Taxonomic name: Euglandina rosea (Ferussac, 1818)
Common names: cannibal snail (English), escargot carnivore de Floride (French), euglandine (French), Rosige Wolfsschnecke (German), rosy wolf snail (English)
Organism type: mollusc
The carnivorous rosy wolfsnail Euglandina rosea was introduced to Indian and Pacific Ocean Islands from the 1950s onwards as a biological control agent for the giant African snail (Achatina fulica). E. rosea is not host specific meaning that native molluscs species are at risk of expatriation or even extinction if this mollusc-eating snail is introduced. Partulid tree snails of the French Polynesian Islands were particularly affected; having evolved separately from each other in isolated valleys, many Partulid tree snails have been lost and today almost all the survivors exist only in zoos.
The shell is large (up to 76 mm in height, 27.5 mm in diameter), thick and has prominent growth lines (University of Florida 2009). The shape of the shell is fusiform with a narrow ovate-lunate aperture and a truncated columella; typically, the shell color is brownish-pink (University of Florida 2009). Adult Euglandina grow from about seven to 10 cm long (Clifford et al. 2003).
natural forests, planted forests, ruderal/disturbed, scrub/shrublands, urban areas
Euglandina rosea is usually found singly in hardwood forests, roadsides and urban gardens in its native range in Florida (Hubricht 1985, University of Florida 2009).
Molluscs are the group most affected by extinction according to the 2007 International Union for Conservation of Nature (IUCN) Red List (Regnier 2009). The Pacific region has a wide diversity of mollusc species, most of them unique to the region, and the majority endemic to single islands or archipelagos (Cowie 1996 1997a, in Cowie and Cook 2001). More and more, these unique species are becoming replaced with a homogenous group of tropical tramp snail and slug species that are increasingly widespread (Cowie 1998a, R.H. Cowie, unpub., in Cowie and Cook 2001). Of the 400 extinct species we listed from oceanic islands, 234 lived on islands to which Euglandina rosea had been introduced, and it is highly probable that of these 234 extinctions, 134 (>50%) of them were ultimately caused by the introduction of E. rosea (Regnier et al. 2009).
E. rosea contributed to the extinctions of endemic Partula tree snails in French Polynesia; the snails are widely distributed on most of the high islands of the tropical Pacific, except for the Hawaiian Islands (Murray et al. 1989, Cowie 1992, Hopper and Smith 1992, in Cowie and Cook 2001). E. rosea also contributed to the marked decline of endemic land snail fauna in Hawaii and Mauritius (Murry et al. 1988; Clarke et al. 1984; Hadfield 1986, Murray et al. 1988, Griffiths et al. 1993, Wells 1995, in Satoshi 2003). The best documented cases are those of the achatinelline tree snails, which are endemic to the Hawaiian Islands (Hadfield 1986, Hadfield et al. 1993). The native species mentioned seem especially vulnerable to heightened levels of predation because of their extremely slow rate of reproduction (Cowie 1992; Hadfield et al. 1993, in Cowie and Cook 2001).
The carnivorous snail was introduced to control numbers of the giant African land snail (Achatina fulica) (Nishida and Napompeth 1975, in Cowie 2000). However, no rigorous scientific evidence exists that E. rosea controls A. fulica (Christensen 1984, in Cowie 2000) and, as a consequence, the World Conservation Union (IUCN) has formally condemned the deliberate introduction of E. rosea and other carnivorous snails. Most governments and other authorities appear to be aware of the potential threat posed to native fauna by E. rosea, however, under pressure to do something about A. fulica, they may misguidedly consider the introduction of E. rosea (and other species such as the flatworm Platydemus manokwari).
Disease transmission: E. rosea was found experimentally to be able to serve as both an intermediate and a paratenic host of Angiostrongylus cantonensis.
Native range: Euglandina rosea is native to the southern east coast of the United States (Clifford et al. 2003). It is native to southeastern Texas, Louisiana, Mississippi, Alabama, Georgia, South Carolina and widespread in Florida including the Keys (University of Florida 2009).
Known introduced range: E. rosea has been introduced into various Pacific Island and Pacific Rim groups, Indian Ocean islands and the Caribbean. It has also been introduced into India, Taiwan and Japan.
Local dispersal methods
Agriculture (local): Deliberate spread by agricultural officials as a biological control agent.
