Les hommes ont oublié cette vérité. Mais tu ne dois pas l'oublier, dit le renard. Tu deviens responsable pour toujours de ce que tu as apprivoisé.
Le Petit Prince, chap. 21

Friday, 30 November 2012

Cats' diet in rural Poland

Krauze-Gryz, D., J. Gryz, J. Goszczyński. 2012. Predation by domestic cats in rural areas of central Poland: an assessment based on two methods, Journal of Zoology, 288 (4): 260-266

Studies of cat trophic behaviour can be based on collections of the prey brought home or the prey eaten by cats (i.e. analyses of scat/gut contents). Both methods involve biases with respect to palatability, prey size and assessment of hunting rates. Furthermore, these methods are often used on different groups of cats (i.e. house-based vs. feral), thus results are difficult to compare. In the present study, cats from the same area (rural areas in central Poland) were studied by both methods: prey brought home and prey eaten (scat and gut analyses). Both methods identified mammals as the most frequent prey (followed by birds). However, differences occurred in the percentages of the four main vertebrate groups brought home versus eaten by cats: reptiles tended to be brought home, whereas amphibians tended to be eaten. No such difference was found for birds and mammals. Second, the relative proportions of presumably more palatable and presumably less palatable prey differed. The relative proportions of mice and voles (the latter eaten more frequently) and the relative proportions of soricomorphs and rodents (the latter eaten more frequently) were different. Finally, small prey items (i.e. invertebrates) were recorded incompletely for the brought-home method. Overall, the prey-brought-home method underrepresented small prey and underestimated the predation rate for cats, whereas the prey-eaten method was less likely to record unpalatable prey. We thus recommend to combine these two methods to obtain fuller and truer assessment of cat predation.

Cats reduce effective protected area

Wierzbowska, I.A, J.Olko, M.Hędrzak, K.R. Crooks. 2012. Free-ranging domestic cats reduce the effective protected area of a Polish national park, Mammalian Biology - Zeitschrift für Säugetierkunde, 77 (3) 204

Poland's Animal Protection Act, as of 2002, made it legal to shoot free-ranging cats and dogs. The act triggered substantial social debate with opponents arguing that this legislation was weakly supported by scientific evidence of the ecological impacts of free-ranging pets. Our main research goal was to examine the activity of free-ranging domestic cats within a Polish protected area by applying radio-telemetry methods to determine space use and degree of encroachment into the national park. We trapped and radio-tracked 19 animals from three sites (focal households) located in Ojcow National Park (ONP) in southern Poland from June 2003 to March 2006. Annual 100% MCP home range size varied from 0.02 km2 to 1.46 km2, and was significantly larger for males (mean ± SE = 0.79 ± 0.34 km2; median = 0.53 km2) than for females (mean ± SE = 0.13 ± 0.05 km2; median = 0.13 km2). The distance travelled by individual cats from focal sites did not significantly differ between males (mean ± SE = 232.00 ± 21.05 m; median = 191 m) and females (mean ± SE = 232.50 ± 12.47 m; median = 228 m), with maximum distances of 1.5 km for males and 1.1 km for females. All monitored cats were in close proximity to nature reserves and ranged into protected areas without any human control. Cats living in the households in the park and its surrounding buffer zone, roaming at 200 m and 1000 m radius distances from their households, occupied from 6% to 100% of the park area, respectively. Our results reveal that free-ranging domestic cats roam through and potentially impact the entire national park, thus reducing its effective protected area.

