How quickly can you deal with rats in Hertfordshire?

We aim to attend rat call-outs same-day or next-day across Hertfordshire. Call 01727 601 007 and we'll give you an honest arrival window rather than an open-ended slot.

How many visits does rat control usually take?

Most domestic rat jobs are resolved over two to three visits — an initial treatment and survey, then follow-ups to confirm activity has stopped and to complete proofing.

Do rats really come up through toilets?

It is uncommon but genuinely possible. Brown rats swim well and can travel through drain runs; a defective or disused connection is almost always the underlying cause.

Is rodenticide safe around children and pets?

All bait is placed in locked, tamper-resistant stations positioned out of reach, and we will use trapping instead wherever bait is unsuitable. You'll be briefed fully before anything is placed.

Why do rats keep coming back after treatment?

Because the route in was never closed. Killing rodents without proofing and drainage repair only creates a vacancy — our jobs are not signed off until the entry point is resolved.

HPE Species Library

Brown rat

Rattus norvegicus

The UK's most common commensal rodent — an adaptable burrowing mammal that follows drains, food waste and warmth into Hertfordshire homes and businesses.

01727 601 007 Identify my pest

Quick facts

Adult weight: 300–500g
Litters per year: 3–6
Gap needed to enter: 15mm
Peak season: Autumn–winter

Also known as: Common rat, Norway rat, Sewer rat

Species at a glance

High risk

Scientific name: Rattus norvegicus
Alternative names: Common rat, Norway rat, Sewer rat
Average size: 20–27cm body, tail slightly shorter
Average weight: 300–500g
Activity: Nocturnal
Diet: Omnivorous and opportunistic. Cereals, food waste, pet food, bird seed, fallen fruit and compost make up most of the urban diet. An adult rat needs roughly 30g of food and 60ml of water a day, and will readily cache food near the nest.
Typical habitat: Burrows, drains, sub-floor voids and loft spaces
Active season: Year-round, peaking autumn to winter

Why the high risk rating: Disease carriage, contaminated food and gnawed electrical cable.

About the brown rat

The brown rat is not native to Britain. It arrived on trading ships from Asia and Russia in the early 1700s and rapidly displaced the smaller black rat. It is a burrowing, neophobic and highly adaptable mammal that lives wherever people concentrate food, shelter and water. In Hertfordshire it is found in sewers and drain runs, railway embankments, riverbanks, farm buildings, decking, garages and — when the weather turns — inside cavity walls and lofts.

Diet: Omnivorous and opportunistic. Cereals, food waste, pet food, bird seed, fallen fruit and compost make up most of the urban diet. An adult rat needs roughly 30g of food and 60ml of water a day, and will readily cache food near the nest.
Breeding: Sexually mature at around 10–12 weeks. A female can produce 3–6 litters a year of 6–11 young, meaning a single undisturbed pair can generate several hundred descendants within a year under good conditions.
Lifespan: Typically 9–18 months in the wild; up to 2–3 years in exceptionally sheltered conditions.

How to identify it

Body 20–27cm with a thick, scaly tail slightly shorter than the body
Coarse grey-brown fur, paler underside, blunt nose and small ears relative to the head
Adults typically 300–500g — far heavier and stockier than a house mouse
Droppings 15–20mm, dark, spindle-shaped and tapered at one end

Signs, behaviour and where they live

Signs of activity

Dark, tapered droppings clustered along walls, in cupboards or in loft insulation
Greasy smear marks where fur repeatedly rubs beams, pipes and joists
Gnaw damage to cables, plastic pipework, food packaging and timber
Scratching or heavy scurrying overhead at night — heavier than a mouse
Burrow holes 60–90mm across near sheds, decking or garden walls
A strong, persistent ammonia-like smell in enclosed voids

Behaviour

Primarily nocturnal, most active in the hours just after dusk
Neophobic — suspicious of new objects, which is why bait take can be slow at first
Strong swimmers, able to travel through drainage systems and enter via toilets
Follow established runs along walls and edges, leaving greasy smear marks
Gnaw constantly to keep continually growing incisors in check

Where you'll find them

Burrow systems beside sheds, decking, compost heaps and garden walls
Defective or unsealed drain runs, inspection chambers and disused pipework
Sub-floor voids, cavity walls, loft insulation and boxed pipe runs
Commercial bin stores, food-waste areas and external service ducts

Seasonal activity in Hertfordshire

Twelve-month activity profile for brown rats, based on our Hertfordshire call-out records.

