Neotropical Hylid Frogs, Genus Smilisca Part 2

Specimens from southern Sinaloa are outstanding in the large size of the tympanum; the tympanum/eye ratio varies from 84.2 to 94.4 (average 87.8). In most other samples the variation in average ratios ranges from 72.2 to 79.3, but specimens from Veracruz have an average ratio of 70.0; Campeche, 65.7; Honduras, 67.0; and Limon, Costa Rica, 68.5.

No noticeable geographic trends in size and proportions are evident.

Specimens from southern Sinaloa are extreme in their large size, relatively short tibia, and large tympani, but in size and relative length of the tibia the Sinaloan frogs are approached by specimens from such far-removed localities as San Salvador, El Salvador, and Chinaja, Guatemala. Frogs from the Caribbean lowlands of Honduras and Costa Rica are relatively large and have relatively long tibiae and small tympani.

The inner metatarsal tubercle is large and high and its shape varies.

The tubercle is most p.r.o.nounced in specimens from northwestern Mexico, Tamaulipas, and the Pacific lowlands of Central America. Possibly the large tubercle is a.s.sociated with drier habitats, where perhaps the frogs use the tubercles for digging.

The ground color of _Smilisca baudini_ is pale green to brown dorsally and white to creamy yellow ventrally. The dorsum is variously marked with dark brown or dark olive-green spots or blotches (Pl. 6A). In most specimens a dark interorbital bar extends across the head to the lateral edges of the eyelid; usually this bar is connected medially to a large dorsal blotch. There is no tendency for the markings on the dorsum to form transverse bands or longitudinal bars. In specimens from the southern part of the range the dorsal dark markings are often fragmented into small spots, especially posteriorly. The limbs are marked by dark transverse bands, usually three on the forearm, three on the thigh, and three or four on the shank. Transverse bands also are present on the tarsi and proximal segments of the fingers and toes. The webbing on the hands and feet is pale grayish brown. The loreal region and upper lip are pale green or tan; the lip usually is boldly marked with broad vertical dark brown bars, especially evident is the bar beneath the eye.

A dark brown or black mark extends from the tympanum to a point above the insertion of the forearm; in some specimens this black mark is narrow or indistinct, but in most individuals it is quite evident. The flanks are pale gray to creamy white with brown or black mottling, which sometimes forms reticulations enclosing white spots. The anterior surfaces of the thighs usually are creamy white with brown mottling, whereas the posterior surfaces of the thighs usually are brown with small cream-colored flecks. A distinct creamy white a.n.a.l stripe usually is present. Usually, there are no white stripes on the outer edges of the tarsi and forearms. In breeding males the throat is gray.

Most variation in coloration does not seem to be correlated with geography. The lips are strongly barred in specimens from throughout the range of the species, except that in some specimens from southern Nicaragua and Costa Rica the lips are pale and in some specimens the vertical bars are indistinct. Six specimens from 7.3 kilometers southwest of Matatan, Sinaloa, are distinctively marked. The dorsum is uniformly grayish green with the only dorsal marks being on the tarsi; canthal and post-tympanic dark marks absent. A broad white l.a.b.i.al stripe is present and interrupted by a single vertical dark mark below the eye.

A white stripe is present on the outer edge of the foot. The flanks and posterior surfaces of the thighs are creamy white, boldly marked with black. Two specimens from Alta Verapaz, Guatemala (CNHM 21006 from Coban and UMMZ 90908 from Finca Canihor), are distinctive in having many narrow transverse bands on the limbs and fine reticulations on the flanks. Two specimens from Limon Province, Costa Rica (KU 34927 from Batan and 36789 from Suretka), lack a dorsal pattern; instead these specimens are nearly uniform brown above and have only a few small dark brown spots on the back and lack transverse bands on the limbs. The post-tympanic dark marks and dark mottling on the flanks are absent.

Specimens lacking the usual dorsal markings are known from scattered localities on the Caribbean lowlands from Guatemala to Costa Rica.

