Diet of feral cats on subantarctic Auckland Island

Feral cats were trapped and cat scats collected at Port Ross, Auckland Island, during two weeks in winter 2007. Eleven cats were caught and 40 scats collected, including from upland tussock areas. Cats? diet predominantly consisted of birds (77.5% occurrence in scats) and mice (52.5% occurrence). The cats were relatively heavy and in good condition compared with other feral cats in New?Zealand populations.     

Feral cats on Stewart Island; their foods,and their effects on kakapo

Abstract

The foods of feral house cats (Felis catus) on Stewart Island were determined by examining 229 scats collected during surveys of the distribution and numbers of kakapo (Strigops habroptilus), an endangered ground-parrot species. Rats occurred in 93% of the scats, birds in 44. 1%, wetas (large orthopterans) in 26.2%, and lizards in 24.0%. Twelve (70.6%) of the 17 species of birds were native. Kakapo remains were found in 6 (5.1%) of the 118 scats collected from areas where kakapo have been recorded.     

The diet of feral cats at New Island, Falkland Islands, and impact on breeding seabirds

We studied the diet of feral cats (Felis catus) on New Island, Falkland Islands, through the analysis of 373 scats collected during the austral summers of 2004/2005 and 2005/2006. The most frequent prey were three introduced mammals (house mice Mus musculus, ship rats Rattus rattus and rabbits Sylvilagus sp.) and the thin-billed prion Pachyptila belcheri (each season present on ca. 21% of the analysed scats). These represent the first systematic data on feral cat diet for the Falklands. A simple bioenergetics model suggests that cats could be eating in the region of 1,500–11,000 prions per season, representing <1% of the local adult and subadult population. Predation on other seabirds nesting on New Island (several penguin species, albatrosses and cormorants) was unimportant, with the possible exception of white-chinned petrels Procellaria aequinoctialis, which nest locally in very small numbers. For each prion eaten, cats were estimated to have killed 1.1–1.9 ship rats during the summer season, and probably more in autumn and winter. Knowing that ship rats are prion predators, it is conceivable that, on the whole, cats are having a positive impact on the prion population, a scenario predicted by general theoretical models. Thus, considering the available information, we would not recommend the implementation of any eradication programme on New Island that would target cats in isolation. Nevertheless, it would be prudent to consider some local action targeting cats and rats around the small New Island white-chinned petrel colony.     

Trophic ecology of feral cats (Felis silvestris f. catus) in the main environments of an oceanic archipelago (Canary Islands): An updated approach

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 invertebrates (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.     

Predation of insects by feral cats (<Emphasis Type="Italic">Felis silvestris catus</Emphasis> L., 1758) on an oceanic island (La Palma,Canary Island)

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.     

How can the Yelkouan shearwater survive feral cat predation? A meta-population structure as a solution?

The Yelkouan shearwater, Puffinus yelkouan, is an endangered Mediterranean endemic species of burrowing petrel threatened by feral cats. The life-history parameters of a small population of Yelkouan shearwaters on the Mediterranean island, Port-Cros, were studied in conjunction with the diet of feral cats, to examine the birds’ vulnerability to introduced cats. Yelkouan shearwaters were the birds most frequently found in cat scats, with 431 ± 72 birds killed per year, and predation highest during the pre-laying period. A demographic model was created using data for P. yelkouan and for closely related shearwater species. Without cat predation, only two of four survival rate scenarios led to a mean growth rate (λ) ≥ 1. The model was constrained to have a stable population growth rate and used to predict predation scenarios compatible with the observed population stability, because the population under study has remained stable at around 180 pairs for at least 20 years despite feral cat predation. The results of assuming that the population is closed were inconsistent with the estimated mortalities due to feral cats, while it was possible to reconcile the observed numbers of breeding pairs with the observed mortalities due to cats by assuming that Port-Cros Island is a sink sustained by immigration. This illustrates that small colonies may need to be sustained by larger ones to avoid being driven to extinction. Unfortunately, the absence of a large geographic-scale ringing program makes the precise identification of the origin of the immigrants impossible in this case.     

