Spotted Shovel-Nosed Frog
Created | Updated Dec 2, 2012
Spotted Shovel-Nosed Frog
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
Today I have for you a watercolour painting of a Spotted Shovel-Nosed Frog, Hemisus guttatus. The scientific name means ‘spotted half-pig’. This is indeed a very pig-like and un-frog-like frog! It has a very round, fat body with short, stubby limbs. Unlike the majority of frogs, it has a relatively small head with small eyes. It has a sharp-pointed, wedge-shaped snout. This snout is a very specific adaptation, and the name gives us the clue: the shovel-nosed frog uses it to dig with!
There are many other frogs that can dig, a great many especially here in South Africa where most of the country is dry and even the moister regions experience dry seasons that can last for months. So, frogs living in such regions have to do something to keep their delicate skins moist during the dry times. The skin is moistened by secretions from glands throughout it. These glands also secrete poisons that protect frogs from predators. The glands can’t secrete these important fluids unless they themselves are supplied with water. Frogs also breathe partly through their skins, and gases can only dissolve into the skins when they are moist. For all these reasons frogs and toads have to seek out moisture and avoid factors that can dry them out. The best way to do this in regions experiencing regular long-lasting droughts is to dig themselves into the soil. Moist subsoil can often be found just a few inches below the surface and once a frog has covered itself with soil it is protected against the intense sunlight and drying winds as well. Frogs can spend months underground like this; in some species they only actually come to the surface for a short time each year to breed, typically when the first intense rains fall in Spring.
But most frogs that dig do not use their noses. Instead they use their hind legs. In fact most of the time one can see just how well a frog is adapted to digging just by studying its hind legs. A great many different kinds, not all closely related to each other, will have the same adaptation: a ridge of hardened skin along the edge of the hind feet. This ridge also works like a kind of shovel. The frog digs by shoving soil outward with the hind feet, and gradually settling into the hollow so formed. So it digs in reverse, moving backward into the hole while facing forward, but keeping on until it’s as deep as it wants to go.
This ‘reverse’ digging method is fairly slow. Most digging creatures have a more direct approach: moles and many other mammalian diggers have strongly clawed, broad front paws and dig into the soil head first. No amphibians have claws to rival those of moles, but this frog (and a few others in different regions of the world) does go for the head-first approach! It shoves its hard, sharp nose into the soil and pushes it out of the way. The eyes, being small, don’t get in the way, and neither does the small, under-slung lower jaw. As soon as it has its head properly in, it assists with its strong front and back legs to push it in deeper, while continuing to loosen the soil and shove it out of the way with its shovel snout. This means that this frog can dig much faster than the digging frogs that use the backwards approach.
Apart from its strange appearance and direct digging method the shovel-nosed frog is not that unusual. It lives around the banks of pans in savannah regions. These pans are shallow bodies of water that are not fed by rivers or streams. They form as accumulations of rain water in flat areas during the Spring and Summer and typically dry out again every Winter. Shovel-nosed frogs share this habitat with a great many other frog species. All of them will come out to breed as soon as the rains start and the pans fill up. Savannah pans at this time are wonderfully atmospheric for all the different frog calls one hears around them at any time of the day or night. The different species sort themselves out in various ways in time and space. Some call at different times from others. Some choose different positions … some sitting on the banks, some clinging to reeds or tall grasses growing out of the shallow water, and some floating in the open water. Some frogs give their calls in the silent pauses in between the calls of others. All of this is to allow a great diversity of species to all call for their own mates without causing a cacophonous confusion.
The spotted shovel-nosed frog digs itself burrows in the muddy banks of the pan. When the Spring rains start, it starts calling from inside its burrow. The call is a long, drawn-out, insect-like buzz. It repeats these at long intervals, and can be heard most of the time while it is raining. The female will come, mate with her chosen male and lay her eggs in an underground chamber. The eggs cling together in a large, rubbery mass. The male, like all frogs, fertilizes them after she lays them. The female stays with the eggs until the tadpoles emerge. Then she digs a tunnel from the nest chamber to the edge of the water. She returns for the tadpoles, carrying them on her back into the tunnel and releasing them into the water. There they develop and metamorphose into little frogs, which then leave the water and dig themselves into the banks of the pan so they would survive when it dries up in the Winter.
These funny frogs, being underground so much, are rarely seen – I haven’t, so far. This particular species is only found in the Kwazulu-Natal savannah region. They are at risk from human developments that destroy or pollute wetlands. Other species are more widespread in South Africa and also the rest of sub-Saharan Africa.
