Sunset frog  (Spicospina flammocaerulea)

The sunset frog is classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Schedule 1 of the Western Australia Wildlife Conservation Act (2).

The sunset frog (Spicospina flammocaerulea) was first discovered in Western Australia as recently as 1994 and was scientifically described in 1997. It is so called because of its striking appearance; it is dark purplish-black above, with bright orange and blue on its belly, reminiscent of the colours at sunset (3). This small frog produces a deep ‘dadukk dadukk’ croak (3). The sunset frog is the only member of the genus Spicospina, and differs greatly from other Australian frogs in colour (orange and blue ventral surface) and appearance (massive glands behind the head) (4).

When the sunset frog was first discovered, it was only known from three sites in south-west Western Australia. Since then, surveys have brought the total number of likely populations to 27, all of which are located near the southern coast of Western Australia. The range of this frog is highly fragmented and it occupies a very restricted area. There is at present a lack of data on the absolute size of known populations (5).

The sunset frog occupies a very specialised habitat. It is found in permanently moist peat swamps which may be relics of an earlier wet landscape with summer rainfall patterns  that changed to a seasonally dry summer climate around 10-12 million years ago. The remaining peat bogs in which this frog lives are kept moist throughout the year, often as a result of seepages of water. Within the bogs, sunset frogs are typically found in the water seepages, in pools and along drainage lines. Modern peat swamps may represent the closest approximation available to Miocene summer wet climates (6).

Relatively little is known about the ecology of the sunset frog. The breeding season occurs from October to January, when males call from water seepages or in large water-filled hollows and shallow pools (3). Females lay an average of 81 eggs singly; these are often supported on algal mats just below the surface of the water. The tadpoles are free-swimming but may be benthic specialists (7).

The very restricted and highly fragmented geographic range of the sunset frog makes it extremely vulnerable to chance events, such as disease or freak weather. However, reports that fires caused a decline in the population size at one site (8) were not substantiated when this site was burnt again in the summer of 2002 and 2003 and frogs bred after the fire (6). Indeed, although wildfire can ignite peat in peat swamps there is also evidence of populations persisting for long periods post fire and that fire can induce breeding activity (9). Further threats to sunset frogs may include introduced feral pigs, which may damage breeding habitat, and inappropriate land management, such as over-grazing, killing vegetation, or inappropriate fire regimes (3) (6). Outbreaks of dieback fungus, Phytophthora cinnamomi, could also pose a significant threat to the species (6). The fact that the populations are so fragmented could result in genetic problems due to inbreeding (3), but there are no reliable data on population size or connectedness (6).

The sunset frog is classified as Vulnerable on the IUCN Red List of Threatened Species because of its highly restricted range. With regards to the conservation of this species, perhaps the most pressing requirement at present is to increase knowledge of its distribution and the threats facing it, allowing accurate estimates of population size and in effective conservation measures to be devised. Research and monitoring to this end is on-going. In addition, many of the sites supporting sunset frogs are situated within national parks, or state forest so the species receives a high level of protection in over two thirds of its known range (8).

For more information on the sunset frog see:

• Amphibia Web:
  http://amphibiaweb.org/cgi-bin/amphib_query?query_src=aw_lists_alpha_&where-genus=Spicospina&where-species=flammocaerulea
• Roberts, J.D., Horwitz, P., Wardell-Johnson, G.,  Maxson, L.R. & Mahony, M.J. (1997) Taxonomy, relationships and conservation of a new genus and species of myobatrachid frog from the high rainfall region of southwestern Australia. Copeia, 1997(2): 373 - 381.