No, not RATs; the warm-blooded, sneaking rodent kind.
Most folks don't like to talk about it. It's kind of embarrassing. The Bay Area has a rat problem, primarily roof rats (Rattus rattus). I have spent more time studying abatement than I ever imagined or wanted to. Here's the benefit of my research.
Rodent (and pest) control is about reducing shelter and food sources. Although the following information is specific to roof rats, most of the abatement measures are applicable to other species and vermin (including raccoons, skunks, and possums).
Rats can nest hundreds of feet away from their hunting grounds. You have to vigilantly maintain your environment as there is little you can do to control your neighbors. You can tell a pathway by the greasy black trail they leave behind (no, that's not soot from the chimney or traffic exhaust). Rats are agile climbers; they will use service wires and cables to "rope up" into your attic.
They also tunnel. Extensively.
Setting traps on a known path is useless as they are VERY smart and will avoid the traps unless there is no other food source. Look for tell-tale signs of activity: droppings, broken snail shells, half eaten fruit, holes under fences, noises, that smell.
They also tunnel. Extensively.
Setting traps on a known path is useless as they are VERY smart and will avoid the traps unless there is no other food source. Look for tell-tale signs of activity: droppings, broken snail shells, half eaten fruit, holes under fences, noises, that smell.
If you think you have mice, think again. Mice are cute.
Roof rat babies are too. They are born in litters of 6 to 8, and start eating solid food around 3 weeks - which means they are out scavenging. Rattus rattus is thought to reach sexual maturity between 3 to 5 months, but most of what we "know" is from studying domestic lab rats because it is difficult to study rats in the wild.
Humans are the only effective control mechanism. Cats and birds of prey will not dent the population. We make the habitat. We are the only ones who can effectively eliminate an infestation.
There are three variables that affect population: sanitation, proofing, and control.
Control: Control is a polite euphemism for "killing". Even though most people don't like the idea of killing, you will have to engage in control if your property is infested. You will know the habitat is no longer desirable when the traps are clean for 6 to 8 weeks.
Please trap instead of using bait. Rodenticide is highly toxic to birds of prey who eat poisoned rats. If that is not sufficient motivation, they will crawl into an inaccessible location - like your walls - and die. The decaying corpses smell really bad, and it takes about 2 weeks for the odor to go away.
Sanitation: It is vital to maintain continuous good housekeeping in and around buildings or the benefits of all other control and proofing measures will be lost and the pests will return quickly.
Sanitation: It is vital to maintain continuous good housekeeping in and around buildings or the benefits of all other control and proofing measures will be lost and the pests will return quickly.
- Make off-the-ground storage for pipes, lumber, firewood, crates, boxes, and gardening equipment.
- Thin or remove dense vegetation, especially hedges and climbing vines on fences and buildings. Prune tree limbs within 3’ of roof. Plants should be no more than 10" high. Remove species that are known to harbor roof rats in the Bay Area:
- Hedera canariensis — Algerian ivy
- Thuja orientalis — Arborvitae
- Bambusa spp. — Bamboo
- Rubus procerus — Himalayan blackberries
- Lonicera caprifolium — Honeysuckle
- Cupressus sempervirens — Italian cypress
- Populus nigra “Italica” — Lombardy poplar
- Juniperus sabina “Tamariscifolia” — Juniper tams
- Phoenix dactylifera — Date Palm trees
- Cortaderia selloana — Pampas grass
- Trachelospermum jasminoides — Star jasmine
- Frequently collect and dispose of garbage and garden debris in cans with tight-fitting covers. If you compost kitchen scraps, invest in a raised tumbler or line the bin with 1/4" mesh screen.
- Store pet food in rodent-proof containers. Do not free-feed outside. Do not free-feed inside, especially if you have a dog or cat door.
- Roof rats particularly love bird seed. Clean around outdoor feeders and in cages daily.
Proofing: Proofing can be a daunting task, especially when dealing with an infestation. A good service will take care of any clean-up, replace fouled insulation, screen, trap, and guarantee their work for at least 3 years. You need to seal all entry points to your home that are larger than 1/4".
- Seal openings around pipes, cables, and wires that enter through walls or foundation
- Repair/replace ventilation screen around foundation and under eaves
- Repair/replace internal screens on roof and attic air vents
- Put screens on rooftop plumbing vent pipes in excess of 2” diameter
- Put screens on windows that open
- Make sure all doors and windows are tight fitting and weatherproofed at the bottom
- Put a tight-fitting cover over the crawl space
You've heard the phrase "like rats fleeing a sinking ship"? There won't be many left in the house after screening, but be prepared to deal with a red mite infestation when the hosts are gone :/
Aside from rodent borne diseases that infect humans (Hantavirus, bubonic plague, salmonellosis, rat-bite fever), there is a significant risk to household pets. Rats hunt caged birds and carry fleas.
Primary sources and for more information:
UC Davis:
City of Berkeley:
Alameda County Vector Conrtol - will conduct free site assessments!
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