Coyotes are thought to be tough, resilient and adaptable, making them appropriate additions to New York, a city with a similar reputation! Recent sightings of coyotes in unexpected places (like a Queens rooftop and near Wall Street) has garnered excitement and attention (and helicopters!) but some scientists think these encounters may become regular seasonal events as young coyotes leave their birth places to try and find a home of their own.
In 1994-1995 the first coyotes were spotted in New York in Woodlawn Cemetery and as roadkill elsewhere in the Bronx. Since that time several coyote pairs have permanently moved to New York, setting up home territories in Pelham Bay and Van Cortlandt Parks with isolated sightings elsewhere, including Inwood Hill Park in Manhattan. Now evidence of around 4 breeding pairs and coyote pups have been found in at least 3 parks.
Although some people think there may have been coyotes in the northeast pre-European settlers, it is more likely that the Eastern coyotes increasingly found nearby are relatives of coyotes found in the plains states and in the central US. They are moving east, expanding their range, taking advantage of an empty ecological niche.
In ecology, niche is a complicated concept with several definitions, however, it is commonly used to indicate the role or function of an organism in an ecosystem. For example niches could include where organisms are found in a food chain, e.g. predators or prey, plants or herbivores, etc. An empty or vacant niche is a role or function in an ecosystem that is not currently being filled by anything. Coyotes are filling the empty niche of predator in our urban ecosystems, a niche once filled by wolves. A central idea in ecology is that two species cannot by definition share a niche. Where there are more than one species with similar traits or roles within an ecosystem (like wolves and coyotes), they will either compete until one of the species is eliminated (known as competitive exclusion) or they will divide the niche into two or more different niches (known as niche differentiation). Wolves are likely strong competitors against coyotes which may have limited their range overlap historically (see this paper about competition between wolves and coyotes in Yellowstone post-wolf reintroduction).
Coyotes are opportunistic feeders meaning that they both hunt for small prey like rats (some scientists estimate that coyotes can eat 1800 rodents in a year!), but they will also scavenge from carcasses killed by other organisms, including roadkill. In this way they fulfill two important roles in an ecosystem.
So let’s review, ecosystems, as many of you may remember from school, are made up of organisms that interact with one another (the living or biotic component) within a physical or non-living (abiotic) environment.
The living component of ecosystems, also often referred to as the community, is often understood to be a web of interactions between organisms. Often these organisms are related by where they fit in the food web (a connection of food chains) and are broadly categorized by their feeding category. For example predators are carnivores, animals that eat other animals (prey). Prey are often herbivores (plant eaters) or sometimes they are also predators of smaller animals (or if they eat both plants and animals – like people do — they are known as omnivores). Plants that eat animals are primarily known as fiction but there are some carnivorous plants. Plants are called primary producers because they don’t feed on other organisms. Rather they produce their own energy through photosynthesis. In order to perform photosynthesis, plants do require nutrients that they gain from soil. Nutrients are provided via scavengers, decomposers, and detritivores which breakdown dead organic materials and complete the food web (for a review of their importance see Dominic Evangelista’s first post).
OK, great, you might be thinking, I’ve known this since grade school. What does this have to do with coyotes in New York City?
To answer that, we need to go back to the early 20th Century. When Times Square looked something like this:
Now humans have always had fear of large predators because for most of our existence as a species we have been prey.
In some areas of the world, unfortunately humans are still prey, but in the urbanized US these concerns are basically non-existent. In large part this is due to the widespread extermination of large predators which began in earnest in the early 20th century in response to lobbying by sport hunters and ranchers who were concerned about predator impacts on their livestock (present day rancher have similar concerns). Previous to 1908, predators were generally hunted on an individual basis, but that year the U.S. Forest Service reportedly killed 359 wolves. And in 1915 the Bureau of Biological Survey, a federally funded organization whose mission was to kill wolves and other large predators, received $125,000 from Congress (Source: The National Audubon Society: Speaking for Nature, A Century Conservation, edited by Les Line, 1999).
These efforts were very successful and by mid-century wolves were essentially eliminated from the continental United States with only small isolated populations remaining in the far north of Minnesota and Michigan.
At the time of these mass hunts, many ecologists believed ecosystems are controlled from the bottom-up, meaning that plants in terrestrial ecosystems and phytoplankton (which also perform photosynthesis) in aquatic ecosystems are the primary determinants of what other organisms are in the ecosystems. Intuitively this makes sense as plants are the foundation of the food web and there is plenty of modern research that supports this hypothesis (see this article by Dr. Judith Weis).
However, in the 1960s, after observing some unexpected consequences of predator removal on ecosystem function, scientists began to hypothesize that ecosystems are controlled from the top-down. Basically, this theory states that predators keep herbivorous prey populations in check, keeping them from growing out of control and decimating plant populations. Therefore when apex predators (top predators or predators that have no predators) are removed there is a trophic cascade, where the loss of the predator trophic (feeding) level, leads to overly large prey populations, which in turn leads to a destruction of the plant or primary producer community (see this article also by Dr. Judith Weis).
Globally, predators are the most endangered group of animals due to similar extermination efforts, and these losses have provided evidence to support the role of top-down controls on ecosystem functioning. For example, in the northeastern United States, the loss of wolves and other large predators contributed to extremely large white tailed deer populations which in many areas are preventing forest regeneration due to high levels of herbivory on tree seedlings (see this link).
These negative impacts have led some people to advocate for the reintroduction of large predators into ecosystems, like wolves into Yellowstone. Reintroduction efforts are often controversial but they do appear in many cases to have positive consequences for ecosystems, but not always to the degree or in the ways scientists have expected (see this link). Ecosystems are complex and their functioning is still not perfectly understood, but it is likely that both top-down and bottom-up forces play a role in structuring ecological communities.
Less controversial than human-mediated reintroductions are situations where nature takes matters into her own hands. In these cases predators, like coyotes, may expand their ranges into areas once occupied by other organisms, like wolves. Therefore, the increasing number of coyotes in New York City can in part be linked to the loss of wolves nearly 100 years ago. Although coyotes only occasionally take down deer or other large prey, they do eat small prey and can keep pest populations in check as well as contribute to waste processing within ecosystems via scavenging. This is why scientists are excited to see coyotes moving into cities like Chicago and New York.
The Gotham Coyote Project seeks to monitor coyote populations in New York City in order to better understand how they behave and their ecological impacts. If you want to help them you can join their citizen science efforts (also see Megan Litwhiler’s post last week). And if you want to know what to do if you are lucky enough to see a coyote, check out this link from New York City Parks Department. Importantly you can contribute to both your own and public safety and coyote survival if you do not approach them or feed them.
In a world where we are rapidly losing biodiversity and climate change threatens to take even more species, conservation has never been more important (for more on this topic see Tony Cullen’s last post. Losing links in the web of life has deleterious consequences across ecosystems and the ecosystem services they provide.