For Muntjac, it should be a minimum of 1.5 m high. The fence should be dug into the ground ("lapped") and firmly pegged or turfed, in much the same way as you might do for rabbit fencing. Muntjac are very determined and will burrow under a badly fixed fence and will jump over anything up to 1.2 m in height.
Mesh size should be a minimum of 100 x 100 mm, but for welfare reasons, a size of 75 x 75 is recommended because a Muntjac's head can become stuck in larger sizes.
they are canny little critters, I have to say I've not seen them jump but I have seen a patch of re stocked woodland that was beautifully fenced to stop everything but due to a badger set it had to have a flap put in for them and lo and behold the muntjac learnt to use it better than the badgers