The danger of pets on islands

The cat was domesticated around 9000 years ago. Since then, domestic cats have traveled with humans to almost all corners of the globe, including many remote islands where they have become feral. And this brings with it many problems. When we introduce an alien species in an ecosystem that is not adapted to this organism, it can trigger a series of problems in chain.

Hace aproximadamente 9000 años los gatos fueron domesticados. Desde entonces se han convertido en compañeros inseparables de muchos humanos, acompañándoles en sus viajes y ocupando prácticamente todos los confines del planeta. Hasta aquí, no parece que haya ningún problema… Pero, muchos de estos gatos, una vez llegan a su nuevo entorno, comienzan a competir por los recursos con otros organismos que no están preparados para defenderse de un predador tan eficiente. Y si esto ocurre en Islas, en las que la vida ha evolucionado en ausencia de estos feroces y eficientes animales, las consecuencias para los ecosistemas pueden ser dramáticas. Con este vídeo, incómodo para muchos, pretendemos llamar la atención de un problema que está afectando, ahora ya a gran escala, a la conservación de nuestra biodiversidad. No es un problema menor y por eso tenemos que implicarnos en buscar soluciones entre todos.

Cats among the most usual targets of eradication programs on islands

Jones, H. P., Holmes, N. D., Butchart, S. H., Tershy, B. R., Kappes, P. J., Corkery, I., ... & Campbell, K. (2016). Invasive mammal eradication on islands results in substantial conservation gains. Proceedings of the National Academy of Sciences, 201521179.

More than US$21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation. We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands. We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands. Seven native species (eight populations) were negatively impacted by invasive mammal eradication. Four threatened species had their International Union for the Conservation of Nature (IUCN) Red List extinction-risk categories reduced as a direct result of invasive mammal eradication, and no species moved to a higher extinction-risk category. We predict that 107 highly threatened birds, mammals, and reptiles on the IUCN Red List—6% of all these highly threatened species—likely have benefitted from invasive mammal eradications on islands. Because monitoring of eradication outcomes is sporadic and limited, the impacts of global eradications are likely greater than we report here. Our results highlight the importance of invasive mammal eradication on islands for protecting the world's most imperiled fauna.

Are Novel Invaders Necessarily Facing Naïve Native Species on Islands?

Gérard, A., Jourdan, H., Millon, A., & Vidal, E. (2016). Knocking on Heaven's Door: Are Novel Invaders Necessarily Facing Naïve Native Species on Islands?. PloS one, 11(3), e0151545.

The impact of alien predator species on insular native biota has often been attributed to island prey naïveté (i.e. lack of, or inefficient, anti-predator behavior). Only rarely, however, has the concept of island prey naïveté been tested, and then only a posteriori (i.e. hundreds or thousands of years after alien species introduction). The presence of native or anciently introduced predators or competitors may be crucial for the recognition and development of adaptive behavior toward unknown predators or competitors of the same archetype (i.e. a set of species that occupy a similar ecological niche and show similar morphological and behavioral traits when interacting with other species).
Here, we tested whether two squamates endemic to New Caledonia, a skink, Caledoniscincus austrocaledonicus, and a gecko, Bavayia septuiclavis, recognized and responded to the odor of two major invaders introduced into the Pacific islands, but not yet into New Caledonia. We chose one predator, the small Indian mongoose Herpestes javanicus and one competitor, the cane toad Rhinella marina, which belong respectively to the same archetype as the following two species already introduced into New Caledonia in the nineteenth century: the feral cat Felis catus and the golden bell frog Litoria aurea. Our experiment reveals that geckos are naïve with respect to the odors of both an unknown predator and an unknown competitor, as well as to the odors of a predator and a competitor they have lived with for centuries. In contrast, skinks seem to have lost some naïveté regarding the odor of a predator they have lived with for centuries and seem “predisposed” to avoid the odor of an unknown potential competitor. These results indicate that insular species living in contact with invasive alien species for centuries may be, although not systematically, predisposed toward developing adaptive behavior with respect to species belonging to the same archetype and introduced into their native range.

