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Amongst domestic animals, the domestic cat, Felis catus, is widely considered to be one of the most serious threats to wildlife conservation. This is particularly evident for island ecosystems, as data for mainland countries are often lacking. In Italy, the European country that is richest in biodiversity, cats are very popular pets. In this work, we aimed at assessing the potential spectrum of wild vertebrates that may be killed by free-ranging domestic cats, and we considered our results within the context of their conservation status and IUCN threat category. We collected data on the impact of cats both through a citizen science approach (wildlife predations by 145 cats belonging to 125 owners) and by following 21 of these 145 cats for 1 year and recording all of the prey they brought home. Domestic cats may kill at least 207 species (2042 predation events) in Italy; among those, 34 are listed as "Threatened" or "Near Threatened" by the IUCN and Italian Red Lists. Birds and mammals such as passerines and rodents were reported to be the groups most commonly killed by free-ranging cats. When considering this diet in functional trait space, we observed that the class occupying the largest functional space was that of birds, followed by mammals, reptiles, and amphibians. Thus, the largest impact was on the functional structure of mammal and bird communities. The use of a collar bell did not affect the predation rate of cats, and the number of prey items brought home decreased with increasing distance from the countryside. We provided strong evidence that free-ranging domestic cats may seriously affect the conservation of threatened and non-threatened wildlife species, which are already suffering from population declines due to other causes, e.g., habitat loss. The mitigation of the impacts of domestic cats on wildlife requires dissemination projects promoting responsible cat ownership, as well as a restriction of free-ranging behavior, particularly at nighttime.
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published: 13 December 2019
doi: 10.3389/fevo.2019.00477
Frontiers in Ecology and Evolution | 1December 2019 | Volume 7 | Article 477
Edited by:
Franco Andreone,
Museo Regionale di Scienze
Naturali, Italy
Reviewed by:
Giovanni Amori,
Italian National Research Council
(CNR), Italy
Giuseppe Bogliani,
University of Pavia, Italy
Emiliano Mori
These authors have contributed
equally to this work
Specialty section:
This article was submitted to
a section of the journal
Frontiers in Ecology and Evolution
Received: 02 May 2019
Accepted: 25 November 2019
Published: 13 December 2019
Mori E, Menchetti M, Camporesi A,
Cavigioli L, Tabarelli de Fatis K and
Girardello M (2019) License to Kill?
Domestic Cats Affect a Wide Range of
Native Fauna in a Highly Biodiverse
Mediterranean Country.
Front. Ecol. Evol. 7:477.
doi: 10.3389/fevo.2019.00477
License to Kill? Domestic Cats Affect
a Wide Range of Native Fauna in a
Highly Biodiverse Mediterranean
Emiliano Mori 1
*, Mattia Menchetti 2,3† , Alberto Camporesi 4, Luca Cavigioli 5,
Karol Tabarelli de Fatis 6and Marco Girardello 7
1Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy, 2Institut de Biologia Evolutiva, Consejo
Superior de Investigaciones Cientificas - Universitat Pompeu Fabra, Barcelona, Spain, 3Dipartimento di Biologia, Università di
Firenze, Sesto Fiorentino, Italy, 4Associazione per la Divulgazione Ambientale e Scientifica, Dovadola, Italy, 5Società di
Scienze Naturali del Verbano Cusio Ossola, Museo di Scienze Naturali, Collegio Mellerio Rosmini, Domodossola, Italy,
6MUSE – Museo delle Scienze, Corso del Lavoro e della Scienza, Trento, Italy, 7cE3c–Centre for Ecology, Evolution and
Environmental Changes/Azorean Biodiversity Group and Universidade dos Açores, Faculty of Agriculture and Environment,
Angra do Heroísmo, Portugal
Amongst domestic animals, the domestic cat, Felis catus, is widely considered to be
one of the most serious threats to wildlife conservation. This is particularly evident for
island ecosystems, as data for mainland countries are often lacking. In Italy, the European
country that is richest in biodiversity, cats are very popular pets. In this work, we aimed
at assessing the potential spectrum of wild vertebrates that may be killed by free-ranging
domestic cats, and we considered our results within the context of their conservation
status and IUCN threat category. We collected data on the impact of cats both through
a citizen science approach (wildlife predations by 145 cats belonging to 125 owners)
and by following 21 of these 145 cats for 1 year and recording all of the prey they
brought home. Domestic cats may kill at least 207 species (2042 predation events) in
Italy; among those, 34 are listed as “Threatened” or “Near Threatened” by the IUCN and
Italian Red Lists. Birds and mammals such as passerines and rodents were reported to
be the groups most commonly killed by free-ranging cats. When considering this diet in
functional trait space, we observed that the class occupying the largest functional space
was that of birds, followed by mammals, reptiles, and amphibians. Thus, the largest
impact was on the functional structure of mammal and bird communities. The use of
a collar bell did not affect the predation rate of cats, and the number of prey items
brought home decreased with increasing distance from the countryside. We provided
strong evidence that free-ranging domestic cats may seriously affect the conservation
of threatened and non-threatened wildlife species, which are already suffering from
population declines due to other causes, e.g., habitat loss. The mitigation of the impacts
of domestic cats on wildlife requires dissemination projects promoting responsible cat
ownership, as well as a restriction of free-ranging behavior, particularly at nighttime.
Keywords: Felis catus, alien species impacts, responsible pet ownership, predation rate, feral species
Mori et al. Impacts of Free-Ranging Cats in Italy
Understanding the processes shaping ecological communities
under multiple disturbances is a crucial challenge in ecology
and conservation biology (e.g., Davis et al., 2000; Cilleros et al.,
2016; Mazel et al., 2017). Biological invasions represent a serious
threat to global biodiversity at all organization levels, from
genes to ecosystems (Wonham, 2006). By definition (Wonham,
2006), domestic species should also be considered “alien” when
they establish free-ranging populations in the wild outside
their native range (Carthey and Banks, 2012; Home et al.,
2017; Boano et al., 2019). The presence of domestic free-
ranging animals may disrupt ecosystems or contribute to local
extinction events (Malo et al., 2011). The impacts of feral
pets include environmental/habitat alterations (e.g., rabbits: Flux
and Fullagar, 1992; pigeons: Boano et al., 2019), predation
of native fauna (e.g., cats: Loss et al., 2013; dogs: Doherty
et al., 2017), hybridization with related wild species (e.g., ferrets:
Davison et al., 1999; cats: Randi et al., 2001; dogs: Bassi
et al., 2017), and disease transmission (e.g., ducks: Hinshaw
et al., 1978; cats: Loss and Marra, 2017). Among mammalian
invaders, domestic carnivores, e.g., dogs (Canis familiaris) and
cats (Felis catus), are reported to exert the most serious damage
(Van’t Woudt, 1990; Doherty et al., 2016; Home et al., 2017).
Furthermore, their management is challenging because of their
association with humans and their consequent appeal to the
public (Green and Gipson, 1994; Natoli, 1994; Thomas et al.,
2013). Negative impacts of free-ranging dogs are well-known
and commonly accepted to occur by the general public (Young
et al., 2011; Hughes and Macdonald, 2013), as dogs may also
attack humans (Scott and Causey, 1973; Home et al., 2017),
whereas negative impacts by domestic cats are often denied or
justified by the public as a form of “natural predatory instinct”
(Hall et al., 2016).
Across the globe, the domestic cat, Felis catus, is the
most popular pet. The Ecology Global Network estimates that
there are 600 million-1 billion domestic cats in the world,
including pets (i.e., largely dependent on human-provided food),
strays/homeless (i.e., poorly dependent on human-provided
food), and feral cats (totally independent from humans),
throughout all of the continents except for Antarctica (www. The behavioral and physiological plasticity of
domestic cats allows them to survive even without food provided
by humans, both in urban areas and natural environments
(Gillies, 2001; Harper, 2005; Cove et al., 2018). Most studies on
the ecological impacts of domestic cats have been conducted in
island ecosystems (Liberg, 1984; Woods et al., 2003; Bonnaud
et al., 2011; Medina et al., 2011), where domestic cats are
responsible for the decline of many seabirds (Keitt et al.,
2002; Hughes et al., 2008; Bonnaud et al., 2009; Faulquier
et al., 2009) and for the local extinction of other terrestrial
vertebrates (Fitzgerald and Turner, 2000; Blackburn et al., 2004;
Medina and Garcìa, 2007; Medina et al., 2011; Kutt, 2012).
