Amazon milk frog

Amazon milk frog（圖片來源：Quartl，採用 CC BY-SA 3.0 授權）

The Amazon milk frog (Trachycephalus resinifictrix) belongs to the family Hylidae and is a medium to large arboreal frog native to the Amazon rainforest of South America. Adults typically reach 6.5 to 10 cm in body length. Their coloration is usually bluish-gray or pale gray, marked with dark brown to black banding, while juveniles show more vivid contrast. As they mature, the skin develops granular glandular structures that secrete a white milky substance used for defense, which gives rise to the common name "milk frog".

Its iris is golden, and the pupil resembles a Maltese cross. Beyond its distinctive appearance, its blood has a slight bluish tint, particularly visible in the mouth and toe pads. These characteristics make it a highly sought-after species among amphibian enthusiasts.

In the wild, the Amazon milk frog is widely distributed across Brazil, Colombia, Ecuador, Peru, Bolivia, Venezuela, Suriname, Guyana, and French Guiana. It primarily inhabits lowland tropical rainforests below 450 meters in elevation. These frogs typically reside in tree hollows or crevices, especially those containing accumulated water, which is essential for reproduction.

They are nocturnal and crepuscular. During the day, they remain hidden in tree cavities or bark crevices, closing their large golden eyes and tucking in their limbs to reduce water loss and remain concealed. At night, they emerge to hunt insects and other small invertebrates. During the breeding season, males call near water-filled tree holes with loud vocalizations that can travel up to 200 meters to attract females.

Wild individuals typically live 8 to 15 years, and under proper care in captivity, they can achieve a similar lifespan.

Housing Requirements in Captivity

As an arboreal species, Amazon milk frogs require enclosures with sufficient vertical space. A glass or acrylic terrarium measuring at least 45 × 45 × 60 cm is recommended, with larger enclosures needed for group housing. An ideal setup mimics a paludarium, with a shallow water section at the base resembling water-filled tree hollows and ample vertical climbing structures above.

In their natural habitat, temperatures remain stable year-round, ranging from 24 to 29°C during the day and dropping slightly to 20 to 24°C at night. Captive conditions should replicate this range. A localized basking area reaching up to 29°C can be provided for thermoregulation. Humidity should be maintained at approximately 70 to 75% during the day and increased to 85 to 90% at night. Misting twice daily is recommended to simulate the humid rainforest environment.

Because they utilize water-filled cavities for breeding, a clean water source is essential. This can be provided via a shallow dish, small pool, or paludarium setup. For juveniles, water depth should remain shallow, around 5 cm, to prevent drowning, and should include rocks, driftwood, or sloped surfaces for easy exit. Adults can be provided with slightly deeper water (10 to 15 cm), but ample terrestrial and climbing areas must remain available, and care should be taken to avoid smooth, escape-proof deep water zones. Water must be dechlorinated, kept clean, and ideally maintained with filtration and regular changes.

The enclosure should be densely furnished with branches, vines, cork bark tubes, and live plants to provide climbing opportunities, shelter, and resting areas. Suitable plants include Philodendron, Dieffenbachia, Monstera, climbing vines, and bromeliads, which also help maintain humidity.

Although nocturnal, a 12-hour light cycle is beneficial for simulating natural conditions and supporting plant growth. Low-intensity UVB lighting aids calcium metabolism and helps prevent metabolic bone disease. Proper ventilation is necessary to prevent excessive moisture buildup, which can promote fungal or bacterial growth and lead to skin diseases.

Amazon milk frogs are generally docile and can be housed in groups, typically 4 to 8 individuals. Group housing allows observation of social behavior and may stimulate breeding, but requires sufficient space to reduce potential male aggression during the breeding season.

Paludarium, but with more terrestrial area and shallower water than shown（圖片來源：Jitka Erbenová (cheva)，採用 CC BY-SA 3.0 授權）

Amazon milk frog and its captive enclosure habitat（圖片來源：Paul Korecky，採用 CC BY-SA 2.0 授權）

Feeding Conditions

Amazon milk frogs are carnivorous, feeding primarily on insects. In the wild, they consume ants, termites, and other small arthropods. In captivity, a varied diet can include small crickets, fruit flies, roach nymphs (such as Dubia roaches), and worms (such as mealworms or silkworm pupae, in moderation). Pre-killed or canned insects can also be offered by using tweezers to mimic movement.

Juveniles should be fed daily, while adults can be fed every 2 to 3 days. Prey size should not exceed the width of the frog's head to prevent feeding difficulties.

Captive-bred insects are often deficient in calcium and vitamins, so they should be dusted with calcium powder and multivitamin supplements (including vitamin D3). This is typically done by placing the insects and supplement powder in a container and gently shaking before feeding.

Milk frogs do not drink water directly; instead, they absorb it through their skin. Therefore, a clean, chlorine-free water source must always be available and changed daily to prevent bacterial growth.

Breeding Conditions

In the wild, the breeding season typically occurs during the rainy season, from November to May. Males call from water-filled tree cavities to attract females. During amplexus, females lay 200 to 1500 eggs on the inner walls of these cavities. The egg mass adheres to the surface and remains suspended above the water. Upon hatching, tadpoles feed on detritus, insect remains, and even conspecific eggs, completing metamorphosis in approximately 1.5 to 2.5 months.

In captivity, breeding can be induced by simulating a dry-to-wet seasonal cycle. Temperature and humidity are slightly reduced for 4 to 6 weeks, light duration is shortened to 10 hours, and feeding is decreased to mimic the dry season. Conditions are then gradually returned to normal, with increased misting to simulate the onset of the rainy season. A water feature should be provided to allow males to call and initiate breeding.

If breeding is successful, tadpoles should be transferred to a shallow aquatic setup with water temperature maintained around 25°C. They can be fed fish food, algae, or finely chopped insects. As limbs begin to develop, platforms must be provided to allow them to leave the water and avoid drowning. After metamorphosis, froglets can be fed fruit flies and small crickets.

Preventing Invasive Spread

Although native to South America, the Amazon milk frog is widely kept in the pet trade across Europe, North America, and Asia. This creates potential ecological risks. If released into the wild, they may become invasive, competing with native amphibians for food and breeding sites, or introducing pathogens such as chytrid fungus, which can devastate local populations and ecosystems.

Owners must never release these frogs into the wild. If unable to continue caring for them, they should seek other keepers or contact legitimate animal rescue organizations.

When purchasing, it is important to ensure a legal source. Captive-bred individuals should always be chosen, and wild-caught specimens from South America should be avoided to prevent overharvesting and illegal wildlife trade.

Author: Shui-Ye You