Eleutherodactylus juanariveroi is only known from the type locality: Sabana Seca, Toa Baja Municipality, in a seasonally flooded herbaceous wetland in the vicinity of the US Naval Security Group Activity Sabana Seca (USNSGASS) and the Caribbean Primate Research Center, Puerto Rico (18 26.127' N, 66 12.092' W, 10-20 m asl)(Rios-López and Thomas 2007).
Habitat and Ecology
The species inhabits the subtropical moist forest life zone. The type locality consists of a palustrine herbaceous wetland at 17 m asl. The wetland is seasonally flooded with fresh water; the soil consists of swamp and marsh organic deposits. Herbaceous vegetation in this habitat includes the toothed midsorus fern (Blechnum serrulatum), willdenow's maiden fern (Thelypteris interrupta), bulltongue arrowhead (Sagittaria lancifolia), flatsedges (Cyperus sp.), spike rushes (Eleocharis sp.), and vines and grasses. The habitat at the type locality occupies ca 180 ha; the species was not found in other wetland sites in the northern coastal plain. Individuals are active between 1900-2200 hours, while perching, sitting, or calling on herbaceous vegetation, between 0.4 m and 1.2 m above water level. Calling sites for males were found to be between 0.6 and 1.2 m above ground level. Egg clutches vary between 1-5 eggs and are mostly deposited on leaf axils of S. lancifolia. Embryos hatch after approximately 19 days (Rios-López and Thomas 2007; N. Rios-López pers. comm. 2008).
This species is thought to have year-round reproduction given the frequency of juveniles found in any given month. However, most adult activity (including calling males) is greater during the warm and wet months (May to November), and diminishes during the cooler and drier months (particularly between the end of January and end of March). It is expected that recruitment rates reflect this seasonal pattern with a greater amount of clutches being produced during the warm and wet months. The seasonal breeding pattern in this frog is similar to that of other species of the genus in Puerto Rico, such as E. antillensis, E. cochranae, E. coqui, E. cooki, E. gryllus and E. portoricensis. (N. Rios-López pers. comm. 2008).
The species appears to be common in the type locality (Rios-López and Thomas 2007). Nonetheless, it is the less abundant species among sympatric Eleutherodactylus (E. brittoni, E. cochranae, E. coqui) (N. Ríos-López pers. comm. 2008).
The type locality of Eleutherodactylus juanariveroi has, in the past, experienced little disturbance partly due to restricted access of local people by the US Naval Security Group Activity Sabana Seca (USNSGASS) and the limited development of military installations in this wetland. However, it is now threatened by private and governmental housing, industrial, and recreational projects that are spreading rapidly through the region after the USNSGASS ceased operations in 2005 (Rios-López and Thomas 2007).
Conservation measures are urgently needed to protect the only wetland system where the species is known to occur, and also the associated limestone hills to the south, which include two watersheds that drains freshwater into this wetland (N. Ríos-López pers. comm. 2008).
Other conservation measures may also include the restoration of wetlands with similar characteristics as those at the type locality, the implementation of ex-situ breeding projects (individuals of this species have been successfully bred in captivity with a relatively simple methodology, N. Ríos-López pers. comm. 2008) and reintroduction of the species (both captive bred and translocated individuals) into these restored wetlands (N. Ríos-López pers. comm. 2008).
Some conservation measures already in place include assigning the species a Critically Endangered (CR) status and the designation of its ecosystem and surroundings as Essential Critical Natural Habitats. This designation, issued by the Departamento de Recursos Naturales y Ambientales (DRNA) of Puerto Rico, provides a legal basis for the regulation and enforcement of the area's conservation. Although this is the first time the DRNA issues this kind of designation, it is being challenged at local courts by a landowner and by the municipal government of Toa Baja. In the meantime, there is still no management plan and no actions have been undertaken to create a Natural Reserve at this site, which limits the protection that this designation can afford (N. Ríos-López pers. comm. 2008).
Eleutherodactylus juanariveroi can be distinguished from similar species by a combination of morphometrics, body colouration, advertisement call features and habitat association (Rios-López and Thomas, 2007).
Neftali Rios-López 2008. Eleutherodactylus juanariveroi. In: IUCN 2014