Brown Rat Here are several pictures of the brown rat, aka Norway rat, scientifically known as Ratus Norvegicus. Find out how the Black rat looks like by click the link above. Brown rats are also expert jumpers, climbers and of course swimmers. Brown rats have an extraordinary ability to reproduce, several times per year. Brown rats carry diseases that may be fatal to humans and pets. Brown rats are one of the most serious mammalian pests on Earth.