The diet of feral cats on islands: a review and a call for more studies

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 predation of rabbits and negatively with the predation of reptiles and invertebrates. Distance from landmass was positively correlated with predation on birds and negatively correlated with the predation of reptiles. The broad range of taxa consumed by feral cats on islands suggests that they have the potential to impact almost any native species, even the smallest ones under several grams, that lack behavioral, morphological or life history adaptations to mammalian predators. Insular feral cat??s reliance on introduced mammals, which evolved with cat predation, suggests that on many islands, populations of native species have already been reduced.     

Comparative analysis of the diet of feral and house cats and wildcat in Europe

Differences in availability of food resources are often manifested in the differentiation of feeding habits of closely related mammal species. Therefore, we assumed that the diet composition and trophic niche of house (i.e., highly dependent on human households), feral (i.e. independent on human households) domestic cats (Felis silvestris catus) and wildcats (Felis s. silvestris) differs. Based on the literature data from Europe (53 study sites), we compared the diet of these three felids analyzed with use of indirect methods (stomach and scat analyses). In the case of the house cat, we additionally compared consumption data obtained directly from prey brought home. Data were expressed as the relative frequency of occurrence to compare dietary patterns. The main prey of the three cat types were small mammals in different ratios. According to the stomach and scat samples, the diet composition of the cat types showed differences in the consumption of rodents, insectivores, wild ungulates, and household food, supporting the “dietary differences originate from varying resources” hypothesis. More opportunistic house cats had a broader trophic niche than feeding specialist wildcats, while feral cats had an intermediate position. The trophic niche breadth of all three cat types increased along a latitudinal gradient from northern to southern areas of Europe. The predation of the house cat which was examined from prey brought home differed from the data obtained by indirect diet analysis; however, it yielded similar results to the diet of the feral cat and the wildcat. Due to their high numbers and similarity of its diet to the wildcat, house cats are a threat to wild animals; therefore, their predation pressure needs to be further investigated.     

The diet of an invasive nonnative predator,the feral ferret <Emphasis Type="Italic">Mustela furo</Emphasis>, and implications for the conservation of ground-nesting birds

Introduced carnivores have had a significant impact on the fauna of a number of countries, particularly on islands. In the British Isles, several offshore islands holding internationally important aggregations of seabirds and shorebirds support self-sustaining feral ferret Mustela furo populations, often as the top terrestrial predator. However, little is known about the interactions between ferrets and both native and nonnative prey in these locations. We examined the diet of feral ferrets on Rathlin Island, Northern Ireland. We determined the frequency of occurrence of prey items and constructed energetic models to determine their potential impact on both native and introduced prey. Rabbits Oryctolagus cuniculus occurred in 75% of scats, while birds, carrion, and brown rats Rattus norvegicus were important secondary items. There was little difference between the diets of males and females. Estimates of the energy requirements of the population at current, and with hypothetically reduced, rabbit availability revealed the potential for carrion to maintain the ferret population over winter. Management options could thus focus on reducing anthropogenic food sources as an immediate way of mitigating the threat to ground-nesting birds, while other strategies, including eradication, are considered.     

A global review of the impacts of invasive cats on island endangered vertebrates

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.     

Diet of the fox Vulpes vulpes in a western Victorian forest

The diet of foxes living in a mixed dry sclerophyll forest at Naringal East near Warrnambool, Victoria was investigated by analysis of scats collected between October 1972 and July 1975. The results indicate that foxes in the study area are opportunistic feeders whose diet consists mainly of rabbits despite the abundance of suitably sized native mammals and an even greater abundance of birds. During summer and autumn the foxes consume large numbers of insects, particularly the black cricket, Gryllus servillei, and the Australian plague locust, Chortoicetes terminifera, and blackberries.     

A review on the impacts of feral cats (Felis silvestris catus) in the Canary Islands: implications for the conservation of its endangered fauna

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.     

