First, a definition:
A Synurbic Species is one that thrives in man-made, urban habitats. It refers to animals that not just live alongside us, but actually live better and in greater numbers when closely associated with people. Syn- is a Greek prefix meaning "with," while -urbic refers to the Latin root urb- meaning "city." Domestic species like pets and crops are not considered synurbic, because we intentionally bring them into contact with us. We invite them and appreciate them. In a sense, we invite synurbic species in as well, but it isn't always a happy relationship.
There are some great examples of truly synurbic species. Some are very obvious- look outside and you'll likely see pigeons, squirrels, and flies; not to mention the less visible but equally present raccoons, house mice, and rats. The visible impact that COVID quarantines in New York City have had on rat populations shows just how dependent they have become on city-dwelling humans. In fact, a lot of pests are synurbic because we provide them exactly the type of habitat they desire. Bed bugs, termites, weeds, and crows appreciate the resources that humans provide.
To them, our homes and cities are simply edible wooden structures with well-watered lawns, ample space to live, and lots of garbage to pick through. What's not to like?
Macaques in Southeast Asia
In Lop Buri, Thailand, the Prang Sam Yod temple is a historical landmark in its own right, but the tourism that it drew burgeoned into its own, very different attraction for crowds. Tourists love to visit with the monkeys, feed them bananas, and take selfies with them. In exchange, the monkeys like to steal their junk food and cometimes their very expensive cameras or purses. The populations of of crab-eating macaques (Macaca fascicularis) in these areas has been thriving for decades.
In the tourist hubs of Southeast Asia, however, the urban-adapted populations are doing rather well. In West Sumatra, Indonesia, a different species, the long-tailed macaque (Macaca fascicularis), has faced a similar change. A study found that troop sizes of long-tailed macaques in urban areas can be more than 100 individuals, while those in their native forests typically only have 12 to 30 at most. It has become a situation where the monkeys must adapt to human presence, or face serious decline.
Unfortunately, those that do not wish to mingle with people are threatened by habitat loss, as well as trapping and trade for pharmaceutical testing and scientific research. Tourism leads to deforestation and urbanization, it is not so much that the monkeys have chosen to interact with people to benefit themselves, rather they have been forced into direct contact and have made the best of a bad situation.
They have become habituated to humans and essentially dependent upon them. In the wake of the country's Coronavirus shutdown, tourism declined dramatically and the monkeys, just like the rats in New York City, became aggressive and hungry because of the lack of food. With interactions such as these, people need to consider the long-term effects that their interaction might have.
Sometimes, that selfie just isn't worth it.
We also worry about the possibility of macaques infecting people with new diseases, but the risk goes both ways. We can easily transmit our diseases to them. Not to mention the impact that junk food has on their overall health. There are more of them able to live in this area because of the tourists, but more unhealthy macaque is not as good as fewer healthy ones.
Several types of bats, living thousands of miles apart, also qualify.
Three different species, the Grey-headed flying fox (Pteropus poliocephalus), the Black flying fox (P. alecto), and the Little red flying fox (P. scapulatus). These bats feed on fruits and nectar from flowering trees, acting as pollinators in much the same way that bees and butterflies do. In Brisbane, they roost in treetops and rarely, if ever, land on the ground, so they aren't likely to have direct contact with humans.
Even so, they are seen every night in swarms leaving their trees to find food. Many people find this worrisome, because droppings and fruit pulp often litter the streets, and bats are well-known as potential disease vectors.From the bats' point of view, however, their ability to adapt to city living has been highly beneficial!
Much of their native habitat has been destroyed to build cities, and deforestation continues throughout Australia. In Brisbane, planting new trees within the city was a priority of the development process. As the city has grown, so too has the canopy of trees that the bats use to roost. Beautiful, tall flowering tree species like jacarandas and weeping figs are abundant, and mangoes are a popular backyard tree for residents. Some of their favorite roosting trees, like the Tipuana tree, aren't even native, but are planted throughout the city as an ornamental addition.
Mexican Free-Tailed Bats in Texas
Under the I-35 bridge crossing the San Antonio River near Camden Street in San Antonio, Texas, nearly 50,000 Mexican Free-Tailed bats (Tadarida brasiliensis) ascend at dusk in a massive flock. It's a popular place to visit on warm evenings, but it is far from the largest of Texas' bat bridge colonies. According to Bat Conservation International, the Congress Avenue Bridge in Austin and the McNeil Road Bridge north of Austin have approximately 1.5 million bats; the Foster Street overpass in San Angelo has 500,000; Seco Creek Bridge near Uvalde has nearly 1 million; and the Salado Culvert near Waco hosts another 500,000!
The Department of Transportation in Texas carefully monitors them, but it also takes care to design bridges to be favorable homes for bats.
Their presence is highly valuable because they eat insects, and are especially good at ridding the skies of mosquitoes.
One of my personal favorite examples, because I see their nest regularly on the underside of bridges and plastered to the sides of buildings, are the cliff swallows (Petrochelidon spp.). Their nests are easily identifiable, and you can often find them tucked under the awning of a roof or hidden in crevices. They build colonies of mud nests that might resemble hives, and have characteristic windows for entry and exit. Chicks await their hunting parents inside of these cozy hollows, but are adept at keeping well hidden. When you drive under bridges, pay attention to the birds above your head, popping in and out of these nests as they dip and dive in daredevil fashion catching flying insects. When feeding in flocks with other species of swallows, they often stay higher in the air.
Mission San Juan Capistrano in Southern California is famous for its annual congregation of swallows, which migrate 6,000 miles from Goya, Argentina to San Juan Capistrano every Spring. This event has been celebrated by the Mission since the 1930s, but the expansion and redesign of the building in the 1990s almost ended it. By 2003, there were few swallows arriving at the Mission, but thankfully efforts began in 2012 to bring them back, and the population is slowly recovering.