How many rats there are in Helsinki? Where do they live? How do the population sizes vary between summer and winter? Do rats in Helsinki breed around the year? How much does the coldness of winters impact rat populations? By using track plates and live-trapping, we aim to understand the spatio-temporal dynamics of urban rat populations. These can be then combined to environmental data readily available for the urban area.

Urban areas can create dispersal barriers between rat populations. With modern genetic tools, we can assess the gene flows between different rat populations in the city and also compare Helsinki rats to rat populations in other cities. Where have our urban rats migrated from? No one knows, but aim to figure that out.

Rats have a reputation of being dirty and disease-ridden animals. While they are substantial disease and parasite sources in warmer region, there is less research done in rats in boreal regions. We don't know which parasite species the rats are carrying and whether they could infect pets or humans, but our parasite surveys will at least give some idea what there is. Parasite dynamics can then be analyzed in the context of spatial and temporal variation in the host populations.

We are just beginning to understand the diversity of viruses carried by boreal rodents. While stereotypically tropics are more known to zoonotic diseases, Finnish rodents spread for example Puumala virus, potentially lethal pathogen. We will assess the viral and bacterial species carried by rats in collaboration with zoonotic virologists.

Rats are well-known urban dwellers. Most people have their own personal stories about rats in Helsinki. While they are not as numerous as in many cities, they can be often seen in certain places. People also have strong feelings towards the rats, which makes them an interesting topic of citizen science. How do the citizen scientists feel about rats? Do their attitudes change when they assist in research with urban rats?