen. There are two questions (1A and 1B). Your specimen should fit one of the choices. I have used an indented key because it has two advantages. First, it makes choice criteria more visible and secondly, it is very easy to see where you "came from".
Since the keys are based on adult characters, how can you determine if your specimen is an adult? The reflecting of the lip (when present) usually occurs when the animal approaches adulthood. If the outer edge of the mouth is soft and flexible while the rest of the shell is otherwise quite firm, the animal is probably a juvenile. Another way to determine a juvenile is by measuring the shell size and counting the number of whorls. Compare these with adult shells of related species. Is your specimen in the correct proportion to be a juvenile?
If you find a specimen that does not fit any of the species, send it to an expert. You may have a new species or an extension to the range of a known species.