Free-ranging domestic cats may affect bird fecundity through
non-lethal indirect effects, i.e., by increasing stress (Bonnington
et al., 2013). An increase in prey species populations after cat
removal from islands suggests that domestic cats represent a
major source of predation in such ecosystems (Gillies, 2001;
Hughes et al., 2008; Siracusa, 2010). Birò et al. (2005) found
a low trophic niche overlap between feral cats and wild cats
Felis silvestris, suggesting the occurrence of niche partitioning
between the two. Conversely, domestic cats are opportunistic
predators, therefore showing a selective advantage over wild
cats, which are specialized to preying upon rodents (Birò et al.,
2005; Széles et al., 2018). Moreover, house-based domestic cats
are often free to move around outside and may increase the
predatory pressure exerted on wildlife (Pearre and Maass, 1998).
Domestic cats frequently kill wild animals without consuming
them and frequently bring prey home as a “gift” to their owners
(Meek, 1998; Woods et al., 2003). Unlike feral cats, house cats
are provided with medical care and shelter by pet owners, so
they are not subjected to fluctuations in prey abundances and
are therefore able to surpass the environmental carrying capacity
(Woods et al., 2003; Tschanz et al., 2011). Furthermore, domestic
cats may rapidly revert to the feral state, maintaining their
populations without human food supply (Birò et al., 2005; Széles
et al., 2018). The use of collars with a bell has been reported
to be a useful method for reducing wildlife killing by domestic
cats (Calver et al., 2007; Gordon et al., 2010). Given the impacts
detected in areas relatively poor in biodiversity (e.g., 1.4–3.7
billion birds and 6.9–20.7 billion mammals killed per year in
the continental USA: Loss et al., 2013), an even stronger effect
may be expected for biodiversity hotspot areas (cf. Home et al.,
2017) such as the Mediterranean basin (Myers et al., 2000).
Within this area, Italy hosts the highest animal species richness
(Oosterbroek, 1994; Maiorano et al., 2007) as well as a high
domestic cat density (nearly 10 million domestic cats: https://; accessed on 7th April 2018), and yet evidence of
the effects of cats on wildlife is still poorly documented (Siracusa,
2010; Ancillotto et al., 2013).
Traditionally, ecologists have studied the relationships
between the severity of impacts of invasive species and the
taxonomic structure of animal communities (e.g., Sanders et al.,
2003; Hejda et al., 2009). Recent advances in the application of
frameworks based on species traits have provided an alternative
approach that allows researchers to quantify responses to
disturbances across taxa and ecosystems (Oliver et al., 2015).
Quantifying the impacts of invasive species on the functional
structure of communities is important for elucidating the
mechanism underpinning invasion processes, as well as for
improving researchers’ ability to predict the impacts of invasive
species on ecosystem functioning (Tilman et al., 1997).
In this work, we conducted a citizen science study to assess the
impact of domestic cat predation on the functional structure of
vertebrate communities in Italy by using a trait-based approach.
Specifically, the aims of this study were to (i) quantify the
predatory pressure of domestic cats on vertebrate prey in relation
to landscape features, and (ii) assess the effect of cat predation on
the functional structure of vertebrate communities. We suggested
that the highest number of species killed by free-roaming cats
would occur in countryside areas and in southern regions, where
the highest species richness is known to occur (Blasi et al., 2014;
Genovesi et al., 2014). Moreover, we also predicted that, given the
results of previous studies, cats with a bell on their collars (Calver
Frontiers in Ecology and Evolution | 2December 2019 | Volume 7 | Article 477
Mori et al. Impacts of Free-Ranging Cats in Italy
FIGURE 1 | Locations of 21 cat owners who monitored the prey their cats returned over the course of 1 year (January–December 2016).
et al., 2007; Gordon et al., 2010) would kill fewer individuals and
species than those without bells.
Citizen Science Survey
We carried out a citizen science survey to collect data
on wild species killed by domestic cats. The project was
advertised through mailing lists (“Italian vertebrates”:, specific Facebook groups dealing
with wildlife in Italy (Table S1), flyers in universities (Pisa, Siena,
Florence, Rome, Milan, Turin, Pavia, and Catania), wildlife
agencies, catteries, and human meeting places. The survey was
also conducted using online platforms and social networks
(Facebook, Twitter) to gather information about domestic cat
predation on wildlife in Italy. In detail, participants were asked to
provide us with photographs of predation by their domestic cats,
with collection between 2014 and 2017. The project was launched
in spring 2014 and kept open until the end of 2017: only data
supported by photographs and attached coordinates were kept
for analyses. We did not ask for any further information from
the cat owners to avoid privacy issues. Environmental variables
were obtained by plotting coordinates on satellite maps. We also
followed up with targeted questions to contributors to increase
the reliability and adequacy of our survey (cf. Home et al., 2017).
Among the surveyed cat owners, we recruited a total of
21 volunteers (Figure 1) through Facebook groups, listed in
Table S1, to monitor predation events by single cats throughout 1
year (January-December 2016) by recording and photographing
all prey items brought home by the owned cat. These data were
also added to the citizen science project described above. The
owners of the 21 cats also gave us information on their cats,
including sex, use of collars with bells, and average period of
outdoor access (hours/day: cf. Frank et al., 2016).
Prey species were grouped according to the International
Union for the Conservation of Nature (IUCN) Red List (www.; accessed on 11.02.2019) and the Italian Red List
(Rondinini et al., 2013).
Data Analysis on the Citizen Science
Mammal and bird trait data (i.e., body mass and diet: Table S2)
were derived from a comprehensive database, including species-
level trait data for all bird and mammal species, taken from key
literature sources (Wilman et al., 2014). The traits of reptiles were
taken from Grimm et al. (2014), whereas those of amphibians
were derived from Trochet et al. (2014). Further published works
used to derive the traits of reptiles and amphibians (i.e., body
mass and diet) are shown in Table S2. We investigated traits
by measuring (i) the quantity of resources consumed and (ii)
body mass, for a total of 11 traits (see Table S2). Trait data
for all of the killed species classes were pooled together into a
single matrix. We used Principal Coordinate Analysis (hereafter,
PCoA) to summarize the major patterns of variation in the
Frontiers in Ecology and Evolution | 3December 2019 | Volume 7 | Article 477
Mori et al. Impacts of Free-Ranging Cats in Italy
resultant trait matrix (Legendre and Legendre, 2012). The main
advantage of this method is that it can use different dissimilarity
matrices from traditional ordination techniques, e.g., Principal
Component Analysis (PCA) (Legendre and Legendre, 2012). We
used the Gower general dissimilarity index (Gower, 1971) and a
distance matrix, as the input matrix contained both continuous
and categorical variables.
Portions of functional space occupied by different classes were
compared using a convex hull approach. The convex hull is the
minimum convex geometry that includes all the observations
considered (Preparata and Shamos, 1985) and has recently been
proposed as a method for representing the volume of functional
space used by a community (Villéger et al., 2008). For each
prey class, we calculated the area of each convex hull. All
the analyses were carried in the software R (version 3.5.1., R
Foundation for Statistical Computing, Wien, Austria). The ape
package was used to perform the Principal Coordinate Analysis.
The code developed has been uploaded to a dedicated github
repository (
Variables Influencing Predation Rate by
Domestic Cats
We assessed the effect of five variables on the killing rate (i.e.,
number of prey brought home) by the 21 domestic cats that were
intensively monitored for 1 year through mixed effect models
computed in the R (version 3.5.1., R Foundation for Statistical
Computing, Wien, Austria) packages lme4 (Bates et al., 2014) and
MuMIn (Barton and Barton, 2015). The variables included in the
models were: latitude, distance from the countryside (measured
as the minimum distance from the house of the cat owner
and the border of human settlements, i.e., where the number
of houses inhabited by humans was <2/100 m2), duration of
cat outdoor activity (hours/day), presence/absence of a collar
with a bell (1 =present; 2 =absent), and sex (1 =male; 2 =
female). Bioclimatic ecoregions (cf. Blasi et al., 2014; Genovesi
et al., 2014) were included in the model as a random factor.
