CathInfo.com

https://sanfrancisco.cbslocal.com/2019/07/24/rat-poison-wildlife-death-rat-population-booming-california-cities/

California is tightening the use of poisons used to kill rats in order to save wildlife including mountain lions, raccoons, etc.

Pet owners complain that coyotes are killing their pets, but coyotes are the chief predators of rats and mice. Therefore, measures to kill coyotes are backfiring as the rat population increases in the cities and suburbs where coyotes coexist with humans.

As a result of coyote control and poison discontinuation, the population of rats is increasing across California especially in San Diego, Los Angeles, and San Francisco where the homeless population is also increasing. California takes better care of illegal migrants than the homeless who have lost their jobs, who are mentally ill, or who are on drugs.

Traditional rat traps do not work very well. Please share any rat traps that you have built yourself.
Here in the foothills, we are plagued with mice, voles, and rats.

Here are some suggestions for  building better rat traps:

https://www.youtube.com/results?search_query=building+better+rat+traps

Here is an inexpensive and simple rat trap that can be built with a 5 gallon bucket, scrap lumber (ramps), glue gun, grain or crackers to use as bait, bottle caps, cardboard, and a few other things found around the house. Pour two inches of soapy water in the bottom of the bucket. The soapy water helps to kill fleas.

This trap is a little expensive at $200.00. However, it works if you live in a rat-infested area where you need to trap seven to 100 rats per night.

The down side is: how do you dispose of all those rats? No solution was given.