This species has been recorded from a very restricted area on Shengena in the South Pare Mountains, Tanzania, having only been found at two sites within Chome Forest Reserve (Loader et al. 2010); as these localities are in close proximity to one another and subject to the same pressures on the forest habitat, the reserve is treated as a single threat-defined location for the purposes of this assessment. It has been found between 1,920 and 2,100 m asl (Loader et al. 2010). Callulina species exhibit a high degree of microendemism (Loader et al. 2010), and so it is not expected to be more widespread. Its estimated extent of occurrence, considering the availability of suitable forest habitat at elevations where this frog occurs, is thought to be around 35 km2 (Loader et al. 2011). The area of occupancy may be as low as 3 km2 if it is only found at the two known localities (Loader et al. 2010).
Habitat and Ecology
This arboreal frog is only known from montane forest dominated by Ocotaea usambarensis trees (Loader et al. 2010). All known specimens were collected in forest pitfall traps, and so its ecology is poorly-known; however individuals have been observed at night on bushes, bark and small tree branches between 1 and 2.2 m high (Loader et al. 2011). 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).
This species is common in the small area where it has been found (Loader et al. 2010). The population trend is unknown.
The montane forest to which this frog is confined is being degraded by "persistent and large-scale logging" for Ocotaea usambarensis (Loader et al. 2010), and logging is ongoing within the Chome protected area (S. Loader pers. comm. June 2011). Timber extraction causes considerable damage to the surrounding habitat, and much of the remaining forest appears to be heavily-logged (Loader et al. 2010). This frog has never been recorded in logged forest (S. Loader pers. comm. June 2011).
It occurs in a proposed nature reserve, currently the Chome Forest Reserve (S. Loader pers. comm. April 2012, Loader et al. 2011), a 140 km2 protected area (WDPA 2010). However, it is unclear whether the protection currently afforded is effective (S. Loader pers. comm. November 2011). No species-specific conservation measures are in place for this species. This reserve needs to be managed to limit the impacts of logging on remaining forest, as this frog appears to be highly intolerant of disturbance. Research is needed to clarify this frog's population status and ecological requirements.
Red List Status
Critically Endangered (CR)
Listed as Critically Endangered on the basis that it has an extent of occurrence of at most 35 km2, it occurs at a single location, and there is a continuing decline in the extent and quality of forest habitat due to large-scale logging operations. Additionally, it may have an area of occupancy as low as 3 km2, although further research is required to verify this.
This species was previously included within Callulina kreffti, formerly considered to be a monotypic species widespread throughout the Eastern Arc Mountains. (Loader et al. 2010).
IUCN SSC Amphibian Specialist Group, 2012. Callulina shengena. The IUCN Red List of Threatened Species 2012: e.T193428A2236156. http://dx.doi.org/10.2305/IUCN.UK.2012-1.RLTS.T193428A2236156.en .Downloaded on 22 January 2019