Bio Facts: Tree Frog, Red-Eyed
Red-Eyed Tree Frog
Central America: Belize, Colombia, Costa Rica, Guatemala, Honduras, Mexico, Nicaragua, and Panama
Near ponds and rivers of tropical lowland and montane rain forests
Male adult length: 2 – 2.5 in. (5.08 – 6.35 cm); female adult length: 2.5 – 3 in. (6.35 – 7.62 cm); coloration: red eyes with a vertical slit pupil, a vertically narrowed noses, a vibrant green body with yellow and blue striped sides, and orange toes. There is a great deal of regional variation in flank and thigh coloration. Young frogs are typically brown in color and turn greener as they mature, although adult frogs can change their color slightly depending on mood and environment.
Up to 5 years
2 – 3 years
In the wild, they eat crickets, moths, flies, and other insects; in the Zoo, they are fed crickets, fruit flies and other invertebrates.
IUCN – Least Concern; CITES – Appendix II
The red-eyed tree frog is nocturnally active. It is arboreal and shelters on the underside of a broad leaf during the day and during the dry season, with limbs folded underneath its body. It has also been found in bromeliads, though this appears to be rare. In suitable habitat, this species is abundant.
Red-eyed tree frogs are not poisonous and rely on camouflage to protect them. During the day, they remain motionless, cover their blue sides with their back legs, tuck their bright feet under their belly, and shut their red eyes. Thus, they appear almost completely green, and well hidden among the foliage.
Some new research has found that during mating season, the male frogs shake the branches they’re sitting on to improve their chances of finding a mate. This branch shaking actually keeps rivals at bay. This is the first evidence that tree-dwelling vertebrates use vibration to communicate. Some frogs communicate by croaking deep sounds for warnings and high sounds for mating.
Breeding occurs during the wet season (late May to November), beginning with the first rains. Mating takes place throughout the rainy season but is particularly frequent in June, and occasionally peaks again in October. Red-eyed tree frogs generally prefer quiet pools of water with overhanging vegetation as breeding sites; the pools may be permanent, seasonal but long-lasting, or temporary. Males make aggressive calls, to deter other males from intruding onto their territories, and advertisement calls, to attract females. The aggressive call sounds like a soft chuckle, and the advertisement call is a “chack” or “chack-chack”, repeated at intervals of 8-60 seconds. Calling begins at dusk and is most frequent in the evening, especially during rains, as males advertise for mates. However, they have also been reported to participate in a brief daybreak chorus of advertisement calls, at a much higher call rate than evening or morning advertisement choruses. On dry nights, males call from higher perches in the tree canopy as opposed to wetter nights or when the ponds are full when they begin calling from the ground and from small trees and bushes near the edges of ponds or backwaters. Calls are generally made from horizontal perches on leaves or branches, although vertical perches on stems are occasionally used. They move about frequently while calling, changing both their positions and the direction of calling. If precipitation or water level conditions are sufficient, males then descend to the breeding sites at the water’s edge and continue calling. Females descend from the canopy, approach selected calling males in a straight line, and allow amplexus to take place. Descent generally occurs slowly hand-over-hand, but parachuting has also been observed in this species, both in the wild and in experimental trials.
Once amplexed, a female will carry the male into the water and remain there for about ten minutes. Pyburn (1970) carried out experiments showing that the purpose of this behavior is to allow the female to absorb water through her skin, into her bladder, in order to make the jelly mass surrounding the clutch of eggs. The pair then moves up into the trees, as the female searches for an appropriate egg deposition site on vegetation overhanging the water. Eggs are generally deposited on either the upper side or lower side of a broad leaf, as high as 12 feet over the water. Sturdy plants and trees at the water’s edge are preferred, but oviposition may also take place on emergent vegetation. Egg clutches may also occasionally be deposited on substrates such as branches or fence wire. Very rarely eggs will be deposited on the ground. This species has also been reported to sometimes make use of a wide variety of other types of sites, such as water-filled depressions made by human and pack animals, completely lacking overhanging vegetation; vines and small trees overhanging cavities of water in fallen trees; passionflower vines growing above a trickle of water from a pig pen; or by attaching eggs to the inside surface of water collection devices. Occasionally clutches are found with leaves partially or completely folded over the eggs. If the deposition site is on top of a leaf, the parents may be protecting the clutch from sun and predators by folding the leaf edge over, where it adheres to the sticky jelly mass surrounding the eggs. Other leaf-breeding frogs (Phyllomedusa iheringi, P. hypochondrialis, and P. sauvagii) protect their clutches within folded leaves. However, Duellman (2001) cautions that for Agalychnis callidryas, the occasional folding may be due to attachment of the eggs to particular types of leaves more prone to curling, as neither he nor others (e.g. Pyburn) have observed this species actively curling leaves during oviposition. Pyburn (1970), in fact, specifically mentions that Agalychnis callidryas lays its eggs on open leaves, in contrast to other phyllomedusine frogs.
Fertilization occurs immediately after egg deposition. Occasionally pairs are attacked by single males, as the intruder attempts to dislodge the first male or attach himself alongside or on the first male’s back. This strategy sometimes succeeds, as molecular analysis has confirmed that multiple paternities do occur and that the second male can contribute significantly to clutch fertilization in the wild.