An examination of feral cats control techniques for the protection of critically endangered species

Leo, B. T. (2016). An examination of predator control techniques for the protection of critically endangered species (Doctoral dissertation).

Feral cats (Felis catus) have been shown to be a main contributor to species decline throughout the world and are especially threatening to insular species that lack adequate defense characteristics. Feral cat control programs have been implemented on islands throughout the world with varied success. Many islands present unique limitations and therefore require custom control strategies. Furthermore, the adaptive nature of feral cat populations makes it difficult to predict space use and the effect of control on population size. To mitigate the impact of feral cats on threatened species, space use data are commonly used to design control strategies. With the use of GPS data logging collars, chapter two describes daily space use and home ranges of feral cats that threaten an endangered species on Rota Island in the Commonwealth of the Northern Mariana Islands. Using 100% Minimum Convex Polygon (MCP), average adult male home range was 1.32 km² and average adult female home range was 0.22 km². Home ranges were deemed fully revealed if asymptotes were reached using incremental analysis. A Michaelis-Menten model was applied to predict home ranges of cats with datasets that did not show convergence. The ability of the model to estimate home ranges of cats with limited location datasets was evaluated by comparing predictions derived from truncations of the full time series of complete datasets. Findings suggest that cat management on Rota should be multifaceted in order to maximize the protection of endangered species and that the Michaelis-Menten model is a useful tool for home range analysis. Chapter three examines the Rota hunting strategy to determine its impacts on the population. A discrete form of the Schaefer model was applied to a 29-month time series of control data. A likelihood framework was used to determine maximum likelihood parameter estimates and calculate population projections to compare control strategies. Model results suggest that the hunting strategy on Rota was effective at initially reducing the cat population, however an unfeasible amount of effort would be required to maintain such a rate of decline. Findings show that it is feasible to maintain cat abundance at lower levels and suggest that a concentrated-effort strategy is preferable to a fixed-effort strategy. While more complex population model forms are available, the Schaefer model is well suited for assessing the impacts of limited predator control programs, such as the one conducted on Rota Island.

For Rare Hawaiian Birds, Cats Are Unwelcome Neighbors

Last fall, a nest camera operated by the Kaua‘i Endangered Seabird Recovery Project recorded a devastating scene. A feral cat extracted an adult shearwater and its chick from their nearly inaccessible mountaintop burrow and killed both birds. (Watch the video here, but be warned that the content is graphic.)...

Continue reading...

Leptospira in free-living sea lions in California and Baja California

Rosalía Avalos-Téllez, Erika M. Carrillo-Casas, Daniel Atilano-López, Carlos R. Godínez-Reyes, Efrén Díaz-Aparicio, David Ramírez-Delgado, María F. Ramírez-Echenique, Margarita Leyva-Leyva, Gerardo Suzán, and Francisco Suárez-Güemes (2016) Pathogenic Leptospira serovars in free-living sea lions in the gulf of California and along the Baja California coast of Mexico. Journal of Wildlife Diseases In-Press.


The California sea lion (Zalophus californianus), a permanent inhabitant of the Gulf of California in Mexico, is susceptible to pathogenic Leptospira spp. infection, which can result in hepatic and renal damage and may lead to renal failure and death. During summer 2013, we used the microscopic agglutination test (MAT) to investigate the prevalence of anti-Leptospira antibodies in blood of clinically healthy sea lion pups from seven rookery islands on the Pacific Coast of Baja California (Pacific Ocean) and in the Gulf of California. We also used PCR to examine blood for Leptospira DNA. Isolation of Leptospira in liquid media was unsuccessful. We found higher antibody prevalence in sea lions from the rookery islands in the gulf than in those from the Pacific Coast. Antibodies against 11 serovars were identified in the Gulf of California population; the most frequent reactions were against serovars Bataviae (90%), Pyrogenes (86%), Wolffi (86%), Celledoni (71%), and Pomona (65%). In the Pacific Ocean population, MAT was positive against eight serovars, where Wolffi (88%), Pomona (75%), and Bataviae (70%) were the most frequent. Serum samples agglutinated with more than one Leptospira serovar. The maximum titer was 3,200. Each island had a different serology profile, and islands combined showed a distinct profile for each region. We detected pathogenic Leptospira DNA in 63% of blood samples, but we found no saprophytic Leptospira. Positive PCR results were obtained in blood samples with high and low MAT titers. Together, these two methods enhance the diagnosis and interpretation of sea lion leptospirosis. Our results may be related to human activities or the presence of other reservoirs with which sea lions interact, and they may also be related to sea lion stranding.

