Trinity College Dublin, Ecology and Evolution
The University of Exeter team visited Ireland this week as part of their ongoing investigation into the biology of the Brent Goose. This species has a remarkable migration, spanning from Northern Canada to Western Europe. The team collects DNA samples, blood for stable isotope analysis and various morphometric and behavioural data. We joined them on Wednesday to help out.
Author
Adam Kane: kanead[at]tcd.ie
Photo credit
Adam Kane
The food chain is a concept that many non-biologists are familiar with. Ecologically-speaking, this should be referred to as a food web, because there is rarely one prey species for a given predator or one predator of any given species.
The biochemistry of metabolism and digestion means we can reconstruct the diet of a member of a given food web with some basic information about the stable isotopes in its tissues and the stable isotope values of the available prey. Simply put, “you are what you eat”. Carbon isotopes generally reflect the “where” of the diet and nitrogen isotopes generally indicate the “what”.
This overview omits several complications. Firstly, the calculation of diet requires a “conversion factor” (trophic enrichment factor or TEF) for any given tissue of an animal. Animal metabolisms tend to retain 15N, so consumers have greater 15N:14N ratios than their prey. Secondly, each tissue is likely to have a different TEF, as it is made to perform a different job in the animal. Thirdly, TEFs can only be derived by feeding animals highly controlled diets, ideally a single food for the length of time it takes for the study tissue to be fully replaced. In the case of teeth and bone, this can be months or even years.
As there are relatively few TEFs available for animal species, many ecologists “borrow” TEFs from other species for their calculations. Having derived TEFs for carbon and nitrogen in badger blood serum, a tissue that is completely replaced several times a month, we demonstrated that badger TEFs differ from fox TEFs. This is important, as foxes are similar in size to badgers and have a similar feeding ecology, and ecologists might be tempted to “borrow” fox TEFs to use in badger studies.
So knowing more about the biochemistry of badgers (in the form of TEFs) will allow us to learn more about their diets. This may be of importance to farmers planning biosecurity measures for their farms, as they will be able to learn if badgers are raiding their crops (in the field or in the barn). It will also help identify when badgers are specialising on different foods and potentially allow farmers to minimise contact between badgers and livestock.
Authors
David Kelly: djkelly[at]tcd.ie
Nicola Marples
Photo credit
wikimedia commons
July and August of this year saw members of the Behavioural and Evolutionary Ecology research group embark on another field season studying the birds of tropical south-east Sulawesi, Indonesia. Principal investigators Dr. Nicola Marples and Dr. Dave Kelly were joined this year by PhD student Seán Kelly, as well as a number of undergraduates from the university. This year’s expedition, carried out in collaboration with Operation Wallacea, consisted of two teams: the mist netting team, led by Dr. Marples and Dr. Kelly, and the behavioural team led by Seán Kelly.
The netting team trapped birds using mist nets at various locations on Buton island, mainland south-east Sulawesi and Wangi-wangi island (of the Wakatobi archipelago). While small passerines such as white-eyes, sunbirds and flowerpeckers were the target species, individuals from a total of 35 species were caught. The season proved to be a great success with over 300 birds trapped and processed. Data on plumage, morphology, age, sex and breeding condition were collected from each bird, which was colour-ringed and released unharmed. A small number of body feathers were also plucked from each bird for later genetic and stable isotope analyses.
The behavioural team spent the season on various islands of the Wakatobi archipelago collecting detailed behavioural ecology data on the white-eye, sunbird and flowerpecker species present. This included information on their diets, competitors, preferred habitats, social habits, courtship and breeding, as well as their foraging and flocking behaviours. Data collection took place in the early morning and evening, walking 1 km transects through scrub, farmland or forest edge habitats. This resulted in some fantastic insights into the behaviour and ecology of these poorly studied species.
From analysis of the plumage, morphometric and genetic data we have found a number of significant differences between bird populations on the Wakatobi archipelago and mainland Sulawesi, as well as between populations within the Wakatobi. It is hoped that the behavioural data gathered this season will help us to understand the selective pressures driving this divergence, giving us further insight into the evolution of this region’s fascinating avifauna.
Author
Seán Kelly: kellys17[at]tcd.ie