Bat breath reveals metabolic substrate use in free-ranging vampires

Christian C. Voigt, Patricia Grasse, Katja Rex, Stefan K. Hetz, John R. Speakman

Research output: Contribution to journalArticle

25 Citations (Scopus)


We analysed the stable carbon isotope ratio in exhaled CO2 (delta(13) C-breath) of free-ranging vampires to assess the type of metabolized substrate (endogenous or exogenous substrate) and its origin, i.e. whether the carbon atoms came from a C-4 food web (grass and cattle) or the C-3 food web in which they were captured (a rainforest remnant and its mammals). For an improved understanding of factors influencing the delta C-13(breath) of vampires, we conducted feeding experiments with captive animals. The mean delta C-13(breath) of starved bats was depleted in C-13 in relation to the diet by 4.6 parts per thousand (n = 10). Once fed with blood, delta C-13(breath) levelled off within a short time approximately 2.2 parts per thousand above the stable carbon isotope signature of the diet. The median time required to exchange 50% of the carbon atoms in exhaled CO2 with carbon atoms from the ingested blood was 18.6 min (mean 29.5 +/- 19.0 min, n = 5). The average delta C-13 of wing membrane and fur in free-ranging vampire bats suggested that bats almost exclusively foraged for cattle blood during the past weeks. The delta C-13(breath) of the same bats averaged -19.1 parts per thousand. Given that all free-ranging vampires were starving and that the delta C-13 of cattle was more in enriched in C-13 by 5-6 parts per thousand than the delta C-13(breath) of vampires, we conclude that the vampire bats of our study metabolised fat that was predominantly built from carbon atoms originating from cattle blood. Since delta C-13 of wing membrane and fur integrates over weeks and months respectively and delta C-13(breath) over hours and days, we also conclude that vampire bats of the studied population consistently ignored rainforest mammals and chose cattle as their prey during and prior to our study.

Original languageEnglish
Pages (from-to)9-16
Number of pages8
JournalJournal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
Issue number1
Early online date15 Aug 2007
Publication statusPublished - Jan 2008


  • exhaled CO2
  • Desmodus rotundus
  • stable carbon isotopes
  • respired CO2
  • diet
  • turnover
  • ratios
  • fractionation
  • tissues
  • blood
  • birds


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