Bornean orangutans on the brink of protein bankruptcy

Erin R. Vogel, Cheryl D. Knott, Brooke E. Crowley, Melissa D. Blakely, Michael D. Larsen, Nathaniel J. Dominy

Research output: Contribution to journalArticle

43 Scopus citations


Protein is a limiting resource that is essential to the growth, maintenance and reproduction of tropical frugivores, yet few studies have examined how wild animals maintain protein balance. During chronic periods of fruit scarcity, Bornean orangutans (Pongo pygmaeus) often catabolize their own fat reserves despite unusually low metabolic requirements. Such energy deficits suggest a marginal existence, and raise the possibility that orangutans also endure periods of negative protein balance. To test this hypothesis, we conducted the first study of protein cycling in a wild primate. Our five year analysis of urinary metabolites revealed evidence of protein recycling when fruit was scarce. During these periods, orangutans consumed more leaves and bark, proteinaceous but tough foods that yielded a mean daily intake of 1.4 g protein kg-1 metabolic mass. Such an amount is inadequate for humans and one-tenth the intake of mountain gorillas, but sufficient to avert, perhaps narrowly, a severe protein deficit. Our findings highlight the functional and adaptive value of traits that maximize protein assimilation during periods of ecological exigency.

Original languageEnglish (US)
Pages (from-to)333-336
Number of pages4
JournalBiology Letters
Issue number3
StatePublished - Jun 23 2012


All Science Journal Classification (ASJC) codes

  • Agricultural and Biological Sciences (miscellaneous)
  • Agricultural and Biological Sciences(all)


  • Borneo
  • Orangutans
  • Protein
  • Urea

Cite this

Vogel, E. R., Knott, C. D., Crowley, B. E., Blakely, M. D., Larsen, M. D., & Dominy, N. J. (2012). Bornean orangutans on the brink of protein bankruptcy. Biology Letters, 8(3), 333-336.