Thursday, 29 November 2012

Canine exiles from Constantinople

Further particulars have been received regarding the condition of the «crowds of dogs» collected from the streets of Constantinople and placed on a neighboring island. In response to protests, it was stated that the dogs were to be killed, but nothing has been done.An account of their terrible ' plight is given in a message from Reuter’s Constantinople representative, -who states:-"In company with a party of English and American friends, I visited the Island of Oxia, in the Sea of Marmora, the place of exile of the dogs. A picture of misery and desolation met our eyes. Dead and dying animals were to be seen everywhere. I saw dogs eating their dead companions. We were soon covered with flies, and were only able to shake them off when we got out to sea again. There were many dogs which still preserved their robust and fit appearance, but the lack of fresh water will doubtless bring those to the same stage as the others. In two respects I noticed an improvement There were some half-dozen men on the island who fed the dogs twice a day, for which purpose bread is imported weekly. The dogs greeted us on landing by wagging their tails and brushing up against us, so if to say, "Take us away from this inhospitable place." Several actually tried to swim behind the dinghy when leaving the island, but soon had to abandon the attempt owing to their weak condition. The men lived in a wooden hut on the elevated part of the island. I was informed by them that there were some 40.000 dogs in the place, though this is evidently an exaggeration. Probably half that number would be nearer the mark and include the total deportation thus far. The death-rate was about 200 a day. An industry has been started on the island by a Frenchman, who skins the dead carcases and boils them for the purpose of extracting the bones, both, skin and bones being exported to Europe. Fresh arrivals at the island now take place once a week only, as the supply is fast diminishing, which is not surprising, seeing that the city has been practically cleared of dogs."

The dogs of Istambul

Pinguet, C. 2008. Les chiens d'Istanbul, Saint-Pourçainsur-Sioule: Bleu Autour

Catherine Pinguet’s Les chiens d’Istanbul (The Dogs of Istanbul) explores the history of stray dogs in Istanbul. The book sheds light on a neglected facet of the past – the perception of dogs by different cultures and religions. Pinguet tellgs the readers about the massacre of Istanbul's stray dogs in 1910 by offering accounts from travelogues and from residents of the city, along with visual materials such as photographs and cartoons. She also covers contemporary issues such as animal shelters, animal rights and societies for animal protection. Les chiens d’Istanbul reflects on a silent aspect of history and interjects itself well into the history of animal welfare as a whole. Pinguet’s humanitarian tone and comparative analysis powerfully relate the story to readers ...

Overview of the impacts of feral cats on Australian native fauna

Chris R.Dickman. 1996. Overview of the Impacts of Feral Cats on Australian Native Fauna. Institute of Wildlife Research and School of Biological Sciences. University of Sydney. Australian Nature Conservation Agency. Pp. 97.

This report provides an overview of the impact of feral cats Felis catus on native fauna of the Pacific region, with particular reference to Australia and its island territories. In Australia, cats take a wide variety of native species of mammals, birds and reptiles, but show evident preference for young rabbits or small marsupials where these are available. Reptiles are taken primarily in and habitats, while birds often feature predominantly in the diet of cats on islands. Despite their catholic diet, population-level impacts of feral cats on native fauna have been poorly documented. There is considerable potential for competition to occur between cats and carnivorous species such as quolls and raptors, but no critical evidence has yet been adduced. There is also potential for amerisal impacts to occur, either via transmission of the pseudophyllidean tapeworm Spirometra erinacei or of the protozoan parasite Toxoplasma gondii, but evidence for deleterious effects in freeliving animals is not compelling. Direct predatory impacts have been inferred from anecdotal and historical evidence, more strongly from failed attempts to reintroduce native species to their former ranges, and most critically from the decimation of island faunas and responses of prey species following experimental removal of cats or reduction of cat numbers. Attributes of the biology of feral cats and their prey species derived from the literature review were used to develop a rank-scoring system to assess the susceptibility of native species to cat predation. Species listed federally as endangered or vulnerable were designated as being at zero, low or high risk of impact from cats according to their attribute scores, and their distributions mapped from primary sources and actual locality data. Based on the number of threatened species they contain, localities and regions within Australia were placed in order of priority for future research to clarify the precise impacts of feral cats. Although difficult and expensive to carry out, controlled and replicated field removal experiments are recommended to elucidate cat impacts in all mainland areas. Removal of cats should take place also on offshore islands and island territories, but only if pilot studies show that this will not release populations of alternative predator species such as introduced rats. If release appears likely, cats should be removed only as a component of an integrated control program that targets all relevant predators.

