Image

Description

The Grassland Earless Dragon of Canberra, Tympanocryptis lineata (Mitchell 1948), is a small lizard of the family Agamidae. Earless dragons form a clade with four species currently recognised (T. pinguicolla in Victoria, T. osbornei on the plains around Cooma, NSW and T. macartneyi present in and around Bathurst NSW)(Mitchell 1948; Smith et al. 1999; Melville et al. 2019) All species of earless dragons differ from other members of the family by lacking an external ear opening and functional tympanum (ear drum). Adult T. lineata range in size from 50-70 mm snout-vent length (SVL), with males typically being shorter than females (Nelson and Cooper 2025).  When tail length is included, males are longer than females, as tails of males are longer but total length is usually less than 150 mm. The adults have stout bodies and short robust legs, with a body mass between five and nine grams (Nelson and Cooper 2025). The main morphological differences separating T. lineata from its congeners are the greater number of mid-dorsal scales, and the greater number of scattered, enlarged, spinous dorsal scales which are also higher than wide (Mitchell 1948; Smith et al. 1999; Melville et al. 2019).

Tympanocryptis lineata is light to dark brown dorsally, with three thin white lines running the length of the body, which separate darker transverse patches into individual segments. Some individuals have yellow or orange colouration on the throat, sides of the head, flanks, or legs. Such colouration has been suggested to be male reproductive colours (Jenkins and Bartell 1980), although even juveniles have been observed to have such colours.  Recently, the significance of colour suggested that males could be coloured in every season, but only females show colours in Spring and Autumn (Nelson and Cooper 2025). Individuals can vary in darkness (light to dark brown) in captivity, suggesting that the integument is capable of melanic changes in association with background or environmental conditions.

Taxonomic Significance

Tympanocryptis lineata is currently recognised as a distinct species within the more widespread and variable Tympanocryptis lineata clade (Melville et al. 2019). 

Distribution

Former Geographical Distribution
Tympanocryptis pinguicolla has been recorded from as far north in New South Wales as Bathurst (Osborne et al. 1993b), south through the ACT to the Monaro grasslands in the Southern Tablelands (Mitchell 1948). One lizard was collected from grassy-grassy/woodland habitat near Toowoomba, Queensland in 1978 (Smith et al. 1999). Within the ACT, past records suggest that the lizard was locally common prior to 1970 (Pryor 1938, Robert Jenkins and David Rowell, pers. comm.), and it was known adjacent to Northbourne Avenue in the 1950s (Young 1992). In Victoria, the species was reported typically from the basalt plains, being known from several locations to the north of Melbourne and as far west as the Geelong area (McCoy 1889, Lucas and Frost 1894, Mitchell 1948, Brereton and Backhouse 1993), where it was described as "not very uncommon" (McCoy 1889). Other old records are from Rutherglen and Maryborough in central Victoria (Lucas and Frost 1894).

Current Known Distribution
Tympanocryptis lineata is currently considered to only be found in and around Canberra A.C.T.

Life History & Ecology

The first reported study of the life history of these lizards suggested that the animals were semelparous; that is, the young hatched in late summer, grew to adult size rapidly (by late autumn-early winter), mated the following spring, and died within one year of birth (Smith 1994). Some adults must live longer than one year, however, as recaptures from a previous year have been documented in subsequent studies (Langston 1996; Nelson et al. 1996; Nelson and Cooper 2025). Females are oviparous, and have been found gravid in both spring and early summer, with the eggs laid in late spring or early summer (Langston 1996). Clutches of two females have both contained 5 eggs (Langston 1996) and clutches laid in 5 artificial burrows contained 3-6 eggs (Nelson, pers. comm.). Other species in the genus lay between 5 and 12 eggs per clutch (Greer 1989). The eggs are laid in shallow nests, and take 9-12 weeks to develop before hatching (Langston 1996). The young possibly disperse soon after hatching, as lizards as small as 0.4 g and 20-25 mm SVL are caught in pit-fall traps in late summer to early autumn (Smith 1994). No information is available concerning hatching success, juvenile mortality or over-winter survival in the field.

T. lineata has been reported to be torpid in winter (Brereton and Backhouse 1993), but active individuals have been observed above ground in mid-June (Cooper, pers. obs.), and individuals have been trapped in pits in August in the ACT (Benson 1999). This suggests that individuals can be active throughout the year, whenever weather conditions are appropriate for activity.  Preferred body temperatures are around 36˚C from studies in the laboratory and active field body temperatures are more varied depending upon time of the year (Nelson and Cooper 2017).

