Rethinking established methodology in micromammal taphonomy: archaeological case studies from Orkney, UK (4th millennium BC – 15th century AD)

Abstract

Micromammals (e.g. rodents, shrews), characterised by their small size, short lifespan and high reproduction rate, are known for rapid adaptability to changing conditions, inhabiting all environments besides the most frigid. They form a variety of relationships with other animals as well as humans, from being prey up to mutualism, commensalism and even taming and domestication. Changes occurring short or long-term within micromammal populations can be a useful proxy for natural as well as human-induced changes. However, their remains from archaeological contexts have seldom been investigated, with a scarcity of methodological studies and incomparability of published data often discouraging research.

Human impact on the environment is especially noticeable in the case of insular environments where humans are responsible for the majority of species introductions. This thesis examines a series of case studies from the Orkney islands off north-east Scotland to develop a micromammal zooarchaeological methodology and investigate the micromammal relationships with predators and human activity in this context. Specifically it has two main aims: 1) perform methodological research on obtained data to investigate established methods as well as to suggest new approaches to data analysis given what data are retrievable from studied assemblages; 2) apply the revised methodology to investigate a range of Orcadian sites, covering two main time periods of intensification of maritime contacts: Neolithic (4000 – 2000 BC) and Norse/mediaeval (600 – 1500 AD) ages. Analysis standardisation and reproducibility through coding in R is also introduced to deal with the large breath of obtained data.

The study provides conclusive results, broadening the understanding of micromammal taphonomy and a range of different assemblages and deposition patterns present within and around anthropic contexts. The breath of utilizable data retrievable from micromammal assemblages is comparable with typical zooarchaeological research on the remains of bigger species, for example including information on age of death or non-predatory taphonomic factors. Spatial and contextual data, particularly, proves to be crucial for understanding the impact of dispersal and burial processes on micromammal accumulations. Moreover, the necessity for consistent sieving is confirmed, lower effort sampling or sieving regimes failing to provide representative and comparable samples. The obtained data can be effectively analysed through statistical methods, including classifying algorithms, bypassing problems encountered in the case of multiple comparisons and deposition patterns. However, the results also show that actualistic research may not be directly comparable with archaeological material without considering non-predatory taphonomic factors and their impact on data representativeness.

Assemblages identified within the studied sites seem to be formed by a variety of factors. Identifiable predatory depositions could be attributed to both owls and diurnal raptors, taxa expected to be found considering modern Orkney fauna and dominant micromammal predators. Cases of non-predatory depositions included deaths of commensal species living and/or nesting within the anthropic environment, self-entrapment in anthropic features such as trenches or pits of single individuals and secondary accumulation in similar features due to dispersal. In general, each site shows multiple different patterns being present, with certain areas or context types (e.g. open/enclosed, natural/usage period/abandonment) exhibiting a predominance of a specific deposition. Intrusiveness is surprisingly rare and, where identified, is characterised by multiple intrusive species within the contexts, with singular species intrusiveness rarely being noted. Some evidence for human interaction with micromammals, direct or indirect, can be noted through additional taphonomic marks such as burning. However, a definitive interpretation of these marks, as of now, cannot be achieved.