Stable isotopes in animal ecology and in investigations of aquatic-terrestrial trophic interactions

Stable isotopes exist naturally everywhere. Stable nitrogen isotope ratios (δ¹⁵N) give information on trophic levels, as consumers usually have higher δ¹⁵N than their diet due to the biochemical processes that take place during digestion. Stable carbon isotope ratios (δ¹³C) differ between different types of plants, due to different photosynthetic pathways, and provide information about diets and habitats.

Stable isotopes do not degrade over time and often differ between different habitats. These attributes allow us to use them to detect past changes in habitat or diet of animals over different time scales, in fresh, as well as, in museum samples. Stable isotopes are, therefore, ecological tools suitable to investigate aquatic-terrestrial connectivity, animal migration and diet. Knowing the diet of animals is useful not only to understand species coexistence, diversity and evolution, but also for conservation purposes. Applications of stable isotopes in animal ecology will be presented, including tracking of aquatic versus terrestrial dietary resources in faeces of bats.