Denisonia maculata 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Elapidae

Scientific Name: Denisonia maculata (Steindachner, 1867)
Common Name(s):
English Ornamental Snake
Hoplocephalus maculatus Steindachner, 1867

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2017
Date Assessed: 2017-06-13
Assessor(s): Venz, M., Vanderduys, E., Hobson, R., Sanderson, C., Dickman, C. & Wilson, S.
Reviewer(s): Bowles, P.
Contributor(s): Macdonald, S.M
Facilitator/Compiler(s): Cox, N.A.
This species is listed as Data Deficient, because it occurs as a severely fragmented population, and there is a continuing decline in the area of the very limited gilgais habitat to which the species is restricted, and while it has an extensive distribution range it has an area of occupancy at most below 6,000 km2 and the high degree of uncertainty surrounding this value suggests that the species could either have an area of occupancy below 2,000 km2 (and possibly below 500 km2), and so warrant listing in a threatened category or as either Near Threatened or Least Concern. It has not been possible to quantify rates of habitat - and presumed attendant population decline over the past 10 years, or to project rates of decline into the future, however, these too are associated with a high degree of uncertainty and may approach or exceed the threshold for listing in a threatened category.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is found in central-eastern Queensland (Cogger 2014), from around Taroom in the south, north to Charters Towers.
Countries occurrence:
Australia (Queensland)
Additional data:
Estimated area of occupancy (AOO) - km2:400-5500
Continuing decline in number of locations:Yes
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Although the species is typically hard to detect, it can be fairly common within the limited extent of suitable habitat within its range. It occurs in pockets of high density, but its abundance is strongly tied to gilgai habitats and densities exhibit a "sharply delineated" drop off away from these waterbodies (Wilson and Swan 2014, S. Wilson pers. comm. 2017). The population is expected to be declining in response to habitat degradation and loss, and the species is thought to occur as a severely fragmented population due to the fragmentary nature of its habitat and its inability to disperse between sites. More than half of the population lies within an area of intense resource extraction, and even relatively moderate disturbance to the species' habitat, such as a spillage of contaminated water, may render individual subpopulations unviable (S. Wilson pers. comm. 2017).
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Population severely fragmented:Yes

Habitat and Ecology [top]

Habitat and Ecology:This species favours low-lying 'gilgai' (ephemeral wetland) areas with cracking clay soil; habitat mapping indicates that the maximum available area of this habitat within the snake's range is around 11,000 km2, although due to finer-scale heterogeneity than the map resolution allows the maximum area of occupancy is probably less than 50% of this area (M. Venz pers. comm. 2017). This is a nocturnal snake species that shelters in soil cracks and sometimes under fallen timber and ground litter during the day. It is viviparous with 3 to 11 young per litter (an average of 6-8). It is an ambush predator that mainly feeds on frogs (Litoria spp., Platypectrum spp.) but has rarely also been documented taking lizards (agamids, gekkonids, scincids) (Shine 1983, Reed and Shine 2002, Cogger 2014).
Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: The species does not really appear in trade.

Threats [top]

Major Threat(s): Changes to soil structure within this species' habitat is a significant threat to subpopulations. This habitat has been very heavily impacted through conversion to agricultural use for crops (sorghum, sunflower, cotton, etc.) that need ploughing. Coal and gas extraction, though both direct impacts on water quality (S. Wilson pers. comm. 2017) and associated habitat loss, is a significant threat within the species' range. Potential threats include water extraction, with the consequent drying of gilgais, and contamination either through chemical spills into the gilgais or diffusion of polluted water into these wetlands (S. Wilson pers. comm. 2017). The majority of the population is found within an "intense resoutce extraction footprint" (S. Wilson pers. comm. 2017), and there are plans to further intensify this activity. It has not been possible to quantify rates of habitat decline resulting from agricultural intensification over the past 10 years on the basis of available data, but it is known to be ongoing and will continue into the future (M. Venz pers. comm. 2017). This is a specialist feeder on amphibians (which may be highly sensitive to water pollution) and consequently these impacts may both directly reduce habitat quality for the snake and potentially reduce prey availability (S. Wilson pers. comm. 2017).

Conservation Actions [top]

Conservation Actions: Under the the federal Environment Protection and Biodiversity Conservation Act 1999, this species is listed as 'Vulnerable'. This species occurs in a limited number of protected areas including Dipperu National Park, Queenland. Gilgai habitat conservation is the lead conservation measure needed, as this is a specialized habitat which is limited in extent within this snake's range, and on which subpopulations are largely reliant.

Citation: Venz, M., Vanderduys, E., Hobson, R., Sanderson, C., Dickman, C. & Wilson, S. 2017. Denisonia maculata. The IUCN Red List of Threatened Species 2017: e.T6488A83768267. . Downloaded on 18 June 2018.
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