Juan Carlos Rando

The cat (Felis catus) is one of the worst invasive species, with well-documented impacts on biodiversity, especially on islands. Despite this, local administrations commonly implement trap–neuter–return (TNR) programmes to manage free-roaming cat populations. Here, we assess the effects of cat colonies on the endemic Tenerife lizard (Gallotia galloti). We used fruit-baited pitfall traps placed near and away from cat colonies to estimate lizard abundance and collect biometric data. Lizard abundance was lower near cat colonies compared with nearby control areas. Moreover, the individuals captured close to the colonies were smaller. Measurements of lizard carcasses found near colonies indicate that cats preferentially prey on larger individuals, explaining both their reduced abundance and their smaller body size. Interestingly, despite their smaller size, lizards near cat colonies presented higher scaled mass index values. Stable isotope analyses (δ13C and δ15N) of faecal samples suggest that these lizards partially rely on dried cat food available within colonies. Overall, cat colonies significantly altered lizard abundance, size structure and body condition. Given the ecological importance of G. galloti as both a seed disperser and prey, our findings highlight the need to limit the spread of free-roaming cat colonies, particularly in protected areas, to mitigate the effects on native biodiversity.

We present the first synthesis of all known terrestrial endemic species extinctions in the biogeographical region of Macaronesia, covering all archipelagos (Azores, Madeira, Selvagens, the Canaries, and Cabo Verde) and multiple taxa (arthropods, birds, bryophytes, fungi, land molluscs, lichens, mammals, reptiles, and vascular plants). This list also includes information on the original distribution of extinct species, extinction chronologies, and likely causes of extinction, as reported by the original works’ authors. Our survey identified 220 extinction records, with the highest numbers observed among land snails (111 species), arthropods (55), birds (27), and reptiles (15). The proportional impact of extinction was greatest among vertebrates: birds (50% of the original endemics lost), mammals (43%), and reptiles (28%). Very few extinctions were recorded in vascular plants or bryophytes, and none in fungi or lichens. However, these low levels of loss may partly reflect the scarcity of historical and fossil records for these taxa. Exactly half of the recorded endemic species losses (including nearly all vertebrates, as well as the arthropods and vascular plants) have extinction chronologies matching with the human occupation of the islands, providing a minimum estimate of the number of extinction events that may be directly or indirectly attributed to human activities.

The Late Quaternary fossil record indicates that formerly in the North Atlantic volcanic Macaronesian archipelagos (Azores, Madeira, Selvagens, Canary Islands, and Cape Verde) there was a higher avian diversity, including numerous now extinct species. Currently, only three gadfly petrels (genus Pterodroma) remain in two archipelagos: the Fea’s petrel, Pt. feae, in Cape Verde (islands of Santiago, Fogo, Santo Antão, and São Nicolau); the Zino’s petrel of Madeira, Pt. madeira, on the island of Madeira; and the Desertas petrel, Pt. deserta, on the islet of Bugio (Desertas Islands, Madeira Archipelago). Herein we describe the former distribution of the genus in Macaronesia based on the palaeontological record. However, the original specific diversity cannot be accurately established through the biometry of their fossil bones but the fossil record of Pterodroma in Macaronesia indicates: (i) its former presence in all Macaronesian archipelagos; (ii) the extinction of at least 16 island populations (73% of its original distribution on these islands); and (iii) the extinction of, at least, one species from Azores, here named Pterodroma zinorum sp. nov.. Radiocarbon dates indicate than this species was still alive at sometime among 1104 and 1672 CE, documenting its extinction in the last millennium.

Understanding the mechanisms underlying species formation and differentiation is a central goal of evolutionary biology and a formidable challenge. This understanding can provide valuable insights into the origins of the astonishing diversity of organisms living on our planet. Avian evolutionary radiations on islands have long fascinated biologists as they provide the ideal variation to study the ecological and evolutionary forces operating on the continuum between incipient lineages to complete speciation. In this review, we summarize the key insights gained from decades of research on adaptive and nonadaptive radiations of both extant and extinct insular bird species. We present a new comprehensive global list of potential avian radiations on oceanic islands, based on published island species checklists, taxonomic studies, and phylogenetic analyses. We demonstrate that our understanding of evolutionary processes is being greatly enhanced through the use of genomic tools. However, to advance the field, it is critical to complement this information with a solid understanding of the ecological and behavioral traits of both extinct and extant avian island species.

Cats, introduced on thousands of islands worldwide, are one of the greatest threats to native wildlife. An analysis of 301 scats was performed in order to study the diet of cats in a National Park in the alpine ecosystem of an oceanic island (Tenerife, Canary Islands). The results were compared with those obtained 35 years ago. In this study, eight types of vertebrates were detected in the cat diet: two endemic reptiles, four introduced mammals, and two birds. Although introduced rabbits were the most important prey, accounting for 53.9% of the biomass in the diet, this figure is among the lowest recorded in the Canary Islands. Data show a shift from the diet 35 years ago, with a decrease in the percentage of rabbits consumed, from 73% of diet biomass in 1986 to 53.9% today, and an increase mainly not only in reptiles but also in native birds. This change is due to a decrease in the rabbit population, probably motivated by the incidence of haemorrhagic disease (RHDV2). Using a daily intake of 170 g, we estimated that a single cat could prey on 1331 vertebrates/year. Assuming a low cat density of 1 cat/km², the total cat population in the National Park would kill 257,739 vertebrates, being native species particularly vulnerable to predation, with 166,249 reptiles and 5588 birds annually. Thus, with the aim of updating and improving management strategies for the conservation of native biodiversity, there is a need for new research on invasive predators on islands where diet may change over time.

