O. ezra's procoracoid and scapula are connected by cartilage. It has no webbing between the toes, and the fifth toe is longer than the third. The frog has a short snout, dark face and its call sounds like an extended multi-note chuckle or cackle.
A typical juvenile has a shiny black dorsum with golden-yellow spots. The venter is dark gray with blue spots, and the iris is metallic green. A typical adult has a smooth, uniform pale peach dorsum. The venter is lemon yellow, while the axilla, groin, fore and aft of thighs, and under shanks are all red-orange.
The transition begins when pink or peach patches began creeping in on the black. They begin in flecks and then grow to eventually cover the entire dorsum, leaving no black at all. While this happens, the yellow spots lighten and eventually disappear, although some might persist after the black has disappeared.
On the ventral side, the blue flecks disappear as the dark venter turns yellow. Red-orange flash colors appear in the axilla, groin, and hidden surfaces of the legs. The green-bronze iris lightens to sky blue to give the adult appearance of a peach or light pink dorsum with bright blue eyes.
Recorded calls reveal that each call consists of 29-32 pulsed notes lasting 2.07 s on average. That gives a mean repetition rate of 14.8 notes per second. The first note in the call lasts about four times longer than subsequent notes. The frequency of the call ranges from 2040–2670 Hz (Kraus and Allison 2009).
O. ezra is a scandent and arboreal species. Adults are typically found at night on the upper surface of leaves 2 m or higher above the ground. Juveniles are more conspicuously perched on leaves and plant stems 1-2 m above the ground in the mid-late afternoon. Animals emitted a rapid, chattering call from dusk into night from their perches on vegetation or trunks of small trees (Klaus and Allison 2009).
Juveniles are black with lemon-yellow spots. When they grow into adulthood, their color changes to peach, while their eyes turn bright blue. It is thought their spotted pattern at the juvenile is meant to warn predators. This theory has yet to be tested.
O. ezra is distinguished from other species in its genus through a combination of the following morphological traits:
-Ligamentous connection of the procoracoid to the scapula
-Well-developed webbing between the toes
-Fifth toe longer than the third
-Wide head
-Relatively long snout
-Smooth or finely granular dorsal skin
-Blue iris
-Red-orange flash markings in the groin and hidden surfaces of the legs
-Ontogenetic change in color pattern from black with lemon-yellow spots in juveniles to uniform light peach in adults
Other species in the genus Oreophryne may share some of these characteristics, but O. ezra is the only species that has this combination of traits.
The peach dorsal color is shared with some adults of the species O. inornata, but the ontogenetic color and pattern transformation is currently known to be unique to O. ezra (Kraus and Allen 2009).
Dissections of one juvenile and one adult revealed the animals feed on ants. The juvenile's stomach was found containing ten ants of the genus Crematogaster; the adult's stomach contained 30 formicine ants (genus undetermined).
Since juveniles perch conspicuously in daylight and are not easily disturbed, thereby indicating a lack of escape mechanism, Klaus and Allison (2009) hypothesize their coloration and patterning serve an aposematic function.
At first glance, they look like two entirely different frog species. One is peach all over its back and has bright blue eyes; the other is black and shiny with lemon-yellow spots on its back. But looks can be deceiving, because the two frogs belong to the same species. Age is all that separates them. The peach-colored individual with a typically yellow ventral side and blood-red groin and thighs is an adult Oreophryne ezra. The speckled one, whose spots range from golden yellow to metallic blue or dull grey and whose eyes are metallic green, is a juvenile.
Many animals transform in appearance when they grow and age, and a few frog species, especially from the African genera Hyperolius and Nectophryne, show remarkable changes like losing or gaining stripes or spots or changing color. No frogs have yet shown the drastic transformation that O. ezra goes through, ditching its patterned skin for a more uniformly colored body and bright blue irises (See also Diagnostic description).
It is thought that the coloration at the juvenile stage might be an example of aposematism, when the bright colors serve to warn potential predators that the animal is toxic. This hypothesis has yet to be tested, especially since it would make little sense for the animal to use that warning signal.
O. ezra lives in cloud forests above 600 metres, or almost 2,000 feet, of elevation, on the peaks of Mt. Rio on an island off the southeastern tip of New Guinea. Their only known habitat is constricted to about 100 hectares, or just under 250 acres. They are not likely under direct threat from human activity because people rarely venture up the mountain as it is considered sacred. If climate change affects rainfall or cloud cover in the area, it might change the frog's already confined and particular habitat (1).
