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Diurnal aggregations of the Legless Lizard Delma inornata (Kluge, 1974) in southern New South Wales.

By Craig Stephenson.

INTRODUCTION

Several aggregations of Delma spp. have been reported in the literature. Bush (1984) recorded seasonal aggregations of D. australis and D. fraseri; Annable (1995) recorded aggregations of D. inornata; in September 1995, Kearney and Valentic found a pair of D. austalis in a Triodia irritans (spinifex/hummock grass) clump in the Big Desert, central - western Victoria (Kearney and Valentic, pers. comm.).
All of these aggregations are understood to have been located beneath or within some form of ground cover. The following note is significant due to the large number of D. inornata involved, the many instances where two or three lizards were concentrated within approximately 1m of bitumen and that the aggregations occurred on an exposed road surface in daylight.

OBSERVATION 

Date: 9th January 1993.

Time: 9:30hrs. -12:30hrs. (Eastern Standard Time, Daylight Savings Time).

Weather Conditions: 24C rising to 35C (approx.). Fine and sunny with no cloud and a slight breeze.

Location: Cobb Highway, southern-central New South Wales, Australia. Between the townships of Wanganella (3513'S, 14449'E) and Hay (3430'S, 14451'E).

Habitat: Naturally treeless alluvial floodplains vegetated with grasses and large, sparsely clustered chenopod shrubs with patches of lignum Muehlenbeckia florulenta.

Notes: On the outskirts of Wanganella the first adult D. inornata was observed on the bitumen. About 500 metres northwards a second larger specimen (estimated at 450mm in total length) was seen. Travelling northwards a total of 67 live adult D. inornata were counted. In over ten instances multiple aggregations were noted. North of Hay township (Cobb Highway), D. inornata were present but infrequently observed. Specimens were sighted on the road well into the heat of the day (35C). On the return trip south towards  the township of Deniliquin four dead on road (DOR) specimens were noted.

DISCUSSION 

Bush (1984) correlated rainfall and temperature as stimuli for aggregations in D. australis and D. fraseri. Maximum aggregations were recorded in the coldest months. Pygopods typically ovulate  in spring and early summer; gravid females have been collected in December (Annable, 1995) and January (Patchell and Shine, 1986; Valentic, 1995). Valentic (pers. comm., 2010) has observed individual D. inornata active in the early afternoon and  nocturnally  (as late as 03:45hrs. EST on one very hot night) along the same stretch of the Cobb Highway in late summer.  A sub- adult D. inornata was observed  active and crossing the Calder Highway at twilight (crepuscular) near Inglewood (3635'S, 14352'E) in central Victoria in late December 2010 (Stephenson and Valentic, pers. obs.), indicating that activity times in D. inornata are broad in scope.
It is presumed that the high number of individual and groups of D. inornata observed (above) relate to;
1. Breeding purposes and/or gravid females basking on the road to facilitate gestation.
2. Favourable conditions on the road surface relating to potential food supply.
3. Both of the above.
Further field work is required to observe in detail the behaviour of D. inornata in early summer, and to see if similar behaviour occurs in other Delma spp. 


ACKNOWLEDGMENT

Rob Valentic critically reviewed a draft manuscript.

 

REFERENCES

Annable, T. J. 1995. Annotated checklist of the reptiles of Wagga Wagga and district, N.S.W.  Herpetofauna 25 (1): 22-28.

Bush, B. 1984. Seasonal Aggregation behaviour in a mixed population of Legless Lizards, Delma australis and D. fraseri. Herpetofauna 16 (1): 1-5.

Patchell, F.C. and Shine, R. 1986. Food habits and reproductive biology of the Australian legless lizards (Pygopodidae). Copeia (1):30-39.

Valentic, R. A. 1995. An additional reproductive record for Delma inornata (Kluge, 1974). Monitor - Journal of the Victorian Herpetological Society. 7 (2):94.