Foundation Savannah Cats
The Savannah cat breed was created by crossing the African seval cat with domestic cats. Felines used in the early breeding included Oriental shorthairs, Egyptian maus, Serengetis, Maine coons, Bengals, and also non-pedigreed domestic cats. These early Savannahs are known as "Foundation" Savannahs (i.e., the cats produced from the first three successive generations bred down from a serval cat).
All foundation savannahs have a letter "F" and a number assigned to them to indicate how many generations it is removed from the serval cat ("F" can also mean 'filial' which in genetics means 'of or relating to a generation or the sequence of generations following the parental generation).
For example:
F1 = at least one parent cat is a serval
F2 = at least one grandparent cat is a serval
F3 = at least one great-grandparent cat is a serval
and so on.
As the Savannah breed continues to progress, it is now common to breed later-generation females back to African serval males instead of breeding them with other domestic breeds. This ensures a more "pure" Savannah and also results in kittens with a higher percentage of serval blood while still retaining their domesticity. In addition, later-generation fertile Savannah males (i.e., F4 or later, as foundation Savannah males are typically infertile) are bred to all generations of Savannah females. For example, an F4 male may be bred back to an F2 female, producing a litter of F3 kittens (the F generation produced is one down from the highest generation of the parents).
Since foundation Savannah cats may retain some of their serval traits more so than a later-generation Savannah, they may be a little more "stand-offish" and therefore may not be for everyone. They typically are not "lap cats," not liking to be held much and will usually become attached to one or two persons in the household. As a result they may be very shy and weary of visitors.
F1 savannahs and F2 male savannahs are typically the largest cats. They range in size from about two-and-a-half times the size of a regular house cat and range in weight form 15-30 pounds. F3 males are also considerably larger than a regular house cat while F3 females and further generations of savannahs subsequently decrease in size but retain their long legs, large ears and exotic appearance.Savannah cats generally attain their full size at about 3 years of age.