Oligosoma tekakahu, Chapple, David G., Bell, Trent P., Chapple, Stephanie N. J., Miller, Kimberly A., Daugherty, Charles H. & Patterson, Geoff B., 2011
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publication ID |
https://doi.org/ 10.5281/zenodo.205462 |
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DOI |
https://doi.org/10.5281/zenodo.6182742 |
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persistent identifier |
https://treatment.plazi.org/id/03AC4C11-8D2D-A427-FF4C-FAAFFE134A42 |
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treatment provided by |
Plazi |
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scientific name |
Oligosoma tekakahu |
| status |
sp. nov. |
Oligosoma tekakahu sp. nov.
Figure 6 View FIGURE 6. a
Oligosoma inconspicuum ‘Te Kakahu’ Chapple et al. 2009: 485 Oligosoma sp. 6 (Te Kakahu skink) Jewell 2008: 89
Holotype. Chalky Island (Te Kakahu), Fiordland (46º 03’S, 166º 31’E), RE006879, adult male (coll. T. Bell, January 2008).
Live animals examined. Chalky Island, Fiordland (46º 03’S, 166º 31’E), 16 animals (7 adult males, 6 adult females, 3 subadults) (data collected by T. Bell, January 2008).
Diagnosis. Oligosoma tekakahu can be distinguished from other related Oligosoma species through a combination of characters ( Figure 4 View FIGURE 4 a – b ). Compared to O. maccanni , O. tekakahu has a glossy appearance, with brown predominating whereas O. maccanni has a greyer ground colour. The ear opening in O. maccanni often has large projecting scales on the interior margin, whereas these are minimal in O. tekakahu . The number of subdigital lamellae in O. maccanni (19–28) does not overlap with O. tekakahu (16). Longitudinal striping is more pronounced in adjacent populations of O. polychroma , which almost always have a pale stripe on the outside of the forelimbs and a prominent mid-dorsal stripe which O. tekakahu lacks. The ear opening in O. polychroma often has prominent projecting scales on the interior margin. The number of subdigital lamellae in O. tekakahu (16) is less than in any other member of the O. inconspicuum species complex. The number of ventral scales in O. tekakahu (68) is fewer than O. toka sp. nov. (70–88). Oligosoma tekakahu has a larger head relative to SVL than any other member of the O. inconspicuum species complex (its head length, 9.8 mm, was longer than any other specimen measured in the study).
Description of holotype. Body elongate, oval in cross-section; limbs moderately well-developed, pentadactyl. Lower eyelid with a transparent palpebral disc, bordered on sides and below by small, oblong granules. Nostril centred just below middle of nasal, pointing up and back, not touching bottom edge of nasal. Supranasals absent. Rostral broader than deep. Frontonasal broader than long, not separated from frontal by prefrontals meeting in midline. Frontal longer than broad, shorter than frontoparietal and interparietal together, in contact with 2 anteriormost supraoculars. Supraoculars 3[left]/4[right], the second is the largest. Frontoparietals distinct, larger than interparietal. A pair of parietals meeting behind interparietal and bordered posteriorly by a pair each of nuchals and temporals, also in contact with interparietal, frontoparietal, third/fourth supraocular and 2 postoculars. Loreals 2, anterior one the larger; anterior loreal in contact with first supralabial, posterior loreal, prefrontal, frontonasal and nasal; posterior loreal in contact with second supralabial, first subocular, upper and lower preocular, prefrontal and anterior loreal. Supralabials 7, the sixth is the largest. Infralabials 6, several of them equal in size; fifth supralabial below centre of eye. Mental broader but shallower than rostral. Suboculars 3 and 4 separated by fifth supralabial. Postmental larger than mental. Chinshields 3 pairs. One primary temporal. Dorsal scales largest, weakly striate. Ventral scales smooth. Subdigital lamellae smooth. Ear opening round, small with no projecting granules. Forelimbs shorter than hindlimbs. Adpressed limbs not meeting in adult. Digits moderately long, sub-cylindrical. Third front digit shorter than the fourth.
Measurements (in mm; holotype only). SVL 67.2; HL 9.8; HW 6.8; AG 35.6; SF 24.0; SE 11.3; EF 13.0. TL unknown (not intact). Ratios for morphological measurements: AG/SF 1.48; SE/EF 0.87; HL/HW 1.44 (in mm; live animals): The mean SVL size (from 14 live animals) was 64.08 mm (range 50–79 mm), and the mean mass was 5.6 g (range 1.6–10 g).
Holotype scale counts. Upper ciliaries 7; lower ciliaries 9; nuchals 3 pairs; midbody scale rows 30; ventral scale rows 73; subdigital lamellae 17; supraciliaries 5; suboculars 6. One primary temporal. Third front digit as long as the fourth.
