A coyote crosses a city street, lit by streetlights (National Park Service)

CSUN ecologists determine what’s on the menu for LA’s coyotes

Urban coyotes eat more garbage, fruit, and domestic cats, and are less picky than neighboring suburban and rural coyotes, according to the results of a study by CSUN ecologists recently published in PLOS ONE.

Coyotes are one of the most successful urban mammals, inhabiting almost every major city in continental North America. One reason they are so successful is their omnivory – coyotes will eat practically anything that fits in their mouth. However, coyotes in cities can come into conflict with people because of their tendency to raid garbage and pet food, and prey on domestic cats and dogs. Former graduate student and lead author Rachel Larson and Professor of Biology Tim Karels worked with collaborators in the National Park Service to discover how coyote diets vary across an urban-to-rural landscape gradient and to determine whether some coyotes are pickier than others.

Lead author Rachel Larson takes a close look at a scat sample under a dissecting scope. (Rachel Larson)
Lead author Rachel Larson takes a close look at a scat sample under a dissecting scope. (Rachel Larson)

The team surveyed sites across Los Angeles, Westlake Village, Thousand Oaks, and Simi Valley to collect coyote scat (the technical name for poop). Dozens of specially-trained community volunteers dissected more than 3,000 scat samples to identify fur, feathers, bones, seeds, insect parts, and anything else that coyotes were eating.

The lead authors also collected whiskers from coyotes captured by the National Park Service and from road-killed coyotes. They analyzed these whiskers for their stable isotope ratios – the ratio of variants of chemical elements that are heavier because they contain more neutrons in their nucleus. Different plants have distinct cabon isotope signatures, and corn is very distinctive from the native plants of southern California. Corn is ubiquitous in the American diet: people eat sweet corn, corn syrup is in many processed foods, and corn is fed to livestock and poultry. Coyote whiskers with high levels of carbon-13, the signature of corn, come from coyotes eating lots of human food. 

Direct evidence of a coyote's people-food diet: most of a McDonald's wrapper found in a scat sample. (Rachel Larson)
Direct evidence of a coyote’s people-food diet: most of a McDonald’s wrapper found in a scat sample. (Rachel Larson)

Urban coyotes ate rabbits and rodents, the common prey of their country cousins, but they also ate lots of garbage, ornamental fruits like figs and palm tree seeds, and domestic cats. Suburban coyotes had a seasonally variable diet, switching between eating their natural prey in the cooler, wetter winter and eating ornamental fruits when they ripen in the summer. Rural coyotes subsisted on a steady diet of rabbits, gophers, and squirrels. Rural and suburban coyotes also tended to be picky, only eating a few different species, while urban coyotes helped themselves to a little of everything at the prey buffet.

Although the researchers were not surprised that urban and suburban coyotes ate human-related foods, they were surprised by how much of it they ate: 60% of urban scats and 20% of suburban scats had human-related items, and the coyotes’ whiskers from both areas showed that up to 45% of their diet could be human food leftovers. Ornamental fruits (25% of urban scats and 23% of suburban scats) and cats (20% of urban scats and 4% of suburban scats) were also important prey items for coyotes. To reduce human-coyote conflicts, homeowners should secure garbage, remove fallen fruit from their yards, and keep their cats indoors.

The complete study is available open access on the PLOS ONE website.