Predation of vertebrates by domestic cats in two Brazilian hotspots: incidental records and literature review

ABSTRACT Domestic cats (Felis catus Linnaeus, 1758) can interact with and cause several negative impacts upon wildlife if unconstrained by their owners. These impacts occur especially because of their innate predatory behavior and, usually the lack of any natural predators, as well as due to their high abundances relative to native carnivores. Although these impacts are well studied in temperate countries, there are but a few records of species used as prey by these carnivores in Brazil. Here, we expand the knowledge of native species preyed upon by domestic cats in Brazil by presenting new records of this predator-prey interaction and reviewing records in the literature. Predation events were recorded through opportunistic encounters between 2016 and 2022. We recorded the predation of 14 native terrestrial vertebrate species (reptiles, amphibians, birds, and mammals) from the Cerrado and Atlantic Forest biomes. Our literature review recovered predation events by cats in the two aforementioned biomes plus in the Amazonia. Our results increase to 48 the number of wild species preyed upon by domestic cats in Brazil, which is probably an underestimation, as this number is much higher in other countries of comparable land size and species diversity. We suggest that cat population control measures should be carried out, especially in protected areas.

Biological invasions are one of the greatest threats to biodiversity worldwide [1] and understanding the processes shaping biological communities under this particular threat is a crucial challenge for conservation [2][3][4].There are thousands of invasive species around the world, and the impacts caused by them include predation, competition, disease transmission [5,6], hybridization [7,8], alteration of natural behaviors in native species [9,10], and even environmental changes [11,12].Although usually not perceived as such, domestic species may be considered as an invasive species when they either establish populations in the wild or have free access to natural areas, and hence, interact with wildlife [13][14][15].
Among invasive mammalian predators, domestic cats (Felis catus Linnaeus, 1758) cause impacts upon a broad set of native terrestrial vertebrates [3,16,17].Cats have even contributed directly to the extinction of at least 63 species worldwide, including reptiles, birds, and mammals [3].For instance, in Australia there are records of predation by domestic cats upon at least 50 endangered species of terrestrial mammals [18].In the USA, free-ranging domestic cats are responsible for killing an estimated 1.4-3.7 billion birds and 6.9-20.7 billion mammals per year [19].The impacts of this invasive predator are aggravated in island ecosystems, where their introduction has played a role in the extinction of 33 island endemic vertebrates [2].This high taxonomic diversity and number of prey species in the diet of domestic cats is the result of opportunistic feeding, a trait that offers selective advantage over wild cats, which are specialized predators [20].
In the Neotropics, one of the most species-rich regions in the world [21], the direct impacts (i.e.predation) caused by domestic cats are poorly explored.This is particularly evident in studies that address the direct impacts of this feline on global scales, where the bibliographies used are mostly from North America (United States and Canada), Europe and Oceania (Australia and New Zealand) [see [6,22].This scenario is no different in Brazil.Studies on the direct impacts of domestic cats in Brazil are scarce, punctual, and scattered throughout the literature [23][24][25][26][27][28][29][30][31], without any attempts so far to provide a list of species affected by this feline.This is worrying given that Brazil has two biodiversity hotspots (Cerrado and Atlantic Forest) and harbors high species richness of different animal groups [32][33][34].Herein, we report new records of native terrestrial vertebrates preyed upon by domestic cats in these two biodiversity hotspots in Brazil, and provide a list of native vertebrates reported as preyed upon by this feline in the country.
Predation events by domestic cats were recorded in five municipalities in the state of Minas Gerais, southeastern Brazil (Figure 1), between 2016 and 2022, in two Brazilian biomes [35].The municipality of João Pinheiro is within the Cerrado biome in a region with relatively vast extensions of well-preserved and connected natural vegetation.The other municipalities (Alto Rio Doce, Ipatinga, Cataguases, and Ubá) are located in the Atlantic Forest biome, in areas highly modified by human activities and with only small forest remnants (<50 hectares) [36] surrounded by pasture and crop plantations.
We recorded predator-prey interactions through occasional encounters (incidental records).During the observations, we approached the predator to photograph the interaction.When possible, we collected the preyed specimens and deposited them as vouchers in the Museu de Zoologia João Moojen at Universidade Federal de Viçosa (MZUFV), Viçosa, Minas Gerais, Brazil.All records involved cats observed near human settlements, that is, they were habituated to humans, and so we assumed they were free-ranging domestic cats [37].
We performed a literature review for predation events of native species by domestic cats in Brazil using the Scopus and Web of Science databases.We used the following search protocol: TITLE-ABS-KEY ("Felis catus" OR "Felis silvestris catus" OR "domestic cat" AND predat* AND brazil*).We also checked the reference list of these articles to look for references that may have "escaped" detection.Moreover, we also searched on Google Scholar ("Felis catus" OR "domestic cat" AND predat* AND Brazil) for additional reports.
We recorded 14 terrestrial vertebrate species preyed upon by domestic cats (Table 1, Figures 2(a-f).During this period, we did not observe a species being preyed upon more than once by a domestic cat, therefore our records are restricted to a single specimen for species of prey.On eleven occasions, cats were carrying away the dead or dying prey, and on two occasions, the prey was eaten in situ.
