Annual Meeting 2025

For two days last month, the RATTUS project had its annual meeting for year 3. This marked the half-way point for the project. We each presented results, methods and quandaries to our advisory board and other guests. The days were packed with ratty discussions of great variety - so what did we actually talk about? What have we been doing these last two years? This post is a brief summation of what went down at the ‘Y3’ annual meeting.

Zooarchaeology & ZooMS - Michelle & Sam

 
The zooarch aspect of the meeting was about morphological identification of rat bones, and whether metrical analysis can be used to underpin the observations currently found in the literature. To date there doesn't appear to be a consistent nomenclature for the different measurements taken on rat/rodent bones, even if the measurements themselves are the same. As my job so far has been focused on sourcing and recording samples for further analysis, and collecting a huge dataset of measurements, we’re only just getting around to really understanding what we’re going to do with the measurements we have, and so the meeting was a great place to hash out where we need to be heading in the next few months. We’re aiming for an inter/intra-observer variability study, or a pilot project to something bigger down the road, and an examination of morphological ID’s that can tie-in with the ZooMS work that Sam has been doing. It was an incredibly helpful exercise, but for now it’s very much ‘watch this space’.

Figure 1: Measuring mandibles. Image credit: Alex Holland.

The ZooMS updates covered all of the new species that have been added to the database since the beginning of the project. This has been used to help develop the black rat and brown rat sampling strategies, allowing us to sample postcranial material, rather than relying on morphologically identifiable cranial elements. There are still a few more species that we’d like to track down, although we are now concentrating on rat-sized species only from the areas we have actual samples from. In addition to the new species, we have also run over 500 archaeological samples, with still many more to come.

Stable Isotopes - Alice

During the recent project meeting I shared some early findings from the ongoing isotope analysis for the RATTUS project. We are analysing carbon and nitrogen isotopes in bones from rats and other comparable fauna to explore rat diet, adaptation, and how these animals lived alongside humans. For isotope analysis, our study is focussed on Medieval and Post-Medieval sites in Britain, as well as Post-Medieval sites in the Netherlands, with the aim of comparing rats from different types of settlements and time periods.

So far, the data is showing promising patterns which were shared and discussed with the group. Despite their small size, rat bones have turned out to be excellent for this kind of analysis, consistently yielding high-quality data.

 

Figure 2: Sampling a rat femur bone for isotope analysis.

We are seeing isotopic differences between settlement types across Britain and the Netherlands (e.g. ‘urban’ vs ‘rural’) and some interesting contrasts between black and brown rats in Amsterdam. One of our largest samples comes from Post-Medieval contexts at Wharram Percy in the Yorkshire Wolds, where I’ve analysed over 60 brown rats. Interestingly, their isotopic values are quite uniform, suggesting a limited dietary range.

Figure 3: Wharram Percy Paul Allison, CC BY-SA 2.0, via Wikimedia Commons.

  

We’re also using isotope data to support radiocarbon dating. During the meeting we had a productive discussion about the impact of reservoirs of “old” carbon in the environment, which can affect radiocarbon dating, making samples appear older than they really are. A recently analysed case from a site in Poland provided a great example, and helped us refine our approach to dealing with these challenges in future analyses.

History - Daan

I used the opportunity of the annual meeting to take a look back at the last year and a half of my research at RATTUS and take stock of what I’ve found so far in digital and physical archives. My initial search through archives was based on a few assumptions: Rats would be most likely to be written about in cases where they were causing (financial) issues; and the most likely places to look was large organisations that dealt in processing or shipping edible resources and had to maintain decently sized bureaucracy that produced and kept records. This guided me to look through financial archives of churches, orphanages, port authorities, breweries, merchant records and local ordinances in London and Amsterdam. Unfortunately, all these sources seem remarkably silent on the topic of rats, vermin or losses due to animals… For now, I suspect this might be because rats were an acceptably small problem that rarely needed explicit mention in administration.

Figure 4: A Dutch merchant’s expense books - unfortunately devoid of rat-related expenses.

Instead, I’ve found quite a few newspaper articles that mention rats: advertisements for rat poisons, unusual rat sightings, stories involving rat catchers, and so on. Notary records include stories of shippers whose cargoes have been eaten up by rats. Other court records have incidental mentions of rats, which can be extremely useful for inferring information about rats. Various government documents discuss rat problems, such as when rats climbed out of London’s new sewers and into people’s toilets in the 19th century, or the many issues the Royal Navy had with rats. Even the patent office shows us some glimpses of 19th Century traps, live or otherwise, for dealing with rats. A lot of these finds wouldn’t have been possible without the amazing work being done in archives in England and especially in the Netherlands of digitising and applying Handwritten Text Recognition software to make these sources fully searchable for particular keywords.

 

Figure 5: The Complete Vermin-Killer (1777) provides various recipes that are supposedly sure-fire ways to deal with rats. As you can see, the first recipe is meant to kill mice and rats, while the second would chase them away.

The next step with all this data is to start contextualising and analysing it, asking both what it might tell us about how people perceived, worried about or dealt with rats, and what it might tell us about the rats themselves: how rats were adapting to human rat-catching strategies as well as other human behaviours and infrastructures.

aDNA - Ele

The ancient DNA work for the project is split into two main projects focusing on our two main species. The discussions of the black rat project really focused on our sample design as we have three main goals. First, we are looking for broad patterns in rat populations. For example, we know that there was an early population collapse around the end of the Roman Empire, but the rats had repopulated Europe by the medieval period. But what was the source of this repopulation? Was it just one event or several? Second, in an ambitious attempt to investigate rat connectivity, we are aiming to collect samples from a wide geography all dating to around the 14th century. Third, we also have a number of case study sites which have rats from contexts before and after the Black Death. Perhaps we will be able to use these samples to see what impact exposure to Yersinia pestis had on rat populations.

 

Figure 6: A depiction of our black rat sample design. 

The brown rat project focuses on phylogeography to untangle the routes that brown rats took to enter Europe a few centuries ago. For this, we need a good spread of brown rat samples from across Europe. We have also collected specimens from Africa, America and Asia to get a comprehensive picture of brown rat movement. Due to the difficulties in getting an accurate radiocarbon date for archaeological remains between about 1650 and 1950, I have been extracting DNA from museum specimens. This has been really interesting because museums often preserve soft tissue as well as bone, which is my usual medium. So, I have been extracting DNA from all kinds of different tissue types, including skin, fur, tails, toes, claws and “osteocrusts” (scrapings of dried tissue). We have almost finished our sample collection, with just a couple of applications still in place, and I am in the midst of brown rat lab work which I am enjoying very much!

Figure 7: Some of the different rats Ele has encountered in museums.

  

Looking ahead - David

The project meeting was a great chance to take stock of the team’s progress so far, and to talk over the remaining gaps – and options to fill them – as we start to wrap up the sample/data collection phase of the project. But it was also a chance to look forward to the next stage of the project, when we move from data gathering to data analysis and interpretation in earnest. In particular, years four and five will see the final methodological strand of the project come online: mathematical modelling of rat populations. Around the same time as the annual meeting, I and Pen Holland from the Biology department here at York were also busy completing the recruitment process for the fourth and final RATTUS post-doc, who will work closely with Pen on this aspect of the project. I’m happy to report that we can now announce a name: Henry Fell will be joining us from November to start modelling the ebbs and flows of rat populations over the past couple of millennia, and the various environmental and anthropogenic factors that may have influenced them. Henry has a broad interdisciplinary background in modelling of ecological systems and a particular interest in plague that will surely tie in well with RATTUS.

 

 

Figure 8: the RATTUS core team and the advisors who could attend in person.