Amazon Milk Frog Facts

Scientific Name: Trachycephalus resinifictrix

Amazon milk frog
Amazon milk frog (Trachycephalus resinifictrix).

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The Amazon milk frog is a large rainforest frog that is named for the poisonous, milky fluid it secretes when stressed. It is also known as the blue milk frog, for the striking blue coloring of its mouth and feet. Its other name is the Mission golden-eyed tree frog, for the black cross shape within its golden eyes. The frog's scientific name is Trachycephalus resinifictrix. Until recently, it was classified in the genus Phrynohyas.

Fast Facts: Amazon Milk Frog

  • Scientific Name: Trachycephalus resinifictrix
  • Common Names: Amazon milk frog, Mission golden-eyed tree frog, blue milk frog
  • Basic Animal Group: Amphibian
  • Size: 2.5-4.0 inches
  • Lifespan: 8 years
  • Diet: Carnivore
  • Habitat: South American rainforest
  • Population: Unknown
  • Conservation Status: Least Concern

Description

The Amazon milk frog is a relatively large frog, reaching a length of 2.5 to 4.0 inches. Mature females are larger than males. Adult frogs are pale blue-gray in color, with black or brown bands. The frog's mouth and toes are blue. The eyes are golden with distinctive black crosses. Juvenile Amazon milk frogs are more deeply colored than adults. As the frog ages, its skin becomes bumpy and speckled.

Habitat and Distribution

The milk frog lives in the rainforest canopy, usually near slow-moving water. The frogs stay in the trees, rarely descending to the forest floor. They live in northern South America, and are widely distributed in the countries of Brazil, Colombia, Ecuador, Guyana, and Peru. They also occur in Venezuela, Trinidad, Tobago, and other islands off the South American coast.

Diet and Behavior

Amazon milk frogs are nocturnal carnivores. They primarily feed on insects, spiders, and other small arthropods, but will take any prey small enough to fit in their mouths. Adult females in captivity have been known to eat the smaller males. Tadpoles eat eggs of their own species.

The "milk" produced by disturbed frogs is gluey, smelly, and poisonous. While tadpoles may be eaten by a variety of predators, including other frogs, the adults face few threats. Adults shed their skin about once a week. They use their legs to peel off the old layer and then eat it.

Reproduction and Offspring

The frogs mate during the rainy season, which may occur anywhere between May and November. Males call loudly to attract mates. The males wrestle for breeding rights, with the victor piggy-back riding (amplexus) the female to water collected in a depression in a tree. The female lays up to 2,500 eggs, which the male then fertilizes. The eggs hatch within 24 hours. Initially, the gray tadpoles feed on detritus in the water. While the female plays no further parenting role after laying eggs, males may bring another female back to the initial nest site to lay eggs. He does not fertilize these eggs. The tadpoles live on unhatched eggs until they can leave the water and hunt on their own. The metamorphosis from tadpoles into coin-sized froglets takes about two months. The life expectancy of wild Amazon milk frogs is unknown, but they typically live around eight years in captivity.

Amazon milk frog adult and young
Young Amazon milk frogs are smooth-skinned and more dramatically colored than adults. Life On White / Getty Images

Conservation Status

The International Union for Conservation of Nature (IUCN) categorizes the Amazon milk frog conservation status as "least concern." The number of wild frogs and their population trend is unknown. The species is protected in Sierra de la Neblina National Park in Venezuela and Parque Nacional Yasuní in Ecuador.

Threats

As an arboreal species, Amazon milk frogs are threatened by deforestation, logging, and clear cutting for agriculture and human settlement. Frogs may be captured for the pet trade, but the species breeds in captivity, so this practice probably poses no significant threat.

Amazon Milks Frogs and Humans

Amazon milk frogs breed well in captivity and are easy to keep, providing their temperature and humidity requirements can be met. When kept as a pet, care should be taken to minimize handling the frog. Captive frogs rarely secrete toxic "milk," but their skin readily absorbs potentially harmful chemicals that may be on a person's hands.

Sources

  • Barrio Amorós, C.L. Amphibians of Venezuela Systematic List, Distribution and References, An Update. Review of Ecology in Latin America 9(3): 1-48. 2004.
  • Duellman, W.E. The frogs of the Hylid genus Phrynohyas Fitzinger, 1843. Miscellaneous Publications, Museum of Zoology, University of Michigan: 1-47. 1956.
  • Goeldi, E.A. Description of Hyla resinifictrix Goeldi, a new Amazonian tree-frog peculiar for its breeding-habits. Proceedings of the Zoological Society of London, 1907: 135-140.
  • La Marca, Enrique; Azevedo-Ramos, Claudia; Reynolds, Robert; Coloma, Luis A.; Ron, Santiago. Trachycephalus resinifictrix . The IUCN Red List of Threatened Species 2010: e.T55823A11373135. doi:10.2305/IUCN.UK.2010-2.RLTS.T55823A11373135.en
  • Zimmerman, B.L. and M. T. Rodrigues. Frogs, snakes, and lizards of INPA-WWF Reserves near Manaus, Brasil. In: A.H. Gentry (ed.), Four Neotropical rainforests. pp. 426-454. Yale University Press, New Haven. 1990.