Cope's Rule, Hypercarnivory, and Extinction in North American Canids

Van Valkenburgh, Blaire
Wang, Xiaoming
Damuth, John

¹Department of Ecology and Evolutionary Biology, University of California at Los Angeles, Los Angeles, CA 90095-1606, USA. ²Department of Vertebrate Paleontology, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA. ³Department of Ecology, Evolution, and Marine Biology, University of California at Santa Barbara, Santa Barbara, CA 93106, USA.

*To whom correspondence should be addressed. E-mail: [email protected]

7 July 2004; accepted 26 August 2004

Science 306(5693):p 101-104, October 1, 2004.

Over the past 50 million years, successive clades of large carnivorous mammals diversified and then declined to extinction. In most instances, the cause of the decline remains a puzzle. Here we argue that energetic constraints and pervasive selection for larger size (Cope's rule) in carnivores lead to dietary specialization (hypercarnivory) and increased vulnerability to extinction. In two major clades of extinct North American canids, the evolution of large size was associated with a dietary shift to hypercarnivory and a decline in species durations. Thus, selection for attributes that promoted individual success resulted in progressive evolutionary failure of their clades.