A Feline Frenzy…. how domestic cats are impacting the environment.

A Feline Frenzy…. how domestic cats are impacting the environment.

It’s been a long, hard day at work, you’re tired and can’t be bothered about making dinner yet. You flop down onto the couch and suddenly realise that Mittens you’re lovable cat who is normally either sprawled out on the couch or meowing for some food is not around. You check all her usual haunts, such as under and in the bed, in the cupboard, and all her other spots where she likes to lie in the sun, but she’s not there. There’s a sudden commotion outside, you switch the outdoor light on and there it is, the source of the commotion, right in front of you lies the body of the crested barbet (Trachyphonus vaillantii) that you had been watching build a nest at the bottom of the garden. While next to it sits Mittens purring gleefully as if she’s done nothing wrong.

I have two cats called Jinx and Jasmine, Jasmine loves catching geckos and has caught one or two birds. Jinx on the other hand thinks he’s an apex predator but more often than not misjudges the pool corner while chasing the bird ending up with the bird escaping and Jinx having one wet leg and one dry leg.

 

The cat on the right is Jasmine and the cat on the left is Jinx

History

Domestic relationships among people and wild animals date back to the last Ice Age, with wild cats (Felis silvestris) among the earliest animals domesticated. Our relationships with dogs and cats has influenced our culture for thousands of years, with current estimates showing us that the cat was domesticated 9,500 years ago. Historically, these animals were known as great hunters, companions, and religious figures and have now taken on a variety of roles such as aiding those with disorders to assisting in conservation. Given their close association with humans, it is not uncommon for these animals to be treated like family members. The amount of these domestic animals worldwide is suggested to be between 448 to 752 million cats. The sheer abundance of these animals creates the potential to have a large influence on the environment in which they interact. The domestic cat has remained extremely efficient at hunting. Domestic cats usually kill small prey but have been recorded killing mammals up to 4 kg, and may kill without a metabolic purpose. However, the impacts of cats and dogs go beyond predation. A growing number studies are acknowledging the diverse and widespread impacts of these animals. Although rural free-ranging cats have greater access to wild animals and undoubtedly take the greatest toll, even urban house pets take live prey when allowed outside.

 

Cats may catch many different types of small animals, not just birds.

Impact on Nature

A study done  over 50 years and over four continents showed that in a free-ranging domestic cats  diet, small mammals make up approximately 70% while birds make up about 20%, the remaining 10% is a variety of other animals. The diets of free-ranging cat populations, however, reflect the food locally available. Observation of free-ranging domestic cats shows that some individuals can kill over 1000 wild animals per year. Some of the data on kills suggest that free-ranging cats living in small towns kill an average of 14 wild animals each per year. Rural cats kill a lot more wild animals than urban cats. Rural cats probably kill over a billion small mammals and hundreds of millions of birds each year. Some of the prey are house mice, rats and other species considered pests, but many are indigenous songbirds and mammals whose populations are already under pressure due to habitat destruction and pesticide pollution. Globally, cats may have been involved in the extinction of more bird species than any other cause, except for habitat destruction.

Cats are contributing to the endangerment of populations of birds such as Least Terns (Sternula antillarum), Piping Plovers(Charadrius melodus) and Loggerhead Shrikes (Lanius ludovicianus). In Florida, marsh rabbits in Key West have been threatened by predation from domestic cats. Cats introduced by people living on the barrier islands of Florida’s coast have depleted several unique species of mice and woodrats close to extinction. Not only do cats prey on many small mammals and birds, but they can outnumber and compete with native predators. Domestic cats eat many of the same animals that indigenous predators do. When present in large numbers, cats can lower the amount of prey for native predators, such as hawks and weasels. Free-ranging domestic cats may also transmit new diseases to wild animals. Domestic cats have spread feline leukemia virus to mountain lions and may have recently infected the endangered Florida Panther with feline panleukopenia (feline distemper) and an immune deficiency disease. These diseases may pose a serious problem to this rare species. Some feral domesticated cats can also carry several diseases that are easily transmitted to humans, including rabies and toxoplasmosis.

Cats differ from wild predators in three important ways: First, humans protect cats from disease, predation and competition, factors that can control numbers of wild predators, such as lions, tigers, foxes, or coyotes. Second, they often have a reliable supply of food provided by their owners and are, therefore, not affected by changes in populations of prey. Whereas populations of indigenous predators will decrease when prey becomes scarce, cats receiving food on a regular bases from people remain abundant and continue to hunt even rare species. Thirdly, unlike many indigenous predators, cat densities are either poorly limited or not limited by territories. These three influences allow domestic cats to exist at much larger densities than indigenous predators. Cats often form large feeding and breeding “colonies” (81 cats were recorded in one colony, and colonies of over 20 are not uncommon). Even when fed regularly by their owners, a cat’s will to hunt remains strong, so it continues hunting.

 

This is my neighbors cat Snowy, she was raised on a farm and loves being outside.

The number of domestic cats in the United States has tripled in the last 40 years. The continued conversion of natural areas to urban combined with the growing number of cat’s shows concerns about interactions of domestic cats and wildlife in these developed areas. Unfortunately, many people around the world remain unaware of the important conservation implications of letting pet cats roam and of feeding stray and feral cats. Due mainly from problems caused from its predation on other species, the domestic cat is listed by the IUCN as one of the “100 of the world’s worst invasive alien species”. It should be emphasized that the invasive species label applies exclusively to outdoor cats, rather than pet cats kept indoors or otherwise kept under control by their owners.

