Common Name: Red-eyed Tree Frog
Latin Name: Agalychnis callidryas
Family: Hylidae

Range:
The Red-eyed Tree Frog inhabits in altitudes sea level up to 1,250m. It ranges in the following countries: Belize, Columbia, Costa Rica, Guatemala, Honduras, Mexico, Nicaragua, and Panama.

Abundance:
While this species is considered abundant, it is also decreasing in population with deforestation.

Coloration and Morphology:
548269_714558517017_17606779_35149822_1854155307_n.jpg
Red-eyed Tree Frog on tree branch in La Selva. (photographed by Justin Morimoto)

Males range about 2 to 2 ½ inches, while females range about 2 ½ to 3 inches. They have red eyes with vertical black pupils. Their dorsum is a bright green color and their underside has a creamy appearance, with sky-blue along the rib and groin regions [3]. The frog’s palms and soles are an orange-yellow color.

These frogs have developed long limbs as well as sucker pads at the tip of each digit, both of which aid in tree climbing, where they mainly live [3]. They also contain a third eye lid, called a nictitating membrane. This protects their brightly colored eyes from dangers, without limiting their vision.

Color and size may vary depending on geographical location. In Costa Rica, Chairez (2011) found that frogs found in La Selva generally varied more in size and were larger than the frogs found in the Soltis Center [1]. Food availability as well as visibility to predators may influence the frogs’ size in different regions. In general, frogs that range in northern regions tend to be smaller with more color contrast than those frogs that inhabit southern regions.

Reproductive cycle:
Mating season extends from October to March. A group of male frogs use their specific croaking calls to attract females. The males wrestle, jumping from leaf to leaf to establish their territory. Once the winning competitor knocks all of the weaker frogs off the tree limbs, he latches onto the back of the female to begin the reproductive cycle. The female uses her long limbs and suckers to cling onto the underside of a leaf, supporting their entire weight. Then the couple partakes in amplexus, in which they hang up side down over a water source. The female keeps her eggs hydrated by storing water in her bladder. As she releases the eggs one at a time on the underside of the leaf, the male fertilizes the eggs. In order to ensure the eggs stay hydrated, females descend to the water, and upon their return they may end up with a different male mate. The eggs hatch in about 6 to 21 days, and the tadpoles fall into the water. The tadpoles swim via their tails and breath through gills. After about 30 days, they start developing lungs to breath on land. After about 6 to 9 weeks they develop hind legs, which allow them to travel on land. After about 3 months, the froglets migrate to the land and eventually climb up trees, where they live for the remainder of their lives. [3]

Habitat:
The Red-eyed Tree Frog lives in tropical lowland as well as secondary forests nearby freshwater ponds. The frogs are usually found near fallen logs. They usually remain up in the trees; however, they come down to bodies of water to hydrate their eggs [2]. Tadpoles and froglets develop in freshwater, and upon reaching maturation, migrate up into the trees. These frogs are nocturnal [3]. They prefer daytime temperatures of 75 to 85 degrees F and nighttime temperatures of 65- 75 degrees F [1].

Ecology:
Their bright blue and black markings on their sides serve to distract their predators. Their green dorsum blends into the leaves; however, if detected by a predator, their bright markings are exposed as they move to avoid being attacked. The flash color remains in the predator’s vision. So when the predator attacks the bright colors, the frog has already traveled ahead of the flashed color. [3]

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Red-eyed Tree Frog in La Selva understory tropical rainforest (photographed by Justin Morimoto)

Behavior:
In regions containing an abundance of frogs, breeding competition is high. Males assert authority by singing their aggressive calls, jumping on leaves to create quivering, and wrestling bouts that can last up to an hour. They found that territoriality and male-male aggression are reduced and sometimes eliminated in regions containing smaller populations. [6]

Diet:
The Red-eyed Tree Frogs are carnivores usually eat crickets, moths, flies, and other insects [3]. Some frogs feast on other small frogs that fit into their mouths.

Interactions with other Species:
Studies have shown a negative relationship between fungus and Red-eye Tree Frog eggs. This fungus causes the eggs to hatch early. Warkentin (2001) found that fungus, ascomycete (Dothideales: Phaeosphaeriaceae), was present on 7% of egg clutches collected from a pond, and when present, it killed 40% of the eggs [4]. A. callidryas eggs hatch early when attacked by egg predators and hatch later when undisturbed, which causes tadpoles to enter the water at different developmental stages [5]. Tadpoles that hatch later have a better chance of survival. Older hatchlings are more likely to avoid the bottom microhabitat where predator shrimp live as well as flee in the presence of shrimp [5].

Personal Experience:
While I personally did not see the Red-eye Tree Frog, my fellow classmates were fortunate enough to observe the species on their late night nature walk. They recorded the frog to be perched on a leaf in a tree in La Selva, about 600 meters from the water. The frog first froze, most likely attempting to camouflage; however once it realize the humans spotted it, the frog jumped off the leaf, exposing it’s blue and black colored limbs, most likely exhibiting it’s defense tactic.


Sources:
[1] Chairez, Erika (2011) Microhabitat Use and Mating Behavior of the Red-eyed Tree
Frog (Agalychnis callidryas), Wildlife & Fisheries Conservation. College Station,
TX. Print.

[2] Frank Solís, Roberto Ibáñez, Georgina Santos-Barrera, Karl-Heinz Jungfer, Juan
Manuel Renjifo, Federico Bolaños (2004) Red List of Threatened Species,
Version 2011.2. <www.iucnredlist.org>. Downloaded on 27 April 2012.

[3] Mattion, C. (1987) Frogs and toads of the world. Facts on File Publication New York,
NY. Print.

[4] Warkentin, Karen M.; Currie, Cameron R.; Rehner, Stephen A. (2001) Egg-killing
Fungus Induces Early Hatching of Red-eyed Tree Frog Eggs Ecology, 82(10),
2001, pp. 2860–2869. Print.

[5] Warkentin , Karen M. (1998) The development of behavioral defenses: a mechanistic
analysis of vulnerability in red-eyed tree frog hatchlings, Department of Zoology,
University of Texas, Austin, TX <http://beheco.oxfordjournals.org/content/10/3/251.full> Downloaded on
27 April 2012.

[6] Gonzalez,Sergio Celio and Briggs, Venetia Samantha (2011). Aggression in froglets
of red-eyed treefrogs, Agalychnis callidryas, Herpetology Notes, volume 4: 315
318. Print.