Trophic habits of feral cats in the high mountain shrublands of the Macaronesian islands (NW Africa,Atlantic Ocean)

Feral cats Felis catus Linnaeus, 1758 have contributed to the extinction of numerous native species on islands, which are clearly sources of global biodiversity. We studied the diet of this introduced predator in the Madeira and Cape Verde archipelagos, which harbour important colonies of endangered seabirds in the high mountain habitats, and compared the results with those obtained in the same habitat in the Canary Islands, Macaronesian archipelago. On Madeira, 461 prey were identified from 143 scat groups. Mammals, overall mice, constituted the basic diet appearing in 95% of cat scats. On Fogo (Cape Verde), 657 prey items were obtained from 145 scats, and mammals were also the most important prey, reaching a frequency of occurrence of 88%. Although introduced mammals were the main prey category on all Macaronesian islands, we observed variation in feral cat diet among these islands. Birds were more frequently consumed on Madeira, lizards on Tenerife (Canaries) and invertebrates on Fogo. No specific differences were observed in relation to La Palma. We suggest that the diet composition on these islands varies according to the respective availability of the different prey types.     

Free-ranging domestic cats (<Emphasis Type="Italic">Felis catus</Emphasis>) on public lands: estimating density,activity, and diet in the Florida Keys

Feral and free-ranging domestic cats (Felis catus) can have strong negative effects on small mammals and birds, particularly in island ecosystems. We deployed camera traps to study free-ranging cats in national wildlife refuges and state parks on Big Pine Key and Key Largo in the Florida Keys, USA, and used spatial capture–recapture models to estimate cat abundance, movement, and activities. We also used stable isotope analyses to examine the diet of cats captured on public lands. Top population models separated cats based on differences in movement and detection with three and two latent groups on Big Pine Key and Key Largo, respectively. We hypothesize that these latent groups represent feral, semi-feral, and indoor/outdoor house cats based on the estimated movement parameters of each group. Estimated cat densities and activity varied between the two islands, with relatively high densities (~4 cats/km²) exhibiting crepuscular diel patterns on Big Pine Key and lower densities (~1 cat/km²) exhibiting nocturnal diel patterns on Key Largo. These differences are most likely related to the higher proportion of house cats on Big Pine relative to Key Largo. Carbon and nitrogen isotope ratios from hair samples of free-ranging cats (n = 43) provided estimates of the proportion of wild and anthropogenic foods in cat diets. At the population level, cats on both islands consumed mostly anthropogenic foods (>80% of the diet), but eight individuals were effective predators of wildlife (>50% of the diet). We provide evidence that cat groups within a population move different distances, exhibit different activity patterns, and that individuals consume wildlife at different rates, which all have implications for managing this invasive predator.     

Laying low: Rugged lowland rainforest preferred by feral cats in the Australian Wet Tropics

Invasive mesopredators are responsible for the decline of many species of native mammals worldwide. Feral cats have been causally linked to multiple extinctions of Australian mammals since European colonization. While feral cats are found throughout Australia, most research has been undertaken in arid habitats, thus there is a limited understanding of feral cat distribution, abundance, and ecology in Australian tropical rainforests. We carried out camera‐trapping surveys at 108 locations across seven study sites, spanning 200 km in the Australian Wet Tropics. Single‐species occupancy analysis was implemented to investigate how environmental factors influence feral cat distribution. Feral cats were detected at a rate of 5.09 photographs/100 days, 11 times higher than previously recorded in the Australian Wet Tropics. The main environmental factors influencing feral cat occupancy were a positive association with terrain ruggedness, a negative association with elevation, and a higher affinity for rainforest than eucalypt forest. These findings were consistent with other studies on feral cat ecology but differed from similar surveys in Australia. Increasingly harsh and consistently wet weather conditions at higher elevations, and improved shelter in topographically complex habitats may drive cat preference for lowland rainforest. Feral cats were positively associated with roads, supporting the theory that roads facilitate access and colonization of feral cats within more remote parts of the rainforest. Higher elevation rainforests with no roads could act as refugia for native prey species within the critical weight range. Regular monitoring of existing roads should be implemented to monitor feral cats, and new linear infrastructure should be limited to prevent encroachment into these areas. This is pertinent as climate change modeling suggests that habitats at higher elevations will become similar to lower elevations, potentially making the environment more suitable for feral cat populations.     