Toxoplasmosis in endangered Hawaiian goose

Work, T. M., Verma, S.K., Su, C., Medeiros, J., Kaiakapu, T., Kwok, O. C., & Dubey, J. P. (2016).Toxoplasma gondii antibody prevalence and two new genotypes of the parasite in endangered Hawaiian geese (Nene: Branta sandvicensis). Journal of WildlifeDiseases.

Toxoplasma gondii is a protozoan parasite transmitted by domestic cats (Felis catus) that has historically caused mortality in native Hawaiian birds. To estimate how widespread exposure to the parasite is in nene (Hawaiian Geese, Branta sandvicensis), we did a serologic survey for T. gondii antibody and genetically characterized parasite DNA from the tissues of dead birds that had confirmed infections by immunohistochemistry. Of 94 geese sampled, prevalence on the island of Kauai, Maui, and Molokai was 21% (n=42), 23% (n=31), and 48% (n=21), respectively. Two new T. gondii genotypes were identified by PCR-restriction fragment length polymorphism from four geese, and these appeared segregated geographically. Exposure to T. gondii in wild nene is widespread and, while the parasite is not a major cause of death, it could have sublethal or behavioral effects. How to translate such information to implement effective ways to manage feral cats in Hawaii poses challenges.

Feral cat killing chick and adult of endangered Newell's Shearwater

Kaua'i Endangered Seabird Recovery Project

A feral cat in Hono o Na Pali NAR killing first an endangered Newell's Shearwater chick and then the adult - in an area with ongoing introduced predator control. Warning : Graphic Content, this is not pleasant viewing. However it needs to be shown to illustrate the serious conservation impact of feral cats in the wilds of Kaua'i.

Predicting free‐roaming cat population densities in urban areas

Flockhart, D. T. T., Norris, D. R., & Coe, J. B. (2016). Predicting free‐roaming cat population densities in urban areas. Animal Conservation.

Although free-roaming cats can have a significant impact on the environment, and substantial resources have been invested to find humane alternatives for managing free-roaming cat populations, there are no empirical estimates of free-roaming cat population size in medium to large cities. In addition, little is known about factors limiting free-roaming cat population size and distribution. Using Guelph, ON, Canada (pop: 120 000; 86.7 km² ) as a case-study, we apply replicated distance transect sampling and likelihood-based hierarchical modelling to compare human-mediated landscape patterns of land use, distance to roads, distance to wooded areas, building density and socio-economic status to explain the abundance of free-roaming cats. We then derive an empirical estimate of total population size and present a spatially explicit prediction of free-roaming cat density across an entire city. Cat abundance was highest in residential areas and lowest in commercial and institutional areas, negatively related to median household income, and positively related to distance from woods and building density. Total population size was estimated to be 7662 (95% bootstrap CI: 6145–9966) for Guelph; free-roaming cat density varied from 0 to 49.4 cats per ha. Our estimate overlapped with an independent estimate of indoor-outdoor cats (11 927; 95% CI: 6361–20 989) derived from random surveys of city residents, which implies our distance transect methodology was relatively robust and unbiased. Our approach used simple geographical information that is readily available for most urban areas in North America and can be applied broadly to inform cat management in urban areas. Finally, our results suggest that free-roaming cat density in cities could be determined by bottom-up processes (e.g. enhanced food availability in residential areas) as well as top-down processes (e.g. enhanced susceptibility to coyote predation near wooded areas) which are typically reserved to explain wildlife populations in natural environments.

Prevalence of selected infectious disease agents in stray cats in Catalonia

Ravicini, S., Castro-López, J., Hawley, J., Brewer, M., Castro, J., Beall, M., & Lappin, M. R. (2016). Prevalence of selected infectious disease agents in stray cats in Catalonia, Spain. Journal of Feline Medicine and Surgery Open Reports, 2(1), 2055116916634109.