Barking island

En 1910, miles de perros callejeros fueron enviados a la isla desierta de Sivriada u Oχeia ( Ὀξεία) en el mar de  Marmara, para evitar su presencia en las calles de Estambul. Un corto de 2010 nos ilustra la historia.

In 1910, thousands of dogs were sent to Sivriada ( Ὀξεία, Oχeia) Island in Marmara Sea, close to Istambul, to avoid their presence in the streets. A shortfilm tells us the story.

Wednesday, 28 November 2012

¿Cuánto matan los gatos?

How much do cats actually kill?

Un reciente cómic ilustra muy gráficamente los resultados de un estudio llevado a cabo por la Universidad de Georgia y National Geographic. El autor concluye que los gatos matan "por diversión" en la mayor parte de los casos.

El estudio, realizado con cámaras que portaban las mascotas muestra que sólo una pequeña proporción de las presas son detectadas por los dueños, mientras que una parte es consumida y el resto abandonada.

Además, el estudio ponía de manifiesto las situaciones arriesgadas a las que se exponían las mascotas.

Spatio-Temporal variation in predation by cats

Thomas R.L., Fellowes M.D.E., Baker P.J. (2012) Spatio-Temporal Variation in Predation by Urban Domestic Cats (Felis catus) and the Acceptability of Possible Management Actions in the UK. PLoS ONE 7(11): e49369. doi:10.1371/journal.pone.0049369

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/year 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.

Tuesday, 27 November 2012

Rabbits killing birds revisited

Zhang, J., M Fan & Y. Kuang. 2006. Rabbits killing birds revisited. Biosciences, 203:100-123

We formulate and study a three-species population model consisting of an endemic prey (bird), an alien prey (rabbit) and an alien predator (cat). Our model overcomes several model construction problems in existing models. Moreover, our model generates richer, more reasonable and realistic dynamics. We explore the possible control strategies to save or restore the bird by controlling or eliminating the rabbit or the cat when the bird is endangered. We confirm the existence of the hyperpredation phenomenon, which is a big potential threat to most endemic prey. Specifically, we show that, in an endemic prey–alien prey–alien predator system, eradication of introduced predators such as the cat alone is not always the best solution to protect endemic insular prey since predator control may fail to protect the indigenous prey when the control of the introduced prey is not carried out simultaneously.

Rabbits killing birds

Courchamp, F., M. Langlais & G. Sugihara. 2000. Rabbits killing birds: modelling the hyperpredation process. Journal of Animal Ecology, 69 (1): 154-164

1. Introduced rabbits are known to have catastrophic effects on oceanic islands, either by direct destruction of the vegetative cover, or by the resulting disturbance of indigenous vertebrates.

2. Another dramatic effect, less well known, but potentially of major importance, is the hyperpredation process. This process, related to apparent competition, predicts that an introduced prey species, well adapted to high predation pressure, could induce the extinction of an indigenous prey, through the sudden increased population size of an introduced predator. In many island ecosystems, the simultaneous presence of introduced feral cats and rabbits is thus potentially a further threat for small vertebrates endemic of these islands.

3. Through a mathematical model, we tested this hypothesis, using a tri-trophic system comprising an indigenous prey (birds), an introduced prey (rabbits) and an introduced predator (cats), and we demonstrated the theoretical existence of the hyperpredation process.

4. In addition, the numerical analysis of the model allowed a quantification of this process. It shows that the conditions required for an indigenous species to cope with the hyperpredation process imply very high intrinsic growth rates and/or carrying capacity, as well as behavioural anti-predator response to the introduced predator. Since these conditions are unlikely to be met, this process is a further potential threat to most indigenous vertebrate prey.

5. Finally, our model shows that, although it can be induced by both types of adaptation together or alone, behavioural adaptations alone are more powerful in generating the hyperpredation process, than are life history traits adaptations. birds per year in USA!!

