Ptenopus maculatus Gray, 1866

Becker, François S., Alexander, Graham J. & Tolley, Krystal A., 2025, Singing on key: An integrative taxonomic revision of barking geckos (Gekkonidae: Ptenopus) with six additional species and keys for morphology and advertisement calls, Vertebrate Zoology 75, pp. 277-323 : 277-323

Ptenopus maculatus Gray, 1866 sensu stricto

Figures 8 , 20 G – H

Common names.

Damaraland barking gecko / Spotted barking gecko

Afrikaans: Damaraland blafgeitjie

Chresonymy.

Ptenopus maculatus Gray, 1866: 640 , pl. 38: 1

Ptenopus garrulus (part) – Boulenger (1885: 15), Brain (1962: 314), Haacke (1964: 3)

Ptenopus garrulus maculatus (part) – Mertens (1955: 51), Haacke (1969: fig. 3 d), Brain (1962: 3, 14), Haacke (1975: 221), Bauer et al. (1993: 127)

Comment.

Ptenopus maculatus was described from “ Damaraland ”, collected by Karl (= Charles) J. Andersson. This species was synonymised under the name ‘ P. garrulus ’ ( Boulenger 1885) . Subsequently, ‘ P. g. maculatus ’ was resurrected at subspecies level ( FitzSimons 1935), which has been regarded as valid ever since. Most of the earliest references to this subspecies, including the initial synonymisation with ‘ P. garrulus ’ (e. g., FitzSimons 1935, 1937 b; Loveridge 1947), referred to specimens included in our treatment of P. adamanteus sp. nov. and P. kenkenses sp. nov., but exclude those from the type locality of ‘ P. maculatus ’. Mertens (1955), Haacke (1975), and several subsequent authors also referred to specimens from a broad geographic range, encompassing that of several species (current manuscript), as ‘ P. g. maculatus ’.

According to Andersson’s notes and the location names used at the time (see map in Andersson 1855 and 1872), “ Damaraland ” referred to the Erongo Region in Namibia. Notably, Andersson stayed at “ Otjimbingue ” [Otjimbingwe] briefly in 1851 and again in the 1860 ’ s for several years, where this species occurs, and where it may have been collected. While staying here, a battle occurred on his property between the Damaras under chief Kamaherero, who had taken shelter at his house after fleeing their enslavement under the “ Namaqua ” (Nama) tribe Afrikaner, then under leadership of Christian Afrikaner (son of Jonker Afrikaner), leading to a victory by the Damara ( Andersson 1875).

From the P. garrulus group species, “ Damaraland ” contains only P. maculatus sensu stricto (as presently treated). Additionally, the type specimens ( BMNH 1946.8.23.53 , 54) and a detailed drawing from the type description match the colour pattern and appearance of P. maculatus sensu stricto. Finally, the morphometric measurements of the BMNH types generally support this classification, and most unambiguously so for BMNH 1946.8.23.54 (Fig. 4 ). Hence, this specimen is assigned as the lectotype.

We elevate the subspecies ‘ P. g. maculatus ’ to full species, thereby restricting the range of P. maculatus sensu stricto to the central and northern Namib Desert, north of the Kuiseb River (Fig. 5 ), and excluding P. adamanteus sp. nov., P. kenkenses sp. nov., P. circumsyrticus sp. nov., and P. australis sp. nov., from P. maculatus sensu stricto

Haacke (1969) described the calls of P. maculatus sensu stricto and of P. circumsyrticus sp. nov., from areas near Gobabeb (Central Namib Desert, Namibia), but was unable to link individual specimens with their calls. Haacke (1969) also described calls of P. adamanteus sp. nov. as ‘ P. g. maculatus ’. The call of P. maculatus sensu stricto is described and distinguished in a standard taxonomic framework below.

Lectotype.

BMNH 1946.8.23.54 , collected from “ South Africa, Damaraland ” (Erongo Region – possibly Otjimbingwe , Namibia,), by Karl (= Charles) J. Andersson prior to 1864 (probably in 1851 or between 1855 and 1858, while travelling through and working in this area), as the lectotype for Ptenopus maculatus .

Paralectotype.

BMNH 1946.8.23.53 , same collection details as the lectotype .

Additional material examined.

See Table S 1 for unvouchered photographed (35) specimens, DNA samples (37 available, 12 sequenced), and call recordings (28) included (total n = 69 excluding types).

Diagnosis.

A moderately large Ptenopus (SVL max. 60 mm, mean 51.7 mm, n = 34) with a moderate tail (TL 69 % [range 58–78 %] of SVL, n = 21) and stout appearance. It is easily distinguished from P. kochi , P. carpi , and P. sceletus sp. nov. by the following characters: Toes being intermediately fringed laterally (vs. weakly fringed in P. carpi and P. sceletus sp. nov., and extensively fringed in P. kochi ), with fringe length being at least half the breadth of the toe between fringes; having MBSR ~ 135 (range 126–146, n = 35; vs.> 180 in P. kochi and usually <135 in P. carpi and P. sceletus sp. nov.); by dorsal colour pattern with four to five large, paired, ovoid markings on a darker background, interspaced by dark brown wavy or broken blotches (vs. more finely spotted in P. kochi and banded in P. carpi and P. sceletus sp. nov.).