Introduced mammals coexist with seabirds at New Island,Falkland Islands: abundance,habitat preferences,and stable isotope analysis of diet

The largest known colony of Thin-billed prions Pachyptila belcheri has been coexisting with introduced mammals for more than 100 years. Three of the introduced mammals are potential predators of adults, eggs and chicks, namely ship rats Rattus rattus, house mice Mus musculus and feral cats Felis catus. We here determine habitat preferences over three seasons and dietary patterns of the unique set of introduced predators at New Island, Falkland Islands, with emphasis on the ship rats. Our study highlights spatial and temporal differences in the levels of interaction between predators and native seabirds. Rats and mice had a preference for areas providing cover in the form of the native tussac grass Parodiochloa flabellata or introduced gorse Ulex europaeus. Their diet differed markedly between areas, over the season and between age groups in rats. During the incubation period of the prions in November–December, ship rats had mixed diets, composed mainly of plants and mammals, while only 3% of rats had ingested birds. The proportion of ingested birds, including scavenged, increased in the prion chick-rearing period, when 60% of the rats consumed prions. We used δ¹³C and δ¹⁵N to compare the importance of marine-derived food between mammal species and individuals, and found that rats in all but one area took diet of partly marine origin, prions being the most frequently encountered marine food. Most house mice at New Island mainly had terrestrial diet. The stable isotope analysis of tissues with different turnover times indicated that individual rats and mice were consistent in their diet over weeks, but opportunistic in the short term. Some individuals (12% of rats and 7% of mice) were highly specialized in marine-derived food. According to the isotope ratios in a small sample of cat faeces, rodents and rabbits were the chief prey of cats at New Island. Although some individuals of all three predators supplement their terrestrial diet with marine-derived food, the current impact of predation by mammals on the large population of Thin-billed prions at New Island appears small due to a number of factors, including the small size of rodent populations and restriction mainly to small areas providing cover. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Ingrid Schenk: deceased     

Effects of predation and habitat structure on the population dynamics of house mice in large outdoor enclosures

This paper examines the effect of different levels of protection from predation on feral house mice. Mice were contained in eight 50×50 m outdoor enclosures. Enclosures allowed access to a suite of freeliving vertebrate predators from the surrounding area, including feral foxes, feral cats and Australian raptors. A 10–15% cover of small, felled cypress pine trees was added in strips to low grassland to increase habitat complexity. Mice were not protected from predation when compared with low grassland pens, possibly because predators were able to focus their hunting activity in the strips. However, when felled trees were covered with wire netting, hence providing higher quality refuge, mouse populations achieved higher densities than in low grassland pens. A predator exclusion treatment was used to confirm the refuge effect was due to a reduction in the impact of predation. Survival rates under the different treatments were generally consistent with population level responses, with mice having lower survival in low grassland pens than in high refuge pens. This is the first study with mammals that confirms the importance of refuges from predators for prey populations.     

Small cats in big trouble? Diet,activity, and habitat use of jungle cats and leopard cats in threatened dry deciduous forests,Cambodia

