Temporal variation in the feeding habits of individual Eurasian otters (Lutra lutra) inferred from stable isotopes in vibrissae

Main area:Ecology
Target group:Biology, Biochemistry
Educational level:Masters, Bachelor
Project description:

The Eurasian otter (Lutra lutra) is a piscivorous mustelid that live in both freshwaters, fjords and coastal habitats. Otters maintain large territories (5 - 40km long) and may alternate between freshwater and marine habitats. Little is known about the dynamics of individual otters’ feeding behaviour and habitat use when living in freshwater-marine habitat systems. Traditional methods and DNA-analyses are not suited to show temporal variations or feeding specialization of individual animals since they only provide snap-shot information of the diet.   

The ratios of stable isotopes of carbon 13C/12C (δ13C) and nitrogen 15N/14N (δ15N) differ in freshwater and marine habitats. Carbon and nitrogen isotopes from the prey are incorporated into the carnivores’ tissues, and a shift in the δ13C and δ15N values occur in each step in the food chain. Thus, the temporal variation in feeding behaviour of individual animals can be assessed through stable isotope analysis of continuously growing and inert tissues such as vibrissae.  

In Denmark, otters inhabit closely associated freshwater and marine habitats. The temporal and individual variations of otters’ diet coastal habitats are examined in vibrissae. The vibrissae from individual otters are sectioned into 2-3 mm long segments and analysed for δ13C and δ15N using a mass spectrometer coupled to an elemental analyzer. The variability of the diet is assessed through chronologically ordered stable isotopes data.

Vibrissae has been sampled from road-killed otters collected in Denmark by Dept. of Bioscience, Aarhus University. The isotope analyses will be performed at Terrestrial Ecology Section, Dept. of Biology, University of Copenhagen.

Supervisors: Anders Michelsen, BIO/KU (andersm@bio.ku.dk) and Morten Elmeros, BIOS/AU (elm@bios.au.dk).

Methods used:Sectioning of hair (vibrissae) of otter, preparation for stable isotope analysis, CN isotope analysis
Keywords:Aquatic biology, Diet of otters , Freshwater and marine animal, Stable isotopes, Denmark
Supervisor(s):  Anders Michelsen