September 18th, 2015

The completion of the Life+ Cap DOM programme!

After five years of work, the Life+ Cap DOM programme, supported by the European Commission and…
August 31st, 2015

[Video] The STOC in French Guiana

Since 2012, GEPOG has been running a STOC (point count) survey in French Guiana, along with the…
August 25th, 2015

[Video] SEOR: a look back over the five years of the programme

A few weeks before the end of the Life+ Cap DOM programme, François-Xavier Couzi, Director of…

Saving the Tuit-tuit

By controlling black rats

Which species ?

The Réunion Cuckoo shrike, or Tuit-tuit, is an endemic species, classified as “Critically endangered since 2008 (IUCN, BirdLife International, 2008). The major factor contributing to its decline is predation by black rats, a species introduced by man which has become invasive on the island and whose presence is maintained by many litters dropped on the Reserve, apart from collection sites.

Réunion cuckooshrike, tuit-tuit, Yabalex

The estimated global population of this species in 2010 was between 25 to 30 breeding pairs, all located in the Roche-Écrite Nature Reserve. This site is now part of the Réunion National Park. Since 2003, SEOR has been monitoring known Tuit-tuit nests and controlling rat populations manually by setting traps. This has enabled the production of 4, then 8 and finally 22 fledglings between 2004 and 2007.

Why ?

To save this species from extinction, it is, however, imperative to identify and implement a methodology for large-scale rat control, to enable larger areas of the forest to be covered at the lowest possible human and financial cost, in order to achieve long term results. The vulnerability of island species is attributed to their restricted distribution range (vulnerability to local destructive events) and associated with small population sizes. On many islands, species evolved without any predators or pathogenic agents, which left them particularly vulnerable to introduced predatory species. The extinction rate of bird species in Réunion is over 50% (at least 18 referenced species); most of those species became extinct during the first century of human settlement (with its commensal organisms). Invasive introduced species affect 67% of globally threatened bird species on oceanic islands and more than half of recent extinctions of island birds have been attributed to introduced mammals (mainly rats and cats). It is estimated that rats alone are responsible for the extinction of 30 bird species throughout the world.

Our actions

The aim of this action is to eradicate rats in an area covering at least 200 ha in the Reserve’s core zone, and to maintain low densities in a peripheral zone of at least 250 ha to prevent rats from recolonizing the core zone. A rat-free area within this zone should enable the Réunion Cuckoo shrike to rebuild its populations up to a viability threshold (estimated at 125 nesting pairs). The aim is to achieve a population of 50 nesting pairs by the end of the project, in 2015. To that end, a method of intensive control with poison baits will be tested and applied for 4 years, in addition to the manual method of trapping. Beforehand, one year will be devoted to consulting the scientific literature, French and New Zealand experts, and to drawing up a baseline assessment of rat densities and the residual Tuit-tuit population. Different types of poison rat bait will also be tested to ensure that there will be no impacts on other species of fauna. Between 2011 and 2015, the combination of manual and aerial regulation will be tested. The results will be evaluated by annual monitoring of rats, Tuit-tuit and other nesting bird species populations.

Through this action, it is estimated that the density of rats in the Reserve’s core zone will be low enough to replace the dispersal of poison bait by the establishment of permanent baiting stations. The Département de la Réunion (French local authorities) and the ONF (French National Forestry Agency) owner and manager of forests in the National Park will be key partners in this component.

Report, involve, raise awareness

At the end of the project, if the method proves to be effective, it could be reproduced in other areas where the introduction of rats has led to a decline in endogenous biodiversity, in particularly on Réunion Island, and on other French overseas islands (Mayotte, Guadeloupe, Martinique, French Polynesia, New Caledonia, the Eparse Islands, Connétable Nature Reserve in French Guiana). This constitutes a demonstration action, since knowledge on large scale rat control remains limited in France and Europe. A seminar on this issue will be held and a technical guide published to disseminate this knowledge.

Keywords : Réunion, Roche-Ecrite Nature Reserve, Réunion Cuckoo shrike