North American coyotes don’t live in South America, nor do crab-eating foxes. But new research suggests that could change, should deforestation in Central America continue.
North and South America have a long history of exchanging animal and plant species, a process that began around 3 million to 4 million years ago ,when the Panamanian Isthmus joined the two continents. New research published in the Journal of Mammalogy reminds us that this process, known as the Great American Biotic Exchange, is still ongoing, as North American coyotes (Canis latrans) and crab-eating foxes (Cerdocyon thous) appear to be heading south toward Colombia.
The scientists, including Roland Kays from North Carolina State University, used camera traps to detect two coyotes in the Darién region of Panama, an area that hosts 6,000-square-kilometers of wilderness forests. These sightings now represent the southernmost known encroachment of coyotes, a full 200 kilometers away from the previous record.
The camera traps also chronicled the spread of crab-eating foxes, showing that the invasive canids are now actively inhabiting new territories.
That these two species have yet to reach South America has to do with the dense Central American forests that are blocking their way. But it’s not the forests per se that are forming the barrier, but rather the jaguars and pumas who call these forests home. Trouble is, these forests, along with their big cats, are disappearing due to human activities. Deforestation in Central America is reducing the amount of habitat available to these native apex predators. With fewer jaguars and pumas around, the coyotes and foxes—both highly adaptive generalists—are moving in. The new study affirms the old adage that nature abhors a vacuum, as these canids are quickly taking advantage of opening niches.
“If deforestation continues in the region, these two invasive canids could represent the first of a new, Not-So-Great American Biotic Interchange, where generalist species adapted to human disturbance cross continents and threaten native biota,” wrote the authors in the new study.
Camera trap surveys in eastern Panama were conducted from 2006 to 2015 and then near the Darién region from 2016 to 2018. The first set of surveys showed that coyote and fox populations had reached an area “where neither species had historically occurred,” according to the research. The more recent surveys confirmed the presence of coyotes along the westernmost boundary of the Darién woodlands, capturing images of two coyotes—including a female who had a wound on her hind left leg, which the researchers suspect was inflicted by a jaguar.
The coyotes and foxes, both nocturnal species, appear to be avoiding each other, based on the evidence. These animals hunt for small prey, but coyotes can also consume fruit. Their presence in these uncharted lands could be catastrophic to native species, who are unfamiliar with these interlopers from the north.
“Coyotes are the ultimate generalist in terms of diet and habitat type,” Kays told Gizmodo in an email. “They mostly hunt, taking prey ranging in size from deer to mouse, but also will nosh on insects or fruit if its available. They can also deal with a huge variety of conditions, from desert to rainforest to Alaskan winters. Also, they are super mobile, can easily get up and run 160 kilometres to find a new territory if needed. Finally, they are super smart and have a super nose, their sense of smell and sensitivity to danger helps them creep around the edges of humanity without getting into trouble—usually.”
Kays said the native South American canids, a group of fox species, are likely most at risk. That said, all prey species on the continent have lived alongside predators for a long time, “so I’m hopeful that we won’t see any terrible massacres” said Kays.
What’s more, the continued expansion of these animals into South America “is not guaranteed,” as the dense Darién forests “harbour habitats and mammal communities that are more intact than those present in central Panama,” according to the research. Problematically, however, the researchers suspect that the foxes could bypass the forest by scurrying along the beach.
Importantly, some of the coyotes, as evidenced by roadkill and sightings, appear to be interbreeding with feral dogs. This manifests as shorter tails, distinctly dog-like faces, and unusual colouring. This has also been documented in eastern North America, where the increased body size has likely helped the hybridised coyotes to expand more rapidly, according to the study. Coyotes in Panama and northeastern Costa Rica don’t appear to be getting bigger, but hybridisation may still have benefits, as the researchers write:
Tropical coyotes are not evolving larger body size, but we hypothesize that hybridisation with dogs could potentially introduce advantageous genes associated with eating fruit. Although northern coyotes commonly eat fruit, this could be an even more important diet item for tropical coyotes given its year-round availability. Dogs have genetic adaptations that aid in the digestion of starches and carbohydrates, thus it is reasonable to speculate that coyote–dog hybridisation could allow coyotes to better utilise new food resources. Whether such traits would outweigh deleterious genes introduced by domestic dogs presents an intriguing hypothesis yet to be tested.
Preserving the integrity of the Darién woodlands is key to preventing the coyotes and foxes from entering Colombia. What’s more, efforts to reduce deforestation and to restore forests would likewise work to counter this troubling trend.