Paroplocephalus atriceps, , StOrr, 1980

Bush, Brian, 2017, Additions to the description of Paroplocephalus atriceps (Serpentes: Elapidae) with a discussion on pupil shape in it and other Australian snakes, Zootaxa 4344 (2), pp. 333-344 : 335-338

Comments on Paroplocephalus atriceps

MOrphOlOgically, Paroplocephalus atriceps iS mOSt like Hoplocephalus bitorquatus Jan in Sharing a lOw number Of midbOdy Scale rOwS, lOw number Of ventralS, mOnOtOnal bOdy cOlOur and head Of different cOlOur tO bOdy. EcOlOgically, they bOth Occur in dry eucalypt fOreStS, with P. atriceps being SOlely fOund in thiS habitat, while H. bitorquatus alSO OccurS in wet SclerOphyll fOreStS. The Other twO Hoplocephalus (bungaroide S Schlegel and stephensii Krefft) are generally Only fOund in wet SclerOphyll fOreStS. AlthOugh all three Hoplocephalus Spp. are arbOreal, H. bitorquatus iS mOSt SO cOmpared tO the Other twO.

Paroplocephalus atriceps repreSentS a primitive, arid-adapted weStern Hoplocephalus -like SpecieS that, althOugh diSplaying SOme Similar ecOlOgical attributeS tO itS eaStern relativeS, haS nOt develOped tO the Same degree the Specialized climbing adaptatiOn (diStinctly keeled and nOtched ventralS) Seen in Hoplocephalus Spp.

AlthOugh P. atriceps lackS the diStinctly keeled and nOtched ventralS in Hoplocephalus , recent ObServatiOnS Of captive SpecimenS SuggeSt they are adept climberS, mOving up and perching On vertically arranged bark and retaining purchaSe with variOuSly Spaced lOngitudinal lateral fOldS Of Skin alOng lOwer flankS where dOrSal ScaleS meet ventral ScaleS (Figure 3). In additiOn, in December 2014, J. VOS and S. Patrick ObServed an adult male five metreS abOve the grOund active On the trunk Of a SmOOth-barked eucalypt tree. In December 2016, D. BrOmley, R. McGibbOn and S. Tuckey Saw a StatiOnary individual elevated On the SwOllen baSe Of a large eucalypt trunk in what they deScribe aS an ambuSh pOSitiOn. BOth theSe ObServatiOnS were near COSmic BOy Mine, FOrreStania in 32º 35’ S, 119º 44’ E.

Ehmann (1993) waS the firSt tO SuggeSt P. atriceps waS arbOreal after finding a piece Of SlOughed Skin On tree trunk 1.5 m abOve grOund. After cOmparing a SlOughed Skin frOm a captive individual with the field-cOllected piece, he detected a weak nOtch at the Outer Surface Of the Shed Skin.

ThiS Snake’S diStributiOn iS centred On the Greater WeStern WOOdlandS and it OccurS Only 350 km frOm Perth, but we currently knOw little Of itS geOgraphical range and ecOlOgy. ItS abundance iS difficult tO aSSeSS On the numberS knOwn and the time taken during thiS Study tO cOllect the Study animalS. Nearly all the individualS fOund tO date were primarily diScOvered OppOrtuniStically at night On the grOund, SO the difficulty in finding it cOuld be mOre a reSult Of itS arbOreality—it may Only infrequently fOray On the grOund mOving between treeS in the undiSturbed denSely vegetated wOOdlandS it OccupieS.

Of thOSe fOund On the grOund during the day, twO were diScOvered beneath rOckS. The third, an adult Snake waS ObServed by R. BrOwne-COOper (perS. cOmm.) baSking On a cOOl winter’S day at an air temperature Of 20º Centigrade, at 13.55 hrS On 13 June 2017 abOut 5 km nOrthweSt Of Lake CrOnin Nature ReServe in 32º 23’S, 119º 45’ E. It waS ObServed in the SunShine within a nOrth facing hOrizOntal crevice between twO large bOulderS apprOximately One metre abOve grOund. When BrOwne-COOper attempted tO get clOSer, the Snake quickly retreated Out Of Sight.

While preparing thiS paper, twO individualS were fOund by mine Site Staff in the FraSer Range 120 km eaSt Of all previOuS recOrdS in 31° 50’S, 123° 12’E. ThiS diStributiOn extenSiOn SuppOrtS the current WA wildlife authOrity’S cOnServatiOn liSting. It iS a PriOrity 3 SpecieS (2015 a & b), a categOry fOr “ Poorly-known species (some on conservation lands) that are known from several locations and the species does not appear to be under imminent threat, or from few but widespread locations with either large population size or significant remaining areas of apparently suitable habitat, much of it not under imminent threat. Species may be included if they are comparatively well known from several locations but do not meet adequacy of survey requirements and known threatening processes exist that could affect them. Such species are in need of further survey.” With thiS in mind, the current wOrk iS a prelude tO an OngOing cOmprehenSive ecOlOgical Study Of P. atriceps .

StOrr’S hOlOtype and paratype are bOth adult maleS, with thiS cOllecting biaS tOwardS adult maleS cOntinuing in the additiOnal 15 individualS examined during thiS Study (adult male 10, adult female 2 and Subadult female 3). ThiS biaS may be due tO Sexually mature, reprOductively ready maleS being far mOre active (On the grOund) and eaSier tO Sample than cOnSpecific femaleS. In a Study Of SOuthweStern AuStralian Pseudonaja a. affinis Maryan and BuSh (1986) fOund a Similar Skewed Sex ratiO tOwardS maleS (22 v 13), hOwever in the Similar-Sized, althOugh terreStrial E. curta Shine (1982) fOund the reverSe waS the caSe (38 v 60). HOwever, with juSt 14 adult P. atriceps available fOr Sexing tO date, thiS diScuSSiOn will be reviSited when Sample Size iS larger.

VenOm—A preliminary inveStigatiOn Of P. atriceps venOm waS carried Out in early 2016. It iS brOadly Similar tO Hoplocephalus in the mOlecular weight Of itS cOmpOnentS, which SuggeSted it tO be a member Of the Tiger Snake grOup Of venOmS (T. JackSOn perS. cOmm.). ThiS waS cOnfirmed in a recent Study by LiSter et al. (2017). AS Such, it iS a medically Significant SpecieS with One caSe hiStOry Of an envenOmatiOn in an adult male repOrted by Allen et al. (2013). The victim experienced venOm-induced cOnSumptiOn cOagulOpathy Similar tO the clinical featureS Of Hoplocephalus envenOming. CSL pOlyvalent Snake antivenOm waS adminiStered and he made a full recOvery.

Diet—There are nO identifiable StOmach cOntentS in the twelve preServed SpecimenS held at the WA MuSeum. The Only cOnfirmed natural prey recOrded during thiS Study iS a large female Ctenophorus cristatus Gray regurgitated ShOrtly after capture by a 614 mm male P. atriceps in December 2016. ThiS dragOn lizard iS uSually diurnally active and terreStrial, inferring the Snake either actively hunted it during the day, Or lOcated it when it waS at reSt in itS burrOw Or under cOver and eaten it On the grOund, rather than in a tree. Many typeS Of diurnal and nOcturnal lizard Suitable aS prey fOr thiS Snake Occur in the Same area Of the Greater WeStern WOOdlandS, including arbOreal geckOS.