Interspecific relationships in a suboptimal habitat, an unexpected ally for the survival of the threatened Tenerife speckled lizard (Gallotia intermedia)

Abstract Anthropogenic-driven environmental changes are pushing species to the limits of their habitats. More often species are restricted to relic or suboptimal habitats that present the minimum requirements to sustain species populations. In this scenario of accelerated environmental change and biodiversity loss, is fundamental to understand why species can survive in such suboptimal conditions. In this study, we show how the Tenerife speckled lizard ( Gallotia intermedia ), a critically endangered endemic reptile from the Canary Islands, can maintain stable populations in relic habitats thanks to its interactions with the yellow-legged gull ( Larus michahellis ) colony. A stable isotope analysis revealed that G. intermedia relies on marine subsidies for its diet and that the foraging area of this reptile is likely to be restricted to the limits of L. michahellis breeding colony. Furthermore, an antipredator behaviour analysis showed that L. michahellis displayed a strong anti-predator or mobbing response against cats, one of the main threats for G. intermedia , thus potentially providing some protection to the reptiles inhabiting the seabird colony. Our results show how unusual and poorly studied biotic interactions can provide valuable resources and conditions for the conservation of a critically endangered species inhabiting a suboptimal or relict habitat.