This frog is known only from two mid-altitude sites within the Kanga Forest Reserve within the Nguru Mountains, Morogoro Region, Tanzania (Loader et al. 2010), at 760 and 1,140 m asl. Intensive searches at other sites within the reserve and at other elevations, totalling a month of survey time, failed to obtain additional records, and the species may be restricted to a narrow elevational band within Kanga (Loader et al. 2010). The recent description of numerous distinct species of Callulina, each with very restricted distributions on particular mountain ranges (Loader et al. 2010) suggests that it is unlikely to be much more widespread. Even if it occurred throughout the reserve, at all elevations, it would have a total extent of occurrence no greater than 66.64 km2, the area of the reserve (Loader et al. 2010, Menegon et al. 2008), and its extent of occurrence and area of occupancy may in fact be lower than 10 km2 (Doggart and Loserian 2007).
Habitat and Ecology
This frog appears to be wholly arboreal in primary submontane humid forest; one of the two collected specimens was found on a branch above head height, the other hidden in leaf axils (Loader et al. 2010). Individuals were heard calling from branches but never from the ground (Loader et al. 2010). The frog's reproductive mode is unknown, however phylogenetic analysis has been used to predict that all brevicipitid frogs reproduce by terrestrial direct development (Müller et al. 2007).
No information is available on population density, as only two specimens are known (Loader et al. 2010). Many frogs were heard calling at the known localities (Loader et al. 2010).
Although there is no evidence of major disturbances to this frog's primary forest habitat such as slash-and-burn agriculture, there is continuing pressure on this forest within Kanga resulting from growth of the surrounding human population, which is particularly acute at the elevations where this species occurs (S. Loader pers. comm. June 2011). Consequently Kanga is considered a single threat-defined location. The extent and impacts of forest decline in areas inhabited by this frog are difficult to evaluate (S. Loader pers. comm. June 2011), but its restricted distribution puts it at high risk from even small changes in forest cover.
This species appears to be confined to Kanga Forest Reserve. This site needs to be managed to enforce its protected status and limit the impacts of human activities on remaining primary forest (S. Loader pers. comm. June 2011). More information is needed on its population status, ecological requirements and the impacts of threats.
Red List Status
Critically Endangered (CR)
Listed as Critically Endangered on the basis that it has an extent of occurrence below 66.64 km2, and potentially below 10 km2, and is known from a single threat-defined location where there is a continuing decline in the extent and quality of its forest habitat due to pressures from an expanding human population.
This species, first recorded in 2004, was first reported in the literature by Menegon et al. (2008), who listed it as "Callulina sp. 4"; it was also referred to as such, referencing this then-unpublished paper, in the technical report by Doggart and Loserian (2007). Populations of Callulina from the nearby Nguru South Forest Reserve, now found to represent three distinct species, were originally included within the presumed widespread, monotypic C. kreffti (Loader et al. 2010). In contrast, the Kanga Forest Reserve form appears never to have been explicitly included within this species concept, having only been discovered after doubts arose concerning the monophyly of C. kreffti (de Sá et al. 2004).
IUCN SSC Amphibian Specialist Group, 2012. Callulina kanga. The IUCN Red List of Threatened Species 2012: e.T193426A2235870. http://dx.doi.org/10.2305/IUCN.UK.2012-1.RLTS.T193426A2235870.en .Downloaded on 24 January 2019