The coloration in life is highly variable; much of the apparent variation is due to metachrosis, for individuals of _Smilisca baudini_ are capable of undergoing drastic and rapid change in coloration. When active at night the frogs usually are pale bright green with olive-green markings, olive-green with brown markings, or pale brown with dark brown markings. The dark markings on the back and dorsal surfaces of the limbs are narrowly outlined by black. The pale area below the eye and just posterior to the broad suborbital dark bar is creamy white, pale green, or ashy gray in life. The presence of this mark is an excellent character by which to identify juveniles of the species. The flanks are creamy yellow, or yellow with brown or black mottling. In most individuals the belly is white, but in specimens from southern El Peten and northern Alta Verapaz, Guatemala, the belly is yellow, especially posteriorly. The iris varies from golden bronze to dull bronze with black reticulations, somewhat darker ventrally.

_Natural History._--Throughout most of its range _Smilisca baudini_ occurs in sub-humid habitats; consequently the activity is controlled by the seasonal nature of the rainfall and usually extends from May or June through September. Throughout Mexico and Central America the species is known to call and breed in June, July, and August. Several records indicate that the breeding season in Central America is more lengthy.

Gaige, Hartweg, and Stuart (1937:4) noted gravid females collected at El Recreo, Nicaragua, in August and September. Schmidt (1941:486) reported calling males in February in British Honduras. Stuart (1958:17) stated that tadpoles were found in mid-February, juveniles in February and March and half-grown individuals from mid-March to mid-May at Tikal, El Peten, Guatemala. Stuart (1961:74) reported juveniles from Tikal in July, and that individuals were active at night when there had been light rain in the dry season in February and March in El Peten, Guatemala. _Smilisca baudini_ seeks daytime retreats in bromeliads, elephant-ear plants (_Xanthosoma_), and beneath bark or in holes in trees. By far the most utilized retreat in the dry season in parts of the range is beneath the outer sheaths of banana plants. Large numbers of these frogs were found in banana plants at Cuautlapan, Veracruz, in March, 1956, in March and December, 1959.

Large breeding congregations of this frog are often found at the time of the first heavy rains in the wet season. Gadow (1908:76) estimated 45,000 frogs at one breeding site in Veracruz. In the vicinity of Tehuantepec, Oaxaca, large numbers of individuals were found around rain pools and roadside ditches in July, 1956, and July, 1958; large concentrations were found near Chinaja, Guatemala, in June, 1960, and near Esparta, Costa Rica in July, 1961. Usually males call from the ground at the edge of the water or not infrequently sit in shallow water, but sometimes males call from bushes and low trees around the water. Stuart (1935:38) recorded individuals calling and breeding throughout the day at La Libertad, Guatemala. _Smilisca baudini_ usually is absent from breeding congregations of hylids; frequently _S. baudini_ breeds alone in small temporary pools separated from large ponds where numerous other species are breeding. In Guerrero and Oaxaca, Mexico, _S.

baudini_ breeds in the same ponds with _Rhinophrynus dorsalis_, _Bufo marmoreus_, _Engystomops pustulosus_, and _Diaglena reticulata_, and in the vicinity of Esparta, Costa Rica, _S. baudini_ breeds in ponds with _Bufo coccifer_, _Hyla staufferi_, and _Phrynohyas venulosa_. In nearly all instances the breeding sites of _S. baudini_ are shallow, temporary pools.

The breeding call of _Smilisca baudini_ consists of a series of short explosive notes. Each note has a duration of 0.09 to 0.13 seconds; two to 15 notes make up a call group. Individual call groups are s.p.a.ced from about 15 seconds to several minutes apart. The notes are moderately high-pitched and resemble "wonk-wonk-wonk." Little vibration is discernible in the notes, which have 140 to 195 pulses per second and a dominant frequency of 2400 to 2725 cycles per second (Pl. 10A).

The eggs are laid as a surface film on the water in temporary pools. The only membrane enclosing the individual eggs is the vitelline membrane.

