Isotopic Studies of Animal Migrations

Understanding species vulnerability and resilience

Museum specimens, such as these prepared skins and skeletons of silky pocket mice (Perognathus flavus) and kangaroo rats (Dipodomys ordii), provide vital historical data for scientific research. One of the many ways researchers can glean information from these specimens is through stable isotope analysis of these specimens. Photo by Tara Smiley

Stable isotopes of carbon, nitrogen, oxygen, and hydrogen are used to evaluate species diets and migration in relation to climate and land-use change. Using isotopic signatures, ERI Fellow Tara Smiley and her team can tackle questions such as: Which birds are better able to tolerate urban levels of disturbance, lighting, and food sources and which are most vulnerable to these human activities? Are bird migration timing and pathways shifting and what does this mean for important ecosystem services, such as seed dispersal or the transmissions of avian diseases over long distances?

Naturally occurring stable isotopes are biogeochemical tracers that differ in their abundances in relation to animals' diets, environment, and migration. For example, oxygen and hydrogen, which make up water, differ in their isotopic abundance in precipitation from Mexico to Indiana to Alaska. As animals consume water and food resources in their local environment, their own tissues reflect the isotopic signature of that precipitation. Along with banding, MOTUS tower radio-tracking, and GPS tracking, isotopic analysis of animal tissues, such as feathers, are one of the primary means of determining animal migration.

Improving our ability to track the movement and dietary ecology of migratory and non-migratory animals, especially those of conservation concern, will guide protection and management decisions for the future. Along with other Institute research projects, this work will help generate new datasets that enhance our understanding of species vulnerability and resilience and dynamic mapping of wildlife migration.