7A Ch16 Cheat Sheet: Rats

🎯 Top 5 Traps

1

Norway rat droppings are 3/4 INCH long. A single rat produces about 50 droppings DAILY. Highest concentrations where rats rest or feed. FRESH = black, glistening, PUTTY consistency. OLD = dry, hard, dull, gray, crumbles. Old droppings moistened by rain may LOOK fresh — crush to test (old crumbles, fresh feels like soft putty). Compare: mouse droppings are 5/16 inch.

2

An adult rat can squeeze through an opening only 1/2 INCH HIGH after gnawing. Their incisors grow 5 INCHES PER YEAR. They gnaw through cinder block, aluminum siding, sun-dried adobe, wallboard, wooden cabinets, LEAD SHEATHING, and plastic and LEAD PIPES. Gnawed holes are 2+ inches in diameter. Repair gnaw holes with COPPER WOOL. Floor drains need sturdy METAL GRATES held firmly in place.

3

Rats are NOT rabies carriers — the US Public Health Service recommends AGAINST anti-rabies treatments for rat or mouse bites. Rabies transmission from rats to humans has never been documented in the US. Rats DO carry: plague (Oriental rat flea), murine typhus (rat flea feces), rat-bite fever (teeth/gums bacteria), salmonella (droppings on food), leptospirosis/Weil's disease (urine in water/food), and trichinosis (nematode via pork-fed hogs eating rat droppings).

4

NEOPHOBIA + sub-lethal poisoning drive BAIT SHYNESS. HOARDING means rats may move toxic bait into LABEL-PROHIBITED locations. Rats avoid new objects (bait stations, traps, blocks of wood) for days. If a sub-lethal dose makes a rat ill, it AVOIDS similar baits/stations forever — and teaches its young. Hoarding has two consequences: rats may move toxic bait where the label does not permit it, AND a baiting program becomes ineffective when rats hoard bait while feeding on regular food.

5

Rat-proofing ("BUILD THEM OUT") is the most successful LONG-TERM control. TRACKING POWDER is the only formulation that works when food and water are plentiful and rats are bait/trap shy — but it is 5 to 40 TIMES MORE CONCENTRATED than baits. Tracking powder relies on rats licking it from their fur during grooming. Apply heavier than insecticide dust but NEVER deeper than 1/8 inch. Do NOT use in suspended ceilings, around air ventilators, or near food/food preparation areas — drift risk.

🔢 Numbers You Must Know

Number

What It Represents

1/2 inch

Smallest opening height through which an adult rat can compress and squeeze (after gnawing)

3/4 inch

Norway rat dropping length AND track footprint length (mouse droppings = 5/16 inch)

50 droppings daily

Single rat output — concentrate where rats rest or feed

5 inches per year

Rat incisor growth rate — drives constant gnawing to keep teeth worn down

20 young per year

Mature female reproduction (4 to 6 at a time) — average field lifespan less than 1 year

4 to 5 weeks

Age of weaning (~1.5 oz); independent at 3 months; learn bait/trap avoidance from mother

1 ounce food / 1/2 to 1 fluid oz water

Daily intake — water dependence drives nest site selection

100 to 150 feet

Typical foraging range from nest — outdoor colonies forage indoors 100 ft away

Up to 20 acres

Home range when "hotel" secondary nest sites are included

30 to 45 feet

Limit of rat vision — nearly color-blind, react to shapes and movement

Less than 18 inches deep / less than 3 feet long

Norway rat outdoor burrow dimensions; openings 2-4 inches diameter; have "bolt holes" for emergency escape

3 ft up / 4 ft horizontal / 50+ ft fall

Athletic capabilities — leap, climb 3-inch pipe outside or 1.5-4 inch inside, swim half-mile, tread water 3 days, fall 50 ft and survive

1/8 inch maximum

Tracking powder application depth — heavier than insecticide dust but never deeper than 1/8 inch

5 to 40 times

Tracking powder rodenticide concentration vs. food baits — much more potent, much more drift risk

15 to 50 feet apart

Effective bait box spacing

10 to 20 feet apart

Snap trap spacing along runways when activity sites are uncertain

12 by 4 inches

Tracking PATCH (non-toxic dust like talc, clay, powdered limestone) — distinct from tracking POWDER

18 to 24 inches

Pallet distance from side walls in warehouses — permits inspection and cleaning around stored food

🔀 Easily Confused

Pair / Group

Distinguishing Feature

Norway rat dropping vs Mouse dropping

Norway rat: 3/4 inch long. Mouse: 5/16 inch. Single rat = 50 droppings/day. Both: fresh = black, putty consistency; old = dry, dull, crumbles. Distinct rat odor can also be distinguished from mouse odor with practice.