Dauphine, N. & R.J. Cooper. 2009. Impacts of free-ranging domestic cats (Felis catus) on birds in the United States: a review of recent research with conservation and management recommendations. Proceedings of the Fourth International Partners in Flight Conference: Tundra to Tropics: 205–219

Las aves americanas se enfrentan a un estimado de 117 a 157 millones de depredadores exóticos en la forma de gatos domésticos (Felis catus) en condición de libertad, los cuales probablemente matan anualmente al menos, mil millones de aves cada año en Estados Unidos. Los gatos han contribuido a la declinación y extinción de las aves a nivel mundial, y pueden ser la mayor causa de la extinción global de las aves luego de la destrucción de hábitat.  En este articulo, yo reviso la reciente investigación científica sobre el impacto que los gatos en condición de libertad causan a las poblaciones de aves en los Estados Unidos, con énfasis en su amenaza a las aves migratorias. Estudios han demostrado que los gatos constituyen una  amenaza importante para muchas poblaciones de aves, incluyendo aquellas especies cuya conservación es prioritaria, a través de la depredación de adultos, las nidadas y los juveniles, compitiendo también con depredadores nativos, tales como las aves de presa. En adicción a la mortalidad directa causada, los gatos causan reducciones en la fecundidad y supervivencia en las aves expuestas al riesgo de depredación,  las mismas que potencialmente y substancialmente dañan y reducen las poblaciones.  Acciónas efectivas para la conservación de las aves requerirá del fortalecimiento y aplicación de leyes que prohíben los gatos en condición de libertad, muchas de las cuales ya han sido promulgadas, así como también una mejora sustancial en la educación y que este esfuerzo por enfrentar los problemas que son causados por los gatos llegue al público en general, y producir métodos para controlar las poblaciones y movimientos de los gatos en condición de libertad.
Feral cat at an illegal cat colony in McAllen, TX, February 2008
 American birds face an estimated 117 to 157 million exotic predators in the form of free-ranging domestic cats (Felis catus), which are estimated to kill at least one billion birds every year in the United States. Cats have contributed to declines and extinctions of birds worldwide and are one of the most important drivers of global bird extinctions. In this paper, we review recent scientifi c research on the impacts of free-ranging cats on birds, with an emphasis on threats to migratory landbirds in the United States. Studies have shown that cats pose threats to many bird populations, including priority species for conservation, through their predation of adult, nestling, and juvenile birds. Cats also have impacts on birds through competition with native predators such as raptors, and through the harboring and transmission of zoonotic and other diseases to birds and other wildlife. In addition to direct mortality, cats may also cause stress responses in birds due to predation risk that may result in bird population declines. A substantial increase in public outreach is urgently needed to educate citizens about the conservation and welfare problems caused and faced by outdoor cats. Effective cat and wildlife management in this context will also require strengthening and enforcing policies and laws that control outdoor cats, many of which are already in place.
Cat-killed Eastern Towhee (Pipilo erythrophthalmus), a PIF-designated species of regional conservation concern, Athens, GA, January 2008

Read more national surveys results on cat predation

Cat fear

Beckerman, A.P., M. Boots & K.J. Gaston. 2007. Urban bird declines and the fear of cats. Animal Conservation, 10 (3): 320-325

The role of domestic cats Felis catus in the troubling, on-going decline of many urban bird populations in the UK is controversial. Debate, in the UK and elsewhere, has centred on the level of avian mortality directly imposed by cats, and on whether this is principally compensatory (the ‘doomed surplus’ hypothesis) or additive (the ‘hapless survivor’ hypothesis). However, it is well established that predators also have indirect, sub-lethal effects on their prey where life-history responses to predation risk affect birth and death rates. Here, using a simple model combining cat predation on birds with a sub-lethal (fear) effect of cat density on bird fecundity, we show that these sub-lethal effects may be substantial for urban songbirds. When cat densities are as high as has been recorded in the UK, and even when predation mortality is low (e.g. <1%), a small reduction in fecundity due to sub-lethal effects (e.g. <1 offspring /year/cat) can result in marked decreases in bird abundances (up to 95%). Thus, low predation rates in urban areas do not necessarily equate with a correspondingly low impact of cats on birds. Sub-lethal effects may depress bird populations to such an extent that low predation rates simply reflect low prey numbers.