Before running the model, we tested for multicollinearity among
variables (i.e., r>|0.6|); no collinearity was detected among our
variables and, therefore, we included all of them in the total
model. Non-significant variables were removed one at a time
until the elimination of terms caused a significant increase in the
residual deviance.
Citizen Science Survey
We collected a total of 2042 entries for vertebrates killed by
domestic cats (minimum number of cats, N=145; number of
owners, N=125) (Figure 2). Among those, 1,533 were killed
in warm months (April–September). Our survey was conducted
throughout Italy, with data originating from 377 locations,
including rural and urban areas, from sea level to mountainous
areas (Figure 2).
The prey killed belonged to at least 207 species (Table S3):
75.8% were classified as “Least Concern” by both the IUCN and
Italian Red Lists, 16.4% were “Near Threatened” or “Threatened,
and the remaining 7.8% included “Data Deficient” or “Not
FIGURE 2 | Locations of origin of our data, including rural areas (green-lined
circles) and urban centers (gray-bricked circles).
Evaluated” species (Table 1;Table S3). Prey-species size ranged
from 1 to 3 grams for juvenile amphibians to about 2 kg for
subadult hares and pheasants.
As to the 21 domestic cats (included among the 145 previously
cited) that were followed for 1 year, the predation rate showed
considerable variation within and among taxonomical classes.
The most impacted classes were mammals (40% of killings),
followed by birds (35%), reptiles (21%), and amphibians (4%).
Over 73% of predations occurred in spring and summer.
A graphical summary of total and within-class predation
frequencies is shown in Figure 3.
The most frequently killed species among mammals was
the house mouse Mus domesticus (10%), although Rattus rattus
(9.4%), Apodemus flavicollis (8.2%), Sciurus vulgaris (8.2%),
and Suncus etruscus (8.2%) were also reported many times:
all of these species are common species (“Least Concern”) in
Italy (Rondinini et al., 2013). As to birds, the most frequently
killed species were Turdus merula (13%), Passer italiae (7.9%),
Streptopelia decaocto (7.9%), and Sylvia atricapilla (7.9%); P.
italiae is endemic to Italy and is declining. In terms of reptiles,
the most frequently killed species were Podarcis muralis (29%),
Hierophis virdiflavus/carbonarius (12.8%), and Lacerta bilineata
(12.8%). Lastly, among amphibians, the most frequently killed
species were Rana dalmatina (40%) and Pelophylax synklepton
esculentus (20%), both listed within the annexes of the Habitat
Directive. A summary of the proportion of species killed by
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Mori et al. Impacts of Free-Ranging Cats in Italy
TABLE 1 | Near threatened, threatened, data deficient, and not evaluated prey species brought home by free-ranging domestic cats in Italy.
Class Order Species Number of individuals killed IUCN Red List Italian Red List
Birds Anseriformes Anas crecca 2 Least Concern Endangered
Birds Anseriformes Aythya ferina 1 Least Concern Endangered
Birds Charadriiformes Scolopax rusticola 6 Least Concern Data Deficient
Birds Charadriiformes Tringa erythropus 1 Least Concern Not Evaluated
Birds Columbiformes Streptopelia turtur 1 Vulnerable Least Concern
Birds Galliformes Alectoris rufa 3 Least Concern Data Deficient
Birds Galliformes Coturnix coturnix 5 Least Concern Data Deficient
Birds Gruiformes Crex crex 1 Least Concern Vulnerable
Birds Passeriformes Acrocephalus melanopogon 1 Least Concern Vulnerable
Birds Passeriformes Carduelis carduelis 19 Least Concern Near Threatened
Birds Passeriformes Carduelis chloris 22 Least Concern Near Threatened
Birds Passeriformes Delichon urbicum 4 Least Concern Near Threatened
Birds Passeriformes Emberiza schoeniclus 2 Least Concern Near Threatened
Birds Passeriformes Ficedula hypoleuca 3 Least Concern Not Evaluated
Birds Passeriformes Hirundo rustica 4 Least Concern Near Threatened
Birds Passeriformes Lanius collurio 2 Least Concern Vulnerable
Birds Passeriformes Passer italiae 79 Vulnerable Vulnerable
Birds Passeriformes Passer montanus 11 Least Concern Vulnerable
Birds Passeriformes Pyrrhula pyrrhula 1 Least Concern Vulnerable
Birds Passeriformes Saxicola rubicola 1 Least Concern Vulnerable
Birds Passeriformes Sylvia undata 1 Near Threatened Vulnerable
Birds Passeriformes Tarsiger cyanurus 1 Least Concern Not Evaluated
Birds Piciformes Jynx torquilla 2 Least Concern Endangered
Birds Strigiformes Asio flammeus 1 Least Concern Not Evaluated
Mammals Chiroptera Eptesicus serotinus 1 Least Concern Near Threatened
Mammals Chiroptera Miniopterus schreibersii 2 Near Threatened Least Concern
Mammals Chiroptera Myotis mystacinus 1 Least Concern Vulnerable
Mammals Chiroptera Myotis nattereri 1 Least Concern Vulnerable
Mammals Chiroptera Nyctalus leisleri 3 Least Concern Near Threatened
Mammals Chiroptera Pipistrellus nathusii 1 Least Concern Near Threatened
Mammals Chiroptera Plecotus auritus 1 Least Concern Near Threatened
Mammals Chiroptera Rhinolophus ferrumequinum 3 Near Threatened Vulnerable
Mammals Chiroptera Rhinolophus hipposideros 2 Near Threatened Vulnerable
Mammals Rodentia Apodemus alpicola 1 Least Concern Data Deficient
Mammals Rodentia Eliomys quercinus 3 Near Threatened Near Threatened
Mammals Soricomorpha Crocidura pachyura 4 Least Concern Data Deficient
Mammals Soricomorpha Sorex antinorii 16 Data Deficient Data Deficient
Mammals Soricomorpha Talpa caeca 2 Least Concern Data Deficient
Reptiles Squamata Anguis veronensis 10 Not Evaluated Least Concern
Reptiles Squamata Archaeolacerta bedriagae 1 Near Threatened Near Threatened
Reptiles Squamata Elaphe quatuorlineata 6 Near Threatened Least Concern
Reptiles Squamata Hierophis carbonarius 10 Not Evaluated Not Evaluated
Reptiles Squamata Malpolon monspessulanus 1 Least Concern Not Evaluated
Reptiles Squamata Podarcis filfolensis 12 Least Concern Vulnerable
Reptiles Squamata Podarcis tiliguerta 3 Least Concern Near Threatened
Reptiles Testudines Testudo hermanni 1 Near Threatened Endangered
Amphibia Anura Bufo bufo 2 Least Concern Vulnerable
Amphibia Anura Hyla arborea 4 Least Concern Not Evaluated
Amphibia Anura Rana latastei 1 Vulnerable Vulnerable
Amphibia Urodela Triturus carnifex 1 Least Concern Near Threatened
Predation rate by 21 cats followed for 1 year.
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Mori et al. Impacts of Free-Ranging Cats in Italy
FIGURE 3 | Reported killings of 21 domestic cats for the following groups of vertebrates: birds, mammals, reptiles, and amphibians. The thickness of black lines
represents the proportion of individuals of each killed species within each taxonomical class.
FIGURE 4 | Proportions of species killed by cats, grouped by threat
categories. The two panels show different groupings according to the IUCN
and Italian Red List species classifications. Legend codes indicate threat
categories: VU, Vulnerable; NT, Near Threatened; LC, Least Concern; DD,
Data Deficient; and NE, Not Evaluated. Alien species (i.e., those introduced to
Italy) were not classified according to the Red List categories.
these 21 cats revealed that two out of the total of 207 are of
conservation concern (Figure 4): one amphibian species, Rana
latastei, is classified as “Vulnerable,” and one reptile, Elaphe
quatuorlineata, is classified as “Near Threatened” by the IUCN
Red List. In contrast, when grouping the species according to the
Italian Red List, they included six “Near Threatened” birds and
one “Vulnerable” amphibian species.
FIGURE 5 | Principal Coordinate Analysis (PCoA) performed on the trait matrix
of killed species. The ordination shows the distribution of different species
within trait space. Convex hulls, displayed in different colors, were calculated
for each taxonomic class.
