Mapping the Cape Rain Frog

Mapping the Cape Rain Frog

Mapping the Cape Rain Frog - Southern Africa : The Cape Rain Frog (Breviceps gibbosus) is endemic to the Western Cape and occurs in two populations: the Cape peninsula extending to the foothills of the Boland, and on the foothills of the Cederberg and Groot Winterhoek. Much of this species historic ex

The Cape Rain Frog (Breviceps gibbosus) is endemic to the Western Cape and occurs in two populations: the Cape peninsula extending to the foothills of the Boland, and on the foothills of the Cederberg and Groot Winterhoek. Much of this species historic extent of occurrence is under agriculture and an urban landscape.

Almost half of the southern distribution is within the urban edge of the City of Cape Town, including residential land and private gardens. Effective conservation in this significant area is dependent on the participation and enthusiasm of citizens and property owners. Also known as the Kaapse reënpadda, the blaasoppie, and the Giant Rain Frog, this species is considered Near Threatened (IUCN, 2010), but it is not known if their population is stable. The adjacent map indicates historical records which are concentrated outside the urban edge (see figure 1) and may not adequately represent the area of occupancy within its urban extent of occurrence. We do know that these frogs are not uncommon in gardens, but exactly how common are they? And where are they? Your help is needed to gain a better understanding of their densities and distribution at a residential scale. Be a Citizen Scientist! It’s as easy as uploading an image.

Cape Rain Frogs are burrowers and can be found on sloping, sandy or loamy, well drained soils. The male will call during the mating season, from late April into spring, by inflating his vocal sac. The call is a long, strongly pulsed whistle (unlike other Rain Frogs). These frogs have some interesting features. For example, they don’t hop, they walk or run. The hindlimbs and feet are used for digging and their feet aren’t webbed. When alarmed, they inflate their bodies into an almost spherical ball. In appearance, the skin of the underside is a mottled brown on cream colour, and is coarsely granular, especially on the throat of males. From above the skin is a darker brown and the eyes are dark and small. The face is flat with a narrow downturned mouth. This species is the largest of Rain frogs with a maximum body length of 80mm (females are larger than males).

Threats to this species include the continued hardening or paving of grounds, and the urban conversion of open spaces. There have been suggestions that predation on this frog may have increased with the recent extension of the Hadada Ibis’ range into the Cape Peninsula. Avoid being an additional threat: do not go digging for them.

The endangered Western Leopard Toad (Amietophrynus pantherinus), much like the Cape Rain Frog, has an extent of occurrence that includes suburban areas. Citizens have added value to conservation efforts by submitting locations of sightings and breeding sites using iSpot, and in-so-doing they (perhaps some of you reading this – thank you for continued efforts and contributions) have helped to draw a more detailed and refined distribution map showing areas of occupancy in the southern suburbs of Cape Town. Similarly, the locational data that you provide will be used to identify populations under threat and to provide a better understanding of the urban extent of this species.

Other species of Rain Frog co-occurs with B. gibbosus these include the Cape Mountain Rain Frog (B. montanus) and the Sand Rain Frog (B. rosei) – the former is much smaller and only occurs in mountainous areas. While a distinguishing characteristic between the Cape Rain Frog and the Sand Rain Frog is the extent of the facial markings (which is the dark band next to the eye). For the Cape Rain Frog this band is indistinct, stretching partly to the forelimb (highlighted in image 2), while for the Sand Rain Frog the facial band is distinct and stretches from eye to armpit.

A feature of iSpot is the ability of fellow users, which include herpetological experts, to view and comment on your uploaded images and to agree with or contest the identifications you’ve assigned. Your contributions from the greenbelt, parks, communal open spaces, and reserves will also be welcomed. Thank you, and have a wonderful wet season!

Reference: Minter, L.R., Burger, M., Harrison, J.A., Braack, H.H., Bishop, P.J. & Kloepfer, D. (2004) Atlas and Red Data Book of the Frogs of South Africa, Lesotho and Swaziland. Smithsonian Institute, Washington, DC, USA.

29 Apr 2015
Zishan