Clutches consist of about 40 green eggs, each surrounded by a clear jelly coat, with each egg having a diameter of about 3.7 mm at oviposition and 5.2 mm when mature enough to hatch. The entire clutch is itself surrounded in more jelly, which is sticky and serves to adhere the clutch to the substrate as well as to prevent desiccation. Females may lay multiple clutches (up to five) in a single night. In between clutches, the female carries the amplectant male down into the water again as she rehydrates. Ovulation is likely to occur twice during the reproductive season, given that gravid females containing ovulated eggs were also found to have equal numbers of immature half-size eggs still within the ovary. This observation also fits with the second peak in mating sometimes observed near the end of the rainy season. Fertilization success is high, with Briggs (2008) noting 100% fertilization in 54 of 56 experimental clutches and reporting that this did not differ from her field observations.
Since the egg clutches are attached to vegetation overhanging the water, hatching tadpoles generally fall into the water below as soon as they hatch. Thus hatching involves a shift in habitat, from aerial to aquatic, with a concomitant change in the suite of potential predators and selection pressures. Occasionally, hatching tadpoles may also fall onto the ground. Tadpoles are able to live out of water for up to 20 hours. Those that fall onto the ground or remain stuck to the leaf may still survive if a later rain washes them into standing water, or if they are able to flip themselves into the water by thrashing about with their tails.
The red-eyed tree frog shows remarkable adaptive plasticity in the timing of hatching. Undisturbed clutches develop essentially synchronously but hatch asynchronously at six to ten days. Most undisturbed embryos will hatch at about seven days, with the study population in Panama hatching on average at about 6-7 days and the study population in Costa Rica hatching at about 7-8 days. Disturbed clutches, however, can undergo early, relatively synchronous hatching, as early as 4 days in Panama or 5 days in Costa Rica. Accelerated hatching can occur in entire clutches or small groups of eggs within a clutch, in response to at least four different natural risks: snake attack, wasp attack, fungus infestation, and flooding or submersion. Hypoxia from exposure to hypoxic gas mixtures also induces early hatching. Fungal attack, flooding, and hypoxia result in more gradual early hatching than immediate threat of predation. The decision to hatch is a behavioral decision since highly energetic movement is required; embryos which remain motionless do not hatch, even though they have reached an appropriate developmental stage. Experiments have shown that red-eyed tree frog embryos assess the temporal pattern of substrate-borne vibrations when making the decision to hatch. Further, they do not hatch at the earliest possible moment following stimulation, but wait some seconds to minutes to evaluate the information before deciding to hatch.
Young froglets (at least from Panama) are able to change color; they are green by day and change to purplish or reddish brown at night.
Red-eyed tree frogs are excellent climbers and have suction-cup toes that help them attach themselves to the underside of leaves, where they rest during the day. They can also be found clinging to branches, tree trunks, and leaves throughout their habitat. Red-eyed tree frogs are also able to swim despite not having much webbing between their toes.
Some believe that the bright, red eyes of A. callidryas act as a form of defense termed startle coloration. Red-eyed tree frogs are nocturnal and rest during the day. If a predator were to happen upon A. callidryas, the frog would awaken, and its eyes would pop open abruptly. The sudden brightness of their red eyes might startle the predator enough to give A. callidryas the mere seconds necessary for the agile frog to jump to safety.
Red-eyed tree frogs are closely related to Chorus Frogs (genus Pseudacris), which have the same body style and many of the same habits, though chorus frog are more vocal.
Young froglets have yellow rather than red eyes, and have lighter-colored flanks lacking whitish bars. The red eye coloration appears first at the periphery of the eye at about two weeks post-metamorphosis, and over a period of several days spreads inward to make the iris wholly red.
They prefer temperatures between 75 - 85°F degrees during the day, between 66 - 77°F during the nighttime, and humidity at around 80%-100%.
The species name callidryas is derived from the Greek words kallos, meaning “beautiful”, and dryas meaning “tree nymph” hence the ever appropriate name: beautiful tree nymph.
These frogs are not considered threatened in their natural environment. However there has been much concern about the overall condition of the rain forest habitat in which they reside. Climate change, deforestation, atmospheric changes, wetland drainage, and pollution have caused dramatic declines in the amphibian population in and among the rain forests of Central and South America.
It is listed as Least Concern in view of its wide distribution, tolerance of a degree of habitat modification, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category. This species is threatened by habitat loss by the destruction of natural forests although it is known to survive in places with a degree of anthropogenic alteration. It is also recorded within the pet trade.
Why do zoos keep this animal? Neotropical frogs are threatened by habitat destruction, disease and other factors. Zoos and aquariums keeping these species want to build up reserve populations and to raise awareness of the global amphibian crisis. Due to its red eyes and the bright colors of its skin, Agalychnis callidryas is particularly suitable for this purpose. Several zoos have also linked their ex situ activities with involvement in situ conservation.
Jacksonville Zoo History:
This species first arrived in our animal collection in 2008. We have bred this species.