When examining the diet in functional trait space, PCoA
analysis revealed that the class occupying the largest functional
space was birds, followed by mammals, reptiles, and amphibians
(Figure 5). Therefore, the largest impact was on the functional
structure of mammal and bird assemblages.
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Mori et al. Impacts of Free-Ranging Cats in Italy
TABLE 2 | Factors affecting the number of prey items brought home by domestic
cats in one year, estimated through a general linear model.
Variable B Standard error P
Distance from the countryside 0.04 0.01 <0.001**
Hours/day outside 0.95 0.24 <0.001**
Intercept 46.28 7.98 0.02*
Asterisks indicate significant P (*<0.05; ** <0.001).
Variables Influencing Killing Rates
The predation rate of the 21 individual cats followed for 1 year
increased with decreasing distance from the countryside and
increasing number of hours of outside activity per day (R2=0.92:
Table 2;Tables S4, S5).
Evidence of the effects of cat predation on wildlife are rare for
country-wide areas and generally comes from US urban and
suburban ecosystems, which are relatively poor in biodiversity
(e.g., Dunn and Tessaglia, 1993; Lepczyk et al., 2003; Loss et al.,
2013; Loss and Marra, 2017). The few European country-wide
studies on this topic are mostly taxon-specific (e.g., bats in Italy:
Ancillotto et al., 2013, 2019; Siberian chipmunks: Mori et al.,
2018). The only general study carried out in continental Europe
(Poland) showed that free-ranging domestic cats mainly prey
on wild mammals (Krauze-Gryz et al., 2012), but this study
was limited to a very few rural areas. Conversely, our survey
was conducted throughout Italy, both in rural areas and urban
centers, from sea level to the mountains. The Mediterranean
basin (i.e., northern Africa, the Middle East, and southern
Europe, including the whole of Italy) is included in a biodiversity
hotspot, i.e., one of the world’s 36 biogeographic regions with
significant levels of biodiversity, which is threatened by human
activities (Noss et al., 2015). Introduced species, including feral
ones, represent one of the main causes of biodiversity crisis,
particularly in these areas (Wonham, 2006). Our analysis showed
that at least 207 species, ranging in size from juvenile neo-
metamorphosed frogs to adult weasels and hares, may be actively
killed by free-ranging domestic cats. Over 30 of these are listed
as “Threatened” by the International Red list, whereas the great
majority (i.e., over 75%) of species killed by free-ranging cats
belong to the “Least Concern” category. This is consistent
with the fact that Least Concern species are—on average—the
most abundant species and thus potentially the most available
to domestic cats, which are opportunistic predators (Loss and
Marra, 2017). However, despite their widespread distribution and
presence, these species may play key roles in the maintenance of
other carnivore species deserving conservation measures, whose
diet is based precisely on the species killed by domestic cats (e.g.,
Bertolino et al., 2015), and this may suggest a strong role for cat
predations in ecosystem functioning. Moreover, the few reported
kills of threatened species may be more deleterious than for many
of the common widespread species. The Italian sparrow, Passer
italiae, is endemic to Italy and is classified as “Vulnerable.” The
high predation rate by domestic cats on this bird may therefore
be a threat to its conservation. Other endemic/near endemic
Italian species that are highly preyed upon by domestic cats in
Italy include the Valais shrew, Sorex antinorii, classified as “Data
Deficient,” the Sicilian shrew, Crocidura sicula, and the Italian
slow worm, Anguis veronensis. Italy plays a key role in Europe
in the conservation of the Eurasian red squirrel, Sciurus vulgaris,
which is threatened by habitat fragmentation and competition
with introduced species (Bertolino and Genovesi, 2003; Bertolino
et al., 2015); this rodent is among the main species killed by
domestic cats (i.e., over 8% predations). Moreover, we confirmed
that free-roaming domestic cats may represent a huge threat to
bat assemblages (Ancillotto et al., 2013), which include a number
of imperiled species representing paramount bioindicators of
environmental quality (Jones et al., 2009).
Free-ranging domestic cats may be active throughout the
day and the night (Cove et al., 2018), therefore potentially
affecting spatiotemporal behavior and the abundance of diurnal
and nocturnal species (Parsons et al., 2018). Accordingly, the
daily number of hours of a cat outside activity significantly
increased the number of prey killed by cats. Furthermore, their
home range size may exceed 10 hectares, even in urban areas
(Pillay et al., 2018), and covering even larger areas in rural
environments (up to 228 hectares, in male cats: Tschanz et al.,
2011; Loss et al., 2013). Distance from the countryside was found
to affect the number of prey items brought home by cats per
year. This is in line with the longer distances traveled by free-
ranging cats in these areas. Conversely, we detected no effect of
the local climatic ecoregion (cf. Blasi et al., 2014) nor of the sex
of the cat on the predation rate, despite intersexual differences
in hunting ability that occur in this species. Additionally, the
presence of a bell on the collar of the cat was not effective
in reducing wildlife killings, in contrast with anecdotal report
by cat owners (unpublished data) and despite reports that, on
islands, bells may reduce predations on birds (Calver et al., 2007;
Gordon et al., 2010). Cat bibs are neoprene triangular pieces
of brightly colored plastic material attached to cat collars that
are used on free-roaming cats to warn possible prey of the
presence of the cat, reducing their probability of being killed.
However, although potentially functional in reducing predation,
cat bibs did not eliminate predation on wildlife by domestic cats
(van Heezik, 2010).
The wide ecological plasticity of domestic cats supports
the fact that the domestic cat is on the “100 of the world’s
worst invasive alien species” list, with populations increasing
worldwide and in a huge variety of habitat types (Loss and
Marra, 2017; Pillay et al., 2018). In this paper, we did not
estimate the population abundance of killed species, so we
cannot describe any impacts at the population level. However,
we provided evidence that the strongest impact of domestic cats
occurs at the functional structure level of mammal and bird
assemblages (Lepczyk et al., 2003; Siracusa, 2010; Bonnington
et al., 2013). Domestic cats are apex predators that show at least
two reproductive peaks per year (Sogliani and Mori, 2019); thus,
they may have few competitors (Castañeda et al., 2018; Sogliani
and Mori, 2019) and may rapidly become the most abundant
carnivorous species (Loss et al., 2013).
Frontiers in Ecology and Evolution | 7December 2019 | Volume 7 | Article 477
Mori et al. Impacts of Free-Ranging Cats in Italy
Reducing the impacts of invasive species on wildlife requires
eradication or at least reduction in population size through
sterilization. Both of these strategies are often blocked by the
general public, particularly when involving charismatic fauna
(e.g., Bertolino and Genovesi, 2003; Crowley et al., 2017, 2018,
2019a). Reproduction control (i.e., sterilization) is reported to
be a good way to control and manage urban populations of
domestic cats, i.e., where human density is the highest and
where eradication projects are mostly boycotted (Natoli et al.,
2006). In rural areas, veterinarians who frequently deal with pet
owners should encourage sterilization, using cat welfare as the
main argument to convince cat owners (cf. Grayson and Calver,
2004). Sterilization would not prevent predation of wildlife by
domestic cats, but it limits the number of offspring and thus
the population size (Jones and Downs, 2011). For ethical reasons
and considering the widespread denial of the negative impacts
of domestic cats in western countries (Loss et al., 2018; Crowley
et al., 2019b), lethal control would be challenging (Natoli et al.,
2006; Thomas et al., 2013).
Citizen science has been proven to be effective in collecting
data involving feral pets. Therefore, we suggest that it could
be used as a tool to lead cat owners toward responsible
ownership, e.g., through social media campaigns and public
divulgation/discussion events in the main urban areas and
meeting points. We strongly recommend cat owners to keep
their pet cats indoors or, at least, limit their ranging bouts by
avoiding nocturnal and crepuscular hours, particularly in warm
months, i.e., when most wild species are active and in their
reproductive periods. Together, the effectiveness of cat bibs for
reducing predation on wildlife should be statistically tested (van
Heezik, 2010). Field studies like this one may provide a scientific
basis on which to build well-supported dissemination campaigns
to fight against misinformation on this topic and, more generally,
on the impacts of biological invasions (Natoli et al., 2006; Loss
et al., 2018). However, scientific articles are unlikely to change
the behavior of pet owners per se. Given the full-blown denial of
the negative impacts of cats, which is also supported by published
position papers (Lynn et al., 2019), the behavior of cat owners
might be difficult to change, even in a biodiversity hotspot such
as the Mediterranean basin. Cat welfare, including the increased
risk of disease contraction in free-roaming individuals (Frenkel
et al., 1970; Slater, 2004) and predation by wild carnivores
(Sogliani and Mori, 2019), should thus be considered as effective
methods to encourage cat owners to keep domestic cats under
controlled conditions (McDonald et al., 2015). Laws state that
it is a misdemeanor offense to not provide cats with adequate
food, shelter, and freedom from pain, preventing cruelty but
also promoting responsible cat ownership. Keeping cats indoors
would help prevent damage to native wildlife and the spread
of diseases and zoonoses from wild species to domestic cats.