Historically, cats have been the cause of at least 33 bird extinctions, making them one of the most important causes of bird extinctions globally. Islands provide a great example for the negative ecological impacts of cats. Global extinctions caused in whole or in part by cats include those of the Stephen’s Island Wren (Xenicus lyalli) in New Zealand and the Guadalupe Storm Petrel (Oceanodroma macrodactyla) and the Socorro Island Dove (Zenaida graysoni) in Mexico. The case of the Stephen’s Island Wren is important in that this species was never observed alive in the wild before its extinction, and that most or all of the museum specimens were collected by a single cat. Cats have also caused many regional extinctions, reducing the ranges and genetic variation of bird species. Extirpations (which means locally extinct) caused partly or wholly by cats include those of Cassin’s Auklet (Ptychoramphus aleuticus) from the Coronado Islands, Mexico, and the Common Diving Petrel (Pelecanoides urinatrix) from Marion Island, South Africa. Finally, cats have caused substantial declines in bird populations, including the Sooty Tern (Sterna fuscata) on Ascension Island (UK), and the Black-vented Shearwater (Puffinus opisthomelas) and Socorro Mockingbird (Mimodes graysoni) on Socorro Island, Mexico.

Cats will catch many birds but rarely eat them for sustenance.

Where humans have reduced or eliminated populations of top-level predators such as wolves (Canis lupus, Canis rufus) and coyotes (Canis latrans), the survival and wandering of free ranging cats are not kept in check by the predator they would  meet in a wild ecosystem.

While indigenous predators are mainly nocturnal, domestic cats may be active during the day as well as at night. Domestic cats are also less intimidated than wild predators to hide from humans, and thus they may hunt in the open in human-dominated areas. Finally, while indigenous predators may eat eggs or nestlings of birds, no indigenous mammalian predator stalks and kills adult birds, as domestic cats do.

Birds remains an important topic in British and European conservation. The number of cats estimated in the UK has grown from 6.7 to 9.2 million. The Royal Society for the Protection of Birds (RSPB), British Trust for Ornithology (BTO) and independent research have suggested many ways in which to reduce the deaths inflicted on wild bird populations by domestic cats. These include restricting the outdoor activity of cats, fitting bells that make them more noticeable to prey and providing food for birds more often which limits their need to feed in places where they are at a greater risk of predation by domestic cats. This may reduce the impact of cats on urban bird populations.

Management Strategies

Traditional ways of animal control for unclaimed pets include sheltering, adoption, rescue, and lethal control in the form of euthanasia. In general, pet control law enforcement efforts have been greater for dogs than for cats, in part for public health and socioeconomic reasons. Thus, while free-ranging dog populations have been effectively handled, the numbers of cats have not been effectively controlled, and increased numbers of feral and stray cats now live in public and private lands across the globe. Often these cats are fed by people or find food in waste disposal areas. Plentiful food resources normally increase cat survival and reproduction, this reduces ranges and movement, thus multiplying cat densities and associated negative impacts on local wildlife.

 

Cats may group together and form colonies.

The most popular option for potentially managing cat predation was fitting pets with a collar-mounted anti-predation device. These have been shown to be effective in lowering predation rates although the reduction may not be of sufficient magnitude to prevent prey declines in all circumstances.

From a conservation perspective, curfews would most likely be effective at dawn and dusk (i.e. during the day) as this is when birds are most likely to be preyed upon but would probably have little effect on predation of small mammals. Curfews are probably the easiest way to manage cat predation.

Concluding Remarks

This post mainly deals with cats and their impacts on wildlife however dogs are not faultless either. Dogs globally also kill many birds, rabbits, deer and other smaller antelope. We all love our pets and care for them as much as we can, however we also need to be aware of the negative impacts they may have on the local environment. If we adopt just one of these tactics which can minimise wildlife mortality, it would be a great step forward for the environment and Mittens may not have the opportunity to wipe out the entire local crested barbet population. Remember too that cats need to be neutered and spayed to prevent unwanted baby Mittens.

References

Beckerman, A.P., Boots, M. & Gaston, K.J. 2007. Urban bird declines and the fear of cats. Animal Conservation, (10) 3:1–6.

Coleman, B.J.S., Temple, S.A. & Craven, S.R. Cats and Wildlife A Conservation Dilemma.1997.

Dauphiné, N. and Cooper R.J. Impacts of free-ranging domestic cats (Felis catus) on birds in the united states : a review of recent research with conservation and management recommendations. 2009. COPA: 205–219.

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. , 7(11): 20–23.

Twardek, W., Peiman, K., Gallagher, A., Cooke, S. 2017. Fido, Fluffy, and wildlife conservation: The environmental consequences of domesticated animals. Environmental Reviews, 25(4): 381-395.

Loss S.R., Will, T. and Peter, Marra, P. 2012. The impact of free-ranging domestic cats on wildlife of the United States. Nature Communications,1396.

Photo credits

Mother nature network

American bird conservancy

Buzzfeed

Vet practice magazine

 


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