LowModerateRisingHigh

January: Moderate activity
Jan
February: Moderate activity
Feb
March: Moderate activity
Mar
April: Moderate activity
Apr
May: Moderate activity
May
June: Moderate activity
Jun
July: Low activity
Jul
August: Low activity
Aug
September: Rising activity
Sep
October: High activity
Oct
November: High activity
Nov
December: High activity
Dec

Peak period: September to January
Right now: Low activity in August

Harvest, falling temperatures and the first frosts push rats from field margins and river corridors into buildings — Hertfordshire call-outs climb sharply from late September.

Hertfordshire Pest WatchLow

Brown rats are usually least noticeable at this point in the year. Harvest, falling temperatures and the first frosts push rats from field margins and river corridors into buildings — Hertfordshire call-outs climb sharply from late September.

Activity appears to be increasing

Current local data is limited. The status shown is based primarily on established seasonal behaviour across Hertfordshire. Last reviewed 1 July 2026.

See all Hertfordshire Pest Watch activity

Why brown rats matter

Health risks

Leptospirosis (Weil's disease) carried in urine and contaminated water
Salmonella, Cryptosporidium and E. coli contamination of food surfaces
Rat-bite fever and secondary infection from bites or scratches
Fleas, mites and ticks introduced into the property with the rodents

Property damage

Gnawed electrical cable — a recognised cause of domestic fire
Punctured water and gas pipework, leading to leaks and escape risk
Compacted and fouled loft insulation, reducing thermal performance
Damaged airbricks, soffits and drainage that create ongoing entry routes

Brown rat evidence recorded during a Hertfordshire pest inspection

Hertfordshire context

Brown rats across Hertfordshire

In Hertfordshire, most rat problems we attend trace back to broken or unsealed drain runs in older housing stock, and to farmland and river corridors — the Lea, the Ver and the Colne — pushing rats indoors each autumn. New-build developments across Stevenage, Hemel Hempstead and Bishop's Stortford also disturb established burrow systems during groundworks.

Evidence centre

What brown rat evidence looks like

External entry point — Gnawed gap at a service pipe entry — the classic route into a sub-floor void. — Entry points
External entry point
Gnawed gap at a service pipe entry — the classic route into a sub-floor void.

Activity inside a void — Runs, smear marks and disturbed insulation recorded during a loft inspection. — Runs & harbourage
Activity inside a void
Runs, smear marks and disturbed insulation recorded during a loft inspection.

Setting the record straight

Common misconceptions

Seeing a rat in daylight means the infestation is enormous.

Daytime sightings often mean competition or disturbance, not necessarily large numbers — but they always mean an established population worth investigating.

You are never more than six feet from a rat.

This is a Victorian invention with no basis in survey data. Density depends entirely on food, harbourage and drainage condition.

Shop-bought bait will solve it.

Amateur bait frequently kills a few individuals in inaccessible voids and leaves the entry point untouched, so the problem returns within weeks.

Prevention and professional treatment

How to prevent them

CCTV drain survey where activity is indoors and no external entry is obvious
Seal gaps over 15mm at service entries, airbricks, soffits and door thresholds
Remove ground-level food sources: bird feeders, fallen fruit, open compost, pet food
Keep bins closed and stored clear of walls and fence lines
Cut back dense ground cover and ivy that provides cover for runs

How we treat them

Full internal and external survey mapping runs, harbourage and entry points
Targeted rodenticide in tamper-resistant stations, or trapping where bait is unsuitable
Drain inspection and repair recommendation where the route is subterranean
Physical proofing to close every identified entry point
Follow-up visits until zero activity is confirmed, with a documented service record