The Obô giant snail – a big snail on a small island

Martina Panisi, conservation biologist with the Forest Giants Project on São Tomé Island, Central Africa, began studying the Obô giant snail (Archachatina bicarinata) in 2017.

Few live specimens were found in the first month of study until she enlisted the help of local hunters.  During the course of the first research on the Obô gaint snail in São Tomé, only 150 live snails where found, after searching in more than 1 800 spots, inside and outside the remote native forests of Obô Natural Park.

Research and understanding regarding the Obô giant snail has been slow, but this should change with the opening of the conservation centre in April 2019. The Forest Giants Project is in the process of developing a snail-breeding manual. “We are successfully breeding three endemic snails,” explains Panisi. “We plan to breed and study 30 specimens, including the Obô giant snail, when he conservation centre opens.”

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Photo:  Forest Giants Project

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Panisi suspects Obô giant snails are detritivorous, feeding on decaying plant matter and leaf litter. The Obô giant snail also likes soft fruits like mango and banana, and taro, a starchy root crop. They do not seem to have a preference for indigenous plants over introduced species.

Snails are important as they are bio-indicators, meaning they are a litmus test of healthy ecosystems. Panisi is trying to reposition the Obô giant snail as the flagship species for Obô Natural Park, as they also have a role in ecosystems, facilitating the decomposition processes in soil. By using games, and painting the snails as plant chefs, the Forest Giant Project aims to increase local community awareness of the snail’s role in decomposer ecology.

Photo:  Forest Giants Project

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“The Obô giant snail is important culturally as it is traditionally used as medicine,” says Panisi.  “This large invertebrate should be regarded as an icon of this Atlantic island, and can be used  as an important tourist attraction and education tool, especially for children.”

Panisi has identified three likely causes that have resulted in the decline of Obô giant snail populations: habitat degradation, over-harvesting, and the introduction of new species like the striped West African giant land snail (Archachatina marginata).

The West African giant land snail was introduced in the 1980s and is now regarded as invasive, but it provides 45% of the island’s protein. Smaller than its island cousin, the West African snail is not sought after for medicine, whereas an Obô giant snail can fetch a hefty price in
the market.

On São Tomé, the West African variety occurs where you won’t find the Obô giant snail, leading Panisi to suspect it might have brought in a disease that affects the other species. The West African giant land snail occurs in low altitudes.

The extent of the Obô giant snail’s decline is representative in the description of the snail by different age groups of São Toméans. “Young children confuse the invasive species with the endemic snail as it is likely they have never seen an Obô giant snail,” explains Panisi. “Teenagers recognise there are two giant land snail species, but have limited knowledge of the Obô giant snail. “Adults have acknowledged the giant snail’s decline and remember collecting them as children. “The elderly complain that the snails have disappeared rapidly in the last decade.”

Photo:  Forest Giants Project

Obô giant snail facts

• The Obô giant snail is an endemic land snail found on São Tomé and Príncipe.
• The size and shape of the Obô giant snail is similar to a croissant.
• It is found in the high altitudes and humid environment of Obô Natural Park.
• Unlike most other snail species, Obô giant snails are diurnal.
• The Forest Giants Project, based in Monte Café, São Tomé, launched in 2018 and is sponsored by the National Geographic Society and Critical Ecosystem Partnership Fund.