Mapping Feral and Stray Cats

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In many parts of the world, feral or stray cats are very common. Feral cats are domestic cats that are wild and have never been tamed while stray cats are cats that were formerly pets but are now homeless.

For a variety of reasons, knowing where these cats are is relevant particularly for the protection of native species threatened by cats.

Almost every campaign to remove or diminish cat populations in areas that were previously devoid of cats has failed. Now, however, GIS and mapping technologies could be used to better protect native species and diminish the threat feral cats have on native species. 

Domestic animals, and those that have escaped and become in wild state (i.e., feral), have increasingly become a major environmental problem for often remote or vulnerable native wildlife.

This is particularly the case in locations such as New Zealand’s Auckland Island, which has tried to limit or prevent introduced species. One group of researchers realized the threat that cats can pose to native wildlife, leading to their decision to map them in Auckland so that their behavior is better understood prior to introducing an intervention.

Stray cats at the São Jorge Castle in Lisbon, Portugal.
Stray cats at the São Jorge Castle in Lisbon, Portugal. Photo: Caitlin Dempsey.

Using GIS and GPS to Map the Movements of Stray and Feral Cats

Using GPS and GIS, the researchers were able to develop detailed movement patterns of feral cats. Researchers have stated it is vital to remove every cat on Auckland, which is a feat never accomplished on a scale as large as Auckland.

By using GIS, and determining how these animals move around, a removal strategy based on the cats’ behavior and range could be developed. The team would spot cats but also place GPS collars on cats to track their wider movements.

A satellite view of the Auckland Islands, south of New Zealand.
A satellite view of the Auckland Islands, south of New Zealand. Auckland Island is the largest island in the island chain. Image: Terra satellite, NASA, May 12, 2004.

In addition to cats, other introduced species such as pigs and mice also created problems for the native wildlife, further complicating the task of removal.[1]  

A similar study looking at the Galapagos Islands found that feral cats did sometimes respond to the presence of hatchlings or young of native species that were spawned on the islands, although this response was not major or direct threat to all species. However, it is not clear if simply cats have a specific, limit range of animals they chose to hunt.

Hatchlings from other threatened reptilian, marine, or other species need to be studied more carefully using similar GPS and mapping approaches before determining the full threat feral cats pose.[2]

Domestic Cats and the Wildland Urban Interface

While feral cats are a problem, especially for vulnerable native wildlife that has evolved without the presence of cats, other research has shown that escaped domesticated cats can also be a problem, but this is often due to houses located near wildlife areas.

In a study in Chile, researchers mapped the presence of escaped cats with that of house locations near a forested area with local wildlife. People who live near wildlife areas and have cats are more likely to have a cat that escapes or is free roaming and harms native wildlife.

Simple measures, such as controlling or managing reproduction within cat populations, might be the easiest answer to limiting cat impact on native wildlife, since few cats were found to venture more than a few kilometers. Given the limited range of most escaped cats, limiting the impact of cats from households near wildlife areas might be a more effective strategy.[3] 

One problem is, however, human populations are increasingly encroaching near or within wildlife areas. The cats that come along with these populations are then likely to pose an increasing problem for native wildlife as encroachment near wildlife areas becomes greater. 

Crowdsourcing Mapping Feral Cats

There are projects that attempt to get the public involved, helping to map feral cats on a publicly accessible map. Feral cats can be reported by people who spot them and upload data about their location and additional information is possible using sites such as Feralscan.

Feralscan maps stray cats in Australia.  Screenshot taken on October 13 2021.
Feralscan maps stray cats in Australia. Screenshot taken on October 13 2021.

Individuals can record sightings, damage, or other signs of cats in an area. In addition to wildlife, sheep populations have been reported to have been impacted by feral cats carrying disease that affect them in Australia, as reported on Feralscan.[4] Another project that enables to create their own local databases of escaped or feral cats is Cat Stats.[5]

Feral cats might not seem very problematic for many of us, but around the world they have had a strong negative impact on native wildlife that has not adapted to the presence of cats. Once cat populations escape from domestic contexts, controlling their population is very difficult. Research is attempting to mitigate this problem through GIS and spatial technologies. The public can also get involved in places where feral cats are particularly harming native species, such as Australia.

References

[1]    For more on the feral cats of Auckland, see:  https://www.esri.com/about/newsroom/blog/gis-analyst-maps-feral-cats-solution/

[2]    For more on the Galapagos and the threat posed by feral cats, see:  MacLeod, A.; Cooke, S.C.; Trillmich, F. The Spatial Ecology of Invasive Feral Cats Felis Catus on San Cristóbal, Galápagos: First Insights from GPS Collars. Mamm Res 202065, 621–628, doi:10.1007/s13364-020-00493-z.

[3]    For more on the impact of cats on native wildlife in Chile, see:  López-Jara, M.J.; Sacristán, I.; Farías, A.A.; Maron-Perez, F.; Acuña, F.; Aguilar, E.; García, S.; Contreras, P.; Silva-Rodríguez, E.A.; Napolitano, C. Free-Roaming Domestic Cats near Conservation Areas in Chile: Spatial Movements, Human Care and Risks for Wildlife. Perspectives in Ecology and Conservation 202119, 387–398, doi:10.1016/j.pecon.2021.02.001.

[4]    For more information on Feralscan, see:  https://www.feralscan.org.au/feralcatscan/default.aspx.

[5]    For more on Cat Stats, see:  https://www.catstats.org/.

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