The mating call of Hyla elaeochroa consists of short notes, repeated at intervals of about 0.40 second. Each note has a duration of 0.12 to 0.24 second. The fundamental frequency varies from 48 to 65 cycles per second, and the notes have 40-50 pulses per second; the dominant frequency is at about 2,900 cycles per second (Table 2, Pl. 4A).
The eggs are deposited in a mass in the water near floating vegetation. William E. Duellman informed me that he observed hatchlings oriented vertically with the tip of the mouth at the surface of the water. They gradually sank to bottom, but swam back to surface again. No additional information is available concerning early development. Tadpoles have been found in shallow grassy ponds in clearings and in temporary woodland ponds.
Tadpoles.—Three hundred and thirty-one tadpoles in various stages of development are available. Thirty-five tadpoles in stage 35 have a mean body length of 8.1 mm. (8.0-9.0 mm.), tail length of 17.7 mm. (15.0-19.5 mm.), and total length of 25.9 mm. (23.0-27.5 mm.). The largest tadpole examined is in stage 40 and has a total length of 34.5 mm. (Table 6).
A typical tadpole, stage 35 of development (KU 104134, from Puerto Viejo, Heredia Province, Costa Rica), has a body length of 9.1 mm., tail length of 17.7 mm., and a total length of 26.8 mm. Other characters are as follows: body depressed anteriorly; body length greater than depth of tail; internarial space as broad as interorbital distance; nostril equidistant between eye and tip of snout; eyes moderately large; mouth anteroventral and triangular; median fourth of upper lip bare; rest of lip bordered by one row of papillae; clumps of small papillae at corners of mouth; tooth rows 2/3; upper rows equal in length; second row interrupted medially; lower rows shorter than upper rows, diminishing in length; beak rather weak with small serrations; spiracle short and nearer eyes than anus; anal opening not reaching edge of ventral fin; caudal musculature attenuated distally (Figs. 2B and 3B).
Table 6.—Sizes of Tadpoles of Hyla elaeochroa in Relation to Developmental Stages.
(Means in parentheses below observed ranges; measurements in mm.)
| Stage | N | Body length | Tail length | Total length |
| 24 | 2 |
4.0-4.0 (4.0) |
8.5-9.0 (8.8) |
12.5-13.0 (12.8) |
| 25 | 64 |
5.0-6.5 (5.7) |
8.5-15.0 (11.8) |
13.5-21.5 (17.6) |
| 27 | 30 |
7.0-7.5 (7.1) |
13.0-16.0 (14.2) |
20.0-23.0 (21.3) |
| 30 | 15 |
7.0-8.0 (7.3) |
13.0-16.5 (15.0) |
20.0-24.0 (22.4) |
| 32 | 30 |
7.5-8.5 (7.8) |
15.0-17.0 (16.1) |
22.5-25.0 (23.8) |
| 35 | 35 |
8.0-9.0 (8.1) |
15.0-19.5 (17.7) |
23.0-27.5 (25.9) |
| 37 | 22 |
8.5-9.5 (9.0) |
16.0-22.0 (18.8) |
25.0-31.0 (27.8) |
| 39 | 14 |
9.5-10.5 (9.9) |
19.0-24.9 (21.1) |
28.5-33.5 (31.0) |
| 40 | 27 |
7.0-11.5 (9.1) |
15.0-23.0 (22.0) |
23.0-34.5 (31.2) |
| 43 | 10 |
8.0-12.0 (10.2) |
11.0-17.0 (13.5) |
20.0-26.0 (23.7) |
| 45 | 16 |
10.0-12.0 (11.2) |
1.0-7.0 (3.4) |
12.0-17.0 (14.6) |
| 46 | 45 |
11.0-13.0 (11.8) | — | — |
In life, dorsum yellowish tan with gray-brown mottling; belly and ventrolateral surfaces silvery-gold or white; black stripe from tip of snout to eye; two black blotches below eye, another blotch extending from eye to base of caudal musculature; caudal musculature and fins gray-brown. In preservative, yellowish tan and silvery-gold colors lost; black reticulations present on tail.
Remarks.—Cope (1876:105) described Hyla elaeochroa from Sipurio, Limón Province, Costa Rica. He based his description on a small specimen, 26.0 mm. in snout-vent length, having a dorsum uniformly colored and lacking an interorbital triangle and blotches on the thighs. Cope (1887) described pigmented specimens from Nicaragua as Hyla quinquevittata, which he diagnosed as having dark brown bars on the hind limbs and five dark brown longitudinal stripes on the dorsum, the median one of which was expanded anteriorly so as to form a large triangular spot between the eyes. He thought this species was related to Hyla eximia Baird and noted that "the hinder legs are much larger; the muzzle is more acuminate and the color bands are much wider" than in eximia. Cope did not compare quinquevittata with elaeochroa, which he had described ten years before. Günther (1901:268), Noble (1918:340), and Nieden (1923:251) regarded both elaeochroa and quinquevittata as valid species. Dunn and Emlen (1932:25) regarded both as synonyms of Hyla rubra, but they made no qualifying statements. Taylor (1952:859) placed quinquevittata as a synonym of elaeochroa and indicated that rubra was another species.
Taylor (1958:37) described Hyla dulcensis from the humid tropical forests of Golfo Dulce, Puntarenas Province, Costa Rica. He thought this species was "related to H. elaeochroa but differs in its somewhat larger size, smaller finger and toe discs, the obsolete canthus rostralis; the loreal region concave and the choanae larger." Duellman (1966a:270) compared adults, tadpoles, and mating calls of dulcensis and elaeochroa and concluded that a single species was involved.
Hyla elaeochroa can be easily confused with the closely related Hyla staufferi. Although the durations of the calls are similar, the call of elaeochroa has only about one third the number of pulses per second, a much lower fundamental frequency, and a lower dominant frequency than that of staufferi. Hyla elaeochroa is larger and has a less pointed snout than does staufferi. Although the skulls of the two species are similar, that of elaeochroa differs in having broad palatines and comparatively larger nasals that are truncate anteriorly. In staufferi the nasal is rounded anteriorly and the palatine is absent.