Natural dispersal (local): Probably once established, natural spread is the main means of spread.
Natural dispersal (local): E. rosea was reported to spread across the island of Moorea at the rate of about 1.2 km per year (Clarke Murray and Johnson 1984).
For a detailed account of the environmental impacts of Euglandina rosea please read: Euglandina rosea (Rosy Wolfsnail) Management Information. The information in this document is summarised below.
The future for some of French Polynesia’s partulids may not be as bleak as once thought; according to recent studies relatively high genetic diversity is represented among living taxa and it may still be possible to preserve a representative sub-sampling of Raiatea and Tahiti’s tree snail diversity (Lee et al. 2009; Ó Foighil 2009).
Physical Control: The ultimate objective of captive breeding programs is the reintroduction of viable populations of endangered species into their natural habitats (Coote et al. 2004). Small exclosures have been built in Hawai‘I and on Moorea (French Polynesia) to protect native tree snails from attack by Euglandina rosea.
Legislation: It is almost impossible to prevent the within-island spread of Euglandina in French Polynesia (Coote et al. 1999). Between-island spread of Euglandina should be prevented by legislation. The Marqueses Islands, the Southern Cooks and the Australs provide refuges for some of the remaining partulid species (Lee et al. 2007a) and should be kept Euglandina-free. E. rosea is now legally considered to be a noxious species in French Polynesia; the introduction of live specimens and their transport from one island to another is forbidden (Meyer 1998).
Other: Since 1986 partulid snails have been the subject of an international breeding programme; the International Partula Conservation Programme manages a breeding programme for 25 species in 15 zoos worldwide. Introducing Society Island partulids to the Austral Islands that are free of the predator might ensure their long-term survival in the wild (Ó Foighil 2009). Coote & Loeve (2003) concluded that E. rosea was extinct in the wild on Huahine, strongly suggesting that the successful re-introduction of partulids into the wild on Huahine might be possible.
Conservation actions in the wild may be limited to identifying and protecting populations of partulid snails that offer some possibility of persistence in the presence of Euglandina (Ó Foighil 2009). Based on laboratory behavioral studies of the effect of temperature on E. rosea movement, Gerlach (1994, in Ó Foighil 2009) hypothesised that an altitudinal refuge above 600 to 700 m would exist for Society Island partulids.
Research and Knowledge: Further research into the biology of E. rosea, and particularly its population dynamics, needs to be carried out. There are no known natural predators, so a species-specific toxin in snail bait, as tested in Hawaii (M. G. Hadfield pers. comm., in Coote et al, 1999), could be a promising approach. A good relationship between the Pacific Island Land Snail Group (PILSG) and the French Polynesian government authorities has developed, and joint initiatives for conservation and research are being planned (Coote et al. 1999).
Education and Knowledge: Despite the lack of evidence supporting Euglandina as a successful biological control agent and despite the abundant evidence of their negative predatory impact on native snail fauna, carnivorous snail introductions continue (Cowrie 1992). Clearly public education about the French Polynesia’s precious natural fauna and the dangers posed to such fauna by carnivorous biological control agents could help to reduce the likelihood of Euglandina being purposefully translocated to new islands. Local willingness and experience are already in place to conserve French Polynesia’s partulid snails (Coote & Loeve 2003).
Euglandina rosea feeds on other snails and slugs, which they track down by following the slime trails left by their prey (Clifford et al. 2003). It appears to prefer smaller individuals, which it swallows whole, but will attack large snails by entering through the shell aperture.
Euglandina rosea is a cross-fertilising egg-laying hermaphrodite. Chiu and Chou (1962, in Univeristy of Florida 2009) gave details of the biology of Euglandina in Taiwan. Individuals live up to 24 months. 25 to 35 eggs are laid in a shallow pocket in the soil. These hatch after 30 to 40 days.
This species has been nominated as among 100 of the "World's Worst" invaders
Reviewed by: Review of updates under progress
Dr. Robert H. Cowie, Center for Conservation Research and Training, University of Hawaii, Honolulu, Hawaii
Compiled by: IUCN SSC Invasive Species Specialist Group
Updates with support from the Overseas Territories Environmental Programme (OTEP) project XOT603, a joint project with the Cayman Islands Government - Department of Environment
Last Modified: Wednesday, 17 February 2010