Euglandina rosea
(rosy predator snail)

E. rosea has had a negative impact on native snail species in the countries into which it has been introduced. It has been responsible for the dramatic decline or eradication of many endemic species, particularly Partulidae and Achatinellinae (Cowie, 2001, 2003). On the Society Islands, French Polynesia, alone, only five of the original 61 species remain (Coote and Loeve, 2003). E. rosea is listed on the IUCN ISSG among 100 of the world's worst invasive species and IUCN has condemned its deliberate introduction as a biological control agent.

The distribution of E. rosea and status of the various introduced populations has been summarized by Griffiths et al. (1993) and by Civeyrel and Simberloff (1996). Surviving populations (the date of introduction is given in parentheses) can be found in Bermuda (introduced 1958-60), Grand Comorro (1970), Guam (1958), Hawaii (1955), Madagascar (1970), Mauritius (1959), Micronesia (?), Moorea (1977), New Caledonia (1974-78), New Guinea (1959-61), Okinawa (1958-61), Palau (1960), Réunion (1966), Rodrigues (ca 1961), Saipan (?), Samoa (1980-84), Seychelles (1966), Society islands (1974), Ta'u (Samoa) (1992) and Vanuatu (1973-74) (Civeyrel and Simberloff, 1996). Cowie (2000, 2003) has updated the distribution of E. rosea, noting that it is also found in Indonesia, Kiribati and the Solomon Islands.

The potential for further spread of E. rosea is primarily through further deliberate introductions. The IUCN ISSG has listed E. rosea amongst 100 of the world's worst invasive species and condemned its use as a biological control agent. However, Cowie (2000) stated that intense pressure from Pacific Islanders to resolve the problem of Achatina fulica may lead to its deliberate official or unofficial release. Increasing trade between countries could also lead to the introduction of E. rosea into new habitats (Cowie, 1998).

Reproductive Biology

E. rosea is an obligate cross-fertilizing hermaphrodite. Its mating behaviour has been described by Ingram and Heming (1942), Chiu and Chou (1962), and most recently by Cook (1985a). The snail lives for about 2 years and adult snails lay 25-35 eggs at each oviposition, producing approximately 100 eggs during their lifespan (Chiu and Chou, 1962). The snail is primarily nocturnal and is usually ground living, but will climb trees (Griffiths et al., 1993) and enter shallow water courses in pursuit of prey (Kinzie, 1992).

Prey Detection and Feeding Behaviour

Several aspects of the feeding behaviour and prey detection in Euglandina have been described by Ingram and Heming (1942), Cook (1985a, b; 1989a, b) and Kinzie (1992). Euglandina appears to detect its prey by following slime trails (Cook, 1985b; Clifford et al., 2003), which it does more than 80% of the time (Clifford et al., 2003) or by detecting dissolved substances in water (Kinzie, 1992). Chemical components of the mucus and perhaps the shell, together with the physical dimensions of the shell are the most important determinants of prey suitability (Cook, 1989a, b). Euglandina will also consume randomly encountered static prey. When contact is made with the prey, it is usually picked up with the foot and swallowed whole, or the soft parts of the prey are extracted from the shell. Which feeding technique is utilized depends on a number of factors, including the relative sizes of predator and prey and probably also the nutrient status of the predator (Cook, 1985b; 1989b). In gastropods of any given species, Euglandina showed a clear preference for the smaller individuals (Chiu and Chou, 1962; Cook, 1989b).

Hadfield et al. (1993) suggested that rats (Rattus rattus, R. norvegicus) might have a significant effect on Euglandina populations, especially as it is typically a ground-dwelling snail.