By ‘standing up’ the questioner is referring to the habit of Munchkin cats to go up on their haunches in what I call the ‘meerkat position’. They rest their body on their feet and not their toes and lift their body into the vertical position. Their strong backs keep them upright. Cats missing a leg or two also tend to do this. Some people call it ‘sitting up’.
Munchkins stand up because they are vertically challenged. The long bones in their legs may be as short as five inches from shoulder blade to toe. They are the founding dwarf cat and their dwarfism is caused by a genetic mutation. Specifically it is a spantaneous automsomal (not sex linked) dominant mutation. It only affects leg length as the body and head are a normal size and shape.
There are many breeds of dwarf cat and all of them will tend to ‘stand up’. This must be an instinctive reaction to their very low height. They want to see more. In terms of the theoretical ability to survive their short legs are a hindrance. Cats need to be vigilant in terms of sight and sound. They are alert almost 24/7 and dwarf cats want to maximise their powers of observation.
Dwarf cats are controversial as cat breeders shouldn’t really create cats with a genetic defect. They can also suffer from a couple of health issues caused by the dwarfism gene: lordosis and pectus excavatum. You can read about the health issues by clicking on this link.
Initially, the creators of dwarf cats failed to gain the acceptance of their cats by the major cat associations: CFA and TICA because of the health issues I suspect. The current status is that TICA accept the Munchkin and Muchkin Longhair but CFA rejects the dwarf cats.
In Germany they call it ‘torture breeding’ (qualzucht) which is perhaps a little extreme but the point is strongly made. There are other cat breeds in this classification such as the Sphynx and Scottish Fold. However, Munchkins are a popular breed and generally pretty healthy. Although less athletic than the average healthy moggie they can jump well, climb trees and run like any other cat. They’re also very cute, sweet and affectionate.
All dwarf cat breeds are crossbred from Munchkins. You can read about them all by clicking on this link.