Tracking patch vs Tracking powder

Tracking patch: NON-TOXIC inert dust (clay, talc/unscented baby powder, powdered limestone) — 12 x 4 inches — to detect tracks. NEVER use flour (attracts insects). Tracking powder: DILUTED RODENTICIDE in dust form — kills rats when they groom. 5-40x more concentrated than baits. DO NOT use a tracking powder to make a tracking patch.

Plague vs Murine typhus

Both transmitted by rat fleas. Plague: bacterial; flea bites infected rat then INOCULATES human directly through bite; bubonic = sudden fever + swollen lymph nodes; pneumonic = highly contagious + often fatal; reservoir in some western US wild rodents. Murine typhus: flea FECES SCRATCHED into bite wound (not inoculated by bite itself); milder disease; California, southeastern, Gulf Coast.

Leptospirosis vs Trichinosis

Leptospirosis (Weil's disease): rat URINE in water or food; enters through mucous membranes or cuts; mild → high fever, jaundice, kidney failure. Trichinosis: NEMATODE (roundworm); rats spread when hogs eat food contaminated with rat droppings; humans get from undercooked PORK; vomiting, diarrhea, abdominal pain.

Rat-bite fever vs Rabies

Rat-bite fever: REAL — bacterium in rat teeth/gums; mild flu-like symptoms but can be fatal, especially to infants. Rabies: rats DO NOT carry rabies in US. US Public Health Service recommends AGAINST anti-rabies treatment for rat/mouse bites. Critical for client communication.

Anticoagulant vs Acute single-dose rodenticide

Anticoagulant (warfarin family — 1940s): multi-feeding required for first generation (warfarin, coumafuryl, chlorophacinone, diphacinone, pindone, valone); single-dose newer ones (brodifacoum, bromadiolone). NO bait shyness. ANTIDOTE = VITAMIN K. Acute non-anticoagulants: bromethalin, cholecalciferol; zinc phosphide is single-dose, somewhat poisonous to all vertebrates, NEVER mix bare-handed (wear gloves).

Bait box vs Bait tray / flimsy plastic station

Tamper-proof bait box: child/pet cannot reach bait but rat can. Usually metal or heavy plastic. SECURED to floor/wall/ground. Clearly labeled with precautionary statement. Bait trays + flimsy plastic/cardboard stations: NOT tamper-proof. Do not satisfy label "tamper-proof" requirements.

Snap trap trigger placement

Place TRIGGER SIDE next to the wall. Rats step on it during regular travel along walls. Use EXPANDED TRIGGERS (treadles) set for light touch. Best baits: peanut butter, hot dog slices, bacon, nutmeats. TIE bait to trigger with string or dental floss. Sprinkle cereal/oatmeal around traps.

Insecticide odor vs Trap effectiveness

Avoid spraying insecticide on/near traps OR storing traps with application equipment. Rats can taste chemicals at PARTS-PER-MILLION concentration — insecticide odor causes them to steer clear. The odor of OTHER RATS, however, IMPROVES a trap's effectiveness.

Rat infestation level: Medium vs High

Medium: old droppings + gnawings; 1-2 rats at NIGHT; no rats in daytime. High: fresh droppings, tracks, gnawings; 3+ rats at night; RATS SEEN IN DAYTIME (key high-infestation indicator).

Active vs Inactive burrow test

Fill burrow opening with WADDED-UP NEWSPAPER or a few leaves and cover with loose soil. Active burrow: rats reopen and clear the hole OVERNIGHT. Look for: opening free of dirt/debris, smooth hard-packed soil, rub marks, fan-shaped soil pushed out.

🦠 Rat Diseases Quick Reference

Disease

Transmission

Key Facts / Symptoms

Plague

ORIENTAL RAT FLEA bites infected rat, then inoculates human

Black Death of Europe (14th century, 25 million deaths). Reservoir in some western US wild rodents. BUBONIC: sudden fever + swollen lymph nodes. PNEUMONIC: highly contagious + often fatal. Last major US urban outbreak: 1924.

Murine typhus

RAT FLEA FECES SCRATCHED into flea-bite wound

California, southeastern + Gulf Coast states. Relatively MILD in humans. Symptoms: fever, severe headache, rash.

Rat-bite fever

Direct rat BITE — bacterium in teeth/gums

Most bites in inner cities; infants and bed-confined elderly bitten in face while sleeping. Mild flu-like symptoms but can be FATAL, particularly to infants.

Salmonella food poisoning

Rat DROPPINGS contaminate stored food, dishes, food preparation surfaces

Symptoms: headache, stomach pain, diarrhea, low-grade fever. Bacteria thrive in rat intestinal tracts and in the sewers/garbage they frequent.

