Brute Tigrex Ecology

Disclaimer: This is merely a plausible explanation for the monster(s) in this article, and should not be considered canon.

Taxonomy
The Black Tigrex has few differences with its cousin Tigrex other than coloration (obviously) and habitat range, residing in Volcanoes rather than Deserts.

Habitat Range
This dark-colored wyvern is found exclusively in volcanic areas, which would imply that the Black tigrex is better suited to much hotter environments than the normal Tigrex.

Ecological Niche
Black Tigrex's role as top predator is no different than that of Tigrex. Its only known competitors include Agnaktor and Rathalos. A fully-grown Uragaan may also present a threat to a Black Tigrex. Unlike the Tigrex, Black Tigrex doesn't seem to travel to temperate areas to prey on Popo, so it definitely needs to make the most of all prey at the volcano. It may hunt Rhenoplos, Rangurotora, Zuwaroposu, Uroktor, immature Uragaan, and the Furogi and Dosufurogi that live in the lower levels of the Volcano.

Biological Adaptations
Just as Tigrex has coloration suited to both tropical sandy deserts and freezing snowy landscape, the Black Tigrex has just the right coloration to blend in with the Volcano's cliffs and crevices. The possible reason for its black coloration may be the huge amount of ash scattered in the Volcano.

Behavior
Black Tigrex appears much more aggressive and more manical in attacking in comparison to Tigrex. Perhaps like Crimson Fatalis, it just recently adapted to the area and the heat is causing its rage.