The Animals That Thrive in Cities

A Red-crowned Parrot in Coahuila, Mexico

Conventional wisdom has it that urban centers are biological dead zones, home to little more than infestations of rats and pigeons, but in truth, cities can provide unexpected ecological niches. Most cities have well-kept green spaces filled with pollinating flowers, as well as tall buildings and other structures that are filled with crevices waiting to be filled. Coral reefs are a useful metaphor here: coral provides shelter to fish, which in turn attracts more fish and turns the reef into a combination hunting and breeding ground. A city can work in the same way: one species exploits a feature of the urban environment, attracting more animals in turn.

These human-reliant animals are called synanthropes and can be found in cities all over the world. For example, the Red-crowned Parrot is indigenous to northern Mexico and southern Texas, but it also has populations in Miami and Los Angeles, formed from their escaping as pets. The irony is that these parrots are endangered in their indigenous areas but thrive elsewhere, with Los Angeles now hosting 3,700 of the birds, more than in all of Mexico. Similar situations have been found in Hawaii with Madagascar-originating geckos or the wall lizards of Trier, Germany.

The parrots' distribution in Los Angeles

Los Angeles’ parrots have been so successful that there have been proposals to intentionally release other endangered birds into cities in the hope that their numbers will rebound. These biodiversity arks could in theory shelter a given species for a time while their natural habitat is restored, saving them from extinction. If the Red-crowned Parrot is any indicator, the project could save other birds, with the parrots now considered naturalized to the California ecosystem, perfectly fitting into its ecological niche.

Of course, the introduction of a foreign species of animal can have unexpected effects on the larger ecosystem. If the animal is predatory, it can overhunt an indigenous group, imperiling the city’s food chain. And while some cities have proven to be unexpected hotspots of life, the exception proves the rule that urban expansion generally imperils ecosystems and the animals living there. The urban ark is a novel idea for conservation, but its use should only come after careful consideration.