On November 19th, 2019, the newspaper La Verdad, in the section Nuestra Tierra - Naturaleza (Our Earth -Nature), published a documented article by Ginés S. Forte about the damage to the biodiversity produced by the overpopulation of cats. Different points of view are described and, due to its interest, we have translated into English and reproduced it below. You can also read the original version (in Spanish) in La Verdad website by clicking here.
There is a great ignorance about the serious threat that this small feline poses in the streets and natural environments, only surpassed by humans as a species more harmful to biodiversity
PIXABAY
GINÉS S. FORTETuesday, November 19th, 2019, 13:07
In 1895 the cat 'Tibbles' became the first pet in the history of discovery of a new species for science. And also, in the only living being of which there is knowledge that extinguished, on its own, a complete species. He did both at the same time, and in a single winter. In fact, it was its predatory instinct that brought to the researchers at the end of the 19th century the knowledge of the existence of Stephens' Wren ('Xinicus lyalli'), a small, chubby and poorly equipped bird for the flight that lived on the island of Stephens. Or, rather, that it died there without anyone had seen it alive never before, except for the cat 'Tibbles'. It killed that winter, on that New Zealand islet just two kilometres long, one wide and almost 300 meters high, at least 13 specimens of this unknown bird, and took their remains to his owner, David Lyall. Lyall was guardian of the lighthouse, fond of ornithology (he sent the bodies to the experts Rotschild and Walter Buller, who certified the discovery) and the man who took the cat to that territory that has passed into natural history for hosting the fastest known extinction.
Listening to the explanations of the experts and reviewing the documentation on the impact of cats on biodiversity, the case of that New Zealand pussy ceases to seem an anecdote to become almost an omen. «The cat is perhaps the most harmful species that exists for biodiversity» explains a specialist as committed to the cause of nature as Rubén Vives, former secretary of Ecologistas an Acción in the Region of Murcia. The technical coordinator of the Life + Ripisilvanatura invasive species project, Jaime Fraile, corroborates the diagnosis. «If the cat does not appear in the 'Spanish catalog of invasive alien species' it is because it has been here since time immemorial, but it does appear in the list of the one hundred most harmful in the world», he says. In particular, the domestic cat ('Felis silvestris catus') is one of the fourteen mammals collected in this infamous list. It is a distinction that falls short: in reality, the cat has become, leaving aside the human being, the predator that has caused more species of vertebrates to disappear from the planet. A study by the Consejo Superior de Investigaciones Científicas (CSIC) concluded a few years ago that cats have participated in 14% of known vertebrate extinctions in recent centuries. «They keep their hunting instinct; even if they live on a couch and give them their thoughts, as soon as they go outside they kill everything: reptiles, amphibians, birds, bats ... wild animals flee when they appear because they feel pressured», Vives says.
«The impact of cats on biodiversity, although perfectly described in the scientific literature, does not seem to have reached the general population», Jorge Sánchez, a biologist at the Asociación de Naturalistas del Sudeste (ANSE), laments. This impact, he warns, «is not only caused by stray cats (feral in the slang of cat fans) but is extensible to what Anglo-Saxons call 'free-ranging cat', that is, cats that have freedom of movement», despite of having a house and owner. Between them, it is estimated that in the United States alone they end up every year with between 1,300 and 4,000 million birds and between 6,300 and 22,300 million mammals, according to research published in 'Nature' in January 2013, which also concludes that these cats are the main source of unnatural mortality of fauna.
«Should we kill cats to save birds? » A ‘National Geographic’ headline asked last month
A more concrete and closer example of their influence in the medium is the depredation they make of geckos ('Rarentola mauritanica'), a reptile that fights cockroaches ('Blattodea'). Hence, when «the cat appears, cockroaches increase», Vives says. As the number of mosquitoes increases, released by the absence of birds, which disappear due to the threat of cats. Last month, a headline of the original edition of 'National Geographic' asked if «Should we kill cats to save the birds? » and the subtitle reminded us that «our feline friends are killing billions of birds every year».
«Even groups that a priori do not seem to bear the impact of cats, suffer it», Sánchez adds, who sets the example of bats ('Chiroptera'). A study collected this year by the database of scientific articles 'BiOne Complete' notes that 38% of these chiroptera entering British recovery centres have signs of cat attacks. Jamaican biologist Damion Whyte has recorded the capture of at least fifteen bats each night for each cat at the exit of its caves at sunset. There are almost 5,500 flying mammals less per year per pussycat.
