Calving seasonality at Pool, Orkney during the first millennium AD: an investigation using intra-tooth isotope ratio analysis of cattle molar enamel

Abstract

The identification of dairying is essential if we are to understand economies of the past, particularly in northwest Europe, where a high degree of lactose tolerance suggests that fresh milk has long been a significant food product. This paper explores a possible link between economic focus and seasonality of calving. Although cattle (Bos taurus) can breed throughout the year, animals living in temperate regions with minimal or no human management tend to breed seasonally, their breeding behaviour being strongly influenced by the availability of food. In order to achieve a year-round supply of fresh milk in the past, it is likely that multiple-season calving was necessary, which would have required additional husbandry effort. Alternatively, for meat-focussed economies or those based on storable dairy products, a strategy of single-season calving in spring may have been favoured to maximise the utilisation of spring and summer vegetation. Cattle birth seasonality is investigated through isotope ratio analysis (δ¹⁸O, δ¹³C) of tooth enamel. Results for cattle from Pool, Orkney dating to the latter part of the first millennium AD suggest that calving occurred during at least three seasons implying that the continuous provision of fresh milk was of economic importance.

Keywords:

• Cattle
• Birth Seasonality
• Dairying
• Fresh Milk
• Carbon and Oxygen Stable Isotopes
• Tooth Enamel
• Orkney

Acknowledgments

We are grateful to Tankerness House Museum, Orkney, for permission to sample the cattle mandibles in their collection, particularly Linda Aiano for facilitating the sampling; Andrew Gledhill (University of Bradford Stable Light Isotope Facility) for his invaluable analytical support; Dr Maura Pellegrini of Oxford University for providing an enamel laboratory standard; and Sophie Boual for help with French translation. We are also grateful to Jim Chalmers of Orkney College UHI; Chris Leyland, Chillingham Park Manager; Professor Stephen Hall of the University of Lincoln; and farmers Ronnie Eunson and Tommy and Mary Isbister of Shetland and Cyril Annal, James Foubister, John Mainland and Kenny Meason of Orkney for the useful information they provided regarding cattle husbandry. We wish to thank the Associate Editor and two anonymous reviewers for their suggestions which helped in the revision of the manuscript. This study was part of a Ph.D. project supported by an AHRC Studentship awarded to Jacqueline Towers.