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« Chat domestique et biodiversité » : Où et quand les chats rapportent-ils des micromammifères à la maison ?
Abstract
Constituée de plusieurs millions d’individus, la population de Chat domestique est actuellement en augmentation en France avec certainement des conséquences sur la faune des petits vertébrés qui constitue ses proies préférées. Le programme « Chat domestique et biodiversité » a pour objectif d’identifier les espèces, ou groupes d’espèces, des proies ramenées à la maison par ces chats afin d’apprécier : i) un
taux relatif, ii) une saisonnalité, et iii) un effet de l’état de dégradation des habitats, sur cette activité prédatrice. Les résultats d’une première analyse portant sur 37 835 proies signalées entre 2015 et 2019, a permis de mettre en évidence plus de 200 espèces rapportées à la maison, où les mammifères sont les plus représentés (68 %), particulièrement les « micromammifères » (62 %). Parmi ces derniers identifiés
à l’espèce, la Souris grise, le Campagnol des champs, et le Mulot sylvestre sont les plus consommés. Considérant ces proies réunies en trois groupes taxonomiques larges (« musaraignes », « campagnols », et « muridés »), il est constaté un pic estival pour les musaraignes, et un large pic incluant automne-hiver pour les rongeurs dans le rapportage. Par ailleurs, les campagnols au sens large sont plus souvent ramenés à la maison dans les habitats peu altérés que dans les habitats très altérés par les activités humaines.
Enfin, il semble que plus de « musaraignes » et de « muridés » sont prédatés dans le nord de la France que dans le sud, probablement en lien avec la répartition géographique des différentes espèces présentes dans ces groupes de proies.
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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.
Urban domestic cat (Felis catus) populations can attain exceedingly high densities and are not limited by natural prey availability. This has generated concerns that they may negatively affect prey populations, leading to calls for management. We enlisted cat-owners to record prey returned home to estimate patterns of predation by free-roaming pets in different localities within the town of Reading, UK and questionnaire surveys were used to quantify attitudes to different possible management strategies. Prey return rates were highly variable: only 20% of cats returned ≥4 dead prey annually. Consequently, approximately 65% of owners received no prey in a given season, but this declined to 22% after eight seasons. The estimated mean predation rate was 18.3 prey cat(-1) year(-1) but this varied markedly both spatially and temporally: per capita predation rates declined with increasing cat density. Comparisons with estimates of the density of six common bird prey species indicated that cats killed numbers equivalent to adult density on c. 39% of occasions. Population modeling studies suggest that such predation rates could significantly reduce the size of local bird populations for common urban species. Conversely, most urban residents did not consider cat predation to be a significant problem. Collar-mounted anti-predation devices were the only management action acceptable to the majority of urban residents (65%), but were less acceptable to cat-owners because of perceived risks to their pets; only 24% of cats were fitted with such devices. Overall, cat predation did appear to be of sufficient magnitude to affect some prey populations, although further investigation of some key aspects of cat predation is warranted. Management of the predation behavior of urban cat populations in the UK is likely to be challenging and achieving this would require considerable engagement with cat owners.
1. A questionnaire survey of the numbers of animals brought home by domestic cats Felis catus was conducted between 1 April and 31 August 1997. A total of 14 370 prey items were brought home by 986 cats living in 618 households. Mammals made up 69% of the items, birds 24%, amphibians 4%, reptiles 1%, fish < 1%, invertebrates 1% and unidentified items 1%. A minimum of 44 species of wild bird, 20 species of wild mammal, four species of reptile and three species of amphibian were recorded.
2. Of a sample of 696 individual cats, 634 (91%) brought home at least one item and the back-transformed mean number of items brought home was 11.3 (95% CI 10.4–12.2). The back-transformed means and number of cats retrieving at least one item from each prey group were: 8.1 (7.4–8.9) mammals for 547 (79%) cats, 4.1 (3.8–4.5) birds for 506 (73%) cats, 2.6 (2.2–3.0) herpetofauna for 145 (21%) cats and 2.2 (1.8–2.7) other items for 98 (14%) cats.
3. The number of birds and herpetofauna brought home per cat was significantly lower in households that provided food for birds. The number of bird species brought home was greater in households providing bird food. The number of birds and herpetofauna brought home per cat was negatively related to the age and condition of the cat. The number of mammals brought home per cat was significantly lower when cats were equipped with bells and when they were kept indoors at night. The number of herpetofauna brought home was significantly greater when cats were kept in at night.