Increased inter- and intra-specific competition would increase
cat stress: responsible owners should alleviate stress by reducing
the encounters between cats and other species/individuals, as well
as by taking care of their health status.
All datasets generated for this study are included in the
article/Supplementary Material.
EM and MM: conceptualization. KT, AC, and LC: data collection.
EM: supervision. MG: methodology. EM, MM, and MG:
writing—original draft. All authors: review and editing.
Authors would like to thank L. Ancillotto and all of the cat owners
who provided data. We thank I. Kay-Lavelle, V. Sfondrini,
and E. Bassett for language revision. Four reviewers and the
Associate Editor, Franco Andreone, improved our first draft with
their comments.
The Supplementary Material for this article can be found
online at:
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Conflict of Interest: The authors declare that the research was conducted in the
absence of any commercial or financial relationships that could be construed as a
potential conflict of interest.
The reviewer GB declared a past co-authorship with one of the authors, EM
to the handling editor.
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Girardello. This is an open-access article distributed under the terms of the Creative
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Frontiers in Ecology and Evolution | 11 December 2019 | Volume 7 | Article 477
... Domestic cats (Felis catus) are opportunistic generalist predators, that have been globally introduced by humans making them one of the 100 worst non-native invasive species in the world [1]. Across the globe, the number of cats is ranging between 600 million to 1 billion [2], while pet cats Disclaimer/Publisher's Note: The statements, opinions, and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content. ...
... If un-owned cats, as opposed to owned pets, cause the majority of the mortality induced by cat predation [7], indoor-outdoor cats still cause substantial wildlife mortality, and studying their hunting behaviour is useful to improve our knowledge about the whole domestic cat population effect on ecosystems. They frequently kill wild animals without consuming them and bring them to their owners as a "gift" [2,17,19]. Accordingly, one way to study such hunting behaviour is to investigate the number and diversity of prey they brought home [8,18,[20][21][22][23][24][25]. Although the fate of prey (i.e., directly eaten, left uneaten or brought back) depends on the nature of the prey itself [25], such method can provide a global account of the variation in the species predated by cats at a national scale. ...
... Citizen science is an interesting tool for ecological issues [26], and is often used to assess effects of domestic cat predation on wildlife communities [2,10,[22][23][24]27]. In this study, we used data on prey brought home by free-ranging domestic cats in France recorded by the citizen science project named "Chat domestique et Biodiversité" led by the French society for the study and protection of mammals (SFEPM) and the National Museum of Natural History of Paris (MNHN). ...
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Domestic cats (Felis catus) are widespread worldwide as the most popular pets. This medium-sized carnivore have well-known negative effects on biodiversity, but there is still need to better understand the proximate causes of its predation. Based on a citizen science project, we assessed the role of spatiotemporal (i.e., latitude, longitude and seasons), climatic (i.e., rainfall), anthropogenic (i.e., human footprint, HFI) and individual (i.e., sex and age) variables on the number of preys returned home by cats in metropolitan France. Over the 5 048 cats monitored between 2015 and 2022, prey from 12 different classes (n= 36 568) were returned, being 68% mammals, 21% birds and 8% squamates. Shrews brought home by cats peaked during summer, while rodents were recorded during summer-autumn. Birds brought home by cats peaked in spring-summer and in autumn, and lizards in spring and in late summer. Lower HFI was associated with more voles and mice brought home and the opposite trend was observed for lizards and birds. Younger cats were more prone to bring home shrews, birds and reptiles. Although environmental factors play a minor role in prey brought home by cats, some geographical characteristics of prey species distribution partly explains the hunting behaviour of cats.
... They can also cause serious problems for farming and livestock management (Young et al. 2011). There is overwhelming evidence that domestic cats, from owned pets to feral cats, are a major threat to global biodiversity owing to predation, fear effects, competition, disease transmission and hybridization (Loss et al. 2013;Woolley et al. 2019;Mori et al. 2019;Trouwborst et al. 2020;Oedin et al. 2021;Salinas-Ramos et al. 2021;Loss et al. 2022). Such strong evidence is nonetheless denied or belittled by many cat owners and lovers. ...
... We conducted a citizen science survey to collect a representative sample of pictures of wild vertebrate species killed or harassed by domestic dogs. Particularly, we surveyed social networks (Facebook and Instagram) and submitted enquiries to specific groups dealing with dogs and/or wild species, following Mori et al. (2019). We requested participants to provide photographs depicting instances of animal species being killed or harassed by dogs, primarily focusing on their own pets, during the period spanning 2002 to 2022. ...
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Domestic dogs Canis familiaris may cause a range of impacts on wildlife through preda-tion, competition, pathogen transmission, harassment and hybridisation with wolves and other wild canids, yet such effects are less known than those of other domestic species. In this work, we have combined citizen science data and information collected by scientists on the potential impact of free-ranging dogs on wildlife in Italy. Citizen science data, obtained through online surveys on social networks, consisted of pictures of wildlife killed or harassed by dogs from 2002 to 2022. Additional records were collected from articles in newspapers. We also provide the results of a diet analysis from domestic dog scats, collected in the countryside in central Italy in 1998-1999, for which we assessed prey selection by comparing consumption with availability. The citizen science survey provided 589 records: dogs attacked and killed 95 species, mostly mammals and birds, including small game species. Among species of conservation concern, dogs attacked/killed Mustela puto-rius and Hystrix cristata, both included in Annex IV of the Habitats Directive, and the Ital-ian endemic Lepus corsicanus and Passer italiae. Over 90% of the attacks were caused by unleashed dogs in the presence of their owner in urban and periurban areas. The 148 dog scats analysed contained 30 prey species, mainly mammals, which made the staple of the dog diet, followed by amorphous material, most likely pet food. Remains of domestic sheep were frequent in the diet, as were hares Lepus europaeus and roe deer Capreolus capreo-lus among wild mammals. Wild boar Sus scrofa ranked first among the selected prey species , followed by hares, whereas roe deer and grey partridges Perdix perdix were negatively selected. The mitigation of the impact of domestic carnivores on wildlife strongly requires awareness raising to promote responsible pet ownership and strict avoidance of dogs' free-ranging behaviour, especially where encounters with wildlife are most likely.
... Overall, the results discussed above suggest cats as more susceptible than dogs to helminth infections through the ingestion of reptiles, as they are more likely to show predatory behavior and can adapt to many types of environments [87]. In an Italian study, 21% of the prey of cats, which are considered excellent hunters, were reptiles [87,88], and the preying of cats on these animals may support the trophic transmission of parasitic diseases [9]. ...
... Overall, the results discussed above suggest cats as more susceptible than dogs to helminth infections through the ingestion of reptiles, as they are more likely to show predatory behavior and can adapt to many types of environments [87]. In an Italian study, 21% of the prey of cats, which are considered excellent hunters, were reptiles [87,88], and the preying of cats on these animals may support the trophic transmission of parasitic diseases [9]. The association between the lizards P. siculus and cestodes, along with T. mauritanica geckos and untreated pets, highlights the possible role of reptiles as sources of helminth infections and potentially zoonotic parasites. ...
