Cover photo by Jean-Paul Brouard.
Find the Bronze Caco in the FBIS database (Freshwater Biodiversity Information System) here.
Family Pyxicephalidae
Identification
The Bronze Caco is a small frog that reaches a maximum length of 23mm. The skin on the upper parts is granular, and the dorsal colouration varies from grey to brown, typically with a bronzy tinge. A number of dark flecked, low warts are scattered across the back. A pale vertebral line is often also present. On the head, a dark facial mask runs from the snout through the eye to near the base of the forearm. A pale band is present below the face mask, along the upper lip from below the nostril to the base of the forearm. The undersides are smooth with dark mottling, especially on the throat, chest and sides. The central belly region is pale with large grey blotches. The tympanum may be hidden or partially obscured.
Habitat
The Bronze Caco inhabits a wide variety of vegetation types in the Fynbos, Savanna, Grassland, Thicket and Forest biomes, occurring in areas of relatively high rainfall (Van Dijk 1971b). Breeding sites include small ponds, dams, vleis, streams, rain pools alongside roads, and inundated grass and pasture.
Behaviour
During dry periods, Bronze Cacos aestivate below the surface, sometimes emerging in large numbers after heavy rain (Wager 1965).
In KwaZulu-Natal, C. nanum commences breeding slightly earlier in the rainy season than C. boettgeri. Males call mainly from sheltered sites in deeper water. Calling males are distinctly territorial, loudly warning encroaching males by means of a territorial call that differs from their typical advertisement call. On warm, drizzly days or after rain, they may begin calling in the mid-morning, although they usually commence in the late afternoon and continue well into the evening.
Eggs are laid in clusters of 8–25, sometimes up to 50 (Wager 1986). As is typical of the genus as a whole, the eggs are anchored to the substrate. Wager (1986) reported that metamorphosed froglets of C. nanum leave the water 17 days after hatching, which may be the quickest growth to metamorphosis known in any frog (Duellman and Trueb 1986).
The Bronze Caco has been reported to feed on mosquitoes in captivity (Wager 1965), and the species probably plays an important role in the control of small insects in undisturbed habitats. Predators have not been recorded.
Status and Conservation
The Bronze Caco is one of the most common frogs in its range and, in the wet season, it can be heard calling from almost every rut, drainage ditch and small pond. The Bronze Caco is known from many protected areas and is not threatened.
Distribution
The range of the Bronze Caco extends from Swellendam (3420AB) in the south Western Cape, eastward along a narrow (c.70 km-wide) coastal strip on the relatively moist southern side of the Cape fold mountains to Port Elizabeth (3325DC). From there, its range extends much further inland (c.350 km), reaching the Zuurberg National Park (3325AD), and eastward past the Amatola Mountains and former Transkei, reaching southern KwaZulu-Natal. It is confined to areas below the escarpment, with the KwaZulu-Natal Drakensberg forming a barrier to the northwest.
Atlas records indicate a second, disjunct distribution in northeastern KwaZulu-Natal around the Mkuze, Hluhluwe and Umfolozi reserves and adjacent lowlands, and extending into adjacent areas of Mozambique. Confirmed records exist from the lowlands of southern Swaziland (2731AA, AB).
The Bronze Caco is absent from higher altitudes along the escarpment, where it is replaced by its closest relative, C. parvum (Mountain Caco).
The atlas records for C. nanum are reliable.
Further Resources
The use of photographs by Jean-Paul Brouard is acknowledged.
Bronze Caco Cacosternum nanum Boulenger, 1887
Other Common Names: Bronze Dainty Frog, Dwarf Dainty Frog (Alternative English Names); Koperblikslanertjie (Afrikaans)
Recommended citation format: Scott, E; Tippett, RM. (2025). Bronze Caco Cacosternum nanum. Biodiversity and Development Institute, Cape Town. Available online at https://thebdi.org/2022/02/17/bronze-caco-cacosternum-nanum/
This species text has been updated and expanded from the text in the
2004 frog atlas: Scott, E. (2004). Bronze Caco Cacosternum nanum. In Minter LR et al 2004.
References:
Minter, LR; Burger, M; Harrison, JA; Braack, HH; Bishop, PJ; Kloepfer, D. (Editors). (2004). Atlas and Red Data Book of the Frogs of South Africa, Lesotho and Swaziland. Smithsonian Institution, Washington, and Avian Demography
Unit, Cape Town.
Carruthers, V; du Preez, L. (2017). Frogs of southern Africa: A Complete Guide. Struik Nature, Cape Town.
Channing, A. (2001) Amphibians of Central and Southern Africa. Protea Book House, Pretoria
