Jamaica’s hylid frogs breed in the water-filled leaf-axils and have adapted to the harsh environments of bromeliads (i.e., low oxygen levels and limited food reserves), by producing rapidly developing eggs and by laying further eggs which are eaten by the first-born larvae. Remarkably, the eggs laid during the first few days are fertilised and later the unfertilized eggs are laid, which the larvae consume rapidly.
Mountain Chicken Frog (Leptodactylus fallax) is highly endangered and limited to Dominica, St. Kits, Martinique and a few neighbouring islands, lays eggs in foam nests underground, and the tadpoles develop without ever seeing water. The startling footage taken by some researchers shows tadpoles feeding on unfertilized eggs produced by their mother. Subsequent research has revealed that the mother uses her rear legs to re-distribute the unusual food, and perhaps to give all of her progeny a chance to feed and survive. The 25-50 tadpoles that she rears require 10,000 to 25,000 unfertilized eggs to see them through metamorphosis to adult stage.
There are some species of poisonous frogs in South America where the males transport tadpoles. The males crouch down in the leaf litter next to the hatching eggs and the tadpoles wriggle up onto the father’s back and he transports them to water. Mothers of the Jamaican cave frog species—Eleutherodactyluscundalli—carry their froglets from the cave into the rain forest. It is the only known example of females transporting froglets.
Dendrobates auratus female lays up to six eggs in a small pool of water. The eggs are encased in a gelatinous substance for protection. The mating season occurs throughout the rainy season, from mid-July to mid-September. During the two week development period, the male returns to the eggs periodically to check on them. Once the tadpoles hatch, they climb onto the males back and he carries them to a place suitable for further development, such as a lake or a stream. For the duration of this trip, the tadpoles are attached to the males back by a mucus secretion, which is soluble only in water so that there is no chance of them accidentally falling off. Once they are at their final destination, the tadpoles are on their own. They take an additional six weeks to develop into adult frogs.
Males of Rhinodermadarwinii, Darwin’s Frog, brood their developing young in their vocal sacs until they metamorphose. The Darwin’s frog males have a very unusual behaviour in the amphibian community. After the male and female mate, the female lays her eggs in moist leaf litter on the forest floor. She then hops off, leaving the male to attend to them. Dutifully he guards the eggs until a few days later when they begin to transform into tiny tadpoles, but still encased in the egg sac. The movement inside the eggs stimulates the father frog to swallow them into the modified vocal sac called gular pouch. There they remain until transformed into miniature adults, upon which he opens his throat and allows them to leave and live on their own.
The commonly named Moustache frog, Vibrissaphora ailaonica undergoes quite a transformation just before the breeding season. The males begin growing long, hair-like skin extensions from one end of their mouth to the other. They also choose a large boulder near a stream and begin building a nest underneath it. From here they will call incessantly for females, and then guard the eggs of any and all females who come and mate with them. The eggs typically take a month to hatch and tadpoles slip into the waters below. Metamorphosis will not fully occur until two years later. The microhylids, Anodenthyla, Platypelis and Plethodontohyla, which are all natives of Madagascar, deposit their eggs in the rain filled axils of plants. Male frogs then stay nearby the eggs for anywhere from 26 to 35 days; the time it takes for the different species to hatch.
The genus Alytes contains the midwife toads, such as A.cisternasii and A. obstetricans . Both species attach the fertilized eggs to their hind legs. This starts by the male wrapping them first around his ankles. Sometimes they mate up to four times, carrying up to 200 eggs upon their bodies. The father frogs then keep the eggs moist by settling into shallow puddles and pools, allowing the eggs to double in size. Midwife toads sense when their eggs are ready to hatch, and will then wade into shallow waters to allow the young tadpoles to escape into water.
Male Leptodactylid, Thoropa petropolitana also cares for the eggs in a similar way. The microhylid males Breviceps adspersus and Synapturanus salseri also do the same.
The frog genus Pristimantis lays eggs on land, which develop directly into miniature adults with no tadpole stage. These are the most widespread and commonly occurring frogs in the New World tropics. In Africa the genus Arthroleptis, known as “squeakers”, are all direct developers. There are also many other direct developing frogs on Madagascar and in Southeast Asia. Among salamanders most species of the largest family, the Plethodontidae, are direct developers.
A few species of frogs give birth to living young. Members of the African genus Nectophrynoides retain eggs in the oviduct and some nourish the young as they grow. These are born as miniature adult. One Puerto Rican species of the genus Eleutherodactylus, now thought to be extinct (E. jasperi), also retained eggs in the oviduct to give live births. Salamandrasalamandra, S. atra and some related species either give birth to larvae or to completely metamorphosed juveniles.