4. Based on the proportion of cats bringing home at least one prey item and the back-transformed means, a British population of approximately 9 million cats was estimated to have brought home in the order of 92 (85–100) million prey items in the period of this survey, including 57 (52–63) million mammals, 27 (25–29) million birds and 5 (4–6) million reptiles and amphibians.
5. An experimental approach should be taken to investigate the factors found by this descriptive survey to influence the numbers of prey brought home by cats. In particular, investigation of potential management practices that could reduce the numbers of wild animals killed and brought home by cats will be useful for wildlife conservation, particularly in suburban areas.
Understanding the habitat-related hunting behavior of house cats Felis catus is needed to evaluate their potential predatory effect on areas they actively visit within their home range. As part of a citizen science program, 30 neutered cats from 25 households were equipped by their owners during, on average, 2 consecutive days per month between January and November 2016 with a GPS programmed to acquire fixes at 1 to 5-mn intervals. Nine cats were located in rural environments, 9 in suburban landscapes, and 12 in urban habitats. For 16 of these cats, preys brought home were recorded daily. Using the recursive distribution movement-based kernel density estimator, rural cats had the largest mean home range area (3.5 ± 0.3 ha), followed by suburban (2.1 ± 0.2 ha) and city cats (1.4 ± 0.1 ha). Moreover, suburban cats enlarged their frequently visited areas in April-June, which corresponded to a peak in small bird preys brought home. Our results suggest that a more diversified landscape may drive domestic cats to increase their home range by benefiting from higher numbers of exploitable areas.
The fragmentation of landscapes, induced by the growing urbanisation, is a major cause of biodiversity loss. Ecological corridors are landscape elements that make up for the negative effects of habitat fragmentation in agricultural or natural landscapes. However, their effectiveness have been rarely assess in an urban context. To do so, we analysed shrews in woodlots, corridors and domestic gardens that are connected or disconnected from a corridor. Indeed, these mammals are very sensitive to fragmentation and could play an important ecological role even in small and isolated areas such as domestic gardens. Ninety-seven shrews, from three species were trapped. In our study, Sorex coronatus, Sorex minutus and Crocidura russula were not widely distributed and mainly occurred in woodlots, corridors and connected gardens. In gardens, shrew occurrences were mainly determined by landscape configuration with negative effects of the distance to the corridor and the distance to the woodlot, stronger for C.russula than Sorex species. At the local scale, garden management and vegetation showed a positive effect mainly for Sorex species. The quality of gardens seems good enough to permit the co-occurrence of several species of shrews and thus competition was not identified as a major process for determining the occurrence. We showed that, as in other ecosystems, ecological corridors in urban context can play an effective role for the distribution of organisms with low dispersal capabilities and should be develop in planning strategies.
Representation of generalized additive models (GAM's) using penalized regression splines allows GAM's to be employed in a straightforward manner using penalized regression methods. Not only is inference facilitated by this approach, but it is also possible to integrate model selection in the form of smoothing parameter selection into model fitting in a computationally efficient manner using well founded criteria such as generalized cross-validation. The current fitting and smoothing parameter selection methods for such models are usually effective, but do not provide the level of numerical stability to which users of linear regression packages, for example, are accustomed. In particular the existing methods cannot deal adequately with numerical rank deficiency of the GAM fitting problem, and it is not straightforward to produce methods that can do so, given that the degree of rank deficiency can be smoothing parameter dependent. In addition, models with the potential flexibility of GAM's can also present practical fitting difficulties as a result of indeterminacy in the model likelihood: Data with many zeros fitted by a model with a log link are a good example. In this article it is proposed that GAM's with a ridge penalty provide a practical solution in such circumstances, and a multiple smoothing parameter selection method suitable for use in the presence of such a penalty is developed. The method is based on the pivoted QR decomposition and the singular value decomposition, so that with or without a ridge penalty it has good error propagation properties and is capable of detecting and coping elegantly with numerical rank deficiency. The method also allows mixtures of user specified and estimated smoothing parameters and the setting of lower bounds on smoothing parameters. In terms of computational efficiency, the method compares well with existing methods. A simulation study compares the method to existing methods, including treating GAM's as mixed models.
RStudio: Integrated development environment for
- R Rstudio
- Pbc
- M A Boston
RStudio Team 2021. RStudio: Integrated development
environment for R. RStudio, PBC, Boston, MA: http://
www.rstudio.com/.