Assume in otters short hair (L) is dominant to long hair (l) and black hair (B) is dominant to brown (b). If you found a black short-haired otter, you could determine its genotype by crossing it to another otter with a genotype of:

llbb

Explanation:

The genotype of the black, short-haired otter could be determined by testing-crossing with a brown, long-haired otter whose genotype would be llbb.

Analysis of the resulting zygote from the cross would give an indication of the genotype of the otter - whether it has two dominant alleles each for the black, short-hair traits or heterozygous.

If the otter has two dominant alleles for the two traits, all the resulting zygote from the test-cross would have black, short-hair, but if it is heterozygous, a mixed phenotype set of zygote would be obtained.

i believe the answer is

Coriolis effect