Individual adult animals have been shown to move as much as 40 m per day (Langston 1996), with some movements in excess of 230 m over longer periods. Nothing is known about movements of juveniles, although this stage may be when dispersal occurs. Movement patterns of juveniles may be the most important observation necessary for understanding the area requirements for success of populations. Population density may be influenced by social interactions, as aggressive encounters between individual lizards, involving vocalisations and displays, have been observed in captive animals (Smith 1994) and in the field (Nelson, pers. comm.). Such interactions may also influence dispersal patterns.

Habitat

Observations in the ACT indicate that the species is found in tussock grasslands, dominated by wallaby grasses (Danthonia spp.), spear grasses (Stipa spp.), tussock grasses (Poa sp.) and possibly Kangaroo Grass (Themeda triandra). Captures in the ACT using pit-fall traps suggest that the animals prefer well-drained natural temperate grasslands that are relatively undisturbed and with minimal pasture improvement. There appears to be a preference for shorter grassland with an open structure or with open areas, and some aspects of the structure of the grassland (such as distribution of tussocks and low, open grass) may be important (Langston 1996). However, the apparently patchy occurrence of T. lineata, even within such areas, may indicate more subtle relationships within their grassland habitats.

Tympanocryptis lineata is known to make use of arthropod burrows in the ACT region (Jenkins and Bartell 1980; Osborne et al. 1993; Smith 1994; Langston 1996; Nelson 2004) or within Stipa tussocks in the ACT (Langston 1996). The use of various shelter sites may vary with season and local environmental conditions, and individuals have been observed to move between burrows (Nelson 2004; Rowell 2014). Individuals have been reported to retreat into arthropod burrows when alarmed (McCoy 1889).

Bibliography

Benson KA (1999). Resource use and selection by the grassland earless dragon, Tympanocryptis lineata pinguicolla: microhabitat and diet. Honours Thesis, University of Canberra, Canberra.

Brereton R, Backhouse G (1993). Flora and Fauna Guarantee Action Statement No 35. Southern Lined Earless Dragon Tympanocryptis pinguicolla. Victoria.

Greer AE (1989). 'The Biology and Evolution of Australian Lizards.' (Surrey Beatty and Sons Pty Ltd: Chipping Norton)

Jenkins R, Bartell R (1980). 'Reptiles of the Australian High Country.' (Inkata: Melbourne)

Langston AC (1996). The ecology and distribution of Tympanocryptis lineata pinguicolla (southern lined earless dragon) in the Australian Capital Territory, Canberra. Honours Thesis, University of Canberra, Canberra.

McCoy F (1889). The white-streaked earless dragon. Prodromus of the Zoology of Victoria: Figures and descriptions of the living species of all classes of the Victorian indigenous animals Melbourne.

Melville J, Chaplin K, Hutchinson M, Sumner J, Gruber B, MacDonald AJ, Sarre SD (2019) Taxonomy and conservation of grassland earless dragons: new species and an assessment of the first possible extinction of a reptile on mainland Australia. Royal Society Open Science 6, 190233.

Mitchell FJ (1948) A revision of the lacertilian genus Tympanocryptis. Records of the South Australian Museum 9, 57-86.

Nelson L, Cooper PD (2025) Population structure, growth and reproduction in two species of Tympanocryptis (Agamidae). Australian Journal of Zoology 73.

Nelson LS (2004). Thermal ecology and implications for life history variation in Tympanocryptis pinguicolla (Grassland Earless Dragon). PhD Thesis, The Australian National University,

Nelson LS, Cooper PD (2017) Seasonal effects on body temperature of the endangered grassland earless dragon, Tympanocryptis pinguicolla, from populations at two elevations. Australian Journal of Zoology 65, 165-178.

Nelson LS, Smith WJS, Goldie R (1996). 1996 Survey program for the Eastern Lined Earless Dragon (Tympanocryptis lineata pinguicolla). ACT Parks and Conservation Service, Canberra.

Osborne WS, Kukolic K, Davis MS, Blackburn R (1993) Recent records of the earless dragon Tympanocryptis lineata pinguicolla in the Canberra region and a description of its habitat. Herpetofauna 23, 16-25.

Rowell A (2014). Monitoring of grassland earless dragon Tympanocryptis pinguicolla at Bonshaw, 2014. Department of Defence report. Canberra.

Smith WJS (1994). The ecology and taxonomy of the southern lined earless dragon (Tympanocryptis lineata pinguicolla) Honours Thesis, The Australian National University, Canberra.

Smith WJS, Osborne WS, Donnellan SC, Cooper PD (1999) The systematic status of earless dragon lizards, Tympanocryptis (Reptilia : Agamidae), in south-eastern Australia. Australian Journal of Zoology 47, 551-564.

Other resources

https://www.act.gov.au/environment/animals-and-plants/act-threatened-species/canberra-grassland-earless-dragon-tympanocryptis-lineata

https://www.dcceew.gov.au/environment/biodiversity/threatened/recovery-plans/comment/draft-recovery-plan-four-grassland-earless-dragons-2023