Boophis arcanus is known from the central east of Madagascar at its type locality, Mahakajy Private Reserve, and from a second locality near Berembi, along the road between Ranomafana and Ifanadiana at 577 m asl. It may also be present at other lowland sites within Ranomafana National Park (Glaw et al. 2010) and more broadly in the region (J. Riemann pers. comm. November 2014). Based on a conservative range spanning these two localities, its extent of occurrence has been estimated at 1,087 km2 and it is thought to occur in fewer than 5 threat-defined locations.
Habitat and Ecology
In Mahakajy, specimens were found at night sitting on leaves 1–2 m high in bushes at the edge of disturbed rainforest (Glaw et al. 2010). In Berembi, the species was found by a stream in gallery forest. Similar to congeners, it presumably breeds in streams by larval development.
This species is only known from 2 adult females collected at Mahakajy in 2004 and 2006 (Glaw et al. 2010). This cryptic species is extremely difficult to identify based on morphological characters, especially since only two specimens have been collected despite intensive searches during three visits to the type locality (Glaw et al. 2010). However, due to ongoing habitat degradation and loss, its population is suspected to be decreasing.
Likely threats outside the park in which it has been recorded include deforestation caused by small-scale forest clearance for charcoal, subsistence agriculture, and cattle pasture.
B. arcanus occurs in Mahakajy Private Reserve, a site receiving some protection, and the species may also be present at lowland sites within Ranomafana National Park (Glaw et al. 2010). Ranomafana National Park is presently well-managed, but is potentially at risk if political instability weakens enforcement there (M. Vences pers. comm. December 2010).
Site and habitat protection is required through the maintenance and improvement of current management practices both in and outside of the protected areas in which it is found.
Further research is required on the species' population size and distribution, life history and ecology, and the threats faced by the species.
Red List Status
Listed as Endangered as this species has an extent of occurrence of 1,087 km2, is known from fewer than 5 threat-defined locations, and there is ongoing decline in the extent and quality of its habitat.
The first data on this species were possibly recorded by Andreone (1994), who noted a small brown Boophis from the Ranomafana area as B. miniatus. Glaw et al. (2001) gave further information on the corresponding voucher specimens from Ifanadiana, a locality not far from Mahakajy (Glaw et al. 2010).
IUCN SSC Amphibian Specialist Group 2015. Boophis arcanus. The IUCN Red List of Threatened Species 2015: e.T49381365A49381418. http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T49381365A49381418.en .Downloaded on 22 January 2019