In ten eggs (KU 62154 from San Salvador, El Salvador) the average diameter of the embryos in first cleavage is 1.3 mm. and of the vitelline membranes, 1.5 mm. Hatchling tadpoles have body lengths of 2.6 to 2.7 mm. and total lengths of 5.1 to 5.4 mm. The body and caudal musculature is brown; the fins are densely flecked with brown. The gills are long and filamentous. Growth and development of tadpoles are summarized in Table 9.

A typical tadpole in stage 30 of development (KU 60018 from Chinaja, Alta Verapaz, Guatemala) has a body length of 8.7 mm., a tail length of 13.6 mm., and a total length of 22.3 mm.; body slightly wider than deep; snout rounded dorsally and laterally; eyes widely separated, directed dorsolaterally; nostril about midway between eye and tip of snout; mouth anteroventral; spiracle sinistral, located about midway on length of body and slightly below midline; a.n.a.l tube dextral; caudal musculature slender, slightly curved upward distally; dorsal fin extending onto body, deepest at about one-third length of tail; depth of dorsal fin slightly more than that of ventral fin at mid-length of tail; dorsal part of body dark brown; pale crescent-shaped mark on posterior part of body; ventral surfaces transparent with scattered brown pigment ventrolaterally, especially below eye; caudal musculature pale tan with a dark brown longitudinal streak on middle of anterior one-third of tail; dorsum of anterior one-third of tail dark brown; brown flecks and blotches on rest of caudal musculature, on all of dorsal fin, and on posterior two-thirds of ventral fin; iris bronze in life (Fig. 11).

Mouth small; median third of upper lip bare; rest of mouth bordered by two rows of conical papillae; lateral fold present; tooth rows 2/3; two upper rows about equal in length; second row broadly interrupted medially, three lower rows complete, first and second equal in length, slightly shorter than upper rows; third lower row shortest; first upper row sharply curved anteriorly in midline; upper beak moderately deep, forming a board arch with slender lateral processes; lower beak more slender, broadly V-shaped; both beaks bearing blunt serrations (Fig. 15A).

In tadpoles having fully developed mouthparts the tooth-row formula of 2/3 is invariable, but the coloration is highly variable. The color and pattern described above is about average. Some tadpoles are much darker, such as those from 11 kilometers north of Vista Hermosa, Oaxaca, (KU 87639-44), 3.5 kilometers east of Yokdzonot, Yucatan (KU 71720), and 4 kilometers west-southwest Puerto Juarez, Quintana Roo, Mexico (KU 71721), whereas others, notably from 17 kilometers northeast of Juchatengo, Oaxaca, Mexico (KU 87645), are much paler and lack the dark markings on the caudal musculature. The variation in intensity of pigmentation possibly can be correlated with environmental conditions, especially the amount of light. In general, tadpoles that were found in open, sunlit pools are pallid by comparison with those from shaded forest pools. These subjective comparisons were made with preserved specimens; detailed comparative data on living tadpoles are not available.

The relative length and depth of the tail are variable; in some individuals the greatest depth of the tail is about at mid-length of the tail, whereas in most specimens the tail is deepest at about one-third its length. The length of the tail relative to the total length is usually 58 to 64 per cent in tadpoles in stages 29 and 30 of development. In some individuals the tail is about 70 per cent of the total length. On the basis of the material examined, these variations in proportions do not show geographical trends. Probably the proportions are a reflection of crowding of the tadpoles in the pools where they are developing or possibly due to water currents or other environmental factors.

Stuart (1948:26) described and ill.u.s.trated the tadpole of _Smilisca baudini_ from Finca Chejel, Alta Verapaz, Guatemala. The description and figures agree with ours, except that the first lower tooth row does not have a sharp angle medially in Stuart's figure. He (1948:27) stated that color in tadpoles from different localities probably varies with soil color and turbidity of water. Maslin (1963:125) described and ill.u.s.trated tadpoles of _S. baudini_ from Piste, Yucatan, Mexico. These specimens are heavily pigmented like specimens that we have examined from the Yucatan Peninsula and from other places in the range of the species. Maslin stated that the a.n.a.l tube is median in the specimens that he examined; we have not studied Maslin's specimens, but all tadpoles of _Smilisca_ that we have examined have a dextral a.n.a.l tube.

