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Ecological replacement involves the introduction of non-native species to habitats beyond their historical range, a factor identified as increasing the risk of failure for translocations. Yet the effectiveness and success of ecological replacement rely in part on the ability of translocatees to adapt, survive and potentially reproduce in a novel environment. We discuss the welfare aspects of translocating captive-reared non-native tortoises, Aldabrachelys gigantea and Astrochelys radiata, to two offshore Mauritian islands, and the costs and success of the projects to date. Because tortoises are long-lived, late-maturing reptiles, we assessed the progress of the translocation by monitoring the survival, health, growth, and breeding by the founders. Between 2000 and 2011, a total of 26 A. gigantea were introduced to Ile aux Aigrettes, and in 2007 twelve sexually immature A. gigantea and twelve male A. radiata were introduced to Round Island, Mauritius. Annual mortality rates were low, with most animals either maintaining or gaining weight. A minimum of 529 hatchlings were produced on Ile aux Aigrettes in 11 years; there was no potential for breeding on Round Island. Project costs were low. We attribute the success of these introductions to the tortoises' generalist diet, habitat requirements, and innate behaviour. Feasibility analyses for ecological replacement and assisted colonisation projects should consider the candidate species' welfare during translocation and in its recipient environment. Our study provides a useful model for how this should be done. In addition to serving as ecological replacements for extinct Mauritian tortoises, we found that releasing small numbers of captive-reared A. gigantea and A. radiata is cost-effective and successful in the short term. The ability to release small numbers of animals is a particularly important attribute for ecological replacement projects since it reduces the potential risk and controversy associated with introducing non-native species.

Aim: To test whether ingestion by endemic frugivores differentially affects the seed germination time, germination percentage and seedling survival of endemic, native and exotic fleshy fruited plant species, and to identify the principal processes and attributes driving such effects. Location: Round Island, Mauritius. Methods: We conducted a germination and seedling survival experiment for 3 months to test whether ingestion (gut passage and deposition in faeces) by the endemic Telfair's skink (Leiolopisma telfairii) had a differential effect on the germination time, germination percentage and seedling survival of two endemic, four native and two exotic fleshy fruited plant species. To assess the importance of factors involved in the ingestion process, we used a factorial design with gut passage (gut-passed vs. not gut-passed), depulping (whole fruit vs. manually depulped seed) and the presence of faecal material (faeces vs. without faeces). In addition, the roles of species-specific traits, seed size and deposition density (average number of seeds per faeces) were examined. Results: Exotic species had a higher germination percentage than indigenous (native and endemic) species when not ingested. Following skink ingestion, there was no longer a difference, as ingestion enhanced germination percentage most in endemic species. The exotic species still germinated faster overall than the indigenous species, despite ingestion accelerating the germination time of endemics. However, ingestion strongly reduced seedling survival of the exotic species, while having no negative effect on the survival of indigenous seedlings. Overall, ingested indigenous seeds were more likely to germinate and the seedlings more likely to survive than ingested exotic seeds and seedlings. Seed size, deposition density and the removal of fruit pulp by either manual depulping or gut passage were important predictors of germination time, germination percentage and seedling survival. Main conclusions: These endemic frugivores can enhance the competitiveness of endemic compared with exotic fleshy fruited plants at the critical germination and seedling establishment stage. Consequently, conservation and restoration of mutualistic endemic plant-animal interactions may be vital to mitigating the degradation of habitats invaded by exotic plants, which is of particular relevance for island ecosystems in which large numbers of endemics are threatened by exotic invaders.