Dry deciduous dipterocarp forests (DDF) cover about 15%–20% of Southeast Asia and are the most threatened forest type in the region. The jungle cat (Felis chaus) is a DDF specialist that occurs only in small isolated populations in Southeast Asia. Despite being one of the rarest felids in the region, almost nothing is known about its ecology. We investigated the ecology of jungle cats and their resource partitioning with the more common leopard cats (Prionailurus bengalensis) in a DDF‐dominated landscape in Srepok Wildlife Sanctuary, Cambodia. We used camera‐trap data collected from 2009 to 2019 and DNA‐confirmed scats to determine the temporal, dietary and spatial overlap between jungle cats and leopard cats. The diet of jungle cats was relatively diverse and consisted of murids (56% biomass consumed), sciurids (15%), hares (Lepus peguensis; 12%), birds (8%), and reptiles (8%), whereas leopard cats had a narrower niche breadth and a diet dominated by smaller prey, primarily murids (73%). Nonetheless, dietary overlap was high because both felid species consumed predominantly small rodents. Both species were primarily nocturnal and had high temporal overlap. Two‐species occupancy modelling suggested jungle cats were restricted to DDF and had low occupancy, whereas leopard cats had higher occupancy and were habitat generalists. Our study confirmed that jungle cats are DDF specialists that likely persist in low numbers due to the harsh conditions of the dry season in this habitat, including annual fires and substantial decreases in small vertebrate prey. The lower occupancy and more diverse diet of jungle cats, together with the broader habitat use of leopard cats, likely facilitated the coexistence of these species. The low occupancy of jungle cats in DDF suggests that protection of large areas of DDF will be required for the long‐term conservation of this rare felid in Southeast Asia.     

Feeding responses of the red fox (<Emphasis Type="Italic">Vulpes vulpes</Emphasis>) to different wild rabbit (<Emphasis Type="Italic">Oryctolagus cuniculus</Emphasis>) densities: a regional approach

We investigate the feeding responses of the red fox (Vulpes vulpes) at a regional scale to different densities of European wild rabbit (Oryctolagus cuniculus) in central–southern Spain. Rabbit abundance indices were obtained in 86 localities during summer 2002. The diet of the fox was studied by analysis of 114 scats collected in 47 of these localities. The feeding response of the fox was examined by a representation of the dry weight percent of rabbit in the diet as a function of the abundance of rabbits; this used data only from those localities where at least 3 scats were collected (70 fox scats from 18 localities). We evaluated the relationship between rabbit abundance and the diversity of the diet of the fox. The feeding patterns of red foxes approximated to Holling’s type III functional response, typical of opportunistic predators. There was a negative relationship between the diversity of the fox’s diet and the abundance of rabbits. Therefore, the fox apparently behaves as a facultative predator, feeding on rabbits when they are abundant and shifting to other prey (and hence a more diverse diet) when rabbits are scarce. These findings are the first step towards understanding the potential role of red foxes in regulating rabbit populations in central–southern Spain.     

Importance of ground weta (

Aerial poisoning using Talon(R) 7-20 baits (active ingredient 20 ppm brodifacoum) was carried out on Motuihe Island, Hauraki Gulf, during the winter of 1997. The operation aimed to eradicate Norway rats (Rattus norvegicus) and house mice (iMus musculus) and to reduce rabbit (Oryctolagus cuniculus) numbers significantly. We studied the diet of feral house cats (Felis earns) before the operation, then monitored the impact of the operation on them to determine whether secondary brodifacoum poisoning caused a reduction in their numbers. Large numbers of rabbits remained after poisoning; this and other observations suggested that insufficient bait had been applied to achieve the aims of the programme. Cat mortality, based on radio- collared animals, was 3/14 (21%). Cats on Motuihe Island appeared to eat rabbit muscle tissue in preference to internal organs; brodifacoum concentrations are lower in muscle than in liver and we suggest that rabbits may be a poorer vector than rodents for secondary poisoning of cats. We also confirmed the risk of an aerial brodifacoum application to a range of non- target bird species. Mortality of pukeko (Porphyrio p. melanotus) and paradise shelducks (Tadorna variegata) was 49% and 60%, respectively. No mortality of New Zealand dotterels (Charadrius obscurus) or variable oystercatchers (Haematopus unicolor) was detected. Twenty-nine individuals of 10 bird species (five indigenous and five introduced) were found dead after the operation and livers of all of them contained residues of brodifacoum; toxin levels averaged 0.84 mu g per g (range 0.12-2.31 mu g per g).