Description
Bufo aucoinae is a moderately large frog, with adult males measuring up to 67.2 mm and adult females measuring up to 104.5 mm in SVL. The head is wider than long. The nearly round tympanum is small and distinct; the tympanic annulus is also distinct. The snout is sharply pointed in dorsal view and rounded in profile, and it lacks a rostral keel. The canthal, supraorbital, supratympanic, postorbital, and parietal crests are low and thin. The preorbital and pretympanic crests are reduced and barely distinct, or lacking altogether. The skin on top of the head is co-ossified to the skull. Nostrils are protuberant and directed dorsolaterally. The canthus rostralis forms a raised, canthal crest. The loreal region is slightly concave. The lip is distinct and rounded. A barely distinct suborbital crest is present that extends anteriorly from the angle of the jaw to nearly the level of the nostril. A notch at the symphysis of the upper jaw is present. Choanae, the posterior nasal apertures, are small, ovoid, and widely spaced (about 5.5 mm apart). The eye-nostril distance is approximately 60% the diameter of the orbit. Teeth and odontoids are absent. The tongue is ovoid, about four times as long as wide, and free posteriorly for about one-fourth its length. The vocal slit is small, about the width of the tongue, and is bilateral. The parotoid glands are also small and distinctly triangular (O'Neill and Mendelson 2004).

The body is robust. Many small, spiculate tubercles are scattered in the interspaces between the cranial crests. Bufo aucoinae lacks transverse folds between the parietal crests. The body dorsal skin has evenly distributed small, spiculate tubercles of relatively equal size, which become larger and less numerous laterally. There are enlarged tubercles in two paravertebral rows. The parotoid gland is smaller than the eyelids, triangular, and extends posteriorly at about 45º to the midline of the body. A lateral row of enlarged tubercles is present or weakly spiculate. The dorsal surfaces of the limbs are covered with small spiculate tubercles, and the skin on the throat and other ventral surfaces is granular. The forelimb is short and robust, and the hand is broad with short, slender fingers. Relative finger length is III > I > IV > II, and webbing and lateral fringes on the fingers are absent. The tips of the fingers are not enlarged, are smooth dorsally, and are demarcated proximally by a distinct dermal fold. The palmar tubercle is distinct, large, subcircular, and larger than the pollical tubercle, and the pollical tubercle is ovoid in shape. Subarticular tubercles are distinct, elevated, triangular in profile, and single except for a distal tubercle on fingers I, III, and IV. Small and distinct supernumerary tubercles of unequal size are scattered evenly over the palm and ventral surfaces of fingers. The hind limbs are long and slender. The tarsal fold is absent. The outer metatarsal tubercle is very small, elevated, and ovoid, while the inner metatarsal tubercle is slightly larger, distinctly elevated, and also ovoid. The toes are long and slender, with relative lengths IV > III > II > I. Lateral fringe is present on all toes. Webbing is thin. The toe tips are smooth dorsally and demarcated proximally by a distinct dermal fold. Subarticular tubercles on the feet are distinct, elevated, triangular in profile, and single. Distinct supernumerary tubercles are also distributed evenly over the ventral surfaces of the feet and toes (O'Neill and Mendelson 2004).

Nuptial pads are present as brown granular patches on dorsal surfaces of Finger I and medial surface of Finger II. Male dorsal spiculae are smaller and more concentrated than female dorsal spiculae. The lateral row of tubercles are present as a series of low, rounded tubercles in males and large, sharply pointed spiculae in females (O'Neill and Mendelson 2004).