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Background Squamate reptiles cohabiting with companion animals may represent a source of helminth infections, especially through predation by dogs and cats with an outdoor lifestyle. Methods In order to assess the role of reptiles as intermediate/paratenic hosts of trophically transmitted helminths, synanthropic reptiles (n = 245) captured from different ecological settings (i.e., households, dog shelters, urban, peri-urban and rural areas or natural parks) of southern Italy were examined for endoparasites. Parasitic cysts (i.e., larval forms of acanthocephalans, cestodes and nematodes) and free helminths (i.e., adult nematodes and digeneans) were morphologically and molecularly identified, and statistical analysis was carried out to evaluate the correlations between reptiles, infections, and ecological settings. Results Overall, 31% of reptiles were positive for at least one helminth, with Podarcis siculus (18.7%) and Tarentola mauritanica (8.1%) being the most frequently infected species. Among the parasites of medical interest, Joyeuxiella echinorhyncoides showed the highest prevalence (19.7%), followed by Diplopylidium acanthotetra (10.5%), Joyeuxiella pasqualei, Mesocestoides lineatus (5.6%) and Physaloptera sp. (3.9%). Macracanthorhynchus hirudinaceus was detected once. Podarcis siculus and T. mauritanica were associated with cestode infections. Conclusions The wide range of helminths detected here in reptiles living in sympatry with pets and the fact that many of these helminth species are parasitic and may infect companion animals (e.g., J. pasqualei, J. echinorhyncoides, D. acanthotetra, Physaloptera sp.) and humans (i.e., Macracanthorhynchushirudinaceus, Mesocestoideslineatus) indicate the potential health risk associated with pets preying on these small vertebrates. Our results indicate the need for complementary investigations of trophically transmitted parasites in dogs and cats living in sympatry with reptiles. Graphical Abstract
... Advocates for containment prioritise concern for wildlife [59] or the welfare problems of free-ranging cats [60]; some authors argue for both [61,62]. A higher proportion of recommendations for containment in Australia and New Zealand may indicate national concern for the environment or cat health risks such as traffic [1,2,63]. ...
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Cats are popular companion animals globally. While the general academic definition of responsible cat ownership is agreed upon, committing to responsible cat ownership is multifaceted, often reflecting regional priorities and values. Utilising a virtual private network (VPN), an English-language online search for ‘responsible cat ownership’ was applied from major cities in 10 different nations, accounting for five different geographic regions and nine different geographic sub-regions. Data were extracted from the first 20 webpages of each search and included author affiliation, country of webpage origin, and all recommendations towards responsible cat ownership. Searches identified 58 different webpages, 142 duplicate results, and 16 different recommendations. Both before (60.5%) and after (58.6%) duplicate exclusion, irrespective of region, most webpages originated from Australia, so recommendations may lack local nuance in other countries. Similarly, local government webpages were the most common author affiliation both before (35.5%) and after (37.9%) duplicate exclusion—moreover, most Australian webpages were authored by local government (55.9%). More than half of all webpages recommended registration and microchipping (65.5%), desexing (65.5%), and containment (60.3%), probably due to the predominance of local government and Australian webpages online—reflecting Australia’s strong legislative stance. Both Australia and New Zealand showed majority recommendations for containment but not for environmental and behavioural enrichment in households. This may be partially explained by the significantly higher agreement in Australia and New Zealand that cats threaten valued wildlife in cities, towns, and rural areas. Unlike the Oceanian nations, other countries clearly recommended improved understanding and provision for cat needs, but with little evidence of support for containment. Thus, divergent welfare considerations inform major webpages associated with attitudes towards cat ownership internationally. Encouraging containment, a responsible cat ownership practice with benefits for cats and wildlife, may be more likely to succeed outside Oceania if cat welfare is emphasised instead of wildlife protection. Within Oceania, more attention could be given to enhancing the well-being of contained cats.
... In the US alone, a study estimated that there are around 1.2-4 billion birds, and 6.3-22.3 billion mammals killed by cats annually (Loss et al., 2013). In another study in Italy, 145 cats brought home 2042 vertebrates from at least 207 different species (Mori et al., 2019) and in the UK, 696 cats were recorded to have brought 2809 dead birds to their household from 44 different species over the course of 5 months (Woods et al., 2003) Only a small fraction of the preys caught by cats (less than 25%) is brought home (Trouwborst et al., 2020), which means that the total preys of cats is considerably higher than the number of prey items they bring home. In Australia, the mortality of birds by cats has been found to be around 377 million birds per year, of which 71% are killed by feral cats in human-unaffected habitats (Woinarski et al., 2017). ...
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Cats and dogs are very common pets in Greece and especially cats, are commonly allowed to roam freely and even become feral. This was thought to have detrimental effects on wildlife, especially birds. I evaluated whether cats and dogs affect the distribution of birds in the north-eastern provinces of Athens. Different areas were sampled and analyzed to determine if areas with different densities of dogs and cats have different densities of birds. Dogs, showed to not impact any bird species apart from Blackbirds which were surprisingly positively correlated with dogs. On the other hand, cats seem to impact Sardinian warblers and blackbirds negatively. Areas with more cats seemed to have a lower number of these two avian species. These findings support that cats can impact wild bird populations and that owners need to be responsible, while it shows no evidence to support that dogs can do the same. However, in this study there were not enough samples to statistically analyze the impact of these two animals on all bird species, while there were also no samples from different natural habitats other than dry Mediterranean bushland with few trees such as pine trees, olive trees and deciduous trees found in gardens.
... 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]. ...
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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.
... Given the emotional value of pet cats to their owners, perhaps unlike feral cats on islands, removal of problematic, owned cats for the benefit of wildlife is not desirable and does not constitute a feasible approach to management in many societies. Confinement indoors or within enclosures offers an alternative approach, and is often strongly advocated by wildlife conservationists (Mori et al., 2019). However, cat owners often consider permanent confinement as an impediment to cats expressing normal feline behaviours, and confinement can be a welfare concern because cat owners may not have appropriate, cat-friendly indoor environments (Tan et al., 2017;Crowley et al., 2019). ...
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In many ecological contexts, predation of wildlife by domestic cats Felis catus, combined with their abundance, is a threat to biodiversity conservation. The predatory behaviour of domestic cats shows remarkable between-individual variation. Many free-roaming cats living as companion animals capture, kill and/or bring home few or no prey, while others are prolific killers and likely contribute disproportionately to any impacts upon wild animal populations. Recent work has identified five owner-ascribed personality factors for cats (“The Feline Five”). We tested whether variation in scores for these five factors, quantifying owners’ characterisation of their cats, was associated with capturing and bringing home wild prey, and was related to variation among cats in numbers of recorded prey. We recruited owners of domestic cats kept as companion animals in southwest England. Owners completed a questionnaire assessing their cats’ behavioural traits, and recorded prey items brought home by their pets. Cats that hunted and brought home wild prey scored high for ‘extraversion’ or low for ‘neuroticism’, when compared to cats that did not bring home wild prey. However, variation in the numbers of prey items captured and brought home by hunting cats was not affected by scores for any of the factors. Owner characterisation of their cats’ personalities holds potential to refine approaches for managing hunting by cats, including approaches that do not compromise cat welfare while effectively reducing predation. For example, extraverted cats might be stimulated and encouraged in physical activity through object play in the home environment, with the aim of decreasing hunting motivation. Cat owners might also be more inclined to adopt strategies that they believe better suit their perceptions of their cat’s personality.
... Even though domestic cats usually eat diets provided by humans, they are instinctive hunters with opportunistic predatory behaviors, and several authors affirm that they cause relevant conservation problems because its relationship with a significant percentage of the total mortality of wildlife in diverse areas of the world (Beckerman et al. 2007;Balogh et al. 2011;Tschanz et al. 2011;Lessa and Bergallo 2012;Kutt 2012;Ferreira et al. 2014;Mori et al. 2019;Legge et al. 2020;Seymour et al. 2020;Trouwborst et al. 2020); in fact, native species can be affected with detrimental consequences including extinction (Gillies and Clout 2003;Kays and DeWan 2004;Millan 2010;Bonnaud et al. 2011;Kutt 2012;Doherty et al. 2016). ...
