Norton's Robber Frog

Eleutherodactylus nortoni is a large sized frog with a snout-vent length ranging from 52.3 – 65.7 mm in males. There is no information to date about females of this species. The head of this frog is greater in width than in length and the snout is short and downward sloping when viewed from the side. It has a curved canthus rostralis with nares that are slightly ventral to the canthus and not very noticeable. The distance from the naris to the anterior edge of the eye is slightly less than the diameter of the eye, and the interorbital distance is significantly less than the diameter of the eye. The tympanum has a diameter that is roughly 1.5 times the distance between the tympanum and the eye. The long, unwebbed forefingers end with large terminal disks (the terminal disk on the third digit is about one-half the size of the tympanum) and have relative lengths of 1 < 2 < 4 < 3. Subarticular tubercles are visible, and the outer metatarsal tubercle being the most lengthy (nearly as long as the fifth toe). Eleutherodactylus nortoni has a dorsum that is covered in wrinkles, the most prominent of which are the dorsolateral folds. In between the eyes are two folds in the anterior-posterior direction that are connected by a perpendicular fold to give an “H” shape. The upper eyelids have a large spine and many smaller pustules. The area between the eyes and nares and the area between the eye and tympanum are covered in pustules as well. The dorsal surfaces of the hindlimbs are grainy and display small, longitudinal wrinkles. The throat and belly are also grainy, and the ventral surfaces of the hindlimbs are smooth (Schwartz 1976).Eleutherodactylus nortoni is most similar to the frogs in the inoptatus group, which includes E. inoptatus, E. ruthae, and E. hypostenor. Eleutherodactylus nortoni is easily distinguished by its short and downward pointing snout, its irregular forest green spots on the dorsum, its dark gray to black throat, chest, and ventral markings, the unique pattern of coloration of its iris, and by its voice. Eleutherodactylus nortoni and E. inoptatus both have a large spine on the upper eyelid. However, whereas the rest of the upper eyelid in E. inoptatus is smooth, it is wrinkled and covered in small pustules in E. nortoni. Moreover, E. inoptatus is a much larger frog than E. nortoni (snout-vent length 64.8 – 73.4 mm in E. inoptatus vs. 52.3 – 65.7 mm in E. nortoni). Eleutherodactylus ruthae and E. nortoni both have irregular spots on the dorsal surface. However, whereas the spots are only forest green in E. nortoni, they are never green in E. ruthae. Eleutherodactylus nortoni has a short, curved snout while E. ruthae’s is pointed. Furthermore, E. nortoni has much larger terminal disks on its fingers than E. ruthae (not all subspecies of E. ruthae even have terminal disks). And lastly, E. ruthae is a smaller frog than E. nortoni as well (snout-vent length 39.6 – 57.8 mm in E. ruthae but tends to be closer to the lower extreme vs. 52.3 – 65.7 mm in E. nortoni). Eleutherodactylus hypostenor has dorsal spots similar to E. nortoni although they do not cover as much of the dorsal surface as those on E. nortoni. Moreover, E. hypostenor is never green in color. Also whereas E. nortoni has a short, downward sloping snout, E. hypostenor has a pointed snout and an uncurved canthus. Lastly, E. nortoni is a slightly larger frog than E. hypostenor (snout-vent length 47.3 – 54.4 mm in E. hypostenor vs. 52.3 – 65.7 mm in E. nortoni; Schwartz 1976).In life, Eleutherodactylus nortoni is lime green with irregular forest green spots on the dorsum. Laterally, the forest green spots are diagonal. More lateral to the diagonal spots are forest green spots that are nearly circular and located between the two pairs of limbs. It has a golden tympanum with a dorsal black spot. There is a pair of raised pale yellow dorsolateral wrinkles, and the rest of the wrinkles on the dorsum are this same pale yellow color. Eleutherodactylus nortoni has a forest green line that goes ventrally from the eye beyond the lips. The femora has three forest green stripes over a lighter green background with gray specks; the most proximal stripe is less prominent than the other two as the gray speckling overshadows it. The foot also has three forest green stripes separated by lighter green with gray mottling. The medial surface of the thigh is silver or silver-green and streaked with the same pale yellow as the wrinkles on the dorsal surface. All the wrinkles on the hindlimbs are pale yellow as well. Eleutherodactylus nortoni has bottle green to black lips with avocado green spots. The ventral surface of this frog is beige. The throat and chest are black and lead into irregular black spots on the belly. The ventral surface of the forelimb is speckled with black. The ventral surface of the hindlimb is speckled with black laterally but the center is beige. The iris is dorsally golden and ventrally silver and has red-orange triangles in the 3-o’clock and 9-o’clock positions that separate the golden and silver colored regions (Schwartz 1976).In some live specimens, the throat and chest are dark gray, as are the irregular spots on the belly. The background color on the ventral surface can be a pale amber color. In comparison to the specimens found in Haiti, those from the Dominican Republic tend to be more pale dorsally and more orange ventrally. Moreover, the Dominican specimens tend to be smaller than the Haitian ones (Schwartz 1976).The species authority is: Schwartz A. 1976. Two new species of Hispaniolan Eleutherodactylus (Leptodactylidae). Herpetologica 32(2): 163-171.Of the five specimens described by Schwartz, James W. Norton, who accompanied Schwartz on the expedition, captured four, including the holotype; Schwartz therefore decided to name the species after Norton (Schwartz 1976).