Blue penguin colony attacked by dogs

Monday, 26 November 2012

Problemática ambiental de los gatos vagabundos

(Resumido y adaptado de J.F.Orueta. 2003 Vertebrados invasores: Problemática ambiental y gestión de sus poblaciones. Ed: Ministerio de Medio Ambiente)

Los gatos, domesticados con mucha probabilidad en Anatolia hace unos cien siglos, serían introducidos en Chipre unos tres milenios más tarde, lo que seguramente ocurrió también en otras islas algún tiempo después (Stahl et al., 2003a).  Junto al perro, probablemente servirían también como fuente de alimento (Vigne & Guilaine, 2004). 

Entre los carnívoros domésticos, básicamente el perro y el gato, se pueden distinguir varios niveles de domesticidad:
- los que son claramente domésticos y se mantienen permanentemente bajo control.

- aquellos a los que sus propietarios proporcionan cuidados pero que les permiten vagabundear con cierta libertad, con lo que tienen ocasión de cazar por puro instinto, aunque estén bien alimentados.

- los animales callejeros, que pueden encontrar alimento en aportes voluntarios de las personas o en basuras, pero que cazan siempre que hay ocasión.

- los asilvestrados, que son ariscos y eluden a las personas desde lejos, que se reproducen en libertad formando poblaciones autosuficientes y que pueden cazar pero también aprovechar desperdicios o animales domésticos.

