In South Africa you will commonly find 3 types of rodents

Rattus Rattus

Ratus Norvegicus

Mus Musculus

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea.
“True rats” are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus.

Many members of other rodent genera and families are also called rats and share many characteristics with true rats.

Rats are typically distinguished from mice by their size; rats are generally large muroid rodents, while mice are generally small muroid rodents.

Generally, when someone discovers a large muroid, its common name includes the term rat, while if it is small, the name includes the term mouse – scientifically, the terms are not confined to members of the Rattus and Mus genera.

Norway Rat  (Rattus Norvegicus)   300 to 528g   body is thicker than the neck, ears and eyes are small. The nose is blunt.

The tail is shorter than the head and body.

The Roof rat ( Rattus Rattus)  125 to 373g  the head is the same size as the body.the eyes and ears are large.The nose  is blunt.

The tail is longer than the head and body.

House Mouse  (Mus musculus) 15 to 20g   tail is the same length as the head and  body.