Become a fan of h2g2
TOAD ON THE TOWN: THE WESTERN LEOPARD TOAD
The Western Leopard Toad, Amietophrynus pardalis, is South Africa's largest toad species, and also one of the most strikingly patterned, with its panther-like spots and blotches. Also this toad is almost completely restricted to the environs of South Africa’s first and currently also one of its largest and most bustling cities, Cape Town.
A Town of Toad Hazards
Cape Town today sprawls all around Table Mountain and over its gentler slopes. The growth of the city and suburbs has consumed a great extent of the original vegetation of the Cape Peninsula, which was fynbos, a shrubby vegetation type unique to South Africa and extremely rich in plant species. But much of it is still preserved, especially on higher ground. The Cape Penninsula gets somewhat more rainfall than the low Cape Flats to east of it, forming rivers, streams, ponds and small pools that frogs and toads like this one may use. Although they can catch insects in the fynbos itself, leopard toads need water for breeding.
This species breeds in the springtime, which is the start of the dry season in the Western Cape, and thus it needs deep, permanent bodies of water. Come early spring these toads will spring into action. Because this is the easiest time to see this species, they're sometimes called August Toads. Actually the season can start any time from late July to early September, depending on when the first warm weather kicks in after the winter. When the time is right the males will seek out positions on the banks of lakes, marshes and ponds from where they call to try and attract females. Their call is a loud snore lasting a second, and repeated every three seconds. Should a male succeed, he will 'hug' the female from behind – actually this clasping is called 'amplexus' – and she will lay her eggs into the water. The eggs are in long strings held together by a jelly–like substance, within which the embryos look like small, black blobs. As she lays them the male fertilizes them from above. The eggs hatch into tadpoles that later metamorphose into small toads in typical fashion.
But because of the human development in the region, toads today run a gauntlet when they start heading for their breeding pools. Most dangerous for the toads is the network of roads, in the crossing of which they run the risk of getting flattened by cars. Fortunately there are many Capetonians aware of these toads, and there is even a volunteer effort every year during the toads' breeding migrations to actually help them safely cross the roads! The volunteers will chase or carry as many toads over the roads as they can, flag down approaching motorists, and also collect population data in the process.
City life in general is not very amphibian-friendly. Apart from roads and cars, the movements of these toads are also hampered by other human–created obstructions such as walls, electric fences and canals. Then there are exotic species brought by people into their habitat, like ducks and alien fish species. Human alterations of water features also may cause them a loss of suitable breeding habitat. Nevertheless these toads are adaptable, and some can now be found in gardens and other suburban environments.
Noxious Warts and Sex-change Organs
This toad reaches a snout-to-vent length of 14 cm/almost 6". Like in many toads, there is a pair of large glandular bumps behind the eyes extending to over the shoulders, called the parotid glands. Smaller raised glandular bumps, the so–called 'warts' of toads, are all over the upper side of the body. As in most toads, these glands exude toxic secretions that protect the toad by making it unpalatable to potential predators.
An interesting feature of toads is that the males have an anatomical structure called 'Bidder's Organ'. This, when stimulated in the lab, can become an ovary and produce eggs – effectively turning the males into females. But we don't know if that ever happens in Nature, and whether it does or not, what Bidder's Organ is actually for.
Untangling Toad Relationships
The Western Leopard Toad has a close relative, the very similar Eastern Leopard Toad, Amietophrynus pardalis. The two species both occur in the very south of South Africa; the Western species mostly around the Cape Peninsula, while the Eastern species occurs from the eastern part of the Western Cape into the western parts of the Eastern Cape, mostly close to the ocean. The leopard toads (both species) belong to the family of True Toads, the Bufonidae. Biologically there is no clear distinction between 'frogs' and 'toads'. 'Frog' is simply used mostly for the prettier, more graceful, less warty species, while 'toads' are for the squatter, less agile, more warty species, but in nature, these factors are of no significance when it comes to actual relationships. The 'true' toads are all called 'toad' and do have visible similarities, and indeed do turn out to form a closely related group, but the relationships within the group still need a lot of work to figure out.
These days genetic studies augment morphological examinations, giving us a clearer picture. The leopard toads used to be included in the genus Bufo which included the majority of species of toad and ranging from the Americas to Europe, Asia and Africa. This genus has now been split up, which is why the leopard toads along with a few other African species are now classified as Amietophrynus. Again we are starting to understand that there is a lot more diversity than meets the eye. Toads, although they may look similar, are an ancient group that has long ago already divided into many different assemblages which spread to different parts of the world where they evolved even further. We are lucky here in South Africa to have several different genera of toads but some species are restricted to very small natural ranges and consequently in need of conservation. In this regard knowledge is power: the more we can understand their uniqueness, the better we can inform the public, the more awareness we can raise, and the better our chances of protecting them.