Phylum: Chordata | Class: Mammalia | Order: Rodentia | Family: Muridae


Economic Importance

  • Rodents are mammals that are characterized by two continuously growing incisors in their upper and lower jaws which must be kept short by gnawing
  • Rodents are global pests of public health, as threats to the welfare of domesticated animals and wi ldlife, and as threats to food safety and security
  • Rodents destroy field crops as well as stored harvested grains
  • Rodents contaminate stored food w ith their shed hair, droppings and urine
  • They can chew through electrical wires and structures causing financial damage
  • The dead skins of rodents known as dander and waste have been shown to cause severe allergies and asthma
  • Rodents carry several insects like mites, ticks and fleas which can bring infestations into home
  • Rodents are known to transmit highly contagious diseases to humans and animals
  • Rodents and their parasites are capable of spreading diseases like salmonellosis, leptospirosis, typhus, Weil's disease, rabies, dysentery, typhoid, cholera, tuberculosis, foot-and-mouth disease and the plague through bites or contamination
  • Rodents may carry fleas infected with Yersinia pes tis , the bacterium that causes plague which killed about one-third of Europe's population during the Great Plague of the 14th Century

Rodent Anatomy

  • The real Muridae are small to slightly larger rodents with long and fairly long tail with few hairs
  • The length of the tail is at least two thirds of the length of the animals
  • The eyes are large, ears are exposed out of the fur and the upper lip is slit
  • They have four toes in their fore feet and five toes in their hind feet
  • Rats are generally larger,heavier and longer than house mice
  • Rats have larger ears and feet
  • The heads of Norway rats are heavy, blunt and chunky, while house mouse heads are small and sharply triangular with pointed muzzles

Rodent Biology

  • Rodents are household pests and are often called commensal pests. Commensal means "eating at the same table with", and rodents are called this due to their close association with humans
  • The three commensal rodents are the house mouse, house rat and the Norway rat
  • All of them have few common characteristics and can rapidly reproduce
  • Rodents gain sexual maturity between 6-8 weeks and the average gestational period is between 19 and 23 days
  • They have an average of 5-12 young ones per litter and they can have 4-6 litters per year
  • Rodents are polyphagus,which means they can eat a variety of foods and do not enter winter sleep

Rodent Life Cycle

  • Mice and rats reproduce rapidly. Their relatively short life span, short gestational periods and rapid sexual maturity make effective rodent control difficult
  • The reproductive cycle and number of rodent offspring increases with adequate food, water and harborage
  • Mice become sexually mature and are able to mate within 6 weeks while rats become sexually mature and are able to mate in 8-12 weeks of age
  • Female mice reproduce up to 8 times in their lifespan, with litters averaging 4 to 7 pups while rats average 4-7 litters per year, with litters averaging 8-12 pups
  • Rodents reproduce year round in favourable environments  with adequate food, water and harborage
  • The general normal life expectancy of house mice, Norway rats and house rats is approximately one year

Rodent Species

House Mouse (Mus musculus)

  • The house mouse have brown to grey fur, and grow to about 10 cm body length and a body weight of up to 30 g
  • They have large outer ears, a pointed snout and a long tail of up to 9 cm
  • They have up to 200 tail rings
  • They live in large families, mostly in dry rooms underneath floor boards and inhabited premises
  • It explores each corner of its habitat using its pronounced capability to jump and swim, its curiosity and intention to move around

House Rat (Rattus rattus)

  • The house rat grows to about 15 to 23 cm body length and a weight of 150 to 200 g
  • They have silk like fur, mouse-like small head and relatively large naked ears. They are greyish black to brownish grey, sometimes with a greenish tone and lighter at the underside
  • The tail is about 18-25 cm longer than the body and has about 270 tail rings
  • The mouse rat lifts its tail while moving and does not leave any trace of it on the ground
  • The so-called roof rat, is a variety of the house rat with lighter colour of fur, originating from South East Asia
  • Prefers to live in groups and they hardly leave their territory

Norwegian Rat (Rattus norvegicus)

  • The Norwegian rat is larger and heavier compared to the house rat, with a length from head to tail of 18 cm to 27 cm,and a tail length of 15 cm to 22 cm
  • The weight of the adults is around 200 g to 500 g
  • The color of their fur is brownish grey
  • They have a blunt snout
  • The ear are covered with short hairs
  • The tail is almost bare
  • The Norwegian rat has relatively smaller ears and eyes compared to the house rat
  • They are good swimmers and are omnivores

Rodent Management Program

  • Complete rodent control is very difficult
  • Sanitation is extremely important for any rodent control
  • Removal of vegetation and rubbish from the building and placing them away from the walls will reduce infestation of rodents
  • Food and feed and their remnants should be safely locked away in tightly closed containers to avoid infestation, because they are attracted by smell
  • Cracks and openings in walls should be quickly closed