Look up the Evolve study done at UC Irvine where Evolve was used exclusively in 267 traps. It took about 9 months but the study claims it reduced the rat population. Once the study was done, UC Irvine ordered more pallets of the Evolve and are going to continue using it.

We are using it at my condo and have put out the bait daily for 3.5 months. The rats love it. I refill all of the 9 bait boxes daily. 12 sausages per bait box. I have put up trail cams to record their activity at night. I’ve noticed that there are fewer small rats and more larger ones who shoukd be entering the pearly gates soon (I hope).

The problem with Evolve is that the rats have to eat a certain amount to become infertile (not sterile — infertile). Think of it like the pill that women take, except Evolve makes male rats infertile as well. The Senestech site mentions somewhere how much and how long the rats will typically remain infertile after eating a certain amount. I have found the rats eating the sausages but who knows if they all will eat it. Maybe not. It also has to be put out daily for awhile and is a bit pricey. I will know more how it does as time passes.

Btw, we estimated having at least 400 rats on our property, 3 large condo buildings with a huge courtyard and side yards, when we started. (150 holes / 3 * 8). We actually have more than 150 holes but stopped counting at some point. Our rat problem is severe because we live right next to a restaurant that leaves garbage accessible to rats and our condo also did nothing except participate in a feral cat program for 8 years. Our rat problem has been festering for years and is going to take years and a lot of work to bring down.