A Distributional Study of the Amphibians of the Isthmus of Tehuantepec, Mexico Part 7

Although _Leptodactylus l.a.b.i.alis_ does not appear to be so abundant as _Leptodactylus melanonotus_, the former was found throughout the lowlands of the isthmus. In the dry season individuals were found along streams, and in the rainy season breeding congregations were found in rain pools, marshes, ponds, and even small puddles. The call is a slow "wort, wort, wort." Males call beneath the water and from beneath rocks and from holes in the ground. The average snout-vent length of eight adult males is 37.2 mm. A completely metamorphosed juvenile obtained at Hueyapan on July 24, 1956, has a snout-vent length of 11 mm.

=Leptodactylus melanonotus= Hallowell

_Oaxaca_: Agua Caliente (25); Cerro Arenal (2); Cerro Quiengola (3); Cerro San Pedro (3); Chivela (2); Coyol; Juchitan; Matias Romero (11); Mixtequilla (2); Papaloapan (2); Salazar (9); Salina Cruz; 11 km. S of Santiago Chivela; Tapanatepec (17); Tehuantepec (176); Tolosita; Union Hidalgo; 27 km. W of Zanatepec (6). _Veracruz_: Acayucan; Cuatotolapam (9); Cosoleacaque; 20 km. ENE of Jesus Carranza (2); 20 km. SE of Minat.i.tlan (2); Novillero; San Lorenzo (6).

This frog is abundant throughout the lowlands of the isthmus, where in the dry season individuals were found along streams and beneath rocks at a spring seepage. In the rainy season males were calling from nearly every bit of standing water. The call is a soft clicking sound resembling that made by striking two small stones together. The average snout-vent length of ten adult males is 41.8 mm. There is considerable variation in the extent of the yellowish brown glandular areas on the belly. Some have none, whereas others have a broad area on the chest, a band along the flanks, and a thin band across the lower abdomen.

Individuals collected in the dry season vary in the same fas.h.i.+on as do those collected in the rainy season, at which time they were breeding.

The glands are equally well-developed in adults of both s.e.xes, and were present in some juveniles with snout-vent lengths of less than 20 mm.

Apparently the development of the glands is not a.s.sociated with maturity, s.e.x, or size.

=Diaglena reticulata= Taylor

_Oaxaca_: Cerro Arenal; Chivela; Salina Cruz (26); San Antonio (3); Tehuantepec (2); 8.6 km. W of Tehuantepec (11); Zarzamora.

Breeding congregations of this rare frog were found 8.6 kilometers west of Tehuantepec on July 5, 1956, and at Salina Cruz on July 6, 1958.

Both choruses took place immediately after torrential rains. In both instances the frogs were in and about open muddy pools in the scrub forest (Pl. 5, fig. 2); males called from the bank near the water, and clasping pairs were found only on land (Pl. 8, figs. 1-2). The call is a loud, nasal "braaa," two to three seconds in duration. Amplexus is axillary.

The dorsal ground color is light yellowish green tending towards olive on the head and fading to yellow on the flanks. The ventral surfaces, including the vocal sac, are white; the iris is golden and flecked with black. The present series agrees well with the description of _reticulata_ (based on two specimens) given by Taylor (1942:60). A detailed a.n.a.lysis of variation, comparison with related species, and descriptions of tadpoles are reserved for a future report.

=Hyla baudini= Dumeril and Bibron

_Oaxaca_: Bisilana; Cerro Quiengola (2); Cerro San Pedro; Coyol; Matias Romero (12); Mixtequilla; Rio Sarabia (7); Salazar; San Antonio; 11 km. S of Santiago Chivela; Santo Domingo (3); Tapanatepec (2); Tehuantepec (23); Tolosita.

_Veracruz_: Acayucan; Amat.i.tlan; Ciudad Aleman (3); Cosamaloapan (2); Cuatotolapam (15); 10 km. SE of Hueyapan; 20 km. S of Jesus Carranza; 38 km. S of Jesus Carranza (2); 20 km. ENE of Jesus Carranza (4); La Oaxaquena (2); Minat.i.tlan (2); Naranja (3); Novillero (9); Rio de las Playas (2); San Lorenzo (5); Tapalapan (2).

Commonly found on both sides of the isthmus, this large tree frog nearly always is a.s.sociated with trees; it is not found in the savannas, although it breeds in savannas adjacent to rainforest. It appears to be somewhat more abundant in scrub forest than in rainforest. In the daytime individuals were found under the outer sheaths of banana plants, in the axils of leaves of elephant ears (_Xanthosoma_), in cavities in trees, and on shaded limbs in the forest. Recently metamorphosed individuals having snout-vent lengths slightly more than 20 mm. were found in the latter part of July.