Excepto la primera categoría, todos los demás pueden infligir daños a la fauna silvestre, especialmente por depredación. En general se produce un fenómeno de facilitación esto es, la población se mantiene a un nivel demográfico estable y superior gracias a los aportes externos de alimento (comida, basuras, etc.); estas poblaciones “subvencionadas” son capaces de ejercer mayor daño que si dependieran exclusivamente de los recursos naturales.
Por su lado, la proporción de gatos a los que se permite vagar libremente es alarmantemente alta, incluso en medio urbano (Gandia et al., 1999). Además, diversas características los hacen depredadores muy eficientes. Los gatos se adaptan fácilmente a ambientes muy diversos, desde áridos a subpolares (Burbidge & Manly, 2002; Pontier et al., 2004) y pueden sobrevivir sin agua en ecosistemas semiáridos si consumen presas vivas. Capturan todo tipo de presas de hasta su misma masa corporal (Paltridge et al., 1997).
Tanto la territorialidad como la sociabilidad de los gatos es variable en función de las áreas y del grado de domesticidad de los individ. Para Ewer (1973), los gatos serían básicamente solitarios pero se organizarían social y jerárquicamente en zonas concretas. En ocasiones, los gatos pueden ser solitarios, pero puede ocurrir que sean territoriales (Genovesi et al., 1995) o no (Molsher, 1999).  En Suecia Liberg (1980) encuentra poblaciones con animales solitarios y otros gregarios y los rangos se solaparían parcialmente en los machos y más ampliamente en las hembras, siempre entre animales del mismo grupo. Sin embargo, puede ocurrir que los rangos se superpongan ampliamente también entre los machos (Gillies et al., 2000). También las áreas de campeo pueden ser muy diferentes según las zonas. En áreas rurales pueden ser de 400 ha (Gillies et al., 2000) pero se conocen casos de hasta 95 km2 (Goltz et al., 2001); en medios urbanos, son muy inferiores (Dards, 1978; Haspel & Calhoon, 1989). Las densidades, por lo tanto, son muy superiores en las ciudades, varios cientos de ejemplares por kilómetro cuadrado (Dards, 1978; Haspel & Calhoon, 1989), pero tan solo en torno a tres o cuatro por kilómetro cuadrado en áreas rurales (Liberg, 1980; Fitzwater, 1994). Aunque Liberg (1980) demuestra que las hembras son más filopátricas que los machos, entre los que sólo los realmente domésticos lo serían, Devillard et al. (2003) comprueban en un ambiente urbano que las hembras no dominantes se ven obligadas a emigrar, lo que no ocurre con los machos. 
El gato y otros dos pequeños carnívoros Mustela erminea y Herpestes javanicus  (posiblemente tomado como sinónimo de H. auropunctatus) están en la lista de la UICN entre las 100 de las peores especies exóticas invasoras.
Los gatos fueron la causa más verosímil para la extinción de varias especies de pequeños mamíferos en Australia antes de la introducción de otras especies (Dickman, 1996), particularmente en islas, sobre todo las más áridas (Burbidge & Manly, 2002).
En la actualidad los gatos asilvestrados siguen siendo la principal amenaza para algunos mamíferos insulares (Humphrey & Barbour, 1981; USFWS, 1999; Álvarez & Ortega, 2003), reptiles (García-Marquez & Martín, 2001; Rando & López, 2001; Mateo & Silva, 2003) y aves (Duvall, 2001; Goltz et al., 2001) y sus nidos (Duarte & Vargas, 2001a). Aun siendo menos eficaces los herpéstidos (Henderson, 1992), los gatos depredan incluso sobre reptiles del tamaño de la iguana (Mitchell et al., 2002). Incluso sin llegar a formar parte esencial de su dieta debido a un consumo accidental, pueden amenazar poblaciones exíguas de algunas especies (García-Márquez & Martín, 2001; Rando & López, 2001; Mateo & Silva, 2003). Lo mismo ocurre con aves amenazadas (Rando & López, 2001; Martín et al., 2002; Mayol, 2003a; Menezes & Oliveira, 2003; Ruiz & Martí, 2003).
Como se ha comentado, cuando un depredador generalista como el gato no depende del número de presas para regular su población debido a que se beneficia de otras fuentes permanentes de comida, la depredación sobre especies raras es insostenible (p. ej. Hawkins, 1998; Courchamp et al. 1999b). Los mesopredadores como el gato se benefician de la ausencia de depredadores de mayor envergadura (Crooks & Soulé, 1999; Molsher, 1999). Los gatos vagabundos no tienen porqué suponer un grave problema para las poblaciones de especies más abundantes en hábitats suburbanos; sin embargo, sí que afectan a las especies más raras, particularmente en los hábitats fragmentados (Barratt, 1994; Crooks & Soulé, 1999). Los gatos son más abundantes cerca de los núcleos de viviendas extraurbanos que lejos de ellos (Odell & Knight, 2001) lo que condiciona la distribución de sus presas (Baker et al., 2003).
En esta misma linea, varios estudios demuestran que la mayor parte de la dieta de los gatos asilvestrados consiste en otras especies alóctonas (en Canarias hasta el 70% en La Gomera, según datos de Nogales y Medina, 1996, y 88% en La Palma, según Medina et al., 2006; 85% en islas subantárticas según Pontier et al. 2002). Sin embargo, lo que muestran estos datos es que las presas más abundantes exacerban el fenómeno de hiperdepredación, es decir, que permiten mantener poblaciones mucho más elevadas de gato que si dependieran exclusivamente de las especies autóctonas. A pesar de que la proporción de aves no es muy grande en su estudio, Pontier et al. (2002) describen cómo dicha proporción cae a lo largo del tiempo, como consecuencia del impacto de los gatos. En Fuerteventura, en torno al 50% de los nidos de Saxicola dacotiae se pierden por depredación por gato, así como algunos adultos mientras incuban (J.C. Illera, com. pers., 2003). En algunas localidades, los reptiles, incluidos endemismos muy amenazados, se presentan en la totalidad de las muestras y llegan a constituir el 60% del número de presas de los gatos (Rando & López, 2001).

