Predation of insects by feral cats (
Felis silvestris catus) on a heterogeneous oceanic island (La Palma, Canary Islands) was studied. A total of 127 invertebrates were identified in the analysis of 500 scats (100 from each habitat of the Island). Invertebrates appear in 18.00% of the scats, representing an insignificant percentage of the total consumed biomass by feral cats on La Palma Island (0.05%). Insects were the most common invertebrate prey both in percentage of occurrence (90.6%) and invertebrate biomass (93.53%), with a total of 115 prey items. Orthoptera, Lepidoptera and Coleoptera were the main prey groups. Among the five main habitats present in La Palma Island, the temperate forest shows the lowest consumption of invertebrates, although insect consumption did not show statistical differences. However Orthoptera and Lepidoptera were more frequently preyed on in the pine forest and in the xerophytic shrub, respectively. Moreover, applying the Simplified Morisita index, a different insect composition of the diet was observed among habitats. Although, none of insects predated by feral cats are threatened, the identification of invertebrate component of the feral cats’ diet is an important tool for the correct understanding of predation significance and to prevent damage to endangered insect species.
8 Medina, F.M. & M. Nogales. 2009. A review on the impacts of feral cats (Felis silvestris catus) in the Canary Islands: implications for the conservation of its endangered fauna. Biodiversity and Conservation 18: 829-846.
Feral cats have been directly responsible for the extinction of numerous species on islands worldwide, including endemic species of mammals, birds and reptiles. The diet of feral cats in the main habitats of the Canary Islands, as generally occurred on oceanic islands, is mainly composed of introduced mammals, and native species of birds, reptiles and insects. The impact of feral cat upon the endangered species was assessed by evaluating their relative abundance in the cats’ diet and by considering their current conservation status. A total of 68 different preys were identified at species level in all studies carried out in the Canary Islands (5 mammals, 16 birds, 15 reptiles and 32 invertebrates). From all the species preyed by feral cats in the Canary Islands, only four of them are considered threatened by the IUCN Red List of Threatened Species: one endemic bird
Saxicola dacotiae and three endemic giant lizards,
Gallotia simonyi,
Gallotia intermedia, and
Gallotia gomerana. Although some efforts on management control have been carried out, it is necessary to enforce these conservation activities on those areas of Tenerife, La Gomera and El Hierro where giant lizards are still present. Furthermore some local areas where endangered bird species are highly predated should be protected. Nevertheless, it is important to take into account the presence of other introduced species such as rats, mice or rabbits in order to avoid problems derived from the hyperpredation process and mesopredator release effect.
9 Nogales, M. & F.M. Medina. 2009. Trophic ecology of feral cats (Felis silvestris f. catus) in the main environments of an oceanic archipelago (Canary Islands): An updated approach. Mammalian Biology 74: 169-181.
The diet of feral cats in the main habitats of the Canary Islands is composed of introduced mammals, birds, reptiles and insects. However, introduced mammals constitute the main source of biomass consumed, followed in importance by reptiles and birds. PCA analysis of biomass revealed the ordination of three different groups, corresponding to the diet in the laurel forest (La Gomera), thermophilous forest (El Hierro) and one large group that include the rest of habitat types. A similar pattern was observed when these habitats were analyzed in a single island (La Palma).
Oryctolagus cuniculus was an important prey in practically all habitats, while
Rattus rattus was frequently captured in the laurel forest,
Mus musculus domesticus in the open shrubs (both xeric and high mountain), reptiles (mainly lizards genus
Gallotia) in the open habitats of Tenerife, birds play a relative role in forest habitats, and large invertabrates (basically Orthoptera and Coleoptera) in the three forest habitats and in the xerophytic shrub of Fuerteventura. Morisita’s index of similarity of diet showed maximum differences between the forest habitats (pine and thermophilous vs. laurel forest), indicating an important heterogeneity in the diet of feral cats in these environments. Shrub habitats showed smaller values of Levin’s niche breadth than those from the forest habitats, showing a broader diet in the latter. Lastly, the diet of feral cats on the Canary Islands follows the general pattern of other islands located at similar latitude and mainly composed by rabbits and mice. However, specific preys such as lizards, rats or birds, play an important role in particular habitats in which they are abundant.