Our literature search of Scopus and Web of Science databases returned 16 peer-reviewed papers, six of which contained data on species preyed upon by domestic cats in Brazil.Checking the reference list of these articles yielded two additional studies and, through Google Scholar, we found three additional records.Overall, we gathered information on 34 wildlife species predated by the domestic cat in Brazil, most of them in the Atlantic Forest (Table S1).Our observations increase to 48 (three amphibians, eight reptiles, 14 birds, and 23 mammals) the number of wild vertebrate species as prey of domestic cats in Brazil.This diversity of prey items is much lower than that observed in other, less diverse, countries such as the United States (58 bird species) and Italy (47 species of mammals, 99 of birds, 25 of reptiles and nine of amphibians) [19,38].For instance, in Australia where impacts of domestic cats have been systematically studied, individuals of at least 151 mammal species (52.4% of the mammal diversity in the country) have been preyed upon by cats [18].Regarding Australian "herptiles", 30 out of 236 (12.7%) known amphibians and 258 out of 997 (25.8%) known reptiles (excluding marine snakes) have been recorded as prey of domestic cats [16,39].Brazil has fewer reptile species (n = 848) than Australia, but greater diversity of amphibians and mammals (n = 1136 and 770, respectively) [32][33][34].These numbers highlight how little we know about the real magnitude of the predation pressure exerted by domestic cats upon wildlife in Brazil.This becomes even clearer if we consider that the conservative estimate of the cat population in Brazil is 14 million individuals [40], approximately four times larger than the cat population estimated in Australia [41].Therefore, the low number of species impacted by domestic cats in Brazil is likely due to the lack of systematic studies including long term observations (of this feline and its prey) encompassing different habitats [see 42,43,44].
Squamate reptiles (lizards, worm lizards, and snakes) are known as prey to a great diversity of predators [42].However, to the best of our knowledge, this study is the first to report snakes as prey of domestic cats in Brazil, highlighting the importance of our findings.Although the negative effects of domestic cat predation are commonly reported for mammals and birds [2,19], reptiles are also severely impacted by this predator.A recent study in an urban environment in Mexico found reptiles to be the most consumed item by domestic cats, surpassing mammals and birds [43].In Australia, an estimated 1.8 million reptiles are killed daily by domestic cats, particularly in hotter and drier environments [6,16].Conversely, the low number of reports of reptiles preyed upon by this domestic animal in Brazil may be the result of both a lack of studies on this topic as well as the need to use methods that increase detection rates of such predator-prey interactions.For instance, about 18 to 23% of the prey captured by domestic cats is taken to their owners' homes [44,45], resulting in underestimates based on direct observation methods.Therefore, methods such as portable video cameras ("KittyCams") [44][45][46] and stomach contents [6,47] and fecal analyses [6,24,31], could increase the accuracy of the diversity of species impacted by this feline.
Cats can prey on bats (Chiroptera, Table 1) [30,48], but despite the potential harmful effects on bat populations, domestic cats can also be used to control vampire bats.For instance, cats have been used as biological control of vampire bats (Desmodus rotundus) in Brazil at least since the 18 th century, when these hematophagous mammals were already impacting cattle ranches in the country [48].A more recent study showed that, in the Brazilian Amazonia, residents of a homestead with three domestic cats did not have any D. rotundus bites, whereas 51% of the individuals of the 11 neighboring families were bitten [23].This suggests that, if properly managed, cats can control D. rotundus populations.This must, however, be assessed with caution, as these carnivores cannot discriminate between harmful and unharmful bats and may also transmit bat rabies to humans.None of the species preyed upon by cats in this study are listed in any conservation threat category according to both the IUCN red list [49] and the Brazilian list of endangered species [50].Although domestic cats have not yet been recorded preying on endangered species, at either global or national levels, in Brazil, this may already be happening, particularly where cats live near protected areas containing threatened taxa.For instance, several endemic and/or threatened species in Brazil are known to occur in areas adjacent to where the present observations were made [51][52][53], and these taxa could also be impacted (if not already) by this invasive predator.The additional impact imposed by domestic cats (on any native species) is further aggravated because the vast majority of observations reported here are within two biodiversity hotspots -areas with high species richness and endemism, and extremely threatened by human activities [54].This scenario can be even more complicated, as in addition to predation, domestic cats can affect wildlife by disturbing and altering natural behaviors [9,10] and transmitting diseases [55].
We acknowledge that our methodology and sample size are limited, thus hampering more accurate and larger-scale inferences about the impacts discussed so far.However, although anecdotal, our records represent novel data on prey items in the diet of free-ranging domestic cats in Brazil, highlighting our lack of knowledge and likely underestimation of this impact in the country.We believe our results will draw the attention of other researchers, as well as decision makers, and boost new studies and conservation actions.In Australia and New Zealand, population control measures, such as castration or euthanasia of domestic cats, have already been adopted as a priority conservation action [56][57][58].These actions have been effective in controlling the sizes of populations of this invasive predator, and have proved beneficial to the conservation of biodiversity in these countries [59][60][61].In Brazil, attempts to control domestic cats have been implemented in the Fernando de Noronha archipelago [62].However, pet protection laws neglect the protection of native species and prohibit the use of lethal methods, reducing the effectiveness of stray cat control and eradication [28,62].Thus, we underline the need for more studies on both the impacts of domestic cats on wildlife (not only as predators), as well as careful analyses of feasible control measures, especially in areas with high relevance for biodiversity conservation.

Table 1 .
New records of native vertebrate species predated by domestic cats in the Brazilian hotspots.All municipalities are in the Brazilian state of Minas Gerais.