Diagnosis: Breviceps macrops has a globose body, short snout and large eyes. It can be distinguished from other rain frogs in southern Africa by the combination of a smooth venter with a transparent vascular window (this character alone distinguishes it from all except B. namaquensis; see photo of the venter in Du Preez and Carruthers 2009); a weakly developed (if present) single basal subarticular tubercle on the hand (double in B. namaquensis); specialized feet, which are paddle-like and smooth and have thick fleshy webbing (unique to B. macrops); exceptionally large and protruding eyes (present also in B. namaquensis); lack of a facial mask (present in B. fuscus, B. gibbosus, sometimes present in B. acutirostris), and locality; this species is confined to a rather narrow coastal strip in northwest Namaqualand (Du Preez and Carruthers 2009).
Description: Breviceps macrops is a short and stout frog, with a body length ranging from 4 mm to 6 mm (Boulenger 1907). It is a specialized burrower, with a spherical body and paddle-like feet (Channing and Wahlberg 2011). The venter has a transparent vascular window in the central and posterior regions of the abdomen. The tympanum is not visible in this species (Boulenger 1907). Eyes are strikingly large and prominent in this small frog (Boulenger 1907). Subarticular tubercles on the hand are absent or weakly developed; if present they are always single (Channing 2001). The extremely short limbs make it impossible for this frog to hop, although it can walk (Boulenger 1907). The coloration of this frog is predominantly yellow and brown, closely matching that of its habitat (Boulenger 1907). The dorsal surface bears smooth warts (Boulenger 1907). Dorsal markings are unique to individual frogs and identification of individuals can be made by photographs (Channing and Wahlberg 2011), although Channing (2001) also reports that the dorsal pattern is usually concealed by a layer of sand adhering to the skin. Males have a deeply wrinkled gular region (Du Preez and Carruthers 2009).
This frog has extensive webbing on its feet, in contrast to other members of the genus Breviceps. Carruthers and Passmore (1978) conjecture that the foot webbing enables traction on loose sand, as the frog moves about on the surface of its sand dune habitat at night (based on its distinctive tracks).
Etymology: The generic name Breviceps comes from the Latin words brevis, meaning "short," and ceps, meaning "head." The specific epithet macrops is derived from the Greek words macro, meaning "large," and ops, meaning "eye." Thus, Breviceps macrops means "short-headed large-eyed frog." The Afrikaans name Melkpadda ("milk frog") refers to the pale color of the dorsum (Channing 2001).
The desert rain frog (Breviceps macrops) is a species of frog in the family Brevicipitidae. It is found in Namibia and South Africa. Its natural habitat is the narrow strip of sandy shores between the sea and the sand dunes. It is threatened by habitat loss.
The desert rain frog is a small, plump species with bulging eyes, a short snout, short limbs, spade-like feet and webbed toes. On the underside it has a transparent area of skin through which its internal organs can be seen. The size of this frog can span between 4 to 6 centimetres (1.6 to 2.4 in). Its colour is yellowish-brown and often has sand adhering to its skin.
It also has an unusual high-pitched cry similar to that of a squeaky toy.
Unlike most other species of frogs, it develops directly from the egg into adults without passing through the tadpole stage. It has a stout body, with small legs, which makes it unable to hop or leap - instead, it walks around on the sand. The frog does not require water in its habitat to survive. The frog possesses comparatively large bulging eyes.
The desert rain frog is mostly found on a small coastal strip of land about 10 kilometres (6.2 mi) wide between the African countries of Namibia and South Africa. The small area of sand dunes often gets a lot of fog, which supplies moisture in an otherwise arid and dry region.
The desert rain frog is nocturnal, spending the day in a burrow which is dug to a depth of 10 to 20 centimetres (3.9 to 7.9 in) where the sand is moist. It emerges on both foggy and clear nights and wanders about over the surface of the dunes. Its footprints are distinctive and are often found around patches of dung where it is presumed to feed on moths, beetles and insect larvae. It digs its way into the sand in the morning, and its presence in a locality can be deduced from the little pile of loose sand dislodged by its burrowing activities. Breeding is by direct development of eggs laid in its burrow and there is no aqueous tadpole stage.
The frog's total habitat range is smaller than 2,000 square kilometres (770 sq mi) and is fragmented and the number of individual frogs seems to be decreasing. It is threatened by habitat loss caused by opencast diamond mining, road construction, as well as increased human settlement.
Breviceps macrops lives along the western coast of South Africa and Namibia in a region known as Namaqualand, an arid coastal desert in the Succulent Karoo ecoregion with large sand dunes and sparse desert vegetation (Van Jaarsveld 1987). During the spring months, this area undergoes a metamorphosis and becomes a field of blooming flowers (Cowling 2001). Breviceps macrops occupies a very narrow strip of land from the high-water mark to 10 kilometers from the coast, within the coastal fog belt (Minter 1998; Cowling 2001). This frog is fossorial, meaning it is adapted to burrowing and underground living. It buries itself in the sand dunes of its habitat (Minter 2004).
This frog is nocturnal, emerging after dark from under the sand on both misty and clear nights. It searches for dung, where it feeds on beetles and moths, and can be followed by its distinctive tracks in the sand dunes (Channing 2001).
At McDougall's Bay, reproduction peaked between June and October, with juveniles found present only during that time span (Channing and Wahlberg 2011). The call is a subdued long drawn-out rising whistle with a dominant frequency of 1.3 kHz and duration of about 200 ms (Channing 2001), with males calling from small excavated depressions or from exposed positions after periods of onshore fog (Du Preez and Carruthers 2009). Males may call in choruses, where one male initiates a call and is subsequently followed by others (Channing 2001). Clutch size is not known for B. macrops, but for other species in the genus Breviceps, clutches range from 13-43 eggs (Channing and Wahlberg 2011).
Individuals were collected at a depth of 10-20 cm below the sand dune's surface; at this depth the sand is moist. A buried frog can be located by a small conical mound of sand on the dune surface, created during the process of its digging down under the surface (Carruthers and Passmore 1978).
Although Carruthers and Passmore (1978) found this species to be abundant in 1977 in its coastal sand dune habitat at Port Nolloth, South Africa, this species is declining (Minter 2004). Channing and Wahlberg (2011) noted that it had only been confirmed from 11 localities in a 400 km coastal strip. Population density may be highest at Port Nolloth, due to a high number of fog-days (120-140 per year) at that locality (Channing and Wahlberg 2011). All records of B. macrops exist in areas with white coastal sands and more than 100 fog-days per year (Channing and Wahlberg 2011).
Namaqualand is rich in diamond and copper deposits. Diamond mining activities (via strip mining) have altered the habitat and caused pollution due to runoff (Smallberger 1975; Channing and Wahlberg 2011), as well as fragmenting populations (Minter 2004). Encroachment by humans has further contributed to habitat loss (Smalberger 1975). Housing development in coastal sand dune areas is threatening habitat as well (Channing and Wahlberg 2011).