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El gato doméstico es una especie invasora que ocasiona problemas para la vida silvestre en todo el mundo, pero el conocimiento de sus efectos en la región neotropical es escaso. En este estudio realizamos una aproximación sobre la mortalidad de fauna silvestre ocasionada por este felino en áreas urbanas y rurales de la región Caribe de Colombia. Encontramos 107 registros de cacería de 31 especies entre anfibios, reptiles, aves y mamíferos, de las cuales se destaca a Cnemidophorus sp. por tener el mayor número de casos (31). Adicionalmente, encontramos un registro de caza de una especie migratoria, Porzana carolina, y dos subespecies endémicas del Caribe colombiano (Erythrolamprus melanotus lamari y Ameiva bifrontata divisa). Los resultados de este trabajo son los primeros documentados para el país, advirtiendo del impacto potencial que puede estar generando el gato doméstico sobre la biodiversidad colombiana. The Domestic cat is an invasive species causing problems for wildlife throughout the world, but knowledge of its effects in the Neotropical region is scarce. In this study, we made an approximation of cases of mortality of wildlife caused by this feline in urban and rural areas of the Caribbean region of Colombia. We found 107 hunting records of 31 species among amphibians, reptiles, birds and mammals, of which highlights Cnemidophorus sp. for having the highest number of cases (31). Additionally, we found a hunting record of a migratory species, Porzana carolina, and two
... Depending on the geographic region, stray cats may suffer from similar poor welfare outcomes to free-ranging owned cats, including road accident trauma [14][15][16][17], poisoning [18], ingestion of hazardous garbage [7], predation by larger carnivores [19], disease [20], and human persecution [21]. Free-ranging cats may also kill or harass wildlife [22][23][24], including threatened species [25][26][27], present a disease risk to people, pets, and wildlife [28][29][30][31][32], and annoy people [1,33]. Therefore, the management of stray cats is an ethical and community concern. ...
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Globally, unowned urban cats are a major concern because they may suffer from poor welfare and cause problems, including public health risks, nuisances, and urban wildlife predation. While management options are often presented as a choice between culling or trap–neuter–return (TNR), for 25 years, the Lonely Miaow (Inc.) charity in Auckland, New Zealand (hereafter LM), has used a third strategy—intensive adoption or trap–assess–resolve (TAR). As of 2019, of 14,611 unowned cats trapped, 64.2% were adopted, 22.2% were euthanized if unsocialised or in grave ill-health, 5.7% were neutered and returned to the site, and 7.9% had other outcomes, such as being transferred to other shelters. Adoption rates increased over this time, exceeding 80.0% in 2018 and 2019. The cost of processing each cat from capture to adoption rose from NZD 58 in 1999 to NZD 234 by 2017. Approximately 80% of colonies (sites where cats were trapped) were around residential areas. Approximately 22% of cats required veterinary treatment after capture; common ailments included respiratory infections, ringworm, dental problems, and trauma. Consistently, 52% of cats were young kittens (<10 weeks old), c. 80% of cats were <1 year old, and only c. 2% were estimated to be >5 years old. TAR avoids euthanasia where possible. Its effectiveness would be enhanced by fewer abandonments of owned cats and kittens, fitting within integrated strategies for the control of unowned cats involving community education. Cat adoptions improve the welfare of cats and, with appropriate husbandry, should alleviate concerns about nuisances, public health, and attacks on wildlife or the cats themselves, essentially benefitting the community and the cats. This case study is relevant to other cities around the world that are seeking to manage unowned cats.
... As such, community science projects provide a practical tool for addressing invasion-related questions that require spatial, temporal, and/or phenological information , particularly in relation to post-border surveillance (Thomas et al. 2017). For instance, community science has been used to delimit the distribution of alien species, during both the early (Eritja et al. 2019;Hourston et al. 2015) and late (Bois et al. 2011;Crall et al. 2015) stages of invasion, to understand alien species' range expansions (Grason et al. 2018), as well as temporal emergence patterns (Maistrello et al. 2016) and even to reveal impacts on native biodiversity (Mori et al. 2019;Roy et al. 2012). Given that community science projects often capture data opportunistically-particularly in the form of presence-only data-they may harbour large uncertainties that must be accounted for in downstream analyses (Bird et al. 2014;Isaac and Pocock 2015;Petersen et al. 2021). ...
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Community science (also often referred to as citizen science) provides a unique opportunity to address questions beyond the scope of other research methods whilst simultaneously engaging communities in the scientific process. This leads to broad educational benefits, empowers people, and can increase public awareness of societally relevant issues such as the biodiversity crisis. As such, community science has become a favourable framework for researching alien species where data on the presence, absence, abundance, phenology, and impact of species is important in informing management decisions. However, uncertainties arising at different stages can limit the interpretation of data and lead to projects failing to achieve their intended outcomes. Focusing on alien species centered community science projects, we identified key research questions and the relevant uncertainties that arise during the process of developing the study design, for example, when collecting the data and during the statistical analyses. Additionally, we assessed uncertainties from a linguistic perspective, and how the communication stages among project coordinators, participants and other stakeholders can alter the way in which information may be interpreted. We discuss existing methods for reducing uncertainty and suggest further solutions to improve data reliability. Further, we make suggestions to reduce the uncertainties that emerge at each project step and provide guidance and recommendations that can be readily applied in practice. Reducing uncertainties is essential and necessary to strengthen the scientific and community outcomes of community science, which is of particular importance to ensure the success of projects aimed at detecting novel alien species and monitoring their dynamics across space and time. Supplementary information: The online version contains supplementary material available at 10.1007/s10530-022-02858-8.
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Cat predation upon bat species has been reported to have significant effects on bat populations in both rural and urban areas. The majority of research in this area has focussed on observational data from bat rehabilitators documenting injuries, and cat owners, when domestic cats present prey. However, this has the potential to under- estimate the number of bats killed or injured by cats. Here, we use forensic DNA analysis techniques to analyze swabs taken from injured bats in the United Kingdom, mainly including Pipistrellus pipistrellus (40 out of 72 specimens). Using quantitative PCR, cat DNA was found in two-thirds of samples submitted by bat rehabilitators. Of these samples, short tandem repeat analysis produced partial DNA profiles for approximately one-third of samples, which could be used to link predation events to individual cats. The use of genetic analysis can complement observational data and potentially provide additional information to give a more accurate estimation of cat predation.
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[The Rock Dove (Columba livia) is a polytypic species originally confined to coastal and inland cliffs of western Palaearctic and northern Ethiopian regions and to those of Indian subcontinent. The present distribution is confused by extensions of range through hybridization with feral stock, which have determined its diffusion in geographical areas and environments that are very different and distant from the original ones, with a naturalized distribution now virtually cosmopolitan. Besides a substantial number of domestic breeds reared and maintained in this state, Columba livia is now represented by the original wild populations, generally in decline, and by feral populations, originated from abandoned or escaped domestic individuals. These populations developed above all, but no exclusively, in the cities, starting from the end of the XVIII century, with a further significant increase during the second post-war period, In this work, after having examined and discussed the distribution of the species resulting from the Pleistocene fossil findings and from the historical ornithological literature, we advance the hypothesis that wherever there are free-living populations showing phenotypic, biometric or genetic characteristics different from the wild morphotype, it is legitimate to consider these populations as an alien complex of domestic origin, to be controlled by culling and, when possible, eradicated. On the side-lines of this work, the Authors hope for a reconsideration of Italian names of this species.] [Article in Italian]
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Some conservationists believe free‐ranging cats pose an enormous risk to biodiversity and public health and therefore should be eliminated from the landscape by any means necessary. They further claim that those who question the science or ethics behind their arguments are science deniers (merchants of doubt) seeking to mislead the public . As much as we share a commitment to conservation of biodiversity and wild nature , we believe these ideas are wrong and fuel an unwarranted moral panic over cats. Those who question the ecological or epidemiological status of cats are not science deniers, and it is a false analogy to compare them with corporate and right‐wing special interests that perpetrate disinformation campaigns over issues such as smoking and climate change. There are good conservation and public‐health reasons and evidence to be skeptical that free‐ranging cats constitute a disaster for biodiversity and human health in all circumstances. Further, there are significant and largely unaddressed ethical and policy issues (e.g., the ethics and efficacy of lethal management) relative to how people ought to value and coexist with cats and native wildlife. Society is better served by a collaborative approach to produce better scientific and ethical knowledge about free‐ranging cats. This article is protected by copyright. All rights reserved
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The potential impact of domestic cats on wildlife is the subject of growing international interest and concern. While feral cats are often the primary focus of research and debate, in many societies a substantial proportion of domestic cats are owned by private individuals. We present a typology that classifies domestic cats in relation to varying degrees of human control over their reproduction, movement, and provisioning. Understanding the perceptions and practices of cat owners will be key to identifying and mitigating any negative ecological effects of cat hunting behaviour. To investigate how cat owners perceive (a) their pets’ hunting behaviour, (b) their responsibilities for managing this, and (c) the mitigation strategies available, we conducted detailed interviews with a diverse sample of cat owners in the United Kingdom. We identified a spectrum of views on hunting behaviour, from owners who perceived hunting as positive (for pest control, or as healthy cat behaviour) to those who were deeply concerned about its consequences for wild animals, their populations, and welfare. However, hunting was widely understood as a normal, natural component of cat behaviour, and owners rarely perceived a strong individual responsibility for preventing or reducing it. Those who did wish to manage hunting perceived several barriers to this, including concern that they were unable to control behaviour effectively without compromising cat welfare, doubt about the efficacy and practicality of popular mitigation measures, and unfamiliarity with alternative options. We recommend that (a) initiatives directed at changing cat owners’ behaviour consider the multiple factors and competing priorities that inform their decision‐making (particularly cat health and welfare and practicality or cost of interventions); (b) researchers work collaboratively with cat owners and veterinary, cat welfare, and conservation organizations to identify effective solutions, and (c) some degree of accountability for managing problematic hunting behaviour should be promoted as a part of “responsible pet ownership” initiatives. A plain language summary is available for this article.
