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Eradication of invasive animals and other island restoration practices in Seychelles: achievements, challenges and scaling up perspectives

Foreign and Commonwealth Office

Rocamora, G.

In recent decades Seychelles has accumulated extensive experience in the management of invasive species and other island restoration practices. Non-government organisations (NGOs), governmental, parastatal and private stakeholders have conducted successful programmes to control and eradicate invasive animals and plants, particularly on small islands of high biodiversity value. Biosecurity protocols have been implemented to prevent (re)infestations. With at least 50 vertebrate populations (33 mammal, 16 bird and one reptile) from 14 different species successfully eradicated, Seychelles is the third country in the world after Australia and the USA for invasive vertebrate eradications from tropical islands, and the seventh when considering all countries. Twenty-four islands have bene?ted from invasive vertebrate eradications and other ecosystem restoration processes to create refuges for native biodiversity. About 470 ha of woodland have been rehabilitated through replanting and recovery of native vegetation, and at least 36 successful island translocations of native birds and reptiles have been conducted. This includes 16 conservation introductions or reintroductions of six endemic land birds (all but one threatened), two of a terrapin species and 18 of Aldabra giant tortoises. Recovery of native species and natural recolonisations have occurred on islands where invasive predators have been removed. As a result, four globally threatened endemic land birds have been down-listed in the IUCN Red List and dozens of other native species including seabirds, land birds, reptiles, invertebrates and plants have also bene?ted. Future challenges include increasing the proportion of the countrys land area free of rats and cats from 3.9% to potentially 15.4%, mainly in the outer islands, and 50% in the long term if Aldabra and Cosmoledo are considered. Factors limiting future eradications and translocations are discussed. Alternative conservation approaches such as mainland-islands are recommended for large islands, and the development of partnerships with nature-based tourism is encouraged to help fund further restoration.

Predator-Free Rakiura. An economic appraisal.

BRB

This report estimates the benefits of making Rakiura and surrounding islands predator free. The proposal is to do this in two phases, starting with the Halfmoon Bay area (denoted in this report as HMB) before progressing to the rest of the island (denoted in this report as full).

Morgan, Gareth

Simmons, Geoff

2014

Control of the ladder snake (Rhinechis scalaris) on Formentera using experimental live-traps

Colomar, V.

Fernández, M.J.

Moreno, J.E.

Pico, G.

The ladder snake (Rhinechis scalaris) is a recent alien invasive species found on Formentera (83 km2), in the Balearic Archipelago (4,492 km2). It has been introduced in the last decade as cargo stowaway hidden within ornamental olive trees from the Iberian Peninsula, causing negative impacts on native fauna. This paper describes the methodology used to reduce the ladder snake population as a fi rst attempt since it was detected in 2006. For this purpose, an experimental live-trap was designed by the wildlife management team of the Consorci per a la Recuperació de la Fauna de les Illes Balears (COFIB) during the 2016 campaign. As a result, 314 R. scalaris were trapped in an area of 472 ha, achieving an effi ciency of up to 0.167 captures per trap and night, and 0.040 captures per unit eff ort on average. This outcome encourages the use of the live-trap as a cost-eff ective method for reducing the snake population in Formentera. Nonetheless, this method should be considered a starting point toward R. scalaris control.

Predation pressures on sooty terns by cats, rats and common mynas on Ascension Island in the South Atlantic

Dickey, R.C.

Hughes, B.J.

Reynolds, S.J.

Despite the presence of invasive black rats (Rattus rattus), common mynas (Acridotheres tristis), and feral domestic cats (Felis catus), sooty terns (Onychoprion fuscatus) breed in large numbers on Ascension Island in the tropical South Atlantic Ocean. These introduced predators impact the terns by destroying eggs or interrupting incubation (mynas), eating eggs (mynas and rats), eating chicks (rats and cats), or eating adults (cats). Between 1990 and 2015, 26 censuses of sooty terns and five of mynas were completed and myna predation was monitored on 10 occasions. Rat relative abundance indices were determined through trapping around the tern colonies and rat predation was monitored by counting chick carcasses. Cat predation was quantified by recording freshly killed terns. Prior to their eradication in 2003, cats had the greatest impact on sooty terns and were depredating 5,800 adults and 3,600 near-fledging chicks (equivalent to the loss of 71,000 eggs) each breeding season. We estimated that 26,000 sooty tern eggs (13% of all those laid) were depredated by approximately 1,000 mynas. Rats were not known to depredate sooty terns prior to cat eradication but in 2005, 131 of 596 ringed (monitored) chicks (22%) were depredated by rats. In 2009 chick carcass density was 0.16 per m2. Predation by rats hugely increased in the absence of cats and was the equivalent of 69,000 eggs. Care is needed when applying our findings to seabirds globally. The scarcity of alternative food sources and seasonally high density of easily available prey in the sooty tern colony may have magnified predation by cats, rats and mynas.

South Africa works towards eradicating introduced house mice from sub-Antarctic Marion Island: the largest island yet attempted for mice

Beaumont, J.

Chauke, L.F.

Chown, S. L.

Cooper, J.

Devanunthan, N.

Dilley, B.J.

Dopolo, M.

Fikizolo, L.

Heine, J.

Henderson, S.

Jacobs, C.A.

Johnson, F.

Kelly, J.

Makhado, A.B.

Marais, C.

Maroga, J.

Mayekiso, M.

McClelland, G.

Mphepya, J.

Muir, D.N. Ngcaba, N. Ngcobo, J.P. Parkes, F. Paulsen, S. Schoombie, K. Springer, C. Stringer,H. Valentine, R.M. Wanless and P.G. Ryan

Preston, G.R.

House mice (Mus musculus) were introduced to South Africas sub-Antarctic Marion Island, the larger of the two Prince Edward Islands, by sealers in the early 19th century. Over the last two centuries they have greatly reduced the abundance of native invertebrates. Domestic cats (Felis catus) taken to the island in 1948 to control mice at the South African weather station soon turned feral, killing large numbers of breeding seabirds. An eradication programme finally removed cats from the island by 1991, in what is still the largest island area cleared of cats at 290 km2. Removal of the cats, coupled with the warmer and drier climate on the island over the last half century, has seen increasing densities of mice accumulating each summer. As resources run out in late summer, the mice seek alternative food sources. Marion is home to globally important seabird populations and since the early 2000s mice have resorted to attacking seabird chicks. Since 2015 c. 5% of summer-breeding albatross fledglings have been killed each year, as well as some winter-breeding petrel and albatross chicks. As a Special Nature Reserve, the Prince Edward Islands are afforded the highest degree of protection under South African environmental legislation. A recent feasibility plan suggests that mice can be eradicated using aerial baiting. The South African Department of Environmental Affairs is planning to mount an eradication attempt in the winter of 2021, following a partnership with the Royal Society for the Protection of Birds to eradicate mice on Gough Island in the winter of 2020. The eradication programme on Marion Island will be spearheaded by the South African Working for Water programme Africas biggest conservation programme focusing on the control of invasive species which is already driving eradication projects against nine other invasive species on Marion Island.

Modelling invasive plant alien species richness in Tenerife (Canary Islands) using Bayesian Generalised Linear Spatial Models

Arévalo, J. R.

Bacaro, G.

Da Re, D.

Fernàndez-Palacios, J. M.

Negrín-Pérez, Z.

Otto, R.

Rocchini, D.

Tordoni, E.

Biological invasions are one of the major threats to biodiversity, especially on islands where the number of endemic species is the highest despite their small area. In the Canary Islands, the relationships among invasive alien species (hereafter IAS) and their environmental and anthropogenic determinants have been thoroughly described but robust provisional models integrating species spatial autocorrelation and patterns of IAS communities are still lacking. In this study, we developed a Generalised Linear Spatial Model for Invasive Alien Species Richness (IASR) under a Bayesian framework, using a methodological approach that encompass GIS and geostatistical analysis. In this study, we hypothesised that the inclusion of spatial autocorrelation can improve model performance thus obtaining more IASR-reliable predictions. In addition, this method provides uncertainty maps that prioritize areas where further sampling e?orts are needed. Our model showed that IASR in Tenerife is mainly driven by a combination of anthropogenic and natural processes, highlighting favourable conditions for IAS from the coastline to about 800 m a.s.l., especially on the windward humid aspect. Among anthropogenic factors, a clear positive relationship between road kernel density estimation and IASR was found. Indeed, road density has recently increased especially in low to mid altitudinal zones on the Canary Islands, strictly associated with urban expansion and it has been widely demonstrated to be one of the main IAS pathways. Hence, higher road density can be related to increased propagule pressure which is, together with source of disturbance, one of the most important factors explaining richness in alien species invasion success. Our main conclusions highlight the importance of considering spatial autocorrelation and researchers prior knowledge to increase the predictive power of statistical models. From a practical perspective, these models and their related uncertainty, will serve as important management tools highlighting those portions of territories that will be more prone to biological invasions and where monitoring e? orts should be directed.

Analysis of the secondary nest of the yellow-legged hornet found in the Balearic Islands reveals its high adaptability to Mediterranean isolated ecosystems

Colomar, V.

Herrera, C.

Leza, M.M.

Marqués, A.

The yellow-legged hornet (Vespa velutina) was detected for the ?rst time in the north of Spain in 2010, but was not detected in Majorca, Balearic Islands until 2015 and only one secondary nest, with 10 combs, was found in the northwest of the island. During 2016, nine more nests were found in the same region. To better understand the biology of V. velutina in isolated conditions, the following objectives were proposed: (I) describe the architecture and structure of nests; (II) analyse the shape of combs and develop a new method to con?rm the circular pattern of breeding; (III) determine the colony size and (IV) determine the succession of workers and sexual individuals throughout the season. For these reasons, nests that were removed were frozen for at least 48 days until analysis. Our results show that this species has a high reproductive potential under isolated conditions. Results reveal that parameters such as weight, height, diameter, number of cells and total individual production are directly related. Moreover, each mature nest can produce up to 9,000 individuals and several hundred potential founder queens. All results inform formulation of an e?cient control or eradication programme in the Balearic Islands, as we are in the early stages of invasion and intervention is essential to eradicate V. velutina on Majorca Island.

Archipelago-wide island restoration in the Galapagos Islands: Reducing costs of invaisve mammal eradication programs and reinvasion risk

BRB