There is a moment each evening at Rimba Orangutan Ecolodge when the jungle shifts gears. As the wooden boardwalks cool down and the sun dips below the dark, tannin-rich waters of the Sekonyer River, the daytime chatter of proboscis monkeys gives way to the deep, enveloping quiet of Tanjung Puting. Then, as if on cue, the night chorus begins.
Sitting on the lodge deck on the edge of the peat swamp forest, cold drink in hand, we listened to the forest wake up in the dark. Among the buzz of cicadas and the soft lap of water against wooden pilings, one sound caught our attention completely: a crisp, high-pitched, musical chirping. It echoed clear and bright through the tree line, sounding for all the world like a solitary songbird singing a delicate lullaby into the humid night air.
We leaned forward, scanning the ink black canopy with our flashlights, expecting to spot a feathered night-wren or an elusive roosting bird perched high in the foliage.
But the rainforest loves a good illusion.
When our guide pointed a beam of light down toward the muddy banks beneath the boardwalk, we didn't find wings or feathers at all. Sitting on a broad, speckled leaf, its large dark eye gleaming in the light, was a tiny, mottled brown amphibian. The songbird we had been admiring was actually Hylarana baramica (the Baram River frog).
Up Close with Hylarana baramica
Unless you are actively looking for it, you might walk right past Hylarana baramica (also known as the brown marsh frog or golden-eared rough-sided frog). It isn't brightly colored like a poison dart frog, but when you look closely at the photo we managed to snap, its unique features are incredible:
- The White-Spotted Lip: Along the edge of its upper lip, it sports a striking pattern of bright white, broken spots that pop against its dark face.
- The "Golden" Ear Disc: Right behind its dark eye sits a large, circular ear drum (tympanum), featuring a distinctive lighter, yellowish center ring.
- Textured Armor: Unlike many slick, smooth-skinned frogs, its back and sides are coarse and bumpy.
- Master of Camouflage: Ranging in color from deep chocolate brown to warm reddish-tan with mottled patterns, its skin is perfectly evolved to blend seamlessly into wet leaf litter and muddy riverbanks. Even when perched on a bright green leaf like the one in our photo, its earthy tones mimic bits of fallen bark or dried foliage.
- Tiger-Striped Legs: Dark brown cross-stripes or bars run down its hind legs, breaking up its outline on forest vegetation.
Why Does a Frog Sound Like a Bird?
In the human mind, high pitches equal birds, while low "ribbits" equal frogs. But Hylarana baramica defies that stereotype entirely. Its call consists of sharp, clear, high-frequency "chips" and musical whistles.
There is a brilliant evolutionary reason for this acoustic trick:
- Cutting Through the Jungle Noise: Rainforests are incredibly loud. Low-pitched sounds get muffled by muddy banks, thick peat, and rushing water. High-frequency sounds cut straight through the dense foliage like a whistle.
- Natural Leaf Amplifiers: These frogs love perching on wide tropical leaves, just like the one in our photograph! Broad leaves act like mini-microphones, giving their high chirps a crisp, echoing quality that echoes through the night air.
A Serenade in the Dark: The Mating Call
That bird like song wasn't just random noise, it was a high stakes romance.
In the peat swamps around Tanjung Puting, male Hylarana baramica gather near shallow pools of water after dusk. Each male finds a choice vantage point a damp root buttress or a sturdy leaf and performs his bird-like chirp to attract female frogs.
Because females choose their mates based on the clarity, pitch, and strength of the call, the jungle floor essentially becomes a late night concert venue. Every sharp whistle is a male declaring his territory and announcing to nearby females that he has found a prime spot for laying eggs.
The Joy of Rainforest Surprises
Traveling through Borneo teaches you to question what your senses tell you. What sounded like a sweet songbird hiding in the treetops turned out to be a tiny, mottled amphibian sitting right on a leaf near our feet.
Next time you are walking through a tropical forest at night and hear a bird singing in total darkness, take a closer look at the vegetation nearby you might just be standing right next to Hylarana baramica.
