Rats and the City: What we learned from alleys

To study Chicago's rats, we teamed up with Landmark Pest Management and went right to the heart of the urban jungle - your friendly neighborhood alley.

 

A typical alley in Chicago. Who wouldn't want to do fieldwork here?

Some blocks have ten times more rat complaints than nearby areas. Our goal was to test what alley characteristics, like food and shelter for rats, might be driving these patterns.

 

These signs indicate alleys where city officials have responded to rat complaints by distributing rodenticide bait.

This was a very different type of habitat survey than we were used to as wildlife ecologists. Instead of walking through forests, a rat safari means taking notes about holes in garbage cans and burrows under dumpsters.

 

Looks like a rat was hard at work here to access something tasty.

 

This burrow entrance is fairly large and very well-used. Bonus points for rat droppings too.

After many conversations about how to measure garbage, we came up with a scoring system for rat attractants like accessible/uncontained garbage, harborage (clutter that rats can use for shelter like debris and vegetation), holes in walls and foundations that permit rat access, and dog waste (did I mention this was glamorous?)

 

In alleys, we measured features we thought would promote rat infestations like accessible garbage (top row), harborage that can serve as shelter (middle row), and the structural integrity of grounds and buildings (bottom row). Alleys that did not have attractants and were in good condition got an overall score of excellent (left column) while alleys with lots of attractants and with holes in walls and foundations got a score of poor (right column).

We found a clear relationship that alleys with more uncontained garbage had more rats and more rat complaints. Not exactly shocking, but important new information for improving rat management and public health!

 

Graph showing an increase in rat complaints with the amount of uncontained garbage.

The clear take-home message is to stash your trash!

 

Next week we'll share what we've learned about the rattiest neighborhoods in Chicago, so stay tuned!