=Hyla ebraccata= Cope

_Oaxaca_: Donaji (17); 43 km. N of Matias Romero (27); Sarabia (6); Tolosita (3); Ubero (17). _Veracruz_: Aquilera.

This small species was found only in forested areas, where calling males were on bushes and trees around rain pools. The call is a harsh squawk repeated at intervals of 15 to 20 seconds, followed by a minute or more of silence, and then repeated. Clasping pairs were found on bushes and in the water.

The dorsum bears a dark chocolate brown hour gla.s.s-shaped mark, which in some individuals is broken into a large mark posteriorly and a smaller triangular one on the head and nape. The dorsal ground color varies from pale cream or ivory to yellow or tan. The intensity of the dorsal pigmentation is subject to rather rapid change. The flanks, hands, and anterior part of the venter are lemon yellow; the feet, thighs, and posterior part of the venter are golden yellow. The dorsal surface of the shank is yellow to tan with chocolate brown bars or spots; the heel is pale yellow. There is a dark brown bar in the loreal region and a dark brown bar extending posteriorly from the eye to a point above the insertion of the forelimb. The iris is a copper color.

The toes are completely webbed; the fingers, one-third webbed. There is a small axillary web that is evident when the forelimbs are at right angles to the body. Twenty males have an average snout-vent length of 28.1 mm.; three females, 35.3 mm. There are no nuptial tuberosities on the pollex of breeding males.

This species has been collected at Coyame and Catemaco in Los Tuxtlas and at various localities in Tabasco; it apparently ranges eastward from southern Veracruz, Mexico, in humid forests to El Peten, Guatemala.

=Hyla loquax= Gaige and Stuart

_Oaxaca_: Donaji (7); 43 km. N of Matias Romero (21).

_Veracruz_: 19 km. N of Acayucan (4); Aquilera (3); 8 km. SW of Coatzacoalcos (36); Cuototolapam (11); Naranja (13); San Lorenzo (8).

In the isthmus this species is known only from the humid forests of the Gulf lowlands; it is also known from Boca del Rio, Veracruz, and from Teapa and Villa Hermosa, Tabasco.

Calling males were found on aquatic plants above the water in deep ponds in the forest where it was necessary for the collector to wade waist-deep in water to obtain them. The call is a loud "hah-onk."

Individuals, when active at night, are yellowish tan above with light olive green spots. The flanks, belly, and vocal sac are yellow, and the anterior and posterior surfaces of the thighs and webbing of the feet are bright orange-red or tomato red. Individuals found during the day are grayish brown with olive markings or reddish brown with black markings. Sleeping individuals are ivory-gray with faint gray markings.

The iris is a bright copper color. Fifteen adult males have an average snout-vent length of 41.7 mm.; they have no h.o.r.n.y nuptial pads on the pollex.

The relations.h.i.+ps of this species are with _Hyla rickardsi_ Taylor, a species known only from the foothills of the Sierra Madre Oriental in the states of Puebla and Veracruz. The distinguis.h.i.+ng characteristics of these species are given in Table 1. Living individuals may be distinguished immediately by the flash colors on the thighs--red in _loquax_ and yellow in _rickardsi_. The calls of the two species are distinctly different; that of _rickardsi_ is a high-pitched, loud rattle continued for several seconds, notably different from the goose-like honk of _loquax_.

TABLE 1.--COMPARISON OF CERTAIN CHARACTERS IN HYLA LOQUAX AND HYLA RICKARDSI

=================================+================+==================== CHARACTER | _loquax_ | _rickardsi_ ---------------------------------+----------------+-------------------- Toe webbing | Full | Three-fourths | | Finger webbing | Three-fourths | One-half | | Average snout-vent length (Male) | 41.7 mm. | 37.4 mm.

| | Tympanum/eye (Male) | 63.2% | 55.8% | | Dorsal leg pattern | Barred | Unmarked | | Tarsal fold | Tubercular | Absent | | Tarsal stripe | Absent or | Broad, indistinct, | indistinct | or absent | | Dorsolateral stripe | Absent | Present | | Light line over a.n.u.s | Broad | Narrow | | Flash colors | Red | Yellow | | Iris color | Copper | Bronze ---------------------------------+----------------+--------------------

The three specimens from San Lorenzo, Veracruz (USNM 123513-5), were identified as _Hyla rickardsi_ by Smith (1947:409). The flash colors have faded in preservative, and so are of no aid in identifying these specimens. Two are adult females with snout-vent lengths of 35 and 39 mm. In possessing a relatively large tympanum and barred thighs, and in lacking a dorsolateral stripe they are typical of _loquax_, but in the amount of webbing on the hands and feet, broad tarsal stripe, and narrow a.n.a.l stripe they are like _rickardsi_. The third specimen, a juvenile, has a snout-vent length of 25 mm. In coloration it resembles the adults; it has more distinct bars on the limbs. On the basis of geography these specimens should be _loquax_, for the closest known record of _rickardsi_ is more than 200 kilometers to the northwest, whereas _loquax_ is known from several localities around San Lorenzo.