Newly metamorphosed young have snout-vent lengths of 12.0 to 15.5 mm.

(average 13.4 in 23 specimens). The largest young are from La Libertad, El Peten, Guatemala; these have snout-vent lengths of 14.0 to 15.5 mm.

(average 14.5 in five specimens). Young from 11 kilometers north of Vista Hermosa, Oaxaca, Mexico, are the smallest and have snout-vent lengths of 12.0 to 12.5 mm. (average 12.3 in three specimens). Recently metamorphosed young usually are dull olive green above and white below; brown transverse bands are visible on the hind limbs. The l.a.b.i.al markings characteristic of the adults are represented only by a creamy white suborbital spot, which is a good diagnostic mark for young of this species. In life the iris is pale gold.

_Remarks_: The considerable variation in color and the extensive geographic distribution of _Smilisca baudini_ have resulted in the proposal of eight specific names for the frogs that we consider to represent one species. Dumeril and Bibron (1841:564) proposed the name _Hyla baudini_ for a specimen (MNHN 4798) from Mexico. Smith and Taylor (1950:347) restricted the type locality to Cordoba, Veracruz, Mexico, an area where the species occurs in abundance. Baird (1854:61) named _Hyla vanvlieti_ from Brownsville, Texas, and (1859:35) labelled the figures of _Hyla vanvlieti_ [= _Hyla baudini_] on plate 38 as _Hyla vociferans_, a _nomen nudum_. Cope (1862:359) named _Hyla muricolor_ from Mirador, Veracruz, Mexico, and (1865:194) used the name _Smilisca daulinia_ for a skeleton that he employed as the basis for the cranial characters diagnostic of the genus _Smilisca_, as defined by him. Although we cannot be certain, Cope apparently inadvertently used _daulinia_ for _baudini_, just as he used _daudinii_ for _baudini_ (1871:205). Brocchi (1877:125) named _Hyla pansosana_ from Panzos, Alta Verapaz, Guatemala.

[Ill.u.s.tration: PLATE 1

A

B

Dorsal views of skulls of young _Smilisca baudini_: (A) recently metamorphosed young (KU 60026), snout-vent length 12.6 mm. 23; (B) young (KU 85438), snout-vent length 32.1 mm. 9.]

[Ill.u.s.tration: PLATE 2

A

B

Skull of adult female _Smilisca baudini_ (KU 68184): (A) Dorsal; (B) Ventral. 4.5.]

[Ill.u.s.tration: PLATE 3

A

B

C

Skull of adult female _Smilisca baudini_ (KU 68184): (A) Lateral; (B) Dorsal view of left mandible; (C) Posterior. 4.5.]

[Ill.u.s.tration: PLATE 4

A B

C D

E F

Palmar views of right hands of _Smilisca_: (A) _S. baudini_ (KU 87177); (B) _S. phaeota_ (KU 64276); (C) _S. cyanosticta_ (KU 87199); (D) _S. sordida_ (KU 91761); (E) _S. puma_ (KU 91716), and (F) _S. sila_ (KU 77408). 3.]

[Ill.u.s.tration: PLATE 5

A B

C D

E F

Ventral aspect of right feet of _Smilisca_: (A) _S. baudini_ (KU 87177); (B) _S. phaeota_ (KU 64276); (C) _S. cyanosticta_ (KU 87199); (D) _S. sordida_ (KU 91761); (E) _S. puma_ (KU 91716), and (F) _S. sila_ (KU 77408). 3.]

[Ill.u.s.tration: PLATE 6

A

B

C

Living _Smilisca_: (A) _S. baudini_ (UMMZ 115179) from 1.7 km. W Xicotencatl, Tamaulipas, Mexico; (B) _S. cyanosticta_ (UMMZ 118163) from Volcan San Martin, Veracruz, Mexico; (C) _S. phaeota_ (KU 64282) from Barranca del Rio Sarapiqui, Heredia Prov., Costa Rica.