Description
This species reaches 44 mm in SVL. The head is flat, and broader than long. The snout profile is moderately truncate, with vertically elliptical, laterally directed nares. Eyes are protuberant, with horizontal pupils, and are considerably larger than the tympana. A distinct supratympanic fold begins at the eye and extends to behind the axilla. Maxillary and vomerine teeth are present. The body and limbs lack skin folds. The skin is smooth on the dorsum, granular/glandular on the venter, and intermediate on the throat. The adpressed hindlimb heels overlap by no more than half the diameter of the eye. The only webbing is on the feet between toes II-V, and all fingers and toes have digital pads.

This species is capable of metachrosis, changing color during the diel cycle. In the daytime, the coloration can change from green to shades of brown or grey, occasionally spotted. The samples from the Mamilla reservoir are turquoise, though this may be a local mutation as samples from other localities do not show bluish color. By day the dark lateral stripe is clearly visible along the flank, generally fragmented into irregular spots, and lacking the inguinal branch of H. arborea. During the spotted phase of the daytime coloration, the gray, brown, or yellow background may have darker or lighter blotches. The presence of green blotches on a rust- or golden-brown background is unique to H. heinzsteinitzi. A white stripe, reduced and somewhat indistinct, runs along the posterior lip. Hidden parts of the legs, especially the thighs, are orange. At nighttime, the coloration varies with temperature, tending to be green at lower temperatures and brown at warmer temperatures. The lateral stripe pales at night, sometimes to the point of vanishing entirely. In captivity, the capacity for metachrosis develops four months after metamorphosis, and is estimated to occur at about six months post-metamorphosis for wild specimens.

Hyla heinzsteinitzi is very similar to the sympatric H. savignyi, but can be distinguished by its truncate snout profile (vs. round in H. savignyi), a fragmented lateral stripe (vs. nearly complete in H. savignyi), a reduced white stripe on the lip, hidden parts of the legs being orange (vs. brown in H. savignyi), the additional spotted phase coloration of green blotches on a brown background, and the call structure, which has a short rise time followed by a long decay time in H. heinzsteinitzi (vs. a similar rise and fall time in H. savignyi). Also, in the Hyla heinsteinitzi specimens from the Mamilla reservoir, the "green" phase of the body color is actually turquoise, a color that is not present in H. savignyi specimens (or H. heinsteinitzi from other localities).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Israel

View distribution map in BerkeleyMapper.

Hyla heinzsteinitzi has so far only been found in Israel, at three Judean Hills localities with altitudes from 730 to 895 m above sea level. All three sites are located within a 13x6 km range. The holotype field locality is the seasonal Mamilla reservoir in central Jerusalem, a limestone cistern dating from at least 614 A.D. that is only filled by winter rains, and is completely dry in the summer. In recent decades the reservoir’s rim was elevated to the point that it cannot fill with rain runoff, but from water seeping through crevices in the limestone walls from the surrounding soaked earth. Another site is Ein Fara, a spring-fed pool at the edge of the Judean desert dominated by Typha australis cattails, on which the frogs sit vertically, head up. The last site is the Wadi at Moza, whose water depth can exceed 1 m and whose local vegetation is dominated by the spiny Rubus sanctus bush, which is also populated with tree frogs. The Mamilla reservoir and Wadi near Moza lie within the Mediterranean climate region with average annual precipitation of 500-700mm and annual temperatures averaging 17-19°C. Ein Fara is on the fringe of the Judean desert, with precipitation of 300mm and temperatures at 19-21°C. H. heinzsteinitzi’s range may possibly extend to H. savignyi's ranges in Israel, as the authors who mapped amphibian distributions for Israel (Mendelssohn and Steinitz 1944; Wahrman 1956; Gerchman and Werner 1990) did not distinguish between the two species.

Life History, Abundance, Activity, and Special Behaviors
Males respond to recorded tree frog calls, which is a good way to find them as they are camouflaged within local vegetation. At Ein Fara, the frogs are found perching heads-up on vegetation, particularly the abundant cattails (Typha australis). At Moza, they perch within spiny bushes (Rubus sanctus). They begin calling about 30 minutes after sunset, gradually assembling into a large chorus.

The advertisement calls are unique and distinctive for this species, regardless of temperature effects or call function. Calls consist of a sequence of evenly spaced segments with a call duration of about 4.02 s at 22-28°C. Segments are notes with an average duration of 0.1001 s and an average repetition rate of 3.67 notes/sec. The energy peak for H. heinzsteinitzi is near the temporal beginning of each segment. In other words, the energy amplitude has a short rise time and a much longer decay time than others in the Hyla arborea group. H. savignyi’s segments are similar in length and have the energy peak in the middle. H. arborea’s and H. sarda’s energy peaks are near the end of the call. H. meridionalis’s energy peak is between the middle and the end, intermediate to those of H. savignyi and H. arborea.

Trends and Threats
The frog’s tiny range and possible constraint to isolated sites pose a potentially serious threat.

Relation to Humans
The tadpoles can be successfully collected and reared.

Possible reasons for amphibian decline

Prolonged drought
Drainage of habitat
Dams changing river flow and/or covering habitat
Loss of genetic diversity from small population phenomena

Comments
Hyla heinzsteinitzi and Hyla savignyi are sympatric and occasionally syntopic. Care should be taken to distinguish between the two.

References

Grach, C., Plesser, Y., and Werner, Y. L. (2007). ''A new, sibling, tree frog from Jerusalem (Amphibia: Anura: Hylidae).'' Journal of Natural History, 41(9-12), 709-728.

Species Account Citation: AmphibiaWeb 2008 Hyla heinzsteinitzi <https://amphibiaweb.org/species/6924> University of California, Berkeley, CA, USA. Accessed Feb 7, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 7 Feb 2025.

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