Tree snail research needs
Partula tree snails and the Euglandina threat
Partula snails Partula conservation Euglandina

Research needs - Euglandina and Platydemus

The introduction of the carnivorous snail Euglandina rosea to Pacific islands has resulted in a mass extinction of land snail species. The problems caused by Euglandina have been added to by the introduction of a snail-killing flatworm Platydemus manokwari. Conservation efforts for the few surviving species of Partula in the south Pacific and Achatinella, Auriculella, Partulina and other tree snails in Hawaii depend on a good knowledge of the ecology of the predators. The available information on Euglandina has been compiled into a population mode of the tree snails and this predator, but this still has weaknesses. There are still some important gaps in our knowledge of Euglandina and very little is known about Platydemus. Basic biological questions could be answered by anyone living or working where these predators can be found. The important questions are listed below:


  • Temperature - the effects of temperature on activity (including feeding rates), growth and reproduction have been studied but could be refined further. How do they respond to both low and high temperatures? We know there is a lower limit for activity which may prevent them becoming established at high altitudes, is there a high temperature limit?
  • Species differences - Euglandina 'rosea' is now know to be a complex of species, they may be ecologically very similar but this needs to be checked. Are there differences in their temperature tolerances? Is one species more arboreal than the other (i.e. is it more likely to follow vertical prey trials)?


  • Feeding rate - how many snails do flatworms eat? We need to know how many snails and what sizes are consumed by different sized flatworms. From this we can start to calculate likely impacts. The reverse of this is also important - how many snails does a flatworm need to eat to survive? In the case of Euglandina areas with very low prey densities act as barriers to the spread of the predators; are some flatworm populations similarly constrained?
  • Feeding preferences - will the flatworms follow prey anywhere; given a choice between hunting on the ground or up trees which do they choose? And how high up a tree will they go if alternative food is available?
  • Reproduction - how many young are produced, how often and from what age? How does prey availability affect reproduction and survival?
  • Temperature - how do different temperatures affect activity, feeding rate, reproduction and growth? What is the lowers/highest temperature for any of these things?
  • Other flatworms - there are many introduced flatworm species, we have no information on whether or not these affect snail populations, basic research should also be carried out on these whenever the opportunity arises

    For more information on the different Euglandina species and inquiries, please contact Norine Yeung, Bishop Museum, Ken Hayes, Bishop Museum/Howard University or John Slapcinsky, Florida Museum of Natural History.

    For Euglandina ecology please contact Justin Gerlach.

    Compiled by Justin Gerlach: contact

    Hosted by Island Biodiversity