Newswise — Increasingly, Americans are choosing packaged, processed foods over a healthier diet. And our foxes, raccoons, and opossums, too, are now consuming fast food of a different variety, finding leftovers from drive-thrus rather than chasing down mice, rats, and birds. The rapid spread of urbanization has humans and animal species living closer together and interacting more than ever before. This is evidenced by kit foxes in urban environments eating the same things as humans—particularly corn syrup.

An article in the December issue of the Journal of Mammalogy reports findings of a study of endangered San Joaquin kit foxes in and around Bakersfield, California. Rapid urbanization has given rise to the field of urban ecology, which includes studies on the impact of human activities on animals and how animals adjust to living in urban environments. One tool ecologists can use to determine animals’ diets and relationships with humans is stable isotope analysis, a method that is quick and cost-effective.

Hair samples from both foxes and people in the study area were collected and compared using isotope analysis. Results show distinct similarities between Bakersfield’s human and fox residents, suggesting a shared food source. Urban foxes had significantly higher carbon and lower nitrogen values than their nonurban counterparts from adjacent areas. The city-dwelling foxes also showed higher cholesterol levels than their country cousins.

The carbon values are an indicator of a diet high in corn or its derivative, corn syrup, and marks a trend distinctly North American. Unlike people in European and South American countries, residents of North America are consuming processed foods containing large amounts of corn products, characterized by high carbon values.

These developments would seem to have negative implications for the urban fox population in terms of a deficient diet causing poorer health and development and lower reproductive rates. However, evidence shows that survival and birth rates are higher among foxes in urban than in nonurban habitats, where they have a greater risk of being a food item because of the greater number of predators.

Full text of the article, “Stable Isotopes Evaluate Exploitation of Anthropogenic Foods by the Endangered San Joaquin Kit Fox (Vulpes macrotis mutica),” Journal of Mammalogy, Vol. 91, No. 6, December 2010 is available at

About the Journal of MammalogyThe Journal of Mammalogy, the flagship publication of the American Society of Mammalogists, publishes original research on both terrestrial and marine mammals. Published since 1919, the highly respected international scientific journal promotes interest in mammals throughout the world by the publication of original and timely research on all aspects of the biology of mammals, including ecology, genetics, conservation, behavior, and physiology. Published six times a year, each volume currently contains more than 1,200 pages. To learn more about the society, please visit:

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