This frog is known from several sites on Bioko Island, Equatorial Guinea where it has been collected on the northeastern face of Pico Basile and also documented on its southwestern slopes (R. Bell and P.J. McLaughlin pers. comm. June 2012, Blackburn 2010). The elevation of the type locality on Pico Basile is 1,820 m asl and specimens recorded near the town of Moka were between 1,321-1,327 m asl (R. Bell and P.J. McLaughlin pers. comm. June 2012). However further sampling could reveal that the species' range is greater than currently estimated. Its current extent of occurrence (EOO) is 242 km², but it should be noted that, were the species to have a uniform distribution throughout the suitable habitat, its range and thus its EOO would always be less than 20,000 km² (Blackburn 2010). It is thought to occur in fewer than five threat-defined locations.
Habitat and Ecology
The species inhabits montane forests and can be found in the leaf litter (Blackburn 2010). Some individuals have been found near streams and it is possible that the species relies on streams or humid microhabitats for certain aspects of their life history (R. Bell pers. comm. July 2012; P. McLaughlin pers. comm. March 2013). At present, its resilience in secondary habitat and tolerance to disturbance is unknown. As with other congeners, it is expected to breed by direct development.
Little is known about the species' relative abundance because it has only recently been described (2010) and only a handful of individuals have been recorded so far. More specifically, between January 2009-January 2013, P. McLaughlin and R. Bell conducted 245 field days throughout Bioko island, resulting in only three confirmed specimens of A. bioko—two of which occurred in the vicinity of the town of Moka; five other specimens have yet to be absolutely identified—despite targeted searching, suggesting that the species does not occur in high densities in collection areas (far less than comparable species) (P. McLaughlin pers. comm. March 2013). However, due to ongoing and increasing habitat loss, its population is presumed to be decreasing.
At the time of its description, its natural habitats on Bioko had suffered little loss (Blackburn 2010). However, possible major threats are present and include the encroachment of farmland, which is ongoing within and along the borders of Pico de Basilé National Park and near the town of Moka, while road construction is also fragmenting and threatening the few areas in which A. bioko has been found, including within the National Park (P. McLaughlin pers. comm. March 2013). Furthermore, as it is a montane species with a relatively restricted range, a possible future threat is the effects of climate change, which in turn may increase the species' susceptibility to infection with Chytridiomycosis (P. McLaughlin pers. comm. March 2013).
The forests of Bioko are legally protected (Blackburn 2010) and this species occurs within the Pico de Basilé National Park and in the the Reserve Scientifique de la Caldera de Luba. Unfortunately, it seems there is no real enforcement of, or within, the borders of Pico de Basilé National Park. Generally speaking there is concern that recent political rearrangements and conflicting laws being passed may have compromised the existence of Bioko's parks, possibly even terminating them; thus making protected areas on Bioko Island no real asset to the species' conservation (P. McLaughlin pers. comm. March 2013).
Further information is needed on this species' population distribution across Bioko Island, its population size and trends, natural history, and the effect of present threats. In light of ongoing habitat destruction, population trends should be monitored to assess its resilience in secondary and degraded habitat, and the protection of the parks in which it occurs needs continued and improved management, and increased enforcement.
Red List Status
The species has been assessed as Endangered due to an extent of occurrence (EOO) of 242 km², it is known from fewer than five threat-defined locations, it is only known to occur in montane forests near places where there is ongoing decline in the quality and extent of its habitat.
This species is in the Arthroleptis poecilonotus species complex (Blackburn 2010).
IUCN SSC Amphibian Specialist Group 2015. Arthroleptis bioko. The IUCN Red List of Threatened Species 2015: e.T16575406A16575409. http://dx.doi.org/10.2305/IUCN.UK.2015-2.RLTS.T16575406A16575409.en .Downloaded on 23 February 2019