En ocasiones se producen efectos indirectos muy graves. En Mallorca, el efecto de los gatos sobre la caza menor ha llevado al uso ilegal e indiscriminado de veneno por parte de los gestores de los cotos de caza, lo que ha repercutido negativamente en todo el gremio de necrófagos (Tewes & Jiménez, 2000).
No sólo en las islas, sino también en áreas continentales los gatos vagabundos y asilvestrados son una amenaza para los vertebrados silvestres, esencialmente por depredación (George, 1974; Churcher & Lawton, 1987; Mitchell & Beck, 1992; Coleman & Temple, 1993; 1995; Coleman et al., 1997; The Mammal Society, 1997; Hawkins, 1998; Crooks & Soulé, 1999; Sanders &  Maloney, 2002). Pero también los gatos salvajes se ven amenazados por introgresión genética (Hubbard et al., 1992 ; Beaumont et al., 2001 ; Daniels et al., 2001; García-Perea, 2002; Huckle, 2002; Pierpaoli et al., 2003) y por transmisión de enfermedades (Courchamp, 1996; Coleman et al., 1997). Existe además un problema de competencia con especies nativas, dado que la disponibilidad de presas para los depredadores autóctonos se ve reducida por la depredación por gatos (George, 1974; Liberg, 1984; Crooks & Soulé, 1999).
Debido a que los gatos son una mascota popular, se han generado conflictos en torno a su control. En muchos casos, los colectivos de defensores de los gatos asilvestrados minimizan o niegan el impacto de estos sobre la fauna silvestre (SFSPCA; ACA 2003a) rechazando incluso que exista un impacto sobre las aves en islas (ACA, 2003b). También mantienen que las colonias de gatos son estables y el hecho de alimentarlos no supone una atracción para ejemplares externos. Se ha comprobado, sin embargo, que las colonias de gatos suponen una fuente importante para poblaciones asilvestradas (Tidemann, 1994; Wilson et al., 1994). 

Sunday, 25 November 2012

Lessons to be learnt from loss of the pipistrelle

A recent paper in the journal Conservation Letters alleges that failure to act quickly on evidence of rapid population decline has led to the first mammal extinction in Australia in the last 50 years, the Christmas Island pipistrelle bat (Pipistrellus murrayi).

Since 26 August 2009, there have been no recordings of the echolocation call of the tiny bat, which is native to Christmas Island. It is now presumed extinct.

In a recently published paper in Conservation Letters, scientists analysed the conservation decision making process associated with the decline of this species and concluded that it illustrated the need for strong leadership on extinction issues.

Among the chain of events analysed was a February 2009 report by Dr Lindy Lumsden – Principal Research Scientist with the Arthur Rylah Institute for Environmental Research, and foremost authority on this species – warning that only 20 bats remained on Christmas Island. Government funding was then allocated to establish a captive breeding program, but that proved too little, too late.

The Christmas Island pipistrelle fed on insects and roosted in tree hollows and decaying vegetation. Just a few decades ago, the bat was widespread on Christmas Island and roosted in groups of 50 or so animals.

‘It is estimated that a single pipistrelle consumes its body weight in insects per night,’ lead author Tara Martin, of CSIRO’s Ecosystem Services, told the conservation website Mongabay.

‘While the loss of the pipistrelle is likely to lead to more insects, it is too early to tell what the long term ecological impact of this will be on the island.’

Scientists are unsure as to what pushed the bat to extinction. It is possible that a combination of stressors was responsible, including invasive animals such as feral cats, the common wolf snake, and a recent invasion of yellow crazy ants. Disease is another possibility, though researchers could find no sign of the bats suffering from illness...


Martin, T. G., S. Nally, A.A. Burbidge, S. Arnall, S.T. Garnett, M.W. Hayward, L.F. Lumsden, P. Menkhorst, E. McDonald-Madden & H.P. Possingham. 2012. Acting fast helps avoid extinction.Conservation Letters, 5(4), 274-280.
Failure to act quickly on evidence of rapid population decline has led to the first mammal extinction in Australia in the last 50 years, the Christmas Island Pipistrelle (Pipistrellus murrayi). The fate of another iconic species, the migratory Orange-bellied Parrot (Neophema chrysogaster), monitored intensively for over 20 years, hangs in the balance. To inform future conservation management and decision making, we investigate the decision process that has led to the plight of both species. Our analysis suggests three globally relevant recommendations for minimizing species extinction worldwide: (1) informed, empowered, and responsive governance and leadership is essential; (2) processes that ensure institutional accountability must be in place, and; (3) decisions must be made whilst there is an opportunity to act. The bottom line is that, unless responsive and accountable institutional processes are in place, decisions will be delayed and extinction will occur.

