Next to another horse
No. Mature horses sleep standing up.
There are no cold blooded horses...
Female horses sleep in the exact same places as male horses, neither sex has any one preferance when it comes to where they sleep.
some examples of a horses functional adaptation, is that that they can sleep standing up. Their coat grows long in cold conditions.
Sea horses sleep by staying where they are
Wild horses, like most horses sleep standing up. Foals take alot of naps laying down.
Arabian horses sleep like most other breeds of horses. Horses can doze on their feet and take little 'cat naps' throughout the day. They will spend a couple of hours on the ground sleeping in a 24 hour period. Most breeds of horses follow this same sleep/wake pattern.
they sleep laying down
no
horses
The Ground
Probably when they get tired, like all other horses.