The recent increase in the number of rats in the Hobart area has prompted the production of this information sheet.
Rats are regarded as pests as they transmit disease, contaminate food and cause physical damage. Rats may transmit diseases by:-
Rats need to be constantly gnawing to keep their incisor teeth short and as a result will damage doors, skirting, upholstery, books, food containers, wires and cables. They have been known to cause fires in buildings.
The best time to observe rodent activity is at night. What to look for:-
Having observed some of the tell-tale signs above, you can make your yard and dwelling uninviting for rats by doing the following:
Sanitation and hygiene
Eliminate rat harbourage areas, - rubbish heaps, old machinery, timber piles, weeds and general litter.
Reduce sources of food – store your garbage in receptacles with tight fitting lids.
Maintain the general cleanliness of the yard.
The importance of maintaining a high standard of hygiene and sanitation cannot be over-emphasised, if an effective rodent eradication and control program is going to be achieved.
Rodent proofing
To prevent rodents from entering and nesting within buildings, all possible entry points around doors, windows, drainage pipes, vents crevices, holes, unsealed services pipes, through walls etc, should be blocked using sturdy, durable materials such as cast iron frills, heavy-gauge metal, cement mortar.
Remember, rodents can gnaw through soft materials such as plastics, wood and soft metals (lead).
Trapping
The simple snap trap is the most effective method of catching rodents. Choose a trap with the strong spring and sensitive trigger.
Bait with bacon, fish, nuts, peanut butter, apple etc depending on the feeding habits of the rat. (experiment with unset traps to avoid trap shyness).
Don’t set traps above food containers where trapped rodents may contaminate food surfaces with urine.
Dispose of caught rats promptly in sealed bags. Wear gloves as rats may have fleas and use inspect repellents to reduce the risk to health.
Chemical control
If the rodent problem is so large that you have to resort to chemical baits, we strongly recommend that you obtain the experience of a Licenced Pest Control Operator for advice on the laying of baits. Whilst these baits can be purchased from supermarkets and hardware stores, they are poisonous and can kill other animals such as pet cats and dogs, and young children. (Council no longer provides chemical baits).
The main rodent problem in the City of Hobart is the Norway rat (Rattus norvegicus) also known as the common rat, sewer rat, water rat or brown rat. The Norway rat is large, about 260mm long, weighing between 250 – 500g, has heavy set body and covered with coarse red/brown fur. It has a blunt snout, small close set ears, finely covered with hair, small eyes and a tail shorter than its body in length (from head to the beginning of tail). They live for 9-12 months, reaching sexual maturity at 3 – 4 months. They produce 8 – 10 young per litter and have 5 – 6 litters per year (gestation period 23 days) Norway rats are typically omnivorous and will eat the same foods and humans and animals. They prefer to eat high protein foods eg. garbage, cereals, fish, meat. They usually consume 20 – 30g of food per day and 20 – 30ml of water. They like to feed in sheltered, undisturbed areas.
Rats are basically social animals, nesting and feeding together, travelling 40 – 50 metres to food and water. Norway rats usually live in burrows which tunnel into stream banks, underneath slab, under buildings, in rubbish heaps, sewers, drains and basements etc. The burrows commonly have bolt holes hidden under debris or grass to facilitate quick getaways. They may enter buildings for food or nest inside buildings in the colder months, or all year around. These nests are usually located in wall voids, roof voids and other area that are undisturbed, offer secrecy and shelter. The nests are constructed of soft material such as paper, fabrics, insulation, rags, cardboard, straw etc. They are creatures of habit. Once they have explored a new environment they establish quite rigid travelling routes and will often create tracks through vegetation. They are suspicious of new foods, bait trays and environmental changes for several days. They are mainly nocturnal animals but may range and feed during the day if the population is large, food is scarce or there is little disturbance or danger. Rates are agile and can squeeze through 12mm holes, climb inside a 40-100 pipe, crawl along a pipe, conduit or wire; jump 2.5m horizontally or 1.0m vertically; drop from 15m without injury; swim for 1km in open water; dive through sewer traps; run 9.5km/h and can gnaw aluminium, lead sheet, plaster, wood or particle board.
Rats' sight is poorly developed and they can’t determine images sharply. Their sense of smell is very keen. Their hearing is also very good and can hear in the ultrasonic range. Being mainly nocturnal animals with poor eyesight they rely on touch sensors (nerve endings) on their whiskers and long guard hairs on their body to help them navigate.
If you have any queries please contact an Environmental Health Officer on 6238 2715.
References: Hadlington, P., Gerozisis, J. 1988; Urban Pest Control in Australia, NSWU Press, Kensington, Australia, pp 244-254.
