Abstract
Over the past 1000 years, rats (Rattus spp.) have become one of the most successful and prolific pests in human society. Despite their cosmopolitan distribution across six continents and ubiquity throughout the world's cities, rat urban ecology remains poorly understood. We investigate the role of human foods in brown rat (Rattus norvegicus) diets in urban and rural areas over a 100 year period (ca AD 1790–1890) in Toronto, Canada using stable carbon (δ13C) and nitrogen (δ15N) isotope analyses of archaeological remains. We found that rat diets from urban sites were of higher quality and were more homogeneous and stable over time. By contrast, in rural areas, they show a wide range of dietary niche specializations that directly overlap, and probably competed, with native omnivorous and herbivorous species. These results demonstrate a link between rodent diets and human population density, providing, to our knowledge, the first long-term dietary perspective on the relative value of different types of human settlements as rodent habitat. This study highlights the potential of using the historical and archaeological record to provide a retrospective on the urban ecology of commensal and synanthropic animals that could be useful for improving animal management and conservation strategies in urban areas.
Highlights
Rats (Rattus spp.) have played an important role in many dimensions of human life
The history of rat dissemination remains sketchy and basic questions persist unanswered, such as, when, where, and which rat populations were involved in early migrations and what aspects of human settlement were most facilitative to their spread [6,7]
By comparing stable carbon (d13C) and nitrogen (d15N) isotopic compositions of zooarchaeology by mass spectrometry (ZooMS)-confirmed rat bone collagen from sites associated with different kinds and intensities of human activity, this research aims to investigate the relationship between rat behaviour and human population density in two key areas: (i) the ways in which rat diets differ with proximity to human settlement density; and (ii) whether rats living among denser urban populations enjoy higher quality diets more consistently than their rural counterparts
Summary
Rats (Rattus spp.) have played an important role in many dimensions of human life. Considerable attention has been paid to how the global dissemination of rats, especially black (Rattus rattus), brown (Rattus norvegicus), and Pacific (Rattus exulans) rats, have been implicated in broad scale environmental destruction [1], the spread of deadly zoonotic diseases that pose significant global health risks [2], and the billions of dollars spent annually on pest control [3,4]. Beyond a general understanding of how rats have followed humans owing to the valuable habitat (i.e. food and shelter) that human-structured ecosystems provide, relatively little is known about how and why rats have been so successful at exploiting their relationship with humans at different temporal and spatial scales [5]. In this context, the history of rat dissemination remains sketchy and basic questions persist unanswered, such as, when, where, and which rat populations were involved in early migrations and what aspects of human settlement were most facilitative to their spread [6,7]. Because rats were often one of the first invasive mammalian species to be introduced by humans to many regions of the globe, a better understanding of their early ecology may
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