Ecological observations on the Critically Endangered Tobago endemic frog Mannophryne olmonae

No previous ecological study has addressed the Critically Endangered (IUCN Red List) Tobago endemic frog Mannophryne olmonae (Aromobatidae) since its initial description in 1983. The species was found in six rivers and 15 first-order streams in northeastern Tobago in 2006. Snout-vent lengths of 126 measured individuals ranged from 9.6-25.7 mm, and the sexes were distinguishable at a length of 18.5 mm. Maximum size was similar in males and females — unlike M. trinitatis from Trinidad, which shows greater sexual size dimorphism. Frogs were found close to streams in forested areas, with a mean distance of 2.0 m from the water's edge, but only calling males were found within the forest itself. Juveniles made up a much larger proportion of the sample than in M. trinitatis. Calling group size averaged 1.9 males, and large choruses were infrequent. Tadpoles were found in isolated pools close to streams, but not in the stream itself; separate size classes suggest multiple deposition by males. There potential listing of M. olmonae as an Environmentally Sensitive Species in the Republic of Trinidad and Tobago is discussed.