Hares (Genus Lepus) are closely related to rabbits and are often confused with them. Generally, hares have longer ears and legs than rabbits, but not exclusively. The young of the hare are also born with open eyes and fur, which contrasts with rabbits. Rabbit babies start out with unopened eyes and no fur. a 'leveret' is a baby hare less than one year old (as opposed to baby rabbits, which are called 'bunnies').
Historical Vikings would have encountered the European hare (Lepus europaeus), which is widespread across Europe. Like many members of the Lepus Genus, hares are considered shy and elusive, especially because they are a major prey species for many animals. However, during mating season for the European Hare in the Spring and Summer, hares become rather bold and territorial. Males fight each other often by 'boxing' and otherwise exhibit 'crazy' behavior, and is the root of the phrase mad as a March hare.
The hare is mentioned in Book 4 in the phrase mad as a March hare, describing a character as very excitable and frantic.
In reality, in addition to phraseology, the hare is commonly hunted around the world as a food source. It also figures into some cultural mythologies, such as a symbol of fertility to ancient Greeks, and is also symbolic at Easter for the same reason.
|“||Norbert the Nutjob was clearly madder than a Mad March Hare having a nervous breakdown.||”|
|— Book 4|
Norbert the Nutjob is described in terms of a 'mad March hare', indicating that he was very angry and frantic, particularly when Hiccup crashed into the Hysteric Tribe's Freya'sday Eve feast and asked for his precious potato.