Ancient and modern scats record broken ecological interactions and a decline in dietary breadth of the critically endangered kakapo parrot (Strigops habroptilus)

Threatened animal taxa are often absent from most of their original habitats, meaning their ecological niche cannot be fully captured by contemporary data alone. Although DNA metabarcoding of scats and coprolites (palaeofaeces) can identify the past and present species interactions of their depositors, the usefulness of coprolites in conservation biology is untested as few endangered taxa have known coprolite records. Here, we perform multilocus metabarcoding sequencing and palynological analysis of dietary plants of >100 coprolites (estimated to date from c. 400-1900 A.D.) and > 100 frozen scats (dating c. 1950 A.D. to present) of the critically endangered, flightless, herbivorous kakapo (Strigops habroptilus), a species that disappeared from its natural range in Aotearoa-New Zealand (NZ) after the 13th C. A.D. We identify 24 orders, 56 families and 67 native plant genera unrecorded in modern kakapo diets (increases of 69, 108 and 75% respectively). We found that southern beeches (Nothofagaceae), which are important canopy-forming trees and not an important kakapo food today, dominated kakapo diets in upland (c. >900 m elevation) habitats. We also found that kakapo frequently consumed hemiparasitic mistletoes (Loranthaceae) and the holoparasitic wood rose (Dactylanthus taylorii), taxa which are nutrient rich, and now threatened by mammalian herbivory and a paucity of dispersers and pollinators. No single dataset or gene identified all taxa in our dataset, demonstrating the value of multiproxy or multigene datasets in studies of animal diets. Our results highlight how contemporary data may considerably underestimate the full dietary breadth of threatened species and demonstrate the potential value of coprolite analysis in conservation biology.

Automated summary

Threatened animal species often cannot be found in their original habitats, making it difficult to fully understand their ecological niche using contemporary data alone. However, by analyzing DNA from scats and coprolites, it is possible to identify past and present species interactions of these animals. In this study, the dietary plants of the critically endangered kakapo were analyzed using DNA metabarcoding and palynological analysis. The results revealed previously unknown plant species in the kakapo's diet, indicating that contemporary data may underestimate the dietary breadth of threatened species and highlighting the potential value of coprolite analysis in conservation biology.