Leptospirosis
(Weil's disease)

Rat URINE in water or food; enters through mucous membranes or skin cuts/abrasions

Mild aches/pains/fever to high fever, jaundice, aseptic meningitis, acute kidney failure, internal bleeding, occasionally death. Seldom fatal in mild form.

Trichinosis

NEMATODE (roundworm) — humans get from raw/undercooked PORK contaminated with the worm

Rats spread by hogs eating food/garbage contaminated with infested rat droppings. Symptoms: vomiting, diarrhea, abdominal pain.

Rabies

NOT a rat-borne disease in the US

Rats in native habitats have NOT been found infected with rabies. Rabies transmission from rats to humans has NEVER been documented in the US. US Public Health Service recommends AGAINST anti-rabies treatments for rat or mouse bites.

🛠️ Rat Control Tools Quick Reference

Tool

When / How

Key Notes

Sanitation

Foundation of every program. Close/repair dumpsters; clean food spills; remove bird feeder + doghouse food; pallets 18-24 in from walls; first-in/first-out rotation.

Baiting programs FAIL if rats have abundant regular food. Reduce normal food supply to make baits competitive.

Rat-proofing (exclusion)

BUILD THEM OUT — most successful long-term form. Seal cracks, holes, openings around pipes/wires. Caulk doors (especially threshold). Repair foundation breaks below ground level. Floor drains: sturdy metal grates.

Repair gnaw holes with COPPER WOOL. Without exclusion, rats reinfest after every knockdown. The only durable control.

Snap trap

Best when rodenticides are too risky, dead-rat odor in walls would be unacceptable, or only a few rats in limited area. Use EXPANDED TRIGGERS, light touch. Trigger side AGAINST wall. Bait: peanut butter, hot dog, bacon, nutmeats — TIED to trigger.

Use ENOUGH traps (12 for house, 100 for warehouse). Set 3 in a row. Leave baited but UNSET first few days. Avoid insecticide on/near traps. Rat odor IMPROVES trap effectiveness.

Glue board

Use larger boards designed for rat size. Place lengthwise FLUSH along wall. Secure with nail/wire so rat can't drag away. Add dab of bait at center.

NOT over food preparation areas. May be considered inhumane. Install in bait stations if children/pets nearby. Check frequently and dispose humanely.

Food baits

Pellets, dry meal, paraffin blocks (wet sites), 45-lb tubs, "place packs" < 1 oz. ANTICOAGULANT (warfarin family) requires multi-feeding for older formulations; single-dose options (brodifacoum, bromadiolone). ANTIDOTE = VITAMIN K.

Place in TAMPER-PROOF BOXES (metal/heavy plastic, secured to floor/wall) when children/pets/wildlife could access. 15-50 ft apart. Limit normal food supply or baits will be rejected. Leave box in place once accepted (neophobia).

Water baits

Rodenticide mixed with water. EXTREMELY effective when rat water supplies are short. Liquid dispensers (best are custom-designed; plastic chick-founts can be used in protected sites).

USE ONLY where no other animals or children can get to them. Highly accessible to non-targets if not protected.

Tracking powder

Rodenticide on talc/clay carrier. Rat licks from fur during grooming. Apply heavier than insecticide dust but NEVER deeper than 1/8 inch. Best sites: wall voids, around rub marks, along pipe/conduit runs, dry burrows (if label permits).

5-40x more concentrated than food baits. ONLY tool that works when food/water plentiful and rats are bait/trap shy. DO NOT use in suspended ceilings, around vents, or near food (drift risk). Acute or slow-acting poisons available.

💡 Memory Hooks

Squeeze rule: "1/2 inch is all they need." Smallest gnaw-then-squeeze opening for an adult rat.

Norway droppings: "3/4 inch and 50 a day." Distinguishes from mouse (5/16 inch) and signals active feeding/resting hot spots.

Rabies myth: "Rats don't carry rabies — Public Health says no anti-rabies treatment." Critical client communication point.

Trap baits + orientation: "Hot dog and peanut butter, tied to the trigger, trigger side to the wall." Standard snap trap setup.

Anticoagulant antidote: "Vitamin K saves the dog who ate warfarin." Critical safety fact for accidental pet exposure.

Tracking powder superpower: "Tracking powder works when nothing else does — but never near food." 5-40x more concentrated than baits; drift is the major risk.

Long-term control: "Build them out." Without exclusion (copper wool gnaw repair, metal floor grates, sealed entries), rats return after every knockdown.

Daytime rats = high infestation: "If you see rats in daylight, the population is high." Key infestation-level indicator.

Patch vs Powder: "Patch = baby powder for tracks; powder = poison." Tracking patch is non-toxic detection; tracking powder is rodenticide.