Rats reveal human history, sometimes set its course

RJ Peltz-Steele CC BY-NC-SA 4.0

A rat extermination program is well signed on the islands of the Azores.

As a tort lawyer, I can be a little obsessed with signs, especially warnings. So I was struck by the abundance of these signs on the islands of the Azores, specifically São Miguel, Terceira, and Pico, where I spent some time this month. The signs warn not to remove bait traps loaded with lethal rodenticide and not to litter, such as might provide food for rats.

Being a key port in the European age of discovery, the Azores are inextricably bound up with the history of human exploration and expansion. A remarkably successful species, rats are a part of that history, because they go where we go. The Azorean bat is the only native land mammal of the Azores. But people long ago brought more, including hedgehogs, rabbits, cats, and the islands' iconic cows, all besides, of course, rats.

The Azorean bat is found in dry forests. In contrast,
I am found here in the much wetter Reserva Florestal
Natural Parcial do Biscoito da Ferraria, on Terceira.
(Photo © Emma Falk, licensed exclusively.)

Unfortunately, the rats are now spreading a potentially fatal pathogen, leptospira, which threatens people and animals in the Azores. So officials have set about efforts to reduce the rat population.

There's been an abundance of research sequencing rat DNA to study the history of human exploration. For example, Gabriel, Mathias, & Searle (2014) studied rats in the Azores specifically. There are books on the history that rats and people share: Anthony Barnett's The Story of Rats (2002) and the New York City-focused Rats (2005) by New Yorker contributor Robert Sullivan. As the latter book suggests, rat research also informs contemporary urban development. Canadian "rat detective" Kaylee Byers wrote a fun first-person narrative for The Conversation (2019) on the value of "23andme" for rats.

Rats have a fan club.

The signs in the Azores reminded me in particular of a superb episode of the Throughline podcast in the spring, "Of Rats and Men," which well summarized the subject.