This species is endemic to a small region in southwestern Madagascar. It is known from many sites within the Isalo Massif, either within or outside the national park (at 700–1,000 m Asl). It ranges from Grotte des Portugais and Amparambatomavo, south in a thin band to Ambatovaky and Sakavato (F. Andreone pers. comm.). Records from near Toliara (Busse and Böhme 1992), and from the Morondava region and Mandena (Glaw and Vences 1994) are probably erroneous (Vences et al. 1999). Its EOO is 2,073 km2.
Habitat and Ecology
This species is usually found around seasonal streams, and in wet canyons (where it is sometimes, but not always, associated with narrow gallery forest). From field observations, it is thought that this species is fairly philopatric and may be restricted to areas along temporary streams where they breed (Vences et al. 2008).
This species breeds in a similar way to other Mantella species, with the eggs laid on the ground and the larvae developing in swamps or in slow running temporary streams. Its lifespan is around three years and it reaches sexual maturity within the first active season after metamorphosis (Guarino et al. 2010).
This species is sometimes locally abundant in suitable habitat. From observations at 60 sites, it appears that this species is widely distributed throughout its entire range within the Isalo Massif (Crottini et al. 2008). However due to declines in the extent and quality of habitat, the population is suspected to be decreasing.
The southern subpopulations have also found to be genetically different and possess different colourations from the northern subpopulations, which could suggest that they need to be considered as two distinct conservation management units (Vences et al. 2008).
The main threat to this species is habitat loss due to grazing and, in some localized regions, due to sapphire mining which is also a high risk for extending into protected areas in the vicinity (Vences et al. 2008). It is actively sought after for the pet trade, and during the rainy season up to several thousand specimens can be collected. Such collecting might pose a major threat to the species, but this has not yet been demonstrated. Fires are common in the Isalo area, however this species demonstrates resilience to this threat and has been observed seeking cover in underground refuges and demonstrating immediate recovery after fires have been extinguished (Crottini et al. 2008).
Species in this genus have also tested positive for Batrachochytrium dendrobatidis (Bd), however currently there have been no negative effects observed within amphibian populations in Madagascar suggesting the Bd strain has a low virulence level (Bletz et al. 2015).
This species occurs in Isalo National Park, although the majority of the genetic diversity of this species occurs outside of this area (Crottini et al. 2008). It is listed on CITES Appendix II.
Trade in this species needs to be very carefully regulated (Andreone et al. 2006).
The population requires close monitoring (Andreone et al. 2006). Further research is also essential to fully understand the distribution, origin, type and virulence of Bd lineages found in Madagascar (Bletz et al. 2015).
Red List Status
Listed as Endangered because its extent of occurrence (EOO) is 2,073 km2, it occurs in fewer than five threat-defined locations, and there is continuing decline in the extent and quality of its habitat around Isalo.
Records of Mantella expectata or M. betsileo from the arid west and southwest Madagascar (including from from Tsingy de Bemaraha) probably refer to a separate, undescribed, species that is not characterized by blue legs (F. Andreone pers. comm., Rabemananjara et al. 2007). Here we consider as Mantella expectata to refer only the populations from Isalo and the thin band further south (F. Glaw pers. comm. May 2016).
IUCN SSC Amphibian Specialist Group 2017. Mantella expectata. The IUCN Red List of Threatened Species 2017: e.T57443A84166737. http://dx.doi.org/10.2305/IUCN.UK.2017-2.RLTS.T57443A84166737.en