Halting the Snail Trail of Destruction

Mission statement:

Small island developing states (SIDS), such as Mauritius, evolve at a distance from larger landmasses. This often results in the development of rich and unique biodiversity. Given the global nature of today, however, flora and fauna is often threatened by the introduction of non-native species. On the islands of Mauritius and Rodrigues, the Madagascar Gecko, the Chinese guava and the apple snail are several threats to the islands’ biodiversity.

Apple snails (Pomacea Canaliculata) were detected in areas utilized for taro cultivation in La Porte Providence, Flacq (East part of Mauritius). Taro is of great economic importance to planters in the region. Without predators, this invasive species is perfectly adapted to Mauritius and is rapidly increasing in size and population. Generally speaking, the threat apple snails pose to indigenous flora and fauna is so great, that the International Union for Conservation of Nature (IUCN) has rated it among the 100 most dangerous alien species.

The aim of this project is to completely eradicate or reduce the apple snail population in the aforementioned area to a tolerable size in order to protect taro farmers’ crops and fresh water biodiversity.

Goals & objectives:

Despite the relatively widespread presence of the apple snail, the team believed that control and eradication was feasible by preparing and implementing an invasive alien species management plan (IASMP).

The goal of the action was to either eradicate the snail from selected agricultural areas, or to suppress the invasive snail population below a predetermined threshold. Below this threshold the taro and other competing species would be able to regain ground. The project directly benefitted 42 small taro planters and owners of wetland plots, including their families. Other beneficiaries included 10-15 part-time planters, watercress growers and local shrimp fishers of La Porte Providence and neighbouring villages in Flacq.

Partners in the action included:

  • Taro Growers Association;
  • National Parks and Conservation Service;
  • Agricultural Research and Extension Unit (AREU);
  • University of Mauritius (UOM).

Achievements:

An Invasive Alien Species Management Plan was selected from the Global Invasive Species Programme (GISP), however, the IASMP was adapted to the local setting with assistance from the aforementioned partners.

According to the IASMP, the following steps were followed:

  • Population census in order to monitor implementation of the IASMP;
  • Development of an eradication plan by Mechanical control, hand picking and biological control by using lilac and tobacco leaf as deterrent;
  • Establish control and preventive measures;
  • Monitor containment.

An initial census was conducted to determine the degree of infestation. The results obtained from a small area were then extrapolated to give figures to estimate the total number of snails present in the wetlands. Papaya leaves was used to attract snails to an area where they were then counted.

Handpicking yielded excellent results and was determined to be the ideal approach for the containment, where feasible. Using papaya to draw the snails out made the exercise particularly efficient.

Collected snail stock were then purchased from the taro planters. The ‘snail buy off method’ was proposed as an incentive to compensate for loss in wetlands resources and also to sustain the handpicking activity throughout the project life.

Biological controls included lilac or tobacco leaves, which are poisonous to apple snails but have no apparent effect on other species in the wetlands. Fresh leaves were used as a biological pest control and applied regularly to decrease the pest population.

Control and preventative measures included informational materials targeting farmers, as well as training of a local project team. Selected members of the local community were trained to carry out the above mentioned activities and control methods. They were responsible for setting up contingency plans and intervening (if necessary), as well as providing advice to the local community. This team also liaised with EPCO to share data and information regularly.

In addition, the local team was responsible for setting up an assembly among the local community which derives resources from the wetlands. The association would be registered under existing local law. The executive committee, with the president as the head, will be responsible for future decision making.

All wetland beneficiaries make a monthly contribution. This money is used for future project financing and maintenance of established control measures.

Monitoring, through ongoing censuses, provides insights regarding not only the impact of initial implementation, but also highlighted where/when corrective action is necessary.