Three Tanzanian Tree-Toads Found to Give Live Birth — Scientists Describe Three New Species

Three Tanzanian tree-toads give birth to live, millimetre-sized toadlets

Scientists have formally described three remarkable species of Tanzanian tree-toads that bypass the free-swimming tadpole stage: the females give birth on land to dozens of fully formed, millimetre-long toadlets. The study, published November 6 in the journal Vertebrate Zoology, combines museum specimens, genetic data and field recordings to distinguish the new species.

Viviparity is rare but adaptive

Viviparity — giving birth to live young rather than laying eggs that hatch into aquatic larvae — is extremely uncommon among amphibians. Of roughly 4,000 known frog and toad species, fewer than 1% are viviparous. Researchers suggest this reproductive strategy may be an adaptation to forest habitats where suitable standing water for egg-laying is scarce.

"Describing these new species that give birth to live young is fascinating and helps us understand the evolutionary flexibility of amphibians," said Dr. Diego José Santana, curator of amphibians and a conservation ecologist at Chicago's Field Museum. Santana was not involved in the new research.

How the discovery was made

Previously, populations now recognized as three distinct species had been grouped under a single name, Nectophrynoides viviparus. The research team reviewed 257 museum specimens — some over 100 years old — from five European collections, extracted DNA where possible, and analysed recorded vocalizations. Differences in call frequency, pulse pattern and duration, together with subtle morphological differences (body size, toe shape and limb gland patterns), supported the separation into three species.

The newly described species are Nectophrynoides luhomeroensis, N. uhehe and N. saliensis. Some female specimens contained large yolky eggs and partially developed embryos, confirming internal nourishment of embryos and live birth.

Biology and brood size

These tree-toads are small — adults reach roughly 37 mm (about 1.5 inches) — and display a variety of colours from pale gray and yellow to brown, red and black. Aquatic-breeding toads may produce enormous clutches (in some cases ~20,000 eggs), while viviparous Nectophrynoides typically produce far smaller broods. Researchers reported typical broods of around 40–60 toadlets, with a maximum recorded brood exceeding 160 fully developed young inside a single female.

Because the young emerge larger and more developed than tiny tadpoles, they may enjoy a survival advantage in environments with limited aquatic habitat.

Conservation concerns

Refining species boundaries has direct conservation value: several Nectophrynoides species have declining populations, and those with small, restricted ranges are especially vulnerable to habitat loss, political instability and climate change. One species, the Kihansi spray toad (N. asperginis), is already extinct in the wild. Another, N. poyntoni, has not been observed since its discovery in 2003.

"Further surveys are needed to fully understand the distribution, ecology, and possible population trends," the study's authors wrote. The researchers emphasised the importance of continued investment in taxonomy and natural-history collections, which made this discovery possible.

Study: Scherz et al., published November 6 in Vertebrate Zoology. Reporting by Mindy Weisberger (source: CNN).