Colouration. Dorsal surface light olive to chestnut brown, often with highly irregular random dark flecks. A broken dorsolateral line formed by a single row of triangular-shaped dark or black flecks runs from the posterior margin of the eye to the base of the tail. This row is bordered by a pale dorsolateral band approximately a half scale row wide above, and by a broad dark brown lateral band, below, which commences from the posterior of eye, passing above limb insertions and concluding near tail base. A pale grey lateroventral band similarly runs from the lower jaw to the tail base. The edges between the lateral band and lateroventral band is variable in markings in individuals, from scattered black and white flecks running across the body mid-laterally, to a rudimentary but broken black above/white below mid-lateral stripes. Ventral surface entirely yellow, or sometimes with pale grey chins. Ventral surface plain without speckling or other markings. Outer surface of forelimbs strong yellowish brown with darker and lighter specks. Juvenile colouration is unknown, but likely to be similar to adults.
Etymology. From Te Kakahu, the Maori name for the type locality (= Chalky Island). The common name is the Te Kakahu skink.
Habitat and life history. Oligosoma tekakahu is currently known only to occupy open coastal herbfield and prostrate shrubs growing on chalk chip strata at one location on northwestern Chalky Island ( Loh 2003; this study; Figure 5 View FIGURE 5 c). Chalky Island is located in the southern part of the FIORD 72.04 Preservation Ecological District ( McEwen 1987), a region which consists of non-glaciated coastal plateaus in the south west (100–500 m asl). Preservation ED is cool, often cloudy and windy, with high annual rainfall (3200–8000 mm), typical of Environment O5 ( Leathwick et al. 2003). At Chalky Island, these skinks occur in generally high densities at the type location with over fifty skinks encountered in a small area of 50 x 50 m over two days (this study). The type location is at an altitude of 134–142 m, at the head of chalk cliffs. The flora around the type location consists of windswept grasses and complex prostrate shrubs including Olearia avicennifolia , O. oporina , Coprosma spp., Metrosideros umbellata, Phormium cookianum, Coriaria arborea, Helischrysum , Poa colensoi , Haloragis erectus , Griselina littoralis , Hebe elliptica , Pimelia lyallii , and Chionochloa conspicua ( Loh 2003) . The skink is currently known to be associated with Olearia avicennifolia , O. oporina , the grasses Carex s pp. and Rytidosperma spp. (this study). Although the extent of habitat similar to the type location is remarkably small on the entire island, O. tekakahu are also likely to also occupy the largely inaccessible coastal vegetation and prostate scrub vegetation along the entire coastline of Chalky Island. Skinks have also adapted to open areas created within the scrub by the cutting of tracks leading to and away from the type location, an observation also recorded by Loh (2003).
Oligosoma tekakahu is a diurnal, terrestrial species, and strongly heliothermic with avid sun-basking behaviour even during windy conditions by utilising sheltered micro-sites ( Loh 2003, TPB, pers. obs.). The following observations on Te Kakahu skinks were made by TPB. The skinks will bask readily on chalk flakes in air temperatures up to 23.8 °C, above which they retreat to bask partially shaded within vegetation. Basking extends to as late as 8 pm in the mid-summer. Oligosoma tekakahu appear to have small home ranges and do not appear to defend territories, often basking in close proximity to other skinks. Skinks generally forage or bask in close proximity to cover or vegetation, but will cross quickly between habitat patches over chalk. The sex ratio of captured skinks was almost equal (8 males: 6 females). Almost all adult female skinks were heavily gravid by January, and three neonates were sighted, suggesting the possibility of an unusually early season parturition period in late January. The smallest reproductively mature individual was a 61 mm SVL gravid female. These skinks flick their tongues relatively frequently as they move. Their tongues were noted to be relatively long and coloured bluish-grey. The incidence of regenerated tails or body scarring evident in the sample (N = 15) was generally high (53%). The New Zealand falcon ( Falco novaezeelandiae ) is likely to be a predator and was recorded daily at the type location during the field work for this study (TPB, pers. obs.). There are no other known sympatric species of lizard on Chalky Island.
Conservation status. The Te Kakahu skink is currently considered Nationally Critical (criterion A. Naturally or unnaturally very small natural population; with qualifiers Conservation Dependent, Data Poor, and One Location) in the New Zealand Department of Conservation’s national threat classification list ( Hitchmough et al. 2010). These skinks appear to be very locally abundant, and may yet be found in new locations on Chalky Island and nearby islands such as the Passage and Coal Islands. Protection is provided by the status of a mammalian predatorfree offshore island within a national park, and along with ongoing monitoring for invasive mammal incursions by the New Zealand Department of Conservation. Potential future threats appear to be the invasive mammal pests (e.g. rats, Rattus spp., and stoats, Mustela erminea ) which are present on the adjacent mainland. These skinks exhibit highly naive behaviour to potentially novel predators, and would likely suffer severe losses as a result of invasion of rats or stoats. Stoats were present until 1999 on Te Kakahu Island and the population is likely to be in the process of recovery from their impacts.
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