Description
Pyxicephalus beytelli is a large African bullfrog that was described based on six male specimens. The males have robust bodies with a snout-vent-length range of 108.3 to 208 mm and a snout-urostyle length range of 101.1 to 200 mm. The head is short and relatively broad in proportion to body size. The head is wider than it is long and wider than the trunk. The snout is relatively short with an eye-snout distance to head length ratio of 0.46. The snout is rounded in the dorsal view, bluntly rounded in profile, and is slightly projected beyond the lower jaw. It has a relatively long snout compared to the width between its nostrils. The slightly projected nostrils are situated closer to the eye than the snout tip. The canthus rostralis is smoothly rounded and the loreal region is slightly concave.The eyes are directed anterolaterally and are slightly protruding. The eyes are relatively small with an eye length to head length ratio of 0.19. The eye diameter is about half of the snout length with an eye length to eye-snout distance ratio of 0.42. The anterior interorbital distance is greater than both the upper eyelid and internarial distance. The internarial distance is subequal to the eye diameter, measuring around 0.9 mm. The distance from the eye to the tympanum is nearly twice the diameter of the tympanum, which is slightly larger than the eye diameter with a measurement of 1.1 mm. The upper jaw is widely spaced with recurved teeth. Males have a single vocal sac. The dorsal surfaces of the head, trunk and limbs have either rounded tubercles or elongated warts. There are 10 – 14 dorsal and lateral longitudinal skin folds that may be continuous or broken. The ventral surface of limbs, gular, and abdomen regions are smooth (du Preez et al. 2024).

The forelimbs are robust, revealing moderately large hands with a hand length to snout-vent-length ratio of 0.21. The thenar tubercle is distinct and the metacarpals do not have supernumerary tubercles. The fingers have a relative length of: IV < II < I < III, and the fingertips are not enlarged into discs. The subarticular tubercles are single and distinct, with one on fingers I and II, and two on fingers III and IV. The fingers are not webbed. The nuptial pads are present on the upper surface of fingers I and II (du Preez et al. 2024).

The hind limbs are stout. The short tibia is about a third of the snout-vent-length. When the legs are held at a right angle to the body, the heels do not reach each other. The foot lacks a tarsal tubercle and outer metatarsal tubercle. However, the inner metatarsal tubercle is prominent and shovel-shaped, continuing as a tarsal ridge. The long toes have a relative length of: I < II < V < III < IV, and have no expanded discs. The subarticular tubercles are very flat to barely visible, with one present on toe I and II, two on toe III, three on toe IV and two on toe V. They also have moderate webbing with a formula of I 1 – 2 II 1.5 – 2 III 2 – 3 IV 3.5 – 2 V and a thin margin of webbing extending to tips (du Preez et al. 2024).

DIAGNOSIS:

