Spatial and Temporal Expression of Vegetation and Atmospheric Variability from Stable Carbon and Nitrogen Isotope Analysis of Bat Guano in the Southern United States

Authors

Christopher M. Wurster, University of St. Andrews
Donald A. McFarlane, Claremont McKenna College; Pitzer College; Scripps CollegeFollow
Michael I. Bird, University of St. Andrews

Document Type

Article

Department

Biology (CMC), WM Keck Science (CMC), Biology (Pitzer), WM Keck Science (Pitzer), Biology (Scripps), WM Keck Science (Scripps), WM Keck Science

Publication Date

2007

Abstract

Stable isotopes of faeces contain information related to the animals feeding ecology. The use of stable isotope values from subfossil faeces as a palaeoenvironmental indicator depends on how faithfully the animal records their local environment. Here we present insectivorous bat guano δ¹³C and δ¹⁵N values from a precipitation gradient across the southern United States and northern Mexico to compare with local vegetation and climate. We find δ¹³C values to be an excellent predictor of expected C₄/CAM vegetation, indicating that the bats are non-selective in their diet. Moreover, we find bat guano δ¹³C values to be strongly correlated with summer precipitation amount and winter precipitation ratio. We also find evidence for a significant relationship with mean annual temperature. In general, we do not find δ¹⁵N values to be related to any parameters along the climatic gradient we examined. Additionally, we measured δ¹³C and δ¹⁵N values of bulk guano deposited annually from 1968 to 1987 in a varved guano deposit at Eagle Creek Cave, Arizona. Neither δ¹³C nor δ¹⁵N values were significantly related to various local meteorological variables; however, we found δ¹³C values of guano to be significantly related to drought and to the North American Monsoon indicating bat guano δ¹³C values preserve an interpretable record of large-scale atmospheric variability.

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DOI

10.1016/j.gca.2007.05.002

Recommended Citation

Wurster, C. M., McFarlane, D. A., and Bird, M. I. (2007). "Spatial and temporal expression of vegetation and atmospheric variability from stable carbon and nitrogen isotope analysis of bat guano in the southern United States." Geochimica et Cosmochimica Acta 71: 3302-3310.