Description
Male Strongylopus springbokensis range from 36.2 – 42.0 mm and a single female specimen in the original description measured 43.5 mm. The head is slightly narrower than the length and the head height is less than half the head width. The eye is approximately a quarter the width of the head, and tympanum is slightly more than half the diameter of the eye. The ulna is slightly shorter than the hand. The first finger has a paddle-like appearance. The tibia is about three-fourths the length of the foot. Breeding males possess sharp asperities on the back of the legs, and four phalanges of the fourth toe are unwebbed (Channing 1986).

At stage 26, three tadpoles reared from eggs were 15 mm long. The mouth is on the ventral surface and not visible from the dorsal view. The oral disc has a single row of mental papillae. Both the suprarostrodont and infrarostrodont are serrated. The keratodont forumula is 1,3+3/1+1,2. The nostrils are somewhat circular and rimmed; they open dorsally and nasal passage is slightly visible from the dorsal view. The ratio of the width of the nostrils to the internarial distance is 0.19. The distance from the snout to the nostrils is slightly less than the distance from the eyes to the nostrils. A single spiracle is present on the left, posterior side of the body, and is visible ventrally and laterally, but not dorsally. The sub-circular opening of the spiracle is slightly constricted. The vent is dextral and reaches the margin of the ventral fin. The tail is approximately the same height as the body, and is rounded at the tip. The tail is twice as long as the body and reaches its maximum height less than a quarter of the way down the tail. The caudal muscles are about a third the height of the body (Channing 1986).

The foot length of S. springbokensis is less than twice the width of the head, which can help distinguish this species from others of the same genus (Channing 2001). The appearance of S. springbokensis is similar to that of S grayii. Strongylopus springbokensis can be differentiated by a wider head and sharper snout, as well as a significantly shorter leg length. In contrast to the generally wide vertebral stripe of S. grayii, the vertebral stripe of S. springbokensis, if present at all, is subtle. In addition to visual differences, the long advertisement call of S. springbokensis is distinct compared to the clicking vocalization of S. grayii (Channing 1986).

In life, the dorsal surface of S. springbokensis is pale yellow-brown. Irregular brown blotches, outlined in a darker shade, are present on the dorsal trunk. The legs are barred on their dorsal surface. Some specimens have a pale vertebral stripe. The ventral surface is uniform in color. Preservation causes a loss in coloration, but the patterning is still visible (Channing 1986).

The dorsal surface of tadpoles is brown, while the fins and ventral surface lack coloration except for some slight markings on the dorsal fin and slight stippling around the gut coils. The suprarostrodont and infrarostrodont are pigmented, and there is a small pale pineal spot (Channing et al. 1986).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: South Africa

View distribution map in BerkeleyMapper.

Strongylopus springbokensis is found exclusively in Namaqualand in the Northern Cape Province of South Africa at an elevation of 200 - 1600 m above sea level. This species has been found from the Knersvlakte (South) to the Orange River (North), and possibly inhabits parts of Namibia (Channing et al. 1986, IUCN 2013). The species’ habitat includes the Succulent Karoo and Fynbos biomes. These areas receive less than 60 mm of rain per year, keeping this species close to permanent or temporary bodies of water. A subpopulation of S. springbokensis lives within the Ritchersveld National Park (Minter et al. 2004).

Life History, Abundance, Activity, and Special Behaviors

Three calls - advertisement, aggression, and release - have been described for S. springbokensis. The former was recorded in the field while the two latter were recorded in the laboratory. The advertisement call is comprised of a succession of 2 - 7 notes, each lasting 0.11 s, with a rate of 185 pulses/second. Note frequencies fall between 0.8 and 8 kHz, and are stressed at 0.8, 2.6, and 3.6 kHz. Call durations ranged from 0.22 – 1.17 seconds (Channing et al. 1986).

The aggression calls were elicited when one calling male approached another. It is comprised of one intense note from 0.4 kHz to over 8 kHz with a maximum amplitude between 0.45 and 1.8 kHz (Channing et al. 1986).

The male release call is a chain of squeaking calls, up to 3 seconds in duration, stressed at 0.8 and 1.2 kHz. Male elicited this call in addition to continuing the advertisement call (Channing et al. 1986).

Strongylopus springbokensis breeds in winter. Calling males were found with hundreds of eggs that were deposited 15 – 20 cm above dry streambeds or water level under rocks, in cracks, in vegetation, or in abandoned rodent burrows. Partially developed tadpoles hatched when they were hydrated. The eggs appeared to develop until the eyes and tail were formed before going into stasis until they were hydrated, at which point they hatch. The ability of the tadpoles to remain in their eggs and arrest development until water is available is apparently an adaptation to surviving in their arid environment (Channing et al. 1986, Channing 2001, Minter et al. 2004).

Trends and Threats

Strongylopus springbokensis was listed by the IUCN Red List as “Data Deficient” in 2001 and “Vulnerable” in 2003, but was changed to “Least Concern” in 2013. The change from “Vulnerable” to “Least Concern” was determined based on the discovery that populations were larger and more stable than originally believed (IUCN 2013).

Possible reasons for amphibian decline

General habitat alteration and loss
Intensified agriculture or grazing
Habitat fragmentation
Local pesticides, fertilizers, and pollutants

Comments

The species authority is: Channing, A. (1986). “A new species of the genus Strongylopus Tschudi from Namaqualand, Cape Province, South Africa (Anura: Ranidae).” Annals of the Cape Provincial Museums (Natural History) , 16(5): 127–135.

Strongylopus springbokensis was initially categorized in the family Ranidae, but is now part of the family Pixicephalidae. Strongylopus springbokensis is expected to be closely related to Strongylopus grayii (Channing 1986). The two species look very similar, and distinguishing characteristics are discussed in the diagnosis section.

The species epithet, “springbokensis” is named after the town from which the species was found, Springbok, Northern Cape, South Africa (Minter et al. 2004). Strongylopus springbokensis was discovered during a tadpole survey when Alan Channing heard strange frog calls near Springbok, South Africa (Channing 1986).

References

Channing, A. (1986). ''A new species of the genus Strongylopus Tschudi from Namaqualand, Cape Province, South Africa (Anura: Ranidae).'' Annals of the Cape Provincial Museums (Natural History) , 16(5), 127–135.

Channing, A. (2001). Amphibians of Central and Southern Africa. Cornell University Press, Ithaca, NY.

IUCN SSC Amphibian Specialist Group. (2013). Strongylopus springbokensis. The IUCN Red List of Threatened Species 2013: e.T58772A18405057. http://dx.doi.org/10.2305/IUCN.UK.2013-2.RLTS.T58772A18405057.en. Downloaded on 15 June 2016.

Minter, L.R., Burger, M., Harrison, J.A., Braack, H.H., Bishop, P.J., and Kloepfer, D. (eds.) (2004). Atlas and Red Data Book of the Frogs of South Africa, Lesotho and Swaziland. Volume 9 SI/MAB Series. Smithsonian, Washington D.C..

Species Account Citation: AmphibiaWeb 2017 Strongylopus springbokensis: Namaqua stream frog <https://amphibiaweb.org/species/5156> University of California, Berkeley, CA, USA. Accessed Nov 26, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Nov 2024.

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