Technique to study poop offers a snapshot of diets, ecosystems, and climate

Abstract

Hundreds of thousands of eider ducks once nested on the remote, rocky beaches of the Canadian Arctic. But sometime late in the 19th century, eiders began to disappear. Inuit oral traditions recall declines well before most scientific seabird censuses came so far north in the 1970s, says paleolimnologist Jules Blais at the University of Ottawa in Canada. To understand exactly when and why past duck populations crashed, Blais uses an emerging tool: stable isotope analysis of duck poop. The story of Baffin Island’s eider ducks is told in stable isotopes of duck poop stored in years of sediment. Researchers across fields are now using fecal isotope analysis to answer a range of research questions. Image credit: Grant Gilchrist (Environment and Climate Change Canada, Ottawa, Canada). Stable isotope analysis itself is nothing new. An established technique in several fields, it uses isotopes to trace physical and biological processes. For example, because isotopes—atoms of an element that vary in their number of neutrons—have slightly different weights, they exist in different kinds of food in distinctive ratios and therefore move into body tissues in distinctive ratios. These ratios are widely used to work backward from bone or hair to infer the diets of animals or ancient humans. But fecal matter hasn’t generally been a go-to material for this kind of isotope research—until recently. Fecal stable isotope analysis is catching on in ecology, paleoecology, and paleoclimatology in part because samples are easy to collect and offer a quick snapshot of an animal’s diet. Some researchers are applying stable isotope analysis to poop to study modern and ancient diets, whereas others use it to reconstruct past ecology, climates, and environments, says paleoecologist Rachel Reid at the Virginia Polytechnic Institute and State University in Blacksburg. In the eider duck case, Blais analyzed the ratio of stable …