Saturday, 24 November 2012

Virus to control island populations of cats

Courchamp F & Sugihara G (1999) Modeling the biological control of an alien predator to protect island species from extinction. Ecological Applications, 9 (1): 112-123.

Introduced feral cat (Felis catus) populations are an important threat to many island vertebrate populations and to bird species in particular. Elimination of feral cat populations is desirable in most of these ecosystems. Release of a parasite species in these mostly immune-naive populations is thought to be an efficient eradication measure. Such an approach is theoretically investigated here, using a mathematical model that describes the effects of introducing a virus into the cat population on population dynamics of both the cat and its prey. We studied the effects of two types of introduced feline viruses: Feline Immunodeficiency Virus and Feline Leukemia Virus, both of which are good candidates for eradicating a cat population. Results show that eradication is possible with Feline Leukemia Virus, if natural immunity is sufficiently low. Feline Immunodeficiency Virus cannot fully eradicate cat populations, but can be an effective agent for long-term control of cat populations on islands where total cat eradication is not possible (e.g., there is a high likelihood of continued introduction of cats) or not desirable (e.g., when rats are present). Culling, which by itself would require a very prolonged and logistically demanding effort to eliminate cat populations, may be more efficient when applied simultaneously with
virus introduction.

Cats protecting birds, revisited

Meng Fan, Yang Kuang, Zhilan Feng, 2005. Cats protecting birds, revisited. Bulletin of Mathematical Biology, 67: 1081–1106

In this paper, we revisit the dynamical interaction among prey (bird), mesopredator (rat), and superpredator (cat) discussed in Courchamp, F., Langlais, M., Sugihara, G., 1999. Cats protecting birds: modelling the mesopredator release effect. Journal of Animal Ecology 68, 282–292. First, we develop a prey–mesopredator–superpredator (i.e., bird–rat–cat, briefly, BRC) model, where the predator’s functional responses are derived based on the classical Holling’s time budget arguments.
Our BRC model overcomes several model construction problems in Courchamp et al. (1999), and admits richer, reasonable and realistic dynamics. We explore the possible control strategies to save or restore the bird by controlling or eliminating the rat or the cat when the bird is endangered. We establish the existence of two types of mesopredator release phenomena: severe mesopredator release, where once superpredators are suppressed, a burst of mesopredators follows which leads their shared prey to extinction; and mild mesopredator release, where the mesopredator release could assert more negative impact on the endemic prey but does not lead the endemic prey to extinction. A sharp sufficient criterion is established for the occurrence of severe mesopredator release. We also show that, in a prey–mesopredator–superpredator trophic food web, eradication of introduced superpredators such as feral domestic cats in the BRC model, is not always the best solution to protect endemic insular prey. The presence of a superpredator may have a beneficial effect in such systems.

Rural free-ranging domestic cats: a survey

Coleman, J. S., & Temple, S. A. (1993). Rural residents' free-ranging domestic cats: a survey. Wildlife Society Bulletin, 21(4), 381-390.

Nationwide, approximately 30% of households have cats. In rural areas where free-ranging cats are usually not regarded as pets, approximately 60% of households have cats. In the state of Wisconsin alone, with approximately 550,000 rural households, the number of rural free-ranging cats (not house pets) may be as high as 2 million. In some parts of rural Wisconsin, densities of free-ranging cats reach 114 cats per square mile. In these areas, cats are several times more abundant than all mid-sized native predators (such as foxes, raccoons, skunks) combined.

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