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Compiled by Atherton de Villiers (May 2009):

WESTERN LEOPARD TOAD
Amietophrynus pantherinus (A. Smith, 1828)

Other common names:
snoring toad, leopard toad, panther toad, August frog,
westelike luiperdskurwepadda

Identification

The western leopard toad can reach an impressive size of about 140 mm in body length; and, as is typical with toads, has a rough skin and two large parotoid glands on either side of the head and neck region behind the eyes. It also has a beautiful pattern of chocolate to reddish-brown patches on a bright yellow background (although duller individuals are also found); with usually a yellow stripe running down the length of the back between the patches. The underside is granular and cream-coloured, with a darkish throat in males.

Other toad species that occupy its habitat in places, generally have a duller brown to greyish upper surface colouring, covered in darker blotches and smaller markings. These species are the raucous toad (Amietophrynus rangeri), the sand toad (Vandijkophrynus angusticeps), and the guttural toad (Amietophrynus gutturalis), an introduced species in the Constantia area of the Cape Peninsula. Of these, the raucous toad is the most similar, but besides colour and pattern differences, it usually has only one elongated patch between the eyes, instead of the usual two of the western leopard toad. It also does not occur on the Cape Peninsula and Cape Flats, which is the best known distribution area of the western leopard toad. However, it does occur in the Overstrand area and juveniles of these toads are particularly similar.

The advertisement call is a deep pulsed snore that continues for about a second and is repeated every three to four seconds. It can also be described as sounding like a tractor or motorcycle engine, or a very loud “purr”. The call is quite different to that of any other frog species in its distribution area. In contrast, the raucous toad has a loud “quack” and many of them indeed sound raucous!

Distribution

The western leopard toad is generally restricted to the coastal lowlands of the southwestern Cape, with a fragmented distribution that extends from the Cape Peninsula southeastwards to the Agulhas Plain, spanning a distance of 140 km. Its distribution also does not extend further inland than about 10 km from the coast and is associated with rivers and large wetland areas.

The earliest distribution records were obtained from the Cape Peninsula and adjoining western part of the Cape Flats (dating back to the 1820s). This area has also been found to contain the largest populations of toads and has produced the most distribution records. These include the following localities (alphabetically) in a largely urban environment: Bergvliet, Cape of Good Hope area (of Table Mountain National Park), Clovelly, Constantia, Diep River, Fish Hoek, Glencairn, Hout Bay, Kalk Bay, Kirstenhof, Kommetjie, Lakeside, Noordhoek, Observatory, Ottery, Philippi, Rondevlei, Scarborough, Southfield, Sun Valley, Strandfontein, Tokai, Zeekoevlei, Valkenberg and some neighbouring areas.

In the coastal region to the southeast, the western leopard toad has been recorded from the Pringle Bay, Betty’s Bay, Kleinmond, Hermanus, Stanford, Gansbaai, Uilenkraalsmond and Pearly Beach areas. Further surveys will attempt to determine the full eastern extent of its distribution, in the Agulhas Plain to Mossel Bay area.

Habitat

The western leopard toad is generally associated with sandy coastal lowlands but, in places, can be found in valleys and on mountain slopes and hills adjoining the lowlands. As is typical with toads, this toad is a wide-ranging species that spends most of its time away from water, and can be found several kilometers from the nearest water body. However, it is always found in the general vicinity of rivers and wetland habitats such as coastal lakes, vleis and pans, in which breeding takes place.

Although this species is endemic (restricted) to the Fynbos Biome, occurring in pristine Fynbos and Strandveld habitats, it has also become adapted to living in modified habitats such as farmlands, suburban parks and gardens, and breeding in artificial water bodies. Furthermore, breeding has been recorded in water bodies where some degree of pollution and eutrophication is evident.

It generally breeds in permanent water bodies but also in seasonal wetlands that retain surface water well into the summer months. The breeding habitat can vary from coastal lakes, vleis, pans and sluggish, meandering rivers, that have stretches of relatively deep, still water, to man-made dams and garden ponds. Typical breeding sites have standing, open water, more than 50 cm deep, with scattered patches of aquatic plants and beds of emergent vegetation such as bulrushes (Typha capensis).

