1. Humans, rats and microbes sharing the urban landscape
A multidisciplinary research project on urban rats
Tuomas Aivelo, University of Helsinki
Nina V. Nygren, University of Tampere

2. More-than-human cities
• Humans and rats sharing
habitat for thousands of years
• Rats are one of the most
successful species in urban
areas
• Consequently, the rat is very
(in)famous commensal
Tuomas Aivelo

3. Brown rat (Rattus norvegicus)
• Originally evolved in East Asia
• Spread over the world from
17th century onwards
• Cosmopolitan, though less
common in tropical areas
• Territorial, lives in family groups
Hans-Joachim Pelz

4. Multiple roles of rats
• Synanthropic wildlife
• Experimental animals
• Pets
• Worshipped animals
• Cultural symbols

5. Urban brown rats
• Brown rats present in European cities from
17th century onwards
Puckett et al., 2016
• Replaced black rats in 19th and 20th century
in Finland
• Population sizes and role in urban ecosystem
poorly known
Parsons et al., 2017
• Urban rats have materially shaped our
infrastructures and practices
Hans-Joachim Pelz

6. Why study urban rats?
• Arguably one of the most successful
synanthropic species
• Emotionally and culturally loaded research
subject
• Surprisingly poorly known more-than-human
networks
• Physiologically, developmentally, etc. best
known mammal species
• Environmental, geographical, socio-economic
etc. data readily available in urban areas
• Environmental change could affect rat
populations
Nina V. Nygren

7. Humans, rats and microbes
• Humans and rats partly share symbiont
communities
Himsworth et al., 2013
• Historically rats have spread diseases,
such as plague
• Current potential pathogens: hepatitis E
and Seoul hantavirus
Purcell et al., 2011; Heyman et al., 2004
• Role of antibiotic resistance
Himsworth et al., 2015
Hans-Joachim Pelz

8. Interfaces of human-rat
infections
• When rats are numerous, citizens might
have direct encounters
• Faeces, food contamination
• Via pets, such as cats and dogs
• Professionals encountering rats
• Sewers
Tuomas Aivelo

9. Rat (management) policy?
• Wicked problem
• Urban rat
management networks
• Growing public
awareness of
nonhuman intelligence
and suffering
Nina V. Nygren

10. • Began in January 2018
Otso Huitu, LUKE
Tuomas Aivelo, U. Helsinki
Suvi Huovelin
Tarja Sironen
Windi Musiazari
Nina V. Nygren, U. Tampere
Esa Koskela, U. Jyväskylä
https://www.helsinki.fi/en/
projects/urban-rats

11. Multidisciplinary approach - questions
Disease ecology
• What parasites and pathogens do
rats carry?
• How do rat symbiont communities
vary spatiotemporally?
Population ecology
• How many rats there are in Helsinki?
• How do rat populations vary
spatiotemporally?
Citizen science
• Can rat populations be reliably
estimated via citizen help?
• Are rats suitable study subject in school?
• How do the citizens feel about studying
rats?
Environmental policy
• What kind of networks has rat
management brought into life in
Helsinki?
• How to live with intelligent
disruptive nonhumans?

12. Multidisciplinary approach - methods
Disease ecology
• Carcasses from
extermination companies
• Analysis of helminths,
viruses and bacteria
Population ecology
• Population estimates from
track plates and mark-
recapture Hacker et al, 2016
• Spatiotemporal variation over
the whole city
Citizen science
• Track plates used by students
• Questionnaires and
interviews
Environmental policy
• Interviews of different actors
• Field ethnography on pest
managers, citizens
• Newspaper articles

13. Population estimates
from track plates
• Over 1.000 lower and
upper secondary school
students in Helsinki take
part
• Possibility to have a good
spatiotemporal coverage
• https://five.epicollect.net/
project/helsingin-
kaupunkirotat
Tuomas Aivelo

