Pekins and Mandarins

[Koekoek]

Just a quick question - can Pekins and Mandarins be kept in the same enclosure or is it better to keep them separate?
The Pekins in question are 2 drakes and 2 hens which were raised from day old ducklings.
Their pen is 6m x 4m.
I know that you should always keep a lot more hens than drakes but does that apply to two species as different from each other as Pekins and Mandarins too?

 

[Speceider]

Mandarins need to be kept as pairs. I believe thast is a bad mix because the pekins are so much larger than the mandarins. They are likely to exclude the mandies from food and water. Also, mandies need to be kept in an enclosed pen.

Clint