Shannon and Werler (1955:383) described _Hyla axillamembrana_ from the lower southern slopes of Los Tuxtlas. The unique type is a small male (27 mm. snout-vent). I have examined the type and find no great differences between it and small specimens of _loquax_. It is not possible to determine the color of the thighs, nor was this information given in the description. _Hyla axillamembrana_ is here considered to be a synonym of _Hyla loquax_.

=Hyla microcephala martini= Smith

_Oaxaca_: Donaji (15); 43 km. N of Matias Romero (19); Rio Sarabia (2); Sarabia (11); Tolosita. _Veracruz_: Acayucan (17); Alvarado (41); Aquilera (21); 8 km. SW of Coatzacoalcos (10); Cosoleacaque (26); 10 km. SE of Hueyapan; Naranja (3); Novillero.

This frog is abundant in the Gulf lowlands of the isthmus, where large breeding congregations were found in gra.s.sy ponds on the savannas and in openings in the forest. Most frequently males were calling from gra.s.ses and reeds in the ponds; many individuals were perched precariously on thin blades as high as one meter above the water. The call is a series of low squeaks.

Individuals found at night were pale yellow above with light brown lines arranged in an irregular pattern on the back, but often forming a cross or an X-shaped mark in the scapular region. There is a brown stripe from the nostril to the eye and thence to the groin. Anteriorly this stripe is bordered above by a thin white or cream-colored line.

Numerous small brown flecks are scattered on the back and dorsal surface of the shank. In most specimens there are thin transverse brown bars on the shank. The thighs and undersides of the limbs are golden yellow; the belly and vocal sac are lemon yellow. The iris is yellowish brown. During the day individuals a.s.sume a pale reddish tan ground color with darker brown markings. Twenty-five adult males from Alvarado have an average snout-vent length of 24.1 mm.

=Hyla picta= Gunther

_Oaxaca_: Donaji (8); Sarabia (11); Tolosita (15); Ubero (6). _Veracruz_: 19 km. N of Acayucan (4); Alvarado (5); Aquilera; 8 km. SW of Coatzacoalcos; 10 km. SE of Hueyapan (7); Lerdo de Tejada; Tula (3).

Widespread in the forests, scrub, and savannas on the Gulf lowlands of the isthmus, these frogs were found breeding at numerous localities.

Males call from gra.s.ses and bushes growing in and about ponds. The call is a high-pitched insect-like trill. At night these frogs are pale yellow above; they change to light grayish tan during the day. A dark stripe extends from the nostril to the eye and thence posteriorly to a point between the axilla and groin. Above this dark stripe is a broader white stripe. Scattered on the dorsum are brown flecks or spots; the shanks are marked with poorly-defined cross-bars. The thighs are deep yellow below and paler above with scattered dark flecks. The belly is white, and the vocal sac is yellow. The iris is golden. Twenty males have an average snout-vent length of 21.5 mm.; three females, 24.0 mm.

=Hyla robertmertensi= Taylor

_Oaxaca_: Tapanatepec (28); 7.5 km. NW of Tapanatepec (38); 7.2 km. WNW of Zanatepec (77).

This species was found in the isthmian region only on the Pacific lowlands at the southern base of the western part of the Sierra Madre de Chiapas. On July 13, 1956, many large choruses were discovered. The calling males were on reeds and thorn scrub in and at the edge of temporary ponds; the call is a cricket-like "creak-creack," quickly followed by a series of notes "creak-eek-eek-eek-eek."

At night the dorsal ground color is pale yellow; this changes to pinkish buff during the day. There is a grayish or brown dark stripe from the nostril to the eye; the stripe continues to the groin. This dark stripe is bordered above by a narrow white stripe. The belly is white, and the vocal sac is yellow. The iris is dull reddish brown.

Twenty-five males have an average snout-vent length of 24.7 mm.

=Hyla staufferi= Cope

_Oaxaca_: Chivela; Huilotepec (5); Juchitan (4); Matias Romero (4); 25 km. N of Matias Romero; Mixtequilla (4); Rio Sarabia (11); 11 km. S of Santiago Chivela; Sarabia (3); Tapanatepec (67); Tehuantepec (66); Tolosita (2); Ubero; Union Hidalgo; Zanatepec (6). _Veracruz_: Acayucan (7); Alvarado (3); Amat.i.tlan; Aquilera; Ciudad Aleman (3); 8 km.

SW of Coatzacoalcos (9); Cosamaloapan (4); Cosoleacaque (8); 10 km. SE of Hueyapan; Lerdo de Tejada; Novillero (6); Tula (2).

This is the only species of small hylid that crosses the isthmus.