Atelopus boulengeri Peracca 1904

Atelopus boulengeri Peracca

Atelopus Boulengeri Peracca, 1904:20 [type locality: “di Gualaquiza e parecchi di S. Jose, Ecuador orientale”].

Atelopus bicolor Noble, 1921:3, fig. 4 [type locality: Cordillera Kutuku, east of Macas, Ecuador, 1800–2000 m].—Rivero, 1963:107.

A.[telopus] boulengeri.—Nieden, 1926:82.—Rivero, 1963:107.

SYNTYPES.—Six specimens, UT An. 560, from San Jose, and eleven specimens, UT An. 559, from Gualaquiza, in the Zoological Museum of the University of Torino, Italy.

DESCRIPTION.—Snout from above with rounded tip, outward curve of muzzle becoming inward curve from nostril to eye; snout, canthus, and upper eyelid fleshy and raised, with fleshy ridge from posterior corner of eye to edge of head. Dorsum of head between these raised, fleshy areas flat, broad and smooth, lying in same plane as broad, flat back. Snout from side slightly protrusive beyond upper lip and lower jaw, nostril lateral, below fleshy area of canthus, and directed slightly posteriorly. Loreal region strongly concave behind nostril; eye overhung by fleshy margin of eyelid, upper lip somewhat fleshy. No tubercles or pustules anywhere on head or body. Dorsum and sides of body smooth or finely wrinkled, belly with more prominent and distinct wrinkles.

Forelimb slender, forearm usually somewhat more fleshy than humeral region, dorsum weakly pustulate, rest of arm smooth. When forelimb is pulled back along body, palm of hand reaches vent. Entire hand fleshy, quite heavy around first digit, which is clearly distinct and prominent, second digit shorter than fourth, subarticular tubercles at base of digits only. Tips of digits prominent, slightly swollen ventrally. Palmar tubercle distinct, plantar tubercle present. Edge of prepollex with horny excrescence in males.

Hind limb slender, smooth except for few low, very indistinct pustules on dorsum. Tibiotarsal articulation reaches to points between posterior margin of eye and arm insertion when carried forward along body; heels do not overlap or touch when tibiofibulae are parallel to femora at right angles to body. Entire foot with fleshy webbing to tips of toes; webbing somewhat excised between last three toes and reaching tip of fourth toe as fringe only; first and second toes almost totally hidden in webbing, tips of all toes free and somewhat prominent, with slight swelling. Subarticular tubercles weak, outer metatarsal tubercle raised and prominent but smaller than the flattened, rounded inner metatarsal tubercle.

COLOR IN ALCOHOL.—Dorsum usually unicolor, chocolate brown, dark brown, or blackish; extending slightly onto sides of body, where it is sharply set off by yellow of sides and belly, both of which are also unicolor. Dorsum of head with dorsal color extending to varying degrees anteriorly; in some it ends at eye level, in others it covers snout. Side of head, lips, chin, and throat all monochrome yellowish. Limbs usually slightly darker yellow than venter, with rings of brown around all joints. Dorsum of first finger and first two toes often lighter than rest of foot. Ventral surfaces of feet usually dark, with lighter tubercles. Brown of dorsum usually extends over posterior margin of legs and forms brown “seat” or “diaper” on rear of venter, with anus usually bright yellow in center of this brown area.

COLOR IN LIFE.—Rich chocolate brown dorsally, with bright yellow laterally and ventrally.

ECOLOGY.—The two specimens collected in 1962 were found along a trail in fairly heavy subtropical forest, in full daylight, about 11:00 A. M. Both were walking, not hopping, along the trail, fully exposed, and made no effort to avoid being captured.

SYNTYPES.—The 17 syntypes agree completely with the description above, with the series exhibiting all the variations mentioned in the description. Some of the specimens from Gualaquiza are somewhat dried, and the digits do not have either as thick or as full a webbing as in fresh specimens, but the San José series is in good condition, and the digits are as described. Only one specimen in the series shows a yellow area at the anus; the rest have the anal region the same color as the dorsum.

COMPARISONS.—The differences between boulengeri and bicolor appear to be the consequence of differences between investigators, rather than between the types. The primary distinguishing characters pointed out by Noble in the description of bicolor were the development of the webbing and several proportions. Noble said the digits of the forefoot were webless, while Peracca described the webbing between the second, third, and fourth fingers as rudimentary, and as relatively well developed between the first and second fingers. The area between these digits is actually quite fleshy, and it appears that Peracca considered this fleshiness equivalent to webbing, while Noble, who illustrated this area clearly in his figure, thought it should not be called webbed at all. The description of the webbing of the hind foot by Peracca is quite consistent with Noble’s figure, although Peracca described the foot as strongly webbed, while Noble said, “toes webbed to the tips…but the web deeply indented, making the toes appear half webbed.” The differences in proportions are quite minor, and could easily be the result of different techniques in measuring. Thus, in boulengeri the head length is contained in the body length 2½ to 3 times, according to Peracca, while in bicolor, according to Noble, the body is 3½ times as long as the head. But Noble clearly indicated that the head length meant from snout to angle of jaw, and no one knows for sure how Peracca made his head length measurement. There are several other standard head length measurements that might give a larger value, and thus a smaller proportion, for Noble’s specimens.

Although there may have been some geographical validity for retaining the two species prior to our field work in 1962, the two specimens we obtained weaken this validity considerably. The type series for boulengeri came from Gualaquiza, a town in the valley of the Río Zamora, at 950 meters. Noble’s specimens came from quite a bit higher in an isolated Cordillera to the east of the valley of the Río Upano, a tributary of the Namangoza, which joins the Zamora to form the Río Santiago. The two new specimens come from the eastern slopes of the main Andean chain at an altitude of 1560 meters, and some distance to the west of the valley of the Namangoza. This indicates an altitudinal range of about 600 meters, with the species occupying the foothills and mountain slopes of the headwater streams of the Santiago up to an altitude of 1560 meters.

Rivero (1963:110) regarded A. bicolor Noble as probably not referable to any other Ecuadorian species, but later (1968:23) indicated that it is “certainly a synonym of A. boulengeri Peracca.” He records four specimens from Turula, which he indicates as being east of Macus, but there is only one specimen in the AMNH from Turula, which is a “tambo” on one of the mule trails from Riobamba to the Amazonian region, and lies northwest of Macas. The bicolor paratypes, AMNH 13133–35, are not from Turula (see below).

SPECIMENS EXAMINED.—ECUADOR: no additional data (AMNH 17427–28, 17430–31). Morona-Santiago Province; Cordillera Cutucú (AMNH 13132—holotype of bicolor, AMNH 13133–35—paratypes of bicolor, UKMNH 108940, USNM 193493), Gualaquiza (UT An. 559—syntypes of boulengeri), Río Piuntza, 1830 m (UKMNH 147071–81), San José (UT An. 560—syntypes of boulengeri), Turula (AMNH 33893), between Mirador and Copal, on mule trail from Sevilla de Oro to Mendez, 1600 m (USNM 193491–92). Loja Province; San Ramón (JAP 8934).

Atelopus boulengeri, Boulenger's stubfoot toad, is a small species of toad in the family Bufonidae endemic to humid montane forest in southern Ecuador. It has not been seen since 1984, but some of the known sites have not been well surveyed, so it may still survive. The threats are habitat loss and the disease chytridiomycosis.