This species is restricted to the forested areas of central and eastern Tobago Island, Trinidad and Tobago. It is found at elevations of between 30 and 490 m asl, its distribution is determined by the presence of suitable streams (Alemu I et al. in prep.). Its range, taken as a proxy for extent of occurrence (EOO), is estimated to be 151 km
Habitat and Ecology
This is a tropical species associated with streams, moist cracks and springs in forested areas. It prefers rocky, shaded streams and tributaries, particularly first order streams (Alemu I et al. in prep.) with substrates of stones, gravel, or silt, and banks of boulders and gravel; it has also been observed in the woody vegetation adjacent to the stream, on moist rocks or near water puddles (M. Patrikeev pers. comm. March 2012). The majority of individuals have been found less than 2 m from the water's edge, but calling males also occur in the forest (Alemu I et al. 2007, J. Alemu I pers. obs. 2012), and call from rock crevices and piles of rocks from sunrise to sunset (Hardy 1983). Eggs are laid in a terrestrial nest on land and males guard the eggs and then carry newly hatched tadpoles on their backs until they are ready to swim (Hardy 1983, Alemu I et al. 2007), males carry tadpoles (11-19 in number) to isolated predator-free pools close to streams (usually flooded rock crevices, but also water-filled tire ruts) where the tadpoles complete their development (Alemu I et al. 2007). Pools with tadpoles were less than 1 m long and 10 cm deep (Lehtinen and Hailey 2008), and although these pools were directly adjacent to streams, no tadpoles were seen in the streams themselves (Alemu I et al. 2007). Metamorphs have been found in lightly flooded leaf litter near Charlotteville (M. Patrikeev pers. comm. March 2012).
The 2004 assessment for this species indicated that subpopulations had declined noticeably over the previous ten years; however, no survey data appeared to be available at that time. In 2006 this species was found in six rivers and 15 first-order streams in northeastern Tobago; it was found to be locally abundant in Doctor’s River, with average density of 1.9 ± 1.1 calling males per 50 m stretch of river or stream (Alemu I et al. 2007). In 2009 it was found in two first-order streams and a seepage near Charlotteville and Cambleton (M. Patrikeev pers. comm. March 2012). In July 2011, Novick (2012) found it in >80% of sampled sites in eastern and central Tobago using standard chorusing survey methodology and identified several subpopulations much further west than had been previously reported. Also in July 2011, Calkins (2012) found this species to be reasonably abundant along 18 streamside transects in central and eastern Tobago. There was widespread evidence of reproduction and recruitment between 2006 and 2011, i.e. many metamorphs and juveniles were encountered (Alemu et al. 2007, Calkins 2012), and tadpole density would reach > 50 individuals per pool (Lehtinen and Hailey 2008). Its population is not considered to be severely fragmented (M. Patrikeev pers. comm. March 2013).
Substantial areas of suitable forest remain in central and northeastern Tobago. Human impacts are probably negligible and consist of illegal tree removal from Tobago Main Ridge Forest Reserve and associated trail clearing and siltation, and also of housing development on private lands at lower elevations (M. Patrikeev pers. comm. March 2012). The amphibian chytrid fungus, Batrachochytrium dendrobatidis, is currently present in this species, with a prevalence of ca 20%, but not associated with clinical disease (Alemu I et al. 2008). It is also unclear whether any perceived population decline was caused by epidemic chytridiomycosis. Increased susceptibility to chytridiomycosis from climate change is possibly limited because this frog is associated with temperatures of 25
It is found in Tobago Main Ridge Forest Reserve (also known as Tobago Forest Reserve), a 3,958 ha area managed by the Tobago House of Assembly (M. Patrikeev pers. comm. March 2012). This is a water catchment or “rain reserve”, established as early as 1776 (UNESCO 2012). It also occurs in privately owned forested estate adjacent to Pirate Bay and Man O' War Bay near Charlotteville and Cambleton, respectively (M. Patrikeev pers. comm. March 2012) and elsewhere in St. John and St. Paul parishes (Alemu I et al. 2007). It has been proposed as an Environmentally Sensitive Species in the Republic of Trinidad and Tobago (Alemu I et al. 2007, Hailey and Cazabon-Mannette 2011). Monitoring of the population status and trend of this species is recommended in view of the perceived decline experienced prior to 2004; a captive breeding programme, in situ population management, or both, might need to be established should a chytridiomycosis outbreak occur in the future.
IUCN SSC Amphibian Specialist Group 2013. Mannophryne olmonae. In: IUCN 2014