From congeners previously included in ‘ P. garrulus ’ it is distinguished by: Higher IN / INSBB ~ 7.2 (range 4.9–8.8, n = 8) than P. circumsyrticus sp. nov. (median 4.5, range 3.6–5.8, n = 13); higher RB / RH ~ 1.17 (range 0.97–1.32, n = 8) than P. australis sp. nov. (<0.97) and P. adamanteus sp. nov. (usually <1.1); higher INSH / NB ~ 1.53 (range 0.60–2.49, n = 8) than P. australis sp. nov. (usually <0.80) and P. adamanteus sp. nov. (usually <1.00); lower MBSR (~ 135, range 126–146, n = 35) than P. kenkenses sp. nov. (≥ 158) and P. garrulus (≥ 156, usually> 170), and somewhat lower than P. adamanteus sp. nov. (median 160, range 141–185, n = 30); lower IOS ~ 34 (range 29–40, n = 35) than other species (usually> 37); lower IOS / MBSR ~ 0.23 (range 0.21–0.27, n = 8) than P. circumsyrticus sp. nov. (usually> 0.27), P. adamanteus sp. nov., and P. australis sp. nov. (usually> 0.25); having 1–2 internasal scales in contact with the rostral, vs. three in P. australis sp. nov.; having a different colour pattern than P. garrulus (usually more finely speckled, ovoid markings being much smaller).

Colouration.

In life (Fig. 8 ), the dorsal colour pattern consists of 4–6 large, cream / yellow / white paired ovoid markings from the neck to tail base with various light, coloured and dark brown juxtaposed speckles, darker colours coalescing into ill-defined paired patches between the oval markings; white ovoid markings laterally. Background dorsal colour is usually light brown or camel with occasional bright orange, pink, or purple speckling. The ventrum is immaculate white. Males have bright yellow gular patches. In some specimens, the yellow pigment extends onto the nose or patchily onto lateral margins of the head and neck.

In preservative, the lighter colours fade to off-white or beige, and all the darker colours appear various shades of dark brown or grey. The yellow fades completely after some days or weeks in ethanol.

Advertisement call.

The advertisement call of P. maculatus (Figs 3 , 20 F typical call, 20 H Hoanib River population) consists of 6 notes (range 4–7, sometimes 8 in Hoanib River population) uttered in rapid succession, with a note rate of 4.99s - 1 (range 2.58–7.17). Note duration is long, 50 ms (range 26–71), with the first note being notably longer than the rest, note 1 duration deviance 138 % (range 39–274); the Hoanib River population has a relatively shorter first note than the typical call. The inter-note intervals are usually short (145 ms [range 88–303]) and regular with inter-note interval range 20 % (range 10–42), although the first interval may be slightly longer. Call density is higher than all other species, mean 0.36 (range 0.17–0.50). Call duration is short (1.1s [range 0.8–1.4]). The basal frequency is 380 Hz (range 301–517) but very soft and may be inestimable, with harmonic bands louder towards the (upper) dominant frequency at 3.4 kHz (range 3.0–3.8), while a clear but softer lower frequency peak is evident at around 1.7 kHz (range 1.4–2.0), just below half the (upper) dominant frequency. Frequency appears to modulate briefly up (~ 0.2 kHz), then drastically down by ~ 0.5 kHz with the first note, and less severely down in the notes following. The first note tends to be louder, have a slightly higher dominant frequency, and a slightly higher (human) perceived pitch than the following notes. Bandwidth (90 %) is difficult to estimate consistently: approximately 0.9–4.8 kHz.

Call period (mean 110 s) varies greatly, but can be as low as 10 seconds during peak chorus activity. Calling commences shortly before or at sunset and may continue throughout the night after moonrise and before moonset. Calling activity is more pronounced around the austral spring and / or summer. Rainy weather usually causes calling activity to cease for days to weeks. This species rarely calls during the day.

Habitat and distribution.

Ptenopus maculatus occurs on hard substrates, not on soft sand. In the southern and central portions of its range it occurs on granite-weathered gravel. The central Namib gravel plains are almost entirely granite-based gravel ( Atlas of Namibia Team 2022 a) and the species is widespread and common in this area. In the northern reaches of its distribution, P. maculatus occurs on silts, in patchy floodplains, riverbeds, or pans. It has not been found closer than 25–50 km, nor further than 200 km, from the coast.

