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The use of isotope ratios to test for seaweed eating in sheep
Author(s) -
Balasse Marie,
Tresset Anne,
Dobney Keith,
Ambrose Stanley H.
Publication year - 2005
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1017/s0952836905006916
Subject(s) - biology , algae , test (biology) , isotope , ecology , zoology , quantum mechanics , physics
Abstract The primitive sheep of North Ronaldsay Island (Orkney), which feed almost exclusively on seaweed, have developed physiological features linked to that diet. The use of seaweed to feed domestic animals, attested for centuries in north‐western Europe, may have appeared soon after the arrival of the first domestic herds during the 5th and 4th millennia bc . The use of isotope analysis of sheep tooth enamel as a means to investigate seaweed grazing in prehistoric times was tested. The teeth of five modern North Ronaldsay sheep were analysed for carbon (δ 13 C) and oxygen (δ 18 O) isotope ratios. Owing to differences in the δ 13 C of marine vs terrestrial plants, the seaweed‐eating sheep have δ 13 C values clearly outside the range expected for terrestrial plant eaters. Results show that one group of individuals relied exclusively on seaweed throughout the year. In a second group, terrestrial plants provided about half the dietary carbon pool during the summer. In individuals relying exclusively on seaweed, the amplitude of seasonal change in the δ 18 O values of tooth enamel was low, possibly because of ingestion of marine water through fresh seaweed consumption. Analysis of a sheep tooth from the Neolithic site of Holm of Papa Westray (Orkney, Scotland), suggests that as early as at the beginning of the 4th millennium bc in the Orkney, seaweed contributed to the winter diet of domestic sheep.