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Trophic level and diet affect patterns of extinction risk in birds and mammals
Research Week
  • Shaley Valentine
  • Edd Hammill, Utah State University
  • Douglas J. McCauley, University of California, Santa Barbara
  • Elizabeth M. P. Madin, Macquarie University, Australia
  • Karen H. Beard, Utah State University
  • Trisha B. Atwood
Graduation Year
S.J. & Jessie E. Quinney College of Natural Resources
Watershed Sciences Department
Faculty Mentor
Trisha Atwood
Presentation Type
Oral Presentation
Extinction is occurring at unprecedented rates. Past studies suggest that traits - including body size and geographic range - are intrinsically linked to extinction risk, generating anecdotal evidence that predators have the greatest extinction risk. However, explicit comparisons are needed to quantify global extinction risk among trophic groups. Because trophic position and diet govern species’ effects on ecosystem processes, understanding the relationships between these traits and extinction risk is crucial for predicting ecosystem-level consequences of extinction. We asked whether trophic level and dietary group are associated with extinction risk in extant mammalian (n=5,451) and bird (n=10,279) species assessed by the IUCN. Diet was characterized from literature-based information based on primary and secondary food items consumed. Predators and herbivores were defined as consuming a >80% animal- or plant-based diet, respectively, while omnivores were defined as consuming a more even distribution of animal and plant groups. Random simulations drawing from species subsets investigated whether extinction risk patterns in trophic levels and dietary groups deviated from null model predictions. Contrary to assumption, fewer predatory mammal species were threatened with extinction (17.2%) compared to null models (21.9%), while a higher percentage (26.8%) of herbivorous mammals were classified as threatened. For birds, extinction risk across trophic levels did not differ from the null model. Within diet groups, a greater percentage of frugivorous and folivorous mammals (27.4% and 28.9%, respectively), and piscivorous birds (23.6%) were classed as threatened compared to null models. These results suggest that the emphasis on the presumed higher extinction risk of predators may be unwarranted, and that the extinction risk for herbivorous mammals is greater than generally recognized. As ecosystem processes are intricately linked to trophic level, we can utilize these results to predict how species declines in specific dietary groups affect future ecosystem functions.
Room 101
Start Date
4-13-2017 12:00 PM
End Date
4-13-2017 1:15 PM
Citation Information
Shaley Valentine, Edd Hammill, Douglas J. McCauley, Elizabeth M. P. Madin, et al.. "Trophic level and diet affect patterns of extinction risk in birds and mammals" (2017)
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