In ethanol preservative, the dorsum of the body is dull brown medially, shading to gray-brown laterally. The top of the head is gray-brown. Color is reduced on the preorbital crest. A lateral row of tubercles coincides with the boundary between the dorsolateral coloration and dark brown lateral coloration. The flanks are slightly paler than the dorsolateral area. Dorsal markings consist of a thin, pale gray dorsal stripe. The dorsal surfaces of the arms and legs are dull brown, and many of the tubercles have red-brown apices. The forearm has a distinct, wide, dark transverse bar. Dark brown lateral coloration extends anteriorly over the tympanic area. Loreal and suborbital regions are dull brown. The lip is pale cream and the parotoid glands are gray-brown. The throat is dull cream and becomes a paler cream anteriorly. The venter is pale cream, and ventral surfaces of the hands are dull cream with pale cream tubercles. The ventral surfaces of the forearms are dark brown, and the ventral surfaces of the legs are dull cream. The mid-dorsal stripe may be faint or distinct. Gray spots are sometimes present on males. Ventral surfaces are usually plain and lack dark markings on the throat and venter, although faint mottling on the chest and throat may be present. Dorsal spiculae and cranial crests may appear distinctly red-brown in color. Juveniles show similar color pattern variation, but have a darker ventral region. This dark ventral coloration fades to the typical plain cream color as the individual matures (O'Neill and Mendelson 2004).

Bufo aucoinae is similar to B. melanochlorus, but can be distinguished by its lack of transverse folds between the parietal crests, weak or absent pretympanic and preorbital crests, relatively unmarked venter, and relatively small and unpigmented vocal sac (O'Neill and Mendelson 2004).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Costa Rica, Panama

View distribution map in BerkeleyMapper.

Bufo aucoinae is distributed over the lowland Pacific southwest area of Costa Rica up to 600 m above sea level. It occurs in lowland moist and wet forests (Savage 2002). A single specimen has also been found in the adjacent region in Chiriqui, Panama (O'Neill and Mendelson 2004).

Life History, Abundance, Activity, and Special Behaviors
Bufo aucoinae is a nocturnal and terrestrial species that belongs to a clade of frog considered intolerant of habitat disturbance (Mendelson pers. comm. cited in IUCN Ryan pers. comm. cited in IUCN). Adults are restricted to primary forest but may migrate across degraded habitat to large streams and rivers where they breed during the dry season (January-February) (Savage 2002; O'Neill and Mendelson 2004).

Bufo aucoinae is syntopic with Smilisca sordida, but does not readily feed on S. sordida eggs (Malone 2006).

Trends and Threats
Bufo aucoinae is listed as Vulnerable by the IUCN (2006) due to having a range of occurrence below 20,000 sq. km, having particular habitat requirements, being sensitive to habitat degradation, and massive habitat fragmentation and degradation within its range. The main threats to this species come from cattle ranching and plantation forestry, as well as loss of access to breeding streams and poisoned rivers from the freshwater shrimp industry (IUCN 2006).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Habitat fragmentation
Local pesticides, fertilizers, and pollutants

Comments
Bufo aucoinae was previously considered part of the species B. melanochlorus. It was named in honor of Lisa Louise Aucoin, who passed away August 2001 as a graduate student at Southeastern Louisiana University (O'Neill and Mendelson 2004).

A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).

References

IUCN, Conservation International, and NatureServe. (2006). Global Amphibian Assessment: Bufo aucoinae. www.globalamphibians.org. Accessed on 14 November 2007.

Malone, J. H. (2006). ''Ecology of the basin construction reproductive mode in Smilisca sordida (Anura: Hylidae).'' Journal of Herpetology, 40(2), 230-239.

O'Neill, E. M., and Mendelson III, J. R. (2004). ''Taxonomy of Costa Rican toads referred to Bufo melanochlorus Cope, with the description of a new species.'' Journal of Herpetology, 38(4), 487-494.

Savage, J. M. (2002). The Amphibians and Reptiles of Costa Rica:a herpetofauna between two continents, between two seas. University of Chicago Press, Chicago, Illinois, USA and London.

Species Account Citation: AmphibiaWeb 2009 Incilius aucoinae <https://amphibiaweb.org/species/6409> University of California, Berkeley, CA, USA. Accessed Dec 22, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Dec 2024.

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