In the west it occurs syntopically with P. carpi and probably with P. sceletus sp. nov. which prefer the same soils. However, these species occur closer to the coast within the fog zone and the range of overlap is minimal. It occurs parapatrically with P. sceletus sp. nov. in the northern portions of its range, where P. maculatus prefers silts while P. sceletus sp. nov. occurs on gravels. Along the edges of the Namib erg, P. maculatus occurs parapatrically alongside P. circumsyrticus sp. nov. and P. kochi (which occur on sand or sandier patches of gravel plains), or occasionally in sympatry or syntopy with these species where the substrates mix.

Natural history.

Like the other species, P. maculatus males call from their burrow entrance and antagonistic behaviours between males are common if two burrow entrances are within ~ 2 m. Aggressors will sometimes utter the advertisement call as they look for the transgressing male, possibly to elicit a response. Males will increase calling frequency if a female approaches the burrow. Males may exit the burrow and approach the female, and after a brief encounter will follow the females into the burrow. Alternatively, the male will remain in place until the female scratches at the burrow entrance; the male then reverses into the burrow and the female follows. The male will utter a muffled version of the advertisement call inside the burrow, where copulation likely commences. After about an hour, the female will emerge partially from the burrow entrance, surveying the surrounding area with her head erect for a long time. This behaviour is repeated throughout the first night after a female moves into a new burrow, and its purpose may be to memorise the location of the new burrow entrance. Males presumably move out of the burrow after the female has moved in, as males and females have not been observed living in the same burrow.

Figures

Figure 3. Box and whisker plots of the bioacoustic characters analysed using ANOVA / Kruskal-Wallis tests, for species of Ptenopus. Numbered characters (numbered as in Methods) and their units are indicated on y-axis labels. Species colours correspond to those on Figure 2 and indicated on the key. Significant differences (according to pairwise post hoc tests) are indicated through homogenous groupings: Species not significantly different in the present character are one group, as indicated by lower-case letters. Species that share the same letters not differing significantly from each other; species with multiple letters are not significantly different from any other species sharing those letters. Approximate divisions between the groups are indicated by dotted lines perpendicular to the y-axis, and the group letters are indicated to the right of each graph.

Figure 4. Box and whisker plots of the morphological characters analysed using ANOVAs or Kruskal-Wallis tests, for cryptic species of the Ptenopus garrulus group. Numbered characters (numbered as in Methods) are indicated on y-axis labels: 1. Internarial / internasal scale base breadth; 2. rostral breadth / height; 3. internasal scale height / nostril breadth; 4. mid-body scale rows; 5. interorbital scales; 6. interorbital / mind-mody scales; 7. inter-nasal scales. Species colours correspond to those on Figure 2 and indicated on the key. Significant differences (according to pairwise post hoc tests) are indicated through homogenous groupings: Species not significantly different in the present character are one group, as indicated by lower-case letters. Species that share the same letters not differing significantly from each other; species with multiple letters are not significantly different from any other species sharing those letters. Approximate divisions between the groups are indicated by dotted lines perpendicular to the y-axis, and the group letters are indicated to the right of each graph.

Figure 5. Revised, interpreted distributions of Ptenopus species in southern Africa (high resolution map, can be zoomed for detail). Some species’ ranges overlap, shown with translucent overlapping shapes on the map. Others likely occur parapatrically along extended contact zones, represented by opaque, touching shapes. For further clarity, co-occurrence patterns for all species pairs are shown on Table 5, and confirmed individual records on Figure 2.

Figure 8. Life colour variation and substrate matching in Ptenopus maculatus: A Unvouchered individual from Gobabeb, Erongo Region, Namibia (– 23.5668, 15.0379); B NMNW R 11693 from Spitzkoppe, Erongo Region, Namibia (– 21.8393, 15.1946); C NMNW R 11668 from the same locality as B; D NMNW R 11688 from Hoanib River, Kunene Region, Namibia (– 19.3630, 13.1502). Photos by Francois S. Becker.

Figure 20. Sonograms (top graphs) and oscillograms (bottom graphs) of representative advertisement calls of Ptenopus species (A – J, species names indicated on graphs). Both x and y axes are directly comparable / equally scaled across species. Specimen numbers and localities: A NMNW R 11585, NE of Koës, Hardap Region, Namibia; B iNaturalist 140169978 (Jacobus Retief), Merweville, Western Cape Province, South Africa; C NMNW R 11622, E of Lüderitz, || Karas Region, Namibia; D NMNW R 11643, SW of Gobabeb, Erongo Region, Namibia; E NMNW R 11657, NE of Keetmanshoop, || Karas Region, Namibia; F NMNW R 11704, Gobabeb; G NMNW R 11716, Hoanib River, Kunene Region, Namibia; H NMNW R 12114, Gobabeb; I NMNW R 11843, NW of Gobabeb; J NMNW R 11790, N of Swakopmund, Erongo Region, Namibia. The audio files on which this figure is based, are made available (File S 2).