14. Challenges in studying rats
• Longitudinal studying very difficult
Parsons et al., 2017
• Shame, hate and disgust
• Rats move three-dimensionally – how
to gain access to sewers and tunnels?
• Research ethics
• Disruptive capabilities of rats
Unknown / Helsinki-kuvia

15. Where have you encountered urban rats?

16. References and literature
• Despret, V. (2004). The body we care for: Figures of anthropo-zoo-genesis. Body & Society, 10(2-3), 111-134.
https://doi.org/10.1177%2F1357034X04042938
• Hacker, K.P., Minter, A., Begon, M., Diggle, P.J., Serrano, S., Reis, M.G., Childs, J.E., Ko, A.I., & Costa, F. (2016). A Comparative Assessment of Track Plates
to Quantify Fine Scale Variations in the Relative Abundance of Norway Rats in Urban Slums. Urban Ecosystems, 19(2), 561-575.
https://doi.org/10.1007%2Fs11252-015-0519-8
• Haraway, D. J. (2016). Staying with the trouble: Making kin in the Chthulucene. Duke University Press.
• Heyman, P., Plyusnina, A., Berny, P., Cochez, Artois, M., Zizi, M., Pirnay, J.P., & Plyusnin, A. (2004). Seoul hantavirus in Europe: first demonstration of the
virus genome in wild Rattus norvegicus captured in France. European Journal of Clinical Microbiology and Infectious Diseases, 23(9), 711-717.
https://doi.org/10.1007/s10096-004-1196-3
• Himsworth, C.G., Parsons, K.L., Jardine, C., & Patrick, D.M. (2013). Rats, cities, people, and pathogens: a systematic review and narrative synthesis of
literature regarding the ecology of rat-associated zoonoses in urban centers. Vector-borne Zoonotic Diseases, 13(6), 349-359.
https://doi.org/10.1089/vbz.2012.1195
• Himsworth, C.G., Zabek, E., Desruisseae, A., Parmley, EJ., Reid-Smith, R., Leslie, M., Ambrose, N., Patrick, D.M., Cox, W. (2016). Journal of Wildlife
Disease, 52(2), 418-421. https://doi.org/10.7589/2015-09-238
• Hinchliffe, S., Kearnes, M. B., Degen, M., & Whatmore, S. (2005). Urban wild things: a cosmopolitical experiment. Environment and planning D: Society
and Space, 23(5), 643-658. https://doi.org/10.1068/d351t
• Kirksey, E. (2015). Emergent ecologies. Duke University Press.
• Parsons, M.H., Banks, P.B., Deutsch, M.A., Corrigan, R.F., & Munsi-South J. (2017). Trends in urban rat ecology: a framework to define the prevailing
knowledge gaps and incentives for academia, pest management professionals (PMPs) and public health agencies to participate. Journal of Urban
Ecology, 3(1), jux005, https://doi.org/10.1093/jue/jux005
• Puckett, E.E., Park, J., Combs, M., Blum, M.J., Bryant, J.E., Caccone, A., Costa, F., Deinum, E.E., Esther, A., Himsworth,C.G, Keightley, P.D., Ko, A., Lundqvist,
Å., McElhinney, L.M., Morand, S., Robins, J., Russelll, J., Strand, T.;M., Suarex, O., Yon, L., & Munsi-South, J. (2016). Global population divergence and
admixture of the brown rat (Rattus norvegicus). Proceedings of the Royal Society B: Biological Sciences, 283(1841), 20161762.
https://doi.org/10.1098/rspb.2016.1762
• Purcell, R.H., Engle, R.E., Rood, M.P., Kabrane-Lazizi, Y., Nguyen, H.T., Govindaran, S., St Claire, M., & Emerson, S.U. (2011). Hepatitis E virus in rats, Los
Angeles, California, USA. Emerging Infectious Diseases, 17(12), 2216-2222. https://doi.org/10.3201/eid1712.110482