Description
Pristimantis rivasi is a medium sized frog described from one female and several males. The female has a snout-vent length of 41 mm while the males ranged from 25.0 - 30.8 mm. The head length is roughly the same as the width. The snout is sub-ovoid with a truncate tip when viewed dorsally, and truncate when viewed in profile. The internarial distance is about half of the eye-nostril distance. The canthus rostralis are rounded. The head has ill-defined occipital ridges and small granules on upper eyelids. The eye diameter is a little more than twice the tympanum diameter. The tympanum is distinct and has a distinct tympanic annulus. The anterior dorsal skin is smooth while the posterior dorsal region is shagreen with small, scattered granules and the ventral skin is areolate. There are no dorsolateral folds. There also is no ulnar tubercle. The fingers have a lateral keel, enlarged outer discs, and fringes. Finger I is shorter than finger II. Males have an ill defined, single nuptial pad. All subarticluar tubercles on hands and feet are distinct and protuberant. There is no calcar and no tarsal tubercles. However, there is a large oval inner metatarsal tubercle and an indistinct, oval outer metatarsal tubercle. The toes have a lateral keel, fringes, and basal webbing. Toes III, IV, and V have relatively broad disks that are slightly smaller than the ones on fingers III and IV (Barrio-Amorós et al. 2010).

DIAGNOSIS:

Pristimantis rivasi can be distinguished from other members of the genus in its range by the presence of a distinct tympanum and tympanic annulus, fringes on the digits, basal webbing, cranial crests, and a lack of a calcar (Barrio-Amorós et al. 2010)

COLORATION:

In life, the dorsum is light or creamy brown to whitish, and there is an X-shaped pattern that is ill-defined (but see variation). They have an incomplete black canthal stripe, a poorly defined black interorbital bar, and a black supratympanic stripe. The iris is a bronze-orange coloration with fine, black lines resembling a net like pattern. The dorsal surface of the fore- and hind limbs have transverse marks that can be dark colored to greenish. The ventral surface of the legs are red. The nuptial pad is white (Barrio-Amorós et al. 2010).

VARIATION:

Variations of dorsal color can range from light brown, creamy brown, to whitish. The contrasting dorsal W, V, or X-shape can be made up of black or brown spots and other marks are dark reddish brown to greenish. Males have vocal slits and a subgular vocal sac. In males, the shapes of the disks on fingers III and IV vary from oval, round, or heart-shaped, but not notched (Barrio-Amorós et al. 2010).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Venezuela

View distribution map in BerkeleyMapper.

The range of P. rivasi is on the east side of the Sierra de Perijá mountain range in Zulia state, Venezuela at elevations between 1,438 to 1,933 meters above sea level (Meza-Joya et al. 2016). The species has also been found in the northern region of the Andes mountain range in Columbia (Barrio-Amorós et al. 2010).

The habitat of P. rivasi includes coffee plantations and the understory in premontane and montane forests (Meza-Joya et al. 2016) where they can be found on leaves of various bushes and palms, not exceeding four meters above ground level (Barrio-Amorós et al. 2010).

Life History, Abundance, Activity, and Special Behaviors
Pristimantis rivasi are a heavily terrestrial species and are most vocal at the beginning of the dry season in March and in July during the evening and late night. Many specimens are found hidden on the leaves of various bushes and trees close to the forest floor (Barrio-Amorós et al. 2010).

Males are often heard calling in abundance from 1800 - 2000 h, tapering off around 0130 h. Some individuals have also been heard loudly calling after heavy rains in the month of September. Their call can be described as an abundance of rhythmic clicking or ticking sound of, “cloc, cloc, cloc, cloc”, lasting up to a minute in length (Barrio-Amorós et al. 2010).

Trends and Threats
Pristimantis rivasi is listed as “Vulnerable” as they are only known from five locations with a 7,015 km² estimated extent of occurrence. However, they are common in all of those localities. Pristimantis rivasi are threatened by habitat loss and deforestation for agriculture. The majority of P. rivasi’s range occurs in one protected area, Sierra de Perijá National Park, in Venezuela (IUCN 2020). However, some areas within the park are being converted for agriculture such as coffee plantations. There are no current management plans in place (Meza-Joya 2016).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Drainage of habitat
Dams changing river flow and/or covering habitat

Comments

PHYLOGENETIC RELATIONSHIPS:

Pristimantis rivasi was placed in the P. unistrigatus species group based on morphology alone (Barrio-Amorós et al. 2010).

ETYMOLOGY

The species epithet, “rivasi” is in honor of Gilson Rivas Fuenmayor, a herpetologist from Venezuela who is one of the first founders of the species (Barrio-Amorós et al. 2010).

OTHER INTERESTING INFORMATION:

Research on P. rivasi is limited because the area they inhabit is subject to various types of hazardous occurrences such as drug trafficking, paramilitary groups, and guerrilla warfare (Barrio-Amorós et al. 2010).

At the time of the species description, P. rivasi was the largest species from the Pristimantis genus found in the Sierra de Perijá mountain range (Barrio-Amorós et al. 2010).

References

Barrio-Amoros, C. L., Rojas-Runjaic, F, Barros, T. R, (2010). “Two new Pristimantis (Anura: Terrarana: Strabomantidae) from the Sierra de Perijá, Venezuela” Zootaxa 2329, 1–21 [link]

IUCN SSC Amphibian Specialist Group. (2020). "Pristimantis rivasi." The IUCN Red List of Threatened Species 2020: e.T194803A109546019. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T194803A109546019.en. Accessed on Downloaded on 25 February 2022

Meza-Joya, F. (2016) "First records of two rain frogs, genus Pristimantis (Anura, Craugastoridae), for Colombia." Check List 12(5), 1971. [link]

Species Account Citation: AmphibiaWeb 2022 Pristimantis rivasi <https://amphibiaweb.org/species/7406> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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