Eleutherodactylus nortoni is found in the deciduous forests of the Massif de la Selle and Massif de la Hotte in Haiti and Sierra de Bahoruco in the Dominican Republic. However, due to habitat loss, much of these forests are now urbanized. This frog species requires trees for cover and protection and is often found in the cafeiéres in Haiti and cafetales in the Dominican Republic, the terms used for coffee bean farms in their respective countries, because the original forest trees are left to provide shade to the crops. Eleutherodactylus nortoni has been found at elevations between 576 – 1,515 m. The lower extreme of the elevation range may be due to the removal of forest trees in the Haitian mountains below Seguin for the cultivation of banana trees. Moreover, the low elevation point in the Dominican Republic was in a moist, lush canyon that is crossed by the Pedernales-Los Arroyos road; both below and above the canyon, the mountains are unsuitable for this frog species as they are covered by arid Acacia forest (Schwartz 1976; Stuart et al. 2008).

Eleutherodactylus nortoni has a unique call that is unlike those of other related species. In one sequence, E. nortoni produces approximately five glissando rising trills and then concludes its call with a whistle. The majority of specimens of E. nortoni that have been captured while calling were found on tall branches and rocks. However, one specimen was found inside a hole on a mound on the forest floor that was presumably formed as a tree root rotted. The cavity in which this specimen was found was not enclosed or roofed and was not constructed by the frog (unlike E. ruthae and E. hypostenor, which burrow underground). Eleutherodactylus nortoni calls during the day, frequently much earlier than sunset, particularly if there is abundant rainfall in the afternoon. The calls are less frequent at night. It lays eggs on the forest floor and breeds by direct development (Schwartz 1976; Stuart et al. 2008).

Eleutherodactylus nortoni is listed as Critically Endangered by the IUCN because severe habitat degradation in Hispaniola, the primary threat to the species, is anticipated to cause an 80% decline over the next ten years. Habitat degradation is a result of mining, charcoaling, and agriculture even in the protected regions of the Massif de la Selle and the Tiburon Peninsula of Haiti and in Sierra de Bahoruco in the Dominican Republic. There is no conservation management of the protected areas in Haiti, and little in the Dominican Republic, where Eleutherodactylus nortoni is found. In order to prevent a massive population decline, it is imperative that the management of the protected areas is strengthened and the remaining habitat is preserved. Moreover, a survey must be conducted to confirm the population status of Eleutherodactylus nortoni (Hedges et al. 2010).

The spiny giant frog or Norton's robber frog (Eleutherodactylus nortoni) is a species of frog in the family Eleutherodactylidae. It is named after James W. Norton who accompanied Albert Schwartz in his 1974 expedition to Hispaniola and collected the holotype.