Amazon Milk Frog

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Program and General Information
Amazon milk frogs are one of the largest frogs in South America growing up to 4 inches in length. They live up in the tree canopies in the rainforests of South America. While they rarely leave the trees, milk frogs prefer to be near slow- moving water. They are a light gray color with patterns of brown or black banding, which fade as they age. The name “milk frog” does not refer to their color; it refers to the poisonous secretions this frog may secrete when threatened.
Breeding takes place between November and May. Females lay ~2000 eggs in slow-moving water or in water trapped in a tree cavity, where males will come and fertilize them. Eggs hatch within 1 day and metamorphosis from tadpole to adult takes about 3 weeks.

Diet
Milk frog’s diet consists of insects, other invertebrates, and other small amphibians. As long as they can fit it in their mouth, a milk frog will try to eat it!

Milk frogs don’t use their tongue to catch prey like other frog species do, but instead ambush prey and use their front limbs to shove the prey into their mouth. Frogs will actually use their eyes in order to swallow their prey. Frog saliva is very thick and while it aids in keeping prey items in their mouth, it also makes swallowing more difficult. So in order to swallow frogs will push their eyeballs into their mouth cavity and push down on the prey against the tongue. This will increase the pressure inside the mouth liquifying that super thick saliva, which releases the prey from the tongue and forces that prey down the throat.

Habitat and Range
Amazon milk frogs can be found throughout Northern South America, but most commonly in Colombia, Brazil, Venezuela, Ecuador, and Bolivia. They spend the majority of their lives up in the tree canopy and rarely, if ever, descend to the rainforest floor. Because of their highly permeable skin, which allows for easy transport of water and oxygen through the skin, milk frogs prefer high humidity and moist environments. They are often found near sources of water, whether that is slow-moving bodies of water on the forest floor or pockets of water in tree cavities.

Milk frogs are nocturnal (awake during the night), and can be found hidden under leaves and vegetation above streams during daylight hours.

Common Physical Features
Amazon milk frogs are a relatively large frog when compared to other species of frogs in the South America. They range from 2.5-4 inches in length with females being larger than males. Milk frogs are typically light gray in color with patterns of brown or black banding. They also have a long snout, large toe pads, and rough and bumpy skin texture. Juveniles are more distinct in color and have a smoother skin texture; bumps on the skin will form and their coloration will fade as they age. This coloration acts as excellent camouflage in the rainforest’s canopy. Milk frogs are a hardy frog with muscular limbs and large feet.

Adaptations: Milk frogs have large toe pads that allow for excellent climbing; in fact the toe pad of the milk frog can hold up to 14x the animal’s body weight! This is especially beneficial since this species of frog is primarily arboreal.

Their scientific name “Trachycephalus” refers to their rounded snout, which they use for pushing aside vegetation to hide amongst. Their common name “milk frog” does not refer to their coloration but to their poisonous secretions. When stressed or threatened, milk frogs may release a milky-white toxin, that although is not as potent as other frog toxins, can cause a predator to become sick. And not only does this toxin assist in deterring predators, but it also acts as a sort of sunscreen for the frog. Milk frogs can rub it all over to aid in water retention to ensure that they do not dry out in the sun.

Milk frogs also have large vocal sacs and are quite vocal, especially at dusk and dawn when they are most active. Males become even more vocal during breeding season while they try to attract a mate.

Behavior and Life Cycle
Because they are mainly an arboreal (tree-dwelling) species, it is very rare that you would see a milk frog on the forest floor. In fact, the only time a milk frog would come down from the trees is during breeding season. Breeding season occurs during the rainy seasons of November through May. The male is responsible for finding a suitable area to lay the eggs, whether that is in a water filled-tree cavity or other source of water. The male will call to females to come and lay their eggs in the water. The female lays ~2000 eggs in a gelatinous mass, which the male will then fertilize. Once the eggs are fertilized, a male may call for another female to lay a mass of eggs next to the fertilized eggs. He will leave these eggs unfertilized so that they do not hatch and can provide food for the newly born tadpoles. This is the end of parent care, though both parents may remain near the vicinity of the hatching site.

Eggs will hatch within one day, and once the tadpoles hatch they must find their own food source and are left to fend for themselves. It takes about 3-5 weeks for tadpoles to metamorphose into froglets. At this point, the frogs will leave their natal area to find a territory of their own. They reach sexual maturity at 1 year.

Conservation Messaging
Conservation of the Natural World
Although population numbers are stable, habitat loss and pollution are a concern for the Amazon Milk frog and could lead to future decline. Human activities, such as residential and commercial development, farming and ranching, construction of roads and railways, and fishing have all contributed to habitat destruction for the milk frog.

Pollution is another big concern for frog species. Amphibian’s permeable skin can easily allow toxins and pollutants to enter their bodies, therefore, they cannot survive in polluted habitats. Tree frogs are considered an important indicator species that warns of future environmental degradation. If population numbers begin to decline then there is a strong possibility that that habitat could be polluted.

What can we do?
Supporting local conservation efforts and organizations is a great way to help ensure species such as the Amazon Milk frog continue to thrive. Switching to a more sustainable lifestyle can also help. By using public transport, turning off lights that are not in use, reducing the use of plastic, and using more organic cleaning products we can help to reduce pollution in our environments.
Remember the phrase, “reduce, reuse, recycle!”

Never remove an animal from the wild! You might think you are helping it, but most people don’t realize the amount of care and time that goes into caring for these animals, and removing them from their natural environment can be detrimental to the wild populations. And while you may think they would make a cute pet, amphibians have a lot of special requirements, such as heating, humidity, nutrition, light, that all need to be considered before purchasing; and always be sure you are buying from a reputable breeder.

Fun Facts
While not all tree frog species are affected, the widespread infectious fungal disease chytridiomycosis has devastated many wild populations worldwide. Chytrid fungus can infect waterways and can cause the keratinized areas of the frogs to thicken. This hinders the ability to pass oxygen and other gasses through the skin and causes the frog to dry out. We can help prevent the spread of the Chytrid fungus by washing items we take into waterways, rinsing off our boots and shoes after being in waterways, and by not handling any wild animals.

Milk frogs are also known as “mission golden-eyed tree frogs” because of their unique yellow/copper eye color.

Bibliography
https://www.npr.org/sections/thetwo-way/2017/01/31/512622260/to-catch-prey-frogs-turn-to-sticky-spit
http://beardsleyzoo.org/amazonmilkfrog-fk1
http://www.iucnredlist.org/details/55823/0 http://amphibianrescue.org/tag/trachycephalus-resinifictrix/ http://www.auduboninstitute.org/animals/frogs-beyond-green/amazon-milk-frog-3022 http://www.clemetzoo.com/animals/index.asp?action=details&camefrom=exhibit&name=RainForest+Amphibian+Exhibits&animals_id=1196
https://www.sfzoo.org/amazon-milk-frog/
https://www.saczoo.org/wp-content/uploads/2016/12/Amazon-Milk-Frog-Factsheet.pdf