Cats are generalist predators that have been widely introduced to the world's 179 000 islands. Once introduced to islands, cats prey on a variety of native species many of which lack evolved defenses against mammalian predators and can suffer severe population declines and even extinction. As islands house a disproportionate share of terrestrial biodiversity, the impacts of invasive cats on islands may have significant biodiversity impacts. Much of this threatened biodiversity can be protected by eradicating cats from islands. Information on the relative impacts of cats on different native species in different types of island ecosystems can increase the efficiency of this conservation tool. We reviewed feral cat impacts on native island vertebrates. Impacts of feral cats on vertebrates have been reported from at least 120 different islands on at least 175 vertebrates (25 reptiles, 123 birds, and 27 mammals), many of which are listed by the International Union for the Conservation of Nature. A meta-analysis suggests that cat impacts were greatest on endemic species, particularly mammals and greater when non-native prey species were also introduced. Feral cats on islands are responsible for at least 14% global bird, mammal, and reptile extinctions and are the principal threat to almost 8% of critically endangered birds, mammals, and reptiles

Cats are among the most successful and damaging invaders on islands and a significant driver of extinction and endangerment. Better understanding of their ecology can improve effective management actions such as eradication. We reviewed 72 studies of insular feral cat diet from 40 islands worldwide. Cats fed on a wide range of species from large birds and medium sized mammals to small insects with at least 248 species consumed (27 mammals, 113 birds, 34 reptiles, 3 amphibians, 2 fish and 69 invertebrates). Three mammals, 29 birds and 3 reptiles recorded in the diet of cats are listed as threatened by the IUCN.However, a few species of introduced mammals were the most frequent prey, and on almost all islands mammals and birds contributed most of the daily food intake. Latitude was positively correlated with the

A great part of the Earth's biodiversity occurs on islands, to which humans have brought a legion of invasive species that have caused population declines and even extinctions. The domestic cat is one of the most damaging species introduced to islands, being a primary extinction driver for at least 33 insular endemic vertebrates. Here, we examine the role of feral cats in the context of the island biodiversity crisis, by combining data from reviews of trophic studies, species conservation status reports, and eradication campaigns. The integration of these reviews permits us to identify priority islands where feral cat eradications are likely to be feasible and where cats are predicted to cause the next vertebrate extinctions. Funding agencies and global conservation organizations can use these results to prioritize scarce conservation funds, and national and regional natural resource management agencies can rank their islands in need of feral cat eradication within a global context.

Summary Indirect seed dispersal in the system Lycium intricatum (Solanaceae)–lizards (Gallotia atlantica)–shrikes (Lanius excubitor) was studied in Alegranza, a xerophytic small island of the Canarian archipelago. A total of 835 seeds (224 obtained from lizard droppings and 611 from shrike pellets) was found by analysing 123 droppings and 146 pellets. Lycium fruit remains (including seeds) were observed in 31.7% of the lizard droppings and 50% of the shrike pellets. As would be expected for legitimate seed dispersers, external seed damage produced by each species was negligible. Lycium seeds were significantly matched with the presence of lizard remains in shrike pellets. Seeds in shrike pellets have come from fruit consumed by lizards that have been predated by the shrikes, and not directly from bird frugivory. Seeds from shrike pellets showed significantly higher germination rates than those from uneaten fruits and lizard droppings. It seems probable that different treatments in the guts of each species and retention time are two main factors influencing the germination process. While gut pass time in G. atlantica has been estimated to be 2.42 days on average, the retention time of a seed inside a shrike gizzard is much shorter (45–55 min). This is a new case of the scarcely known phenomenon of indirect seed dispersal, which seems to acquire a relatively important role in small islands where the animal–plant interaction is very intense and all the elements of the system are native.

Aim Few data sets exist on the role of gulls as seed dispersal agents. Our purpose is to quantify the number of seeds dispersed, to assess damage to the seeds regurgitated and those expelled via cloaca, to check for possible differences in seed viability and germination rates, to study the seed retention time, and to evaluate gulls as adequate dispersal agents throughout the Canary Islands and for the colonization of this archipelago by this plant species (or its ancestor), from Africa. Location This study was developed in ‘Los Islotes’, a small archipelago located off the northern part of Lanzarote Island (Canaries). Methods We counted the number of seeds in each pellet and dropping collected and we measured and weighed them. Seed viability and germination from the three treatments (plants, pellets and droppings) were studied. Gut pass time (GPT) was assessed in two gulls by using glass beads (similar in size with Rubia fruticosa Ait. seeds). We employed a combination of univariate and bivariate statistical tests to analyse the data. Results From 81 pellets and 84 droppings, we extracted a total of 60,679 seeds (48,460 and 12,219, respectively). Data obtained in the GPT experiments show that a similar number of seeds are defecated and regurgitated. No externally damaged seed was observed and the majority were viable, giving more than 95% in all treatments (seeds from plants, droppings and pellets). Most seeds on these treatments showed germination rates of over 80%, verifying the importance of the gulls as legitimate dispersers of this Macaronesian endemic plant species. Taking into account that the gulls’ flight cruise speed is about 31–40 km h–1 and mean GPT of these birds is between 9.51 and 16.92 h, they could cover a distance between 295 and 677 km before expelling the seeds. This distance is well within the range of colonization of the different islands of the Canaries and the neighbouring archipelagos of Salvages and Madeira from the north‐west of Africa, where the ancestor of this plant may have originated. Main conclusions The results support the idea that gulls could have been one of the main agents responsible for the movement of R. fruticosa seeds among the islands of the Canaries and for the colonization of the Macaronesian archipelagos from Africa. Furthermore, this study suggests that gulls are generalist feeding seabirds with high capacity for seed transport and high long‐distance power displacements, could have played a more important role than that currently recognized by most authors, in the colonization of oceanic islands by some plants whose genetic origins were located at long‐distances.

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We have studied the unusual phenomenon of secondary seed dispersal of Lycium intricatum seeds on a small oceanic Atlantic island (Alegranza, Canarian Archipelago) in which a small frugivorous lizard (Gallotia atlantica) and two different predatory birds participate, a shrike (Lanius excubitor) and a kestrel (Falco tinnunculus). Endemic lizards that are common prey of both bird species consume Lycium fruits. Lizard remains were significantly matched with the presence of Lycium fruits in the regurgitation pellets of the two predatory birds. Seeds were found in 7.3% of the lizard droppings, 31.0% of kestrel pellets and 55.7% of shrike regurgitations. The mean number of seeds per dropping or pellet was 4.8 ±4 in lizard, 20.2 ±34.5 in shrike and 6.7 ±8.1 in kestrel. The percentage of viable seeds showed significant differences among all four treatments, decreasing in the following direction: seeds collected directly from plants (98.0%), shrikes (88.0%), lizards (72.3%), and kestrels (31.7%). Seeds from Lycium fresh fruits and shrike pellets showed significantly higher germination rates than those from lizard droppings and kestrel pellets. While lizards and shrikes are effective seed dispersers, kestrel gut treatment decreases seed viability. Seed viability is always higher than seed germination in each of the four treatments. In this island environment, Lycium seeds are under an important random influence during the seed dispersal process. Secondary seed dispersal seems to acquire a relevant dimension in small and remote insular environments or isolated continental systems where interactions among the different elements involved are intense, all of them are abundant native residents, and they have been coexisting for a long time. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 75, 345–352.