Using Isotopes to Understand the Movement Patterns and Diet of Albatross and Pterosaurs

Abstract

Isotopes are useful tools for elucidating ecological unknowns in modern and prehistoric organisms. Two of the organisms that have lacked the application of 87Sr/86Sr methodologies to understand their movement patterns are albatross and pterosaurs. Albatross has also been mentioned many times within the literature as a modern analog for pterosaur flight behavior. Along with strontium, there is a severe lack of dietary evidence resulting from isotopic studies focusing on the pterosaur's fossil record. Within this thesis, albatross 87Sr/86Sr compositions will serve as an isotopic baseline to be used as a comparison to pterosaur isotopic signatures and will provide additional context on the level of variability recorded in 87Sr/86Sr during extended trans-oceanic flying. δ13C, δ15N will be used as a baseline for pterosaur dietary 44Ca/42Ca signals. In Chapter 1, 87Sr/86Sr and δ13C within bone and feather tissues, along with δ18O compositions in bone, were used to understand six differing albatross species movement patterns. Our data showed a strong marine signal in the 87Sr/86Sr bone material, while the feathers showed some pull towards volcanic islands, while δ13C and δ18O within their respective tissues showed partitioning between species in relation to their movement patterns. δ13C, δ15N showed dietary partitioning between species. Chapter 2 shows our pterosaur samples lacking any marine 87Sr/86Sr compositions in both sampled formations across all clades, while our 44Ca/42Ca compositions showed niche partitioning between pterosaur clades. This thesis is the first to apply 87Sr/86Sr methodologies to albatross. It has been shown that 87Sr/86Sr on long-term scales in albatrosses show almost pure marine compositions and lack the nuance of compositions closer to terrestrial values seen within the shorter-term feathers. This baseline has shown that our pterosaur material compositions are not analogous to albatross ecological behaviors, and new thought processes on pterosaur flight behaviors should be explored. Along with this, other clades of pterosaurs should be studied with 87Sr/86Sr to understand the correctness of their modern analogs. Our dietary signals in our albatross samples showed known dietary composition seen in the literature, but it shows that our pterosaur samples, which range across differing clades, should also see partitioning of diets, which we do see. Our pterosaur dietary data shows the usefulness of applying 44Ca/42Ca to the pterosaur fossil record and should be applied to other clades.