Evolution of vertebrate endemics in oceanic islands follows a predictable pattern, known as the island rule, according to which gigantism arises in originally small-sized species and dwarfism in large ones. Species of extinct insular giant rodents are known from all over the world. In the Canary Islands, two examples of giant rats, † Canariomys bravoi and † Canariomys tamarani , endemic to Tenerife and Gran Canaria, respectively, disappeared soon after human settlement. The highly derived morphological features of these insular endemic rodents hamper the reconstruction of their evolutionary histories. We have retrieved partial nuclear and mitochondrial data from † C. bravoi and used this information to explore its evolutionary affinities. The resulting dated phylogeny confidently places † C. bravoi within the African grass rat clade ( Arvicanthis niloticus ). The estimated divergence time, 650 000 years ago (95% higher posterior densities: 373 000–944 000), points toward an island colonization during the Günz–Mindel interglacial stage. † Canariomys bravoi ancestors would have reached the island via passive rafting and then underwent a yearly increase of mean body mass calculated between 0.0015 g and 0.0023 g; this corresponds to fast evolutionary rates (in darwins (d), ranging from 7.09 d to 2.78 d) that are well above those observed for non-insular mammals.

Este trabajo presenta los resultados del estudio pluridisciplinar de un asentamiento temporal preeuropeo situado en la Reserva Natural Especial de las Dunas de Maspalomas (Gran Canaria). Carece de estructuras estables de habitación, pero conserva de manera excepcional una estructura de combustión sobre la arena dunar. El sitio se ocupó en el cambio del I al II milenio AD, una etapa para la que se cuenta con escasos paralelos en la isla. Allí se desarrollaron actividades ligadas a la explotación estacional de pastos y recursos marinos, reflejando un comportamiento oportunista y austero, a juzgar por la sencillez del ajuar documentado.

Cats have accompanied humans since they were domesticated, spreading and settling in a large number of islands where they modify environments and prey on native species. In the Canary Islands, several studies have shown that cat’s prey on native species, including Critically Endangered species such as the giant lizards of Tenerife (Gallotia intermedia), La Gomera (G. bravoana) and El Hierro (G. simonyi). This study focuses on the trophic ecology of the cat in Montaña de Guaza, where a population of the giant lizard of Tenerife is located. The current results show important changes in the diet of this alien species at this area in relation to the obtained by others author in 2004. The main changes detected are the low level of consumption of mammals and the high levels of birds and lizards. These changes seem to be a direct consequence of a low density of rabbit (Oryctolagus cuniculus), the main prey at the different habitats of Canary Islands, probably due to the rabbit hemorrhagic disease virus (RHDV) incidence. The high consumption of reptiles detected in this study could explain the reduction of both distribution area and number of giant lizards at this locality.

The original bird fauna of most oceanic islands has been affected by recent extinction processes associated with human arrival and its subsequent impacts. In the volcanic Macaronesian archipelagos (Azores, Madeira, Selvagens, Canary Islands and Cape Verde), in the North Atlantic, the Late Quaternary fossil record indicates that there was formerly a higher avian diversity, including a high number of now extinct endemic species. This assemblage of extinct birds includes endemic insular quails (Galliformes: Phasianidae). In this study, we describe three newly discovered extinct species of quails, two of which inhabited the archipelago of Madeira (Coturnix lignorum sp. nov. from Madeira Island and Coturnix alabrevis sp. nov. from Porto Santo Island) and one from Cape Verde (Coturnix centensis sp. nov.). The fossil record also indicates the presence of additional species of extinct endemic quails on other Macaronesian islands. These birds plus the extinct Canary Island quail (Coturnix gomerae) indicate a high former endemic diversity of this genus in Macaronesia, a feature unique among oceanic archipelagos. Anatomical traits show that the new taxa were flightless ground dwellers, making them vulnerable to human interference, with their extinction being linked to human arrival and subsequent habitat alterations and the introduction of invasive species.

We used carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes to examine the foraging ecology of Tenerife giant rats (Canariomys bravoi) and lizards (Gallotia goliath) in northwestern Tenerife, which until recently, were the island’s largest terrestrial vertebrates. We combined new isotope data for 28 C. bravoi and 14 G. goliath with published regional data for both species and then compared these with data for co-occurring extant taxa and modern C₃ plants. Isotope data suggest both extinct species relied primarily on C₃ resources and were trophic omnivores. However, the two species appear to have partitioned their resources when living in sympatry. Isotopic overlap between C. bravoi and Rattus spp., and between G. goliath, extant Gallotia galloti, and introduced rabbits (Oryctolagus cuniculus) suggests reliance on similar foods. We radiocarbon dated four C. bravoi and two G. goliath with the most extreme isotope values. These new dates do not settle the question of what triggered the demise of either species. Nevertheless, the data are most consistent with anthropogenically-induced extinction. Temporal isotopic trends contradict expectations if regional climate were responsible, and confidence intervals for radiocarbon dates suggest it is highly likely that both species were present when humans first settled the island.