Are leopard geckos communal?

Due to the individual nature of leopard geckos (ie the fact they every one is different and unique) its a difficult question to answer. As a general rule however, providing some general rules are followed leopard geckos are for the most part communal. It is important to remember a number of key rules of thumb:

Males should never be kept together as they are prone to fighting which can escalate quite severely during breeding season. The only time I would really consider housing two males together would be in a very large vivarium where you can provide a large cohort of females to keep them thoroughly busy. Even then I would tread extremely carefully.
Never keep leopard geckos of different sizes together, it is just asking for trouble (bullying may become a particular problem).
Never keep a mature male with an immature female, male leopard geckos are not really upstanding moral citizens, they have few problems with trying it on with a female before she is ready. On a more serious note, this does present very real problems as the immature female is unlikely to have the relavent resources to complete the pregnancy and it will put undue pressure on her body.
If you see any signs of fighting (beyond an initial sizing up when introducing new geckos - it is important to monitor this heavily, particularly over the first day or so, any signs of real trouble then remove immediately) you should seperate them immediately. Not all leopard geckos are cut out for communal life.
If you notice one leopard gecko to be loosing weight it is possible that bullying is occurring and the skinny gecko isn’t getting enough food. The skinny gecko must be separated and kept alone.

Generally, female leopard geckos live quite happily together. Males should never be kept more than one per enclosure, as they will fight for prime basking spots and females. This is especially likely to happen in breeding season.

Breeding pairs can be kept together but you should be careful that you don’t get the male pestering the female often as this may stress her out. Trios (1 male 2 females) generally work better because the male has more females to “look after” so they don’t get pestered so much. It should be noted that you shouldn't keep males with females unless you have the time and equipment to care for the eggs and young. You should also be confident homes can found for the young (this often isn't as easy as people presume it will be).

There are some individuals which just don’t cope well in group situations. They may become aggressive towards other individuals or they may, at the opposite end of the scale, become shy and go off their food.

If you see any fighting, signs of fighting or a leopard gecko which looks like it is loosing weight it is essential that you split them up straight away because this is a dangerous situation for the submissive leopard gecko to be in.

How much space do communal leopard geckos need?

Ultimately more leopard geckos require more space. I wouldn’t try to keep a pair in anything less than a 36x15x15inch vivarium. A trio should b kept in something at least 36x18x18in although 4ft would be better.