Objectives. The objective of the current study was to investigate the prevalence rates of the following infectious agents in 116 stray cats in the Barcelona area of Spain: Anaplasma phagocytophilum, Bartonella species, Borrelia burgdorferi, Chlamydia felis, Dirofilaria immitis, Ehrlichia species, feline calicivirus (FCV), feline herpesvirus-1 (FHV-1), feline leukaemia virus (FeLV), feline immunodeficiency virus (FIV), haemoplasmas, Mycoplasma species and Rickettsia species.
Methods. Serum antibodies were used to estimate the prevalence of exposure to A phagocytophilum, Bartonella species, B. burgdorferi, Ehrlichia species and FIV; serum antigens were used to assess for infection by D. immitis and FeLV; and molecular assays were used to amplify nucleic acids of Anaplasma species, Bartonella species, C. felis, D. immitis, Ehrlichia species, FCV, FHV-1, haemoplasmas, Mycoplasma species and Rickettsia species from blood and nasal or oral swabs.
Results. Of the 116 cats, 63 (54.3%) had evidence of infection by Bartonella species, FeLV, FIV or a haemoplasma. Anaplasma species, Ehrlichia species or Rickettsia species DNA was not amplified from these cats. A total of 18/116 cats (15.5%) were positive for FCV RNA (six cats), Mycoplasma species DNA (six cats), FHV-1 DNA (three cats) or C. felis DNA (three cats).
Conclusions and relevance. This study documents that shelter cats in Catalonia are exposed to many infectious agents with clinical and zoonotic significance, and that flea control is indicated for cats in the region.

Spatial ecology and prey choice of tagged feral cats

van der Ende, J. M. (2015). Spatial ecology and prey choice of tagged feral cats on Schiermonnikoog. M.Sc. Dissertation.  Master of Science in Geographical Information Systems (UNIGIS) Faculty of Economics and Business Administration Vrije Universiteit Amsterdam
The Netherlands

Feral cats (Felis catus) inhabiting the island Schiermonnikoog, The Netherlands, are a potential threat for local prey species populations. To improve the understanding and retrieve more insight in the spatial ecology of this invasive predator, ten feral cats (5 male : 5 female; 5 adult : 5 subadult) were equipped with GPS tags and followed from May till July 2014. Spatio-temporal analyses were used. The home ranges we calculated using Minimum Convex Polygon and Kernel density estimators and tested for differences in sex, age and time. The displacement distance and habitat use was compared between day and night. Locomotive behaviour was compared between subjects using a pre-defined dimension dyad with daily movement variables. In addition, scats were collected and analysed on prey remains and compared with the prey present in the area.
Average 3-month home ranges were found to be 81 and 158ha using Kernel density 95% and Minimum Convex Polygon 95% home ranges respectively. Home range sizes were not significantly different between sexes or age classes. However, nocturnal home range sizes were bigger than the diurnal ones. The nocturnal habitat use did differ from the diurnal use, suggesting a small preference for short salt marsh vegetation during the night. The cats showed a higher nightly displacement (M=45m/15min) compared to during the day (M=22m/15min). The cats were very variable in their daily migration (range M=198-528m) and cumulative daily displacement (range M=1.5-4.1km). A new visualisation technique was proposed to identify differences and similarities between the feral cats and seemed to work well. Hares (Lepus europaeus) contributed the most to the diet in terms of relative prey volume, but Common vole (Microtus arvalis) was the most numerous prey item found in the scats.
In conclusion this study describes the spatial ecology of feral cats and give new insights in the behaviour of feral cats in a natural part of a Dutch Waddensea island. The home ranges of males are not necessarily bigger than female ones. They tend to use short salt marsh vegetation more during the night which could indicate they hunt on the nocturnal species foraging there like hares and rabbits. Bird remains are found in the scats which indicate a potential threat for the bird population by this invasive introduced predator. However in this research no indication is found they actively search and hunt on birds. Further research using acceleration data might be useful to better quantify their hunting behaviour.