In 2003, during my inaugural journey to Latin America, I explored the lush landscapes of Costa Rica. At one of the hostels, a vibrant poster showcasing the country’s rich amphibian diversity caught my eye. Among the array of colorful frogs, one stood out: the splendid leaf frog, then known as Agalychnis calcarifer. In 2005, taxonomic revisions reclassified it into the newly established Cruziohyla genus, alongside another species. By 2018, further studies split Cruziohyla calcarifer into two distinct species, with the Costa Rican population renamed Cruziohyla sylviae, or Sylvia’s tree frog.
The image of Cruziohyla sylviae was mesmerizing. This large tree frog boasted a striking dark green dorsal surface paired with a vivid orange ventral side. Its flanks were adorned with delicate black stripes against an orange backdrop, and its orange eyes, with vertical pupils signaling its nocturnal nature, featured a grey center. The frog’s wide foot-webbing and large, rounded adhesive discs on its toes added a charming, almost whimsical touch to its appearance. Captivated, I ventured into the Costa Rican rainforest to find this species. Unfamiliar with their habits, I didn’t locate any, though I encountered plenty of red-eyed tree frogs.
Years later, in 2014, I found myself in Ecuador’s Amazon rainforest, primarily searching for nocturnal insects and arachnids. The weather had been favorable until a heavy, warm rain blanketed the forest one night, creating a dense fog that enveloped the understory. Initially, I thought the rain would hinder my observations, but I was wrong. The warm, misty conditions transformed the forest into a vibrant symphony of life. Thousands of creatures emerged—orthopterans and amphibians filled the air with calls, while arachnids and velvet worms roamed freely. It was a naturalist’s paradise.
Amid the cacophony of frog calls from the canopy, one stood out: a short, distinctive “moo,” unlike the typical “cluck” of most tree frogs. Following the sound, I discovered its source—a Cruziohyla craspedopus, the fringe tree frog. My heart raced. In my view, this is the most breathtaking tree frog species. Its dark green dorsum, speckled with bluish patches resembling moss or lichens, blends seamlessly with the rainforest foliage. The frog’s body margins feature long, delicate “fringes,” particularly prominent on the hind legs, which males extend during courtship to signal to others.
As a high-canopy dweller, C. craspedopus is elusive and rarely seen. I never imagined I’d encounter one in the wild, yet the warm fog drew out nearly ten individuals that night. After learning their preferred resting spots, I could even spot them during the day. These frogs descend from the canopy only to breed. During amplexus, where the male clasps the female’s back, pairs navigate the canopy to find small water bodies, often beneath fallen trees. Females lay egg clutches above the water, allowing hatching tadpoles to drop into their aquatic nursery. Despite checking under numerous fallen trees while searching for Amblypygi, I couldn’t find any egg clutches. Perhaps next time.
Image source: gilwizen.com