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Feral cats (Felis catus) are predators that cause widespread loss of native wildlife in urban ecosystems. Despite these risks, cats are commonly released as control agents for city rats (Rattus spp.). Cats can influence their prey directly by killing or indirectly through changes to feeding or space-use. However, cats prefer defenseless prey, and there are no data suggesting that cats influence large (>300 g) urban rats. We used a pre-existing radiofrequency identification assay (microchipped rats and field cameras) and ethograms to assess the impact of cats, including temporal and space use patterns, on an active rat colony. From Dec 27, 2017 through May 28, 2018 we captured 306 videos of pre-identified cats and/or rats that shared the same space. There were three instances of predation and 20 stalking events. Logistic regression showed the likelihood of a rat being seen on a particular day is associated with the number of cats seen on the same day (OR = 0.1, p < 0.001) or previous day (OR = 0.15, p < 0.001). Space-use was also impacted. For every additional cat sighting, a rat is 1.19 times more likely to move in the direction of shelter. Our findings of low levels of predation support why ecologists believe the risks to native wildlife outweighs any benefits of releasing cats. Even though rats were less likely to be seen, they simply shifted their movements and remained present in the system. Our findings that cat presence led to fewer rat sightings may explain the common perception of their value as rat-predators despite the associated risks.
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Aim Although the effects of life history traits on population density have been investigated widely, how spatial environmental variation influences population density for a large range of organisms and at a broad spatial scale is poorly known. Filling this knowledge gap is crucial for global species management and conservation planning and to understand the potential impact of environmental changes on multiple species. Location Global. Time period Present. Major taxa studied Terrestrial amphibians, reptiles, birds and mammals. Methods We collected population density estimates for a range of terrestrial vertebrates, including 364 estimates for amphibians, 850 for reptiles, 5,667 for birds and 7,651 for mammals. We contrasted the importance of life history traits and environmental predictors using mixed models and tested different hypotheses to explain the variation in population density for the four groups. We assessed the predictive accuracy of models through cross‐validation and mapped the partial response of vertebrate population density to environmental variables globally. Results Amphibians were more abundant in wet areas with high productivity levels, whereas reptiles showed relatively higher densities in arid areas with low productivity and stable temperatures. The density of birds and mammals was typically high in temperate wet areas with intermediate levels of productivity. The models showed good predictive abilities, with pseudo‐R² ranging between 0.68 (birds) and 0.83 (reptiles). Main conclusions Traits determine most of the variation in population density across species, whereas environmental conditions explain the intraspecific variation across populations. Species traits, resource availability and climatic stability have a different influence on the population density of the four groups. These models can be used to predict the average species population density over large areas and be used to explore macroecological patterns and inform conservation analyses.
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Misinformation (or denialism), the disingenuous assertion of information contradicting overwhelming scientific consensus, increasingly poses a challenge for invasion biology. The issue of free-ranging domestic cats (Felis catus) provides an example of this misinformation: overwhelming consensus shows that cats are invasive species that impact wildlife and human health yet free-ranging cat advocates propagate misinformation about such impacts to support policies keeping cats on the landscape. These advocates also attempt to discredit peer-reviewed scientific research on cat impacts, as exemplified by the response to a high-profile paper estimating cats annually kill billions of U.S. birds and mammals (Loss et al. in Nat Commun 4:1396, 2013). Although favorably received by scientific and invasive species management communities, an effort was launched to discredit this paper by criticizing its methods, including a report commissioned by a feral cat advocacy group and a post by a feral cat blogger. These same organizations and individuals have made similar criticisms at scientific conferences and policy roundtables. Given the realized effects of this campaign in influencing invasive species policy, we here respond to these criticisms and show they are characterized by numerous errors and misrepresentations. We conclude that the criticisms are part of the broader campaign to fabricate doubt about outdoor cat impacts and stymie policies favoring removal of cats from the landscape. Because misinformation surrounding cats is emblematic of the broader issue of misinformation and denialism, this response will not only facilitate evidence-based policy for managing cats but also stimulate research and discussion into causes and impacts of misinformation in invasion biology.
Proximity to humans is a primary stressor for wildlife, especially in urban habitats where frequent disturbance may occur. Several bat species often roost in buildings but while the effects of disturbance inside the roost are well documented, little is known about those occurring in the proximity of roosts. We tested the effects of anthropogenic stressors on bats by monitoring reactions to disturbance in a colony of greater horseshoe bats (Rhinolophus ferrumequinum). We assessed disturbance by recording and quantifying the presence of people, domestic cats and noise sources near the roost. Disturbance outside the roost caused the disruption of roosting clusters; when cats entered the roost, bats decreased indoor flight activity. Emergence timing was delayed when people were close to the roost exit, and the delay increased along with the number of people. The occurrence of a cat increased the degree of group clustering during emergence. Cats entered the roost especially when young bats were present, and bat remains occurred in 30% of the cat scats we examined. We show that the occurence of human activities near roosts and free-ranging domestic cats are important albeit overlooked sources of disturbance.
Foxes and cats are the most abundant medium-sized urban carnivores. To date, however, there has been a lack of effort to synthesize data on the spatial and trophic resources used by these two carnivores, despite the importance of this information for assessing their similarity and roles in urban food webs. In this paper, we first synthesize all available information on the trophic patterns and home-range size of these two predators based on a total of 91 studies. Second, we conduct statistical analyses to test the influence of environmental and biological variables such as regional differences, habitat characteristics, age, and sexual status on their home-range size and diet patterns within urban habitats, and then evaluate the methods used to investigate these components. Our findings highlight the lack of studies that simultaneously monitor the diet and home-range size of both predators within urban habitats. To the best of our knowledge, this is the first study to compare fox and cat home-range size and diet. Foxes exhibited larger ranges than cats, while intact cats showed larger home ranges than desexed cats. Diet diversity obtained for both predators confirmed their trophic plasticity within urban habitats. Both predators consumed fewer mammals and invertebrates in highly disturbed habitats compared to medium ones. We also found that the procedure of data acquisition significantly influenced fox and cat home-range sizes. In terms of diet, the type of recovered samples had a significant effect on the diet composition of both predators. To improve our understanding of the relative impact of these two urban carnivores on urban wildlife, we recommend simultaneously studying both species in future studies. Moreover, methodological standards for both diet and home-range size studies are needed to allow comparisons.
The diet of suburban foxes has been studied by analysing 200 scats collected monthly between July 2016 and July 2017, along fixed itineraries around two villages in central Italy. A significant seasonal variation in the diet was found. Fruits (berries) and coleopterans prevailed in the warm months and were replaced by feral domestic cats (mostly kittens) in the cold ones. The local overwhelming importance of the domestic cat in diet confirms the opportunistic feeding behaviour of red foxes, which may switch their diet towards easily accessible food categories, when preferred items are poorly available. Keywords: Red fox, Feral domestic cats, Red fox feeding habits, Red fox feeding ecology, Red fox diet, Diet analysis, Scat analysis, Trophic niche, Red fox biology, Mesopredator coexistence, Intraguild predation, Interspecific killing, Vulpes vulpes, Felis catus, Carnivora.