This species, which is endemic to Tanzania, is known only from the Mrora Forest on Mafia Island, and from the Jozani Forest on Zanzibar (and from an unmapped, unspecified locality on the east of Zanzibar). All records are from close to sea level.
Habitat and Ecology
It is terrestrial, occurring in lowland coastal forest. Some of its remaining habitat is degraded, and it seems to display some adaptability to living in such habitats. Its breeding behaviour is unknown, but it might breed in puddles in tree roots like Stephopaedes anotis.
It is probably an uncommon species.
Its habitat is being degraded rapidly on Mafia for agriculture, wood extraction, and human settlements.
It possibly occurs in the Mafia Marine Park, but this remains to be confirmed, and improved protection of remaining suitable habitat on Mafia is a priority. On Zanzibar, the Jozani Forest, the largest tract of forest remaining on the main island, has recently had its protection status upgraded to that of a national park.
John Poynton, Kim Howell 2004. Mertensophryne howelli. In: IUCN 2014