Romain Broch, sales and marketing manager (ANZ) for Liphatech, gives a top to tail overview of rat anatomy.
Most pest professionals will know that roof rats are smaller than Norway rats, with a longer tail and other distinguishing superficial features. But what do you know about their sensory organs and other body parts?
Rats possess two incisors and six molars in the upper jaw and same in the lower jaw. Incisors are constantly growing at about 0.4mm per day and are kept sharp by constantly gnawing on hard materials – an obvious sign of a rodent infestation.
Rats have a secondary odour detection organ called the vomeronasal (VNO) or Jacobson’s organ. The VNO is located on the floor of the nasal cavity with a narrow opening inside the nostrils. When rats sniff and lick, molecules adhere to the moist nose and dissolve. The VNO contains olfactory receptors involved in the detection of pheromones and chemicals found in urine and other secretions.
Urine markings are a way of communication within the colony. As well as providing individual recognition, it contains clues to an individual’s sexual maturity, reproductive status and social status within the colony. The VMO therefore plays a vital role in social hierarchy, mate attraction, aggression, copulation and parental care.
Rats’ eyes have a transparent third lid called nictitating membrane. Their eyesight is poor and they will only be able to recognise objects from distances under 15m and detect motion from 10m away. They are colour-blind but can perceive different shades of colour.
Rats’ ears collect sound waves in the ultrasonic range. They can also emit ultrasonic sounds to communicate or assess their environment (locating objects and negotiate obstacles).
The vibrassae are long stiff hairs with a sensory function. Located at the front of the head around the nose, cheeks, lower jaws, chin and eyes and although they are associated with the sense of touch, actually little is known about their exact function.
The hairs that cover a rat’s body provide insulation and protect the skin from moisture and parasites. The fur colour acts as camouflage and may in part explain the variations in colour between regions for the same species.
Rats have five ‘fingers’ on each limb, with the forelimbs being used for holding and grasping, while the lower limbs give support for running, jumping and climbing. Rats are quadrupeds and walk on their toes.
The Norway rat’s tail length is about the size of their body and head combined. Roof rats have a tail that is longer than the head and body. The tail helps with balance when travelling on narrow edges (wires, fences, etc.) and with leverage when climbing.
As rats don’t sweat, the tail plays a role in regulating body temperature by constricting or expanding blood vessels.
Romain Broch, Sales and Marketing Manager, ANZ, Liphatech