Life history

The western leopard toad is an “explosive breeder”. This means that breeding is restricted to sporadic short bursts of activity, lasting for up to a week or so at a time, and is not continuous throughout the breeding season. Breeding usually takes place during August, but has also been recorded in late July and in September; and some breeding calls have even been heard in early October. The commencement of breeding appears to depend largely on rainfall and temperature, and has been found to occur during warmer spells following periods of rain, but this requires further investigation.

The first indication that breeding is about to commence, is when large numbers of adult toads appear after dark, particularly on a rainy night, to converge on selected breeding sites, hence the old popular name: “the August frog”. Some toads migrate a few kilometres to reach their breeding sites and the same sites are used each breeding season.

At the breeding sites, the advertisement calls of the males are generally heard in choruses of around 50 individuals, but as many as an estimated 200 males have been heard chorusing at a large breeding site. The calling is generally at night, but during peak breeding periods, sporadic calling is sometimes heard during the day. Sites with very large numbers of males may call night and day continuously. Calling males seek cover amongst stands of emergent vegetation (e.g. bulrushes) during the day, but at night areas of open water are also utilized. The males have a habit of calling from a floating position with limbs outstretched, and amplexing (mating) pairs tend to utilize areas of open water for spawning.

The females deposit thousands of eggs in gelatinous strings. On one occasion a pair was reported to have produced 24 476 eggs. Thereafter, metamorphosis generally takes more than 10 weeks, but is influenced by factors such as food availability for the tadpoles, and the type, temperature and volume of the water body. The relatively small, dark, benthic tadpoles develop into tiny 11 mm long toadlets that leave the water in October-December in their thousands. Relatively few of the offspring develop into adults, taking about 2-4 years. Most fall victim to a variety of predators (including their own kind) and other hazards.

Conservation status

The western leopard toad is classified as an Endangered species. This is based on: its restricted distribution and habitat, habitat that is severely fragmented; and a continuing decline in the extent of distribution, area and quality of habitat, and the number of locations/populations and mature individuals. In particular, although the largest recorded populations occur in a largely urban environment on the Cape Peninsula and Cape Flats, these are increasingly being threatened by urbanization; and there have been no recent records of this toad from the middle part of its distribution range, extending from Pringle Bay to Hermanus.

Furthermore, although this toad occurs in some protected nature areas, most of the known breeding and foraging habitat is situated outside of these areas. Protected areas that have suitable breeding habitat include: Zandvlei Nature Reserve (including the adjoining Westlake Wetland Conservation area), Rondevlei and Zeekoevlei nature reserves, and Table Mountain National Park.

In the urban environment of the City of Cape Town, the western leopard toad is known to breed in certain public open space and green-belt areas, as well as golf courses, and is often encountered in surrounding gardens. These are important sanctuaries, but with increasing development, road traffic and associated threats, the long-term survival of local populations is potentially threatened.

The overall conservation status of the western leopard toad would improve if it is found to occur in the extensive coastal lowlands that extend from the Agulhas Plain to Mossel Bay area. This is a distinct possibility as there have been unconfirmed sightings of this species in this largely undeveloped region that includes nature reserves.

Threats

The western leopard toad is threatened throughout most of its range by general development and habitat degradation. While breeding generally takes place in larger, more secure water bodies, urban development poses an obvious threat around these water bodies, by causing habitat fragmentation and restricting the foraging area and movement of toads. This results in reduced population size, and can cause restricted or completely interrupted gene flow between populations.

In the urban environment, toads are forced to negotiate roads and barriers, such as walls, embankments and canals, while foraging and migrating to and from breeding sites. Expanding urban development and increased road traffic results in the death of hundreds of toads each year, especially during the breeding season. Artificial water bodies with vertical sides, such as swimming pools, canalized rivers and stormwater drains, represent additional deathtraps that pose a threat to local populations.

At some breeding sites on the Cape Peninsula and Cape Flats, specific threats include: pollutants; introduced predatory fish (e.g. barbell); invasive floating plants that choke the water surface and stagnate the water (e.g. water hyacinth); and captive populations of alien ducks that consume toad eggs and tadpoles, and foul the water.