Most of the time, frogs deposit their eggs in a pond or stream and leave their offspring to fend for themselves. Limborg's Frogs, however...
Limborg's Frog (Limnonectes limborgi) is a small frog species occuring in the humid forests of Southeast Asia. Male Limborg's Frogs, such as the one above, advertise their presence (and availability!) to females with a deep, raspy "craaawk" from underneath the leaf litter.
If you happen to be in the forests of Southeast Asia, the best way to actually see one of these frogs is to track down the exact patch of leaf-litter a call is coming from, and carefully clear away the leaves, one at a time. If you're lucky, you'll uncover something rather unexpected- a frog in a nest!
Rather than breed in ponds or streams like most species of frog, male Limborg's Frog carefully excavates nests in the mud on the forest floor (see above), away from water. Males then advertise their location in the hope that a female will stop by and lay some eggs in their nest. Compared to some frog species, which may deposit hundreds or thousands of eggs at a time, female Limborg's Frogs deposit less than a dozen in a nest.These eggs are then carefully guarded by the males (by sitting on top of them!).
For over 50 years, it was assumed that the eggs of Limborg's Frog skipped the tadpole stage entirely and developed straight to little frogs within the egg (this kind of development is known as 'direct development', and is relatively rare in the frog world). However, by crawling on our hands and knees in the forests of Vietnam and Cambodia, my colleagues and I discovered that their eggs don't skip the tadpole stage at all! Rather, their eggs hatch into tadpoles (like 'typical' frogs), but (unlike typical frogs) live entirely within the cosy confines of their nest. Interestingly, because there's not enough food for the tadpoles inside the nest, they skip feeding altogether, and live off internal yolk stores (which is why the tadpoles below have white bellies).
So why do male Limborg's Frogs go to all the trouble of carefully constructing nests and guarding them for weeks on end? Well, it seems from our observations that most of their eggs survive and develop into tadpoles inside these nests. This is actually quite rare in frogs- usually the vast majority of eggs deposited by frogs will become tasty treats for fish, birds, aquatic invertebrates or some other hungry predator. Therefore, by making nests in mud away from water, and guarding their brood, the offspring of Limborg's Frog seem to stand a much higher chance of survival than if they were left to fend for themselves in a pond or stream full of predators. And for this species, it's the male that does most of the work!
Our observations of Limborg's Frog were carried out during field expeditions in search of amphibians in Vietnam and Cambodia and were, depending on the expedition, a collaboration between the Australian Museum, Conservation International, University of Science- Ho Chi Minh City, Vinh University, Flora and Fauna International Cambodia and/or Ministry of Environment, Cambodia.
Reference: Rowley, J. J. L., & Altig, R. (2012). Nidicolous development in Limnonectes limborgi (Anura, Dicroglossidae). Amphibia-Reptilia 33: 145-149. article.
Interested in our amphibian research and conservation work in Southeast Asia? Read more here.