Gloger’s Law states that warm-blooded animals (birds and mammals) have more melanin (black color pigments) in a hot humid environments such as the equator. The law was named after German zoologist Constantin Wilhelm Lambert Gloge (1803-1863). The darker skin color in animals better protects the intense solar UV radiation.
The rule can be applicable at the species level where different populations of the same species living in different latitudes possess different pigmentation. Humans living in high humid or equatorial regions possess darker skin color than their counterparts living away from the equatorial regions.