10 Medina, F.M. & M. Nogales. 2007. Habitat use of feral cats in the main environments of an Atlantic Island (La Palma, Canary Islands). Folia Zooliga 56(3): 277–283
In this study we assess the habitat use of feral cats in the five main habitats represented on La Palma Island in the Canary Islands. We determined habitat use by the presence of faeces. Faeces persistence time was significantly different between habitats, being clearly lower in the laurel forest (the wettest) than in the other habitats. This humid environment promotes the high presence of invertebrate decomposers such as Isopoda and Diplopoda. Once the effect of differential persistence times for faeces among the different habitats was controlled for, data obtained indicated that feral cats showed no differences in the use of the five main habitats present on La Palma Island. Although cats selected closed habitats more frequently than open ones, because they prefer cover for hunting, no statistical differences were found in the island habitats studied.
11 Medina, F. M., M. López-Darias & M. Nogales. 2008. Food habits of feral cats (Felis sylvestris f. catus, L. 1758) in insular semiarid environments (Fuerteventura, Canary Islands). Wildlife Research 35: 162-169.
In this study, we present the first data on diet and impacts of feral cats on a semiarid island (Fuerteventura, Canary Islands). A total of 614 prey was identified in the 209 scats analysed. Introduced mammals, specially rabbits and mice, were the most consumed vertebrate prey and constituted more than 90% of biomass. Barbary ground squirrels, Algerian hedgehogs, and rats were preyed upon less even though they were abundant on the island. Invertebrates, mainly Orthoptera, Coleoptera, Hymenoptera and Odonata, were the second most important prey items (in terms of actual numbers) but they contributed only minimally with respect to biomass (<1.1%). The presence of terrestrial molluscs in the diet was interesting because they are a rare prey in an insular context. Birds and reptiles occurred at a low frequency. A total of 677 seeds was counted, mainly belonging to
Lycium intricatum (Solanaceae) and two unidentified plant species. Levin’s niche breadth was narrow due to the high consumption of mammals. Morisita’s index showed a similar trophic overlap in diet with respect to the other xeric habitats of the Canarian archipelago. Considering that more than 90% of biomass corresponded to introduced mammals, we conclude that feral cats are not having a large direct impact on the native prey species.
12 Medina, F.M. y M. Nogales. 1993. Diet of the feral cat (Felis catus L.) in the xerophytic zone of the Macizo de Teno (Northwestern Tenerife. Doñana Acta Vertebrata, 20 (2): 291-297
The diet of the Feral cat (Felis catus) was studied in the xerophytic zone of Tenerife, by analyzing 200 scats. A total of 477 prey items were identified. Mammals (
Oryctolagus cuniculus, Mus musculus and Rattus sp.) constitued the basis of the diet occurring in 86% of the samples and representing 85,4% of the consumed biomass. Reptiles occurred in 57% of the scats and representing 13,6% of the biomass. The lizard (
Gallotia galloti), endemic of the western Canary Islands, was frequenetly captured, occurring in 54% of the scat groups and representing 13% of the total biomass. This percentage is very importan in the world context of the diet. Birds and insects (frequence of occurrence less than 5%) were insignificant in the diet.
Cabo Verde
13 Medina, F. M., P. Oliveira, P. Geraldes, J. Melo & N. Barros. 2012. Diet of feral cats Felis catus L., 1758 on Santa Luzia, Cape Verde Islands. Zoologia Caboverdiana 3 (2): 67-73.
The diet of feral cats Felis catus on Santa Luzia, Cape Verde Islands, was studied. A total of 147 prey items were identified during the analysis of 26 scat groups collected during the summer of 2010. House mouse Mus musculus was the most important prey, both in percentage of biomass and number of preys consumed (89.7% and n= 117, respectively). Reptiles were the second most important prey, represented by one skink species (Chioninia stangeri) and an unidentified gecko species. The remainder of the identified prey consisted of one bird species (Passer iagoensis) and one undetermined Tettigoniidae species (Insecta). No endangered species were identified in scats of this introduced predator, but future surveys must be carried out to further avoid threats to the island’s biodiversity.