As an exculpation, it should be noted that the cat only limits itself to fulfilling its role as predator. The ravages it causes are ultimately due to the human being, who is the one who introduces him in environments that do not belong to him and in which he destroys what he finds within reach of his claws. «It has been shown that one of the most direct impacts experienced when urbanizing a wild environment is the appearance of cats», the expert of Ecologistas en Acción explains. «They greatly reduce the biodiversity of wild species». Where more disorders cause is in natural environments. Although it is not very common for cats to enter spaces far away from houses, where they come from, they do exert an important influence in areas, sometimes protected, close to them, such as the spaces of El Valle and Carrascoy, to the south from the city of Murcia. In these places they display at least a double threat: they press wildlife, on the one hand, and, no less worrying, they mix with wildcats ('Felis silvestris'), among which they generate an alarming hybridization. To the point that «most of the current population of wildcats in the Region of Murcia is a hybrid second generation». This is concluded by a thesis a few years ago on the presence of several species of mammals in the Autonomous Community cited by Vives and published by the University of Murcia. «It's very worrying: the wild cat's genes are being lost», he says. «We are sampling in the mountains of the southeast peninsula and there are not as many wildcats as expected». In the Sierra de la Pila, for example, which is a very favourable area, due to its large forest area, «no wildcat has appeared in the fifteen sampling chambers we have placed».
Meanwhile, the domestic cat kingdom is far from falling in. There is no clear census on the felines that roam in the Region of Murcia, whether they have a known address or are purely street. «Around the municipality of Murcia, the City Council estimates between 10,000 and 12,000 copies in the street, but it is a very conservative number», Vives estimates. Ecologistas en Acción uses as a base the census that a group of animalists has verified in the hamlet of La Alberca, where cats population is around 250 specimen, to infer that in the entire municipality it can exceed 25,000 cats, and between 75,000 and 100,000 in the Autonomous Community. If each one catches at least one prey a day, although «they usually hunt more, we already have the explanation of how all insectivorous birds disappear from cities», for example.
Ecologistas en Acción estimates a cat population about 100.000 specimen in the Region of Murcia
With this panorama, what can be done? «A massive sterilization», Vives responds. «There are too many and they put too much pressure». The naturalist is blunt: «We can do many things for biodiversity, for the environment, but what good is it if cats come later and end all that». For the moment, Jaime Fraile explains, «most municipalities in Spain, similar to what happens in various countries in Europe, begin to apply the CSR protocol», acronym for Capture, Sterilization and Release. For natural areas (where in addition to rodents they also hunt birds and small reptiles, compete with other predators, hybridize and genetically contaminate native wildcat populations, and transmit diseases) «the door opens to lethal control means because the pressure social is not that big».
This social pressure comes mainly from animalist sectors of urban environments. The biologist Jorge Sánchez points out the «strong polarization» between them and the «conservationists who propose cat management as an invasive species». The American Public Library of Sciences, known by the acronym in English PLOS, collected in 2012 a scientific article that shows «a distorted view of reality» among people who act as caretakers of feline colonies, who fail to understand that «the outdoor cats represent a global threat to the conservation of terrestrial vertebrates», in the words of their authors. Sánchez warns that the current legislation «is being used to encourage the creation of feline colonies», which in principle the Animal Protection Law admits to putting under the management of individuals or animal defence entities, but only for feral cats that must be sterilized.
Other studies, such as the one published in 2015 by the National Centre for Biotechnological Information of the United States (NCBI) on the perception that the owners of domestic cats have, show that training campaigns on the danger they pose in the environment hardly influence this people. Nor do they affect works that call into question the supposed efficacy of 'Felis silvestris catus' to eliminate annoying rats. Scholars from New York University Fordham, for example, observed for 79 days a colony of a hundred and fifty rats in waste management facilities. In total, the cats in the area only ended up with two of them in all that time.
The species is limited to fulfilling its predatory role, it is the human being who has introduced it in environments that do not correspond it
It is not easy for conservationists to show the dark side of the cat, a being that is perceived with a luminous aura that takes thousands of years, more than 9,000 at least, next to us. The nineteenth-century French writer Victor Hugo is credited with a phrase that perfectly sums up the fascination of the human being for the little cat: «God made the cat to offer man the pleasure of petting a tiger». Warned by the data collected in this report, Elena, a cat lover next to this journalist, responded bluntly as a reply to the arguments that one by one tried to show her the threats they represent: «Yes, whatever you say, but finally they fulfil an important aesthetic function». Few can disagree with this statement about an animal so capable of giving life, figuratively, to many people as to literally take it away from many more beings; as Tibbles did with Stephens' Wren, whom he put on the map of the species at the same time that he removed it from it forever.
P. PLEUL
To eradicate them as a plague or protect them: there is no agreement
Rubén Vives, of Ecologistas en Acción of the Region of Murcia, advocates active sterilization campaigns undertaken by the Administration so that the number of cats «does not get out of control». The expert warns of feeding, in many cases reinforced, that humans give him and that he influences «a very high reproduction rate of cats». To end the problem, «the Australian Government has proposed sacrificing hundreds of thousands of cats; in other countries of the world they also consider controlling them», and even in a municipality in southern New Zealand, Omaui, its City Council has proposed to treat them as a pest and eradicate them directly so that the native animals return to recover the space that the feline pets have taken to them.
In the Region of Murcia there are regulations that even fine those who feed stray cats. On the other hand, there is a pressure from animalist groups to prevent municipalities from removing the felines from the streets, although they agree on the need to sterilize them.
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