Spoon ear or Loffohr rabbits are due to a recent mutation that makes the ear rounder and more open toward the middle and bottom portions of the ear, so they are somewhat spoon-shaped. It gives the rabbits a mouse-ear appearance.

The genetic mechanisms for spoon ear are still not fully understood, but it appears to be recessive, and at least some types of spoon ear appear to be X-linked. X-linked traits, when recessive, show up more frequently in male mammals. This is because in females, if she has one normal copy of the gene, it acts to produce the normal traits, suppressing the traits of the mutated version of the gene. However, because male mammals only have on X chromosome, they can only have one copy of any gene that is found on the X chromosome. If they inherit the mutated version of the gene, they will always show it. 

This author notes that there are rabbits with similar to identical phenotypes (outward appearance) as Loffohr rabbits which do NOT appear to have achieved that phenotype via an X-linked, recessive inheritance mode. There may be multiple mutations across similar genes that cause similar ear shapes. Some may also be no-genetic congenital defects caused by faulty development before birth. Such congenital defects may be the result of environmental contaminants, the mother lacking certain nutrients during gestation, or other factors.