At the time of the species description, there were five known Pyxicephalus species and one undescribed Pyxicephalus species. Pyxicephalus beytelli is similar to all other species of African bullfrogs in morphology and burrowing behavior. It is assigned to the genus Pyxicephalus based on the presence of maxillary teeth, vomerine teeth, two large sharp projections on the lower jaw, and a strongly flanged inner metatarsal tubercle. Additionally, no outer metatarsal tubercle are present. However, there are several features that differentiate the species from its congeners. Specifically, P. beytelli is larger than, P. angusticeps, which has a smaller maximum snout-vent length of 78.7 mm, P. edulis, which has a maximum snout-vent length of 103 mm, and the undescribed Pyxicephalus, which has a maximum snout-vent length of 120 mm. Pyxicephalus beytelli has a mean head width to snout-urostyle length ratio of 0.5, distinguishing it from P. edulis, which has a ratio of 0.43 and P. angusticeps with a ratio of 0.39. Moreover, its odontoids are longer than wide, distinguishing it from P. angusticeps and P. obbianus. The mean eye-tympanum distance to tympanum diameter ratio is 1.3 in P. beytelli, distinguishing it from the smaller ratios of P. angusticeps and P. edulis with ratios of 0.74 and 0.75 respectively. The tympanum is also smaller or equal to the eye in P. beytelli, distinguishing it from P. obbianus, which has a much larger tympanum. The eye-tympanum distance is more than one tympanum width in P. beytelli, differing from P. angusticeps, where it is equal to or less than one tympanum, and P. obbianus, where the tympanum is adjacent to the eye. Additionally, the eye and tympanum are nearly equal in diameter in P. beytelli, with a mean eye diameter to tympanum diameter ratio of 1.01, distinguishing it from species with larger eyes, such as P. angusticeps with a ratio of 1.47, P. edulis with 1.54, and P. adspersus with 1.41. On the feet, the subarticular tubercles are very small to barely visible in P. beytelli, compared to the relatively distinct tubercles in P. adspersus and the undescribed Pyxicephalus. With regards to color, there is a white spot on the tympanum that distinguishes P. beytelli from P. adspersus. Additionally, P. beytelli’s golden yellow back with black patterning also differentiates it from P. adspersus, P. obbianus, P. edulis and the undescribed Pyxicephalus. Specifically, P. beytelli does not have cream colored lateral stripes or mottles. Pyxicephalus beytelli has speckling between its dorsal mottles whereas P. angusticeps and P. obbianus have none. Pyxicephalus beytelli also has strongly developed dorsal skin ridges as opposed to the oval dorsal warts of P. angusticeps and P. obbianus. Lastly, P. beytelli can be differentiated by its strongly pulsed call that ranges from 0.2 – 0.55 seconds, which is shorter than the 0.56 – 1.79 second call of P. adspersus but is longer than the call of P. angusticeps, which ranges from 0.08 – 0.21 seconds. The call of P. beytelli also has a lower emphasized frequency of 172.3 – 258.4 Hz as opposed to P. angusticeps that has a range of 301.5 – 775.2 Hz (du Preez et al. 2024).

COLORATION:

In life, the dorsal surface coloration ranges from golden-yellow to dark orange in the groin area and has dark patches with pale centers in transverse bands over the body. It may also have scattered networks-like patches of thin black lines. Laterally, there are no black blotches, but there are few black lines. There is a distinct yellow vertebral line. The thigh and tibia are barred and have scattered transverse black lines. The interorbital bar is edged in black. The tympanum has a prominent white dot in the center. The gular region is white with scattered gray blotches. The abdomen is white and immaculate. The nuptial pads are pale (du Preez et al. 2024).

In preservative, the dorsum is gray with black blotches and lines. There is also a prominent thin white vertebral line from the snout to vent. The tympanum is distinctly black with a white center. The gular region has light gray blotching. The abdomen is gray, ventrally smooth, and immaculate (du Preez et al. 2024).

VARIATION:

No females were collected at the time of the species description, so sexual dimorphism could not be evaluated. However, male specimens vary in their dorsal background coloration from asparagus green to yellow with patterns of silver-blue blotches. All the paratypes have distinct barring on their upper jaw, a prominent vertebral line, a tympanum that is as large as the eye, and a prominent white tympanic patch. However, a specimen collected in the Okavango was lime green with dark gray-blue blotches (du Preez et al. 2024).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Angola, Botswana, Namibia, Zambia

View distribution map in BerkeleyMapper.

Pyxicephalus beytelli is known from western Botswana, north-eastern Namibia, south-western Zambia and southern Angola. However, based on its habitat preference of savanna woodland and grassland, it is believed that the species may also be found throughout northern and north-western Botswana, northern and north-eastern Namibia, south-western Zambia, south-eastern Angola and in north-eastern Zimbabwe (du Preez et al. 2024).

Life History, Abundance, Activity, and Special Behaviors
While no specific differences in mating behavior have been observed for P. beytelli, African bullfrogs generally exhibit intriguing breeding behaviors. Most are explosive breeders, mating during the day. Males call from shallow water, extending their front limbs to display bright yellow-orange on their upper arms or the pale white or yellow color of their throat. Dominant males chase away rivals and mate with multiple females, while non-dominant males distantly form a lek in an attempt to attract females (du Preez et al. 2024).

