Santa Cruz dwarf frog  (Physalaemus soaresi)

The Santa Cruz dwarf frog is classified as Endangered (EN) on the IUCN Red List (1).

The Santa Cruz dwarf frog (Physalaemus soaresi) is a small amphibian known only from two locations in south-eastern Brazil (2). Like related Physalaemus species, it has relatively smooth skin, a rather pointed snout, and lