Ability to Respond Total:10 / 25Ability to Respond = ( Ease of Response + Tools in Place )
Confidence:High
Confidence Notes:
Impact
Spread
Notes
Score
Spread Rate
Norway rats are prolific. A litter of rats averages around 7 individuals that reach reproductive maturity in 5 weeks and have a gestation period of only 21 days. As a result, the population can grow from 2 to 15,000 within a year.
5
Spread Amount
The Norway rat occurs in all 50 states. They adapt easily to many environments and live in close association with humans. They can be found throughout lowland California in urban and agricultural zones.
5
Damage
Notes
Score
Ecological
Rats can cause significant damage to natural resources, including both flora and fauna. Especially in areas of mild climate, like Hawaii, where rats are not confined to infrastructure, they can pose a significant threat.
4
Agricultural
Can damage many different crops and consume feed in livestock and poultry operations. For outdoor poultry operations, rats may also consume eggs and even small chicks.
4
Infrastructure
Norway rats often burrow, sometimes causing damage to foundations and slabs. Rats commonly chew and gnaw on all types of material, including plumbing, electrical, and drywall. Also, when rats get into attics and their feces/urine/nests ruin insulation.
4
Cultural
Rats are generally seen in a negative light by the public, and as such, people tend to avoid areas high rat density.
1
Health
Rats are hosts to many pathogens, including the trichinella worm, leptospirosis, salmonella bacteria, bubonic plague, and murine typhus fever. Rat bites may cause bacterial rat-bite fever or infection.
4
Benefit
Notes
Score
Ecological
Prey species for raptors, carnivores, and other mesopredators.
1
Agricultural
0
Infrastructure
0
Cultural
0
Health
0
Total
26
Ability to Respond
Ease of Response
Notes
Score
Detection
Due to nocturnal activities they may be difficult to see, but their presence may be detected by feces, chew marks, and partially consumed food stuffs.
2
Control
Extirpation of Norway rats from California is extremely unlikely. Control within specific residences/buildings is attainable, but vigilant monitoring of recolonization is key.
2
Tools in Place
Notes
Score
Entry
Not much exists, vector control and public health mostly, because they are so widely established in CA. Classified as nongame mammals by the California Fish and Game Code.
1
Control
Although control at a broader scale is unlikely, control within the residence is most often attainable. Present populations may be trapped or poisoned, and usually minor efforts, of covering entry points with wire or other barrier to limit buildling access
2
Outreach
Public outreach could be improved in urban areas when people are inadvertently attracting rats (e.g. back yard poultry, exposed compost piles, uncovered trash bins, gardens) and do not know their risk of rat infestation increases with those activities.