The advertisement call is brief and distinctly pulsed. The call duration varies from 0.2 – 0.55 seconds, with a dominant frequency of 172 – 258 Hz. The pulse rate of each note varies from 56 – 88 per sec (du Preez et al. 2024).

Pyxicephalus beytelli lay eggs that float as a film on water surfaces, possibly as an adaptation to extremely hot weather conditions, unlike similar species such as P. adspersus and P. edulis that lay eggs that sink to the bottom (du Preez et al. 2024).

Several herons (Ardea spp.), Marabou Storks (Leptoptilos crumenifer), and Rock Monitors (Varanus albigularis) were observed to prey on adult P. beytelli (du Preez et al. 2024).

Pyxicephalus beytelli occurs sympatrically with P. adspersus in Khaudum National Park in northern Namibia (du Preez et al. 2024).

Larva
Tadpoles of P. beytelli are described to be similar to those of P. edulis from South Luangwa, Zambia. Pyxicephalus edulis tadpoles are large-bodied; including the length of its tail, the species measures at 55 mm long. The head is wedge-shaped in profile and has small eyes. The keratinized jaw sheaths are heavy. The spiracle opening is narrow and is laterally visible. The dorsal fin originates on the back of the head and then curves to an evenly rounded tail tip. The dorsal and ventral fins are symmetrical (Channing et al. 2012).

The labial tooth formula is 5(3-5)/3. There are multiple lateral rows of papilla and a double posterior row.

In life, P. edulis tadpoles are dark and large-bodied. The keratinised jaw sheaths are darkly pigmented (Channing et al. 2012).

Tadpoles of P. beytelli form large schools and are found in shallow temporary pools after a rainfall event (du Preez et al. 2024).

Tadpoles of P. beytelli develop rapidly, as their spawning grounds have a high risk of drying out. The tadpoles feed on debris and come to the surface to gulp air. Twenty-one days after an observed spawning event, large numbers of metamorphs with remnants of their tails, were found at the water's edge (du Preez et al. 2024).

There were no observations of cannibalism by P. beytelli metamorphs (du Preez et al. 2024).

Trends and Threats
Although P. beytelli is often consumed as food, the species authority recommend a “Least Concern” species status as it is widely distributed and can be found in protected areas as well as degraded habitat near villages and farms (du Preez et al. 2024).

Relation to Humans
Pyxicephalus beytelli are collected during breeding events and are sold alongside roads in Namibia and in Angola (du Preez et al. 2024).

Possible reasons for amphibian decline

General habitat alteration and loss
Intentional mortality (over-harvesting, pet trade or collecting)

Comments
Based on Maximum Likelihood analyses and of 16S rRNA mtDNA and tyrosinase exon 1 nDNA, it was determined that P. beytelli is sister to P. adspersus, which it was previously considered to be (du Preez et al. 2024).

OTHER INTERESTING INFORMATION:

Pyxicephalus beytelli is the largest frog to be described in 104 years (du Preez et al. 2024).

References
Channing, A., Rodel, M.-O., Channing, J. (2012). Tadpoles of Africa: The Biology and Identification of All Known Tadpoles in Sub-Saharan Africa. Edition Chimaira.

du Preez, L. H., Netherlands, E. C., Rödel, M. O., and Channing, A. (2024). A new bullfrog from southern Africa (Pyxicephalidae, Pyxicephalus Tschudi, 1838). African Journal of Herpetology, 73(1), 61–89. [link]

du Preez, L. H., Lumpkin, S. K., Netherlands, E., Channing, A. Unique breeding biology of the recently described Beytell’s bullfrog Pyxicephalus beytelli. African Journal of Ecology, 62(3), e13311. [link]

Species Account Citation: AmphibiaWeb 2024 Pyxicephalus beytelli: Beytell's Bullfrog <https://amphibiaweb.org/species/9848> University of California, Berkeley, CA, USA. Accessed Feb 5, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Feb 2025.

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