The extinction of large herbivores, often keystone species, can dramatically modify plant communities and impose key biotic thresholds that may prevent an ecosystem returning to its previous state and threaten native biodiversity. A potentially innovative, yet controversial, landscape-based long-term restoration approach is to replace missing plant-herbivore interactions with non-native herbivores. Aldabran giant (Aldabrachelys gigantea) and Madagascan radiated (Astrochelys radiata) tortoises, taxonomically and functionally similar to the extinct Mauritian giant tortoises (Cylindraspis spp.), were introduced to Round Island, Mauritius, in 2007 to control the non-native plants that were threatening persistence of native species. We monitored the response of the plant community to tortoise grazing for 11 months in enclosures before the tortoises were released and, compared the cost of using tortoises as weeders with the cost of using manual labor. At the end of this period, plant biomass; vegetation height and cover; and adult, seedling, flower, and seed abundance were 3-136 times greater in adjacent control plots than in the tortoise enclosures. After their release, the free-roaming tortoises grazed on most non-native plants and significantly reduced vegetation cover, height, and seed production, reflecting findings from the enclosure study. The tortoises generally did not eat native species, although they consumed those native species that increased in abundance following the eradication of mammalian herbivores. Our results suggest that introduced non-native tortoises are a more cost-effective approach to control non-native vegetation than manual weeding. Numerous long-term outcomes (e.g., change in species composition and soil seed bank) are possible following tortoise releases. Monitoring and adaptive management are needed to ensure that the replacement herbivores promote the recovery of native plants. La extinción de grandes herbívoros, casi siempre especies clave, puede modificar dramáticamente a las comunidades de plantas e imponer umbrales bióticos claves que pueden impedir que un ecosistema regrese a su estado previo y que amenacen a la biodiversidad nativa. Una aproximación potencialmente innovadora, a largo plazo basada en el paisaje, pero controversial, consiste en reemplazar las interacciones herbívoro-planta faltantes con herbívoros no-nativos. Aldabrachelys gigantea y Astrochelys radiata son tortugas terrestres similares funcional y taxonómicamente a la especie extinta Cylindraspis spp., que fueron introducidas a Round Island, Mauricio, en 2007 para controlar a las plantas no-nativas que estaban amenazando la persistencia de especies nativas. Monitoreamos la respuesta de la comunidad vegetal al forrajeo de las tortugas durante 11 meses en encierros antes de que las tortugas fueran liberadas y comparamos el costo de usar a las tortugas como eliminadores de hierbas con el costo de usar labor manual. Al final de este periodo la biomasa vegetal, la altura y cobertura de la vegetación, y la abundancia de adultos, plántulas, flores y semillas eran entre 3-316 veces más grandes en terrenos control adyacentes que en los encierros con tortugas. Después de su liberación, las tortugas forrajearon a casi todas las plantas no-nativas y redujeron significativamente la cobertura de la vegetación, altura y producción de semilla, igualando los resultados del estudio de los encierros. Las tortugas en general no comieron especies nativas aunque sí consumieron aquellas especies nativas cuya abundancia incrementó después de la erradicación de mamíferos herbívoros. Nuestros resultados sugieren que las tortugas no-nativas introducidas son una aproximación más económica que el deshierbe manual para controlar a la vegetación no-nativa. Numerosos resultados a largo plazo (e.g., cambios en la composición de especies y el banco de semillas en el suelo) son posibles una vez liberadas las tortugas. Se requiere de monitoreo y manejo adaptativo para asegurar que los herbívoros de reemplazo promuevan la recuperación de las plantas nativas.

Emerging Infectious Diseases (EIDs) are recognised as global extinction drivers of threatened species. Unfortunately, biodiversity managers have few tested solutions to manage them when often the desperate need for solutions necessitates a response. Here we test in situ biosecurity protocols to assess the efficacy of managing Psittacine beak and feather disease (PBFD), one of the most common and emergent viral diseases in wild parrots (Psittaciformes) that is currently affecting numerous threatened species globally. In response to an outbreak of PBFD in Mauritius “echo” parakeets ( Psittacula eques ), managers implemented a set of biosecurity protocols to limit transmission and impact of Beak and feather disease virus (BFDV). Here we used a reciprocal design experiment on the wild population to test whether BFDV management reduced viral prevalence and viral load, and improved nestling body condition and fledge success. Whilst management reduced the probability of nestling infection by approximately 11% there was no observed impact on BFDV load and nestling body condition. In contrast to expectations there was lower fledge success in nests with added BFDV biosecurity (83% in untreated vs. 79% in treated nests). Our results clearly illustrate that management for wildlife conservation should be critically evaluated through targeted monitoring and experimental manipulation, and this evaluation should always focus on the fundamental objective of conservation.

For conservation managers tasked with recovering threatened species, genetic structure can exacerbate the rate of loss of genetic diversity because alleles unique to a sub-population are more likely to be lost by the effects of random genetic drift than if a population is panmictic. Given that intensive management techniques commonly used to recover threatened species frequently involve movement of individuals within and between populations, managers need to be aware not only of pre-existing levels of genetic structure but also of the potential effects that intensive management might have on these patterns. The Mauritius parakeet ( Psittacula echo ) has been the subject of an intensive conservation programme, involving translocation and reintroduction that has recovered the population from less than 20 individuals in 1987 to approximately 500 in 2010. Analysis of genotype data derived from 18 microsatellite markers developed for this species reveals a clear signal of structure in the population before intensive management began, but which subsequently disappears following management intervention. This study illustrates the impacts that conservation management can have on the genetic structure of an island endemic population and demonstrates how translocations or reintroductions can benefit populations of endangered species by reducing the risk of loss of genetic diversity.