An Investigation of Cattle Birth Seasonality using δ13C and δ18O Profiles within First Molar Enamel

J Towers,A Gledhill,J Montgomery,J Bond

doi:10.1111/arcm.12055

Abstract

Cattle (Bos taurus) are biologically able to breed year‐round, potentially giving farmers the freedom to choose a calving strategy to best meet their economic goals. Thus, an accurate method to determine cattle birth seasonality from archaeological remains would prove to be a valuable tool when investigating a prehistoric farming community. This paper presents the results of intra‐tooth isotope ratio analysis (δ18O, δ13C) of first, second and third molars from 15 cattle. The principal outcome is a possible new approach to determining cattle birth seasonality utilizing both carbon and oxygen isotope ratio measurements of first molar enamel. Although this technique requires verification through more extensive testing, particularly of modern material, initial results suggest that it may produce more accurate predictions of birth seasonality than techniques based on intra‐tooth δ18O measurements of second and third molars.

Highlights

The ability to detect past animal husbandry practices is essential if the economic basis of a prehistoric community is to be understood
By analysing a series of intra-tooth enamel samples extracted along the length of a molar crown from cusp to cervix, the seasonal variation in oxygen isotope ratio can be revealed (Fricke and O’Neil 1996)
This study has introduced a possible new approach to determine cattle birth seasonality that utilises both carbon and oxygen isotope ratio measurements of cattle first molar enamel

Summary

Introduction

The ability to detect past animal husbandry practices is essential if the economic basis of a prehistoric community is to be understood. By analysing a series of intra-tooth enamel samples extracted along the length of a molar crown from cusp to cervix, the seasonal variation in oxygen isotope ratio can be revealed (Fricke and O’Neil 1996). By comparing the positioning of minima or maxima within the second or third molars of a number of cattle present in an archaeological assemblage, seasonality of birth, i.e. whether calving was restricted to a narrow time period or spread across a number of seasons, may be estimated. Cattle molar crown formation can be described simplistically as sequential, progressing from the cusp to the cervix over a period of several months, the actual process is much more complex. By means of detailed radiographic and optical examination of hypsodont molars from goats and sheep, Suga (1982) concluded that enamel mineralization follows two principal phases: matrix deposition and maturation. It is possible that the total length of time required for enamel mineralization is variable within a single tooth, as observed in deciduous bovine incisors (Deutsch et al 1979), and between different teeth of similar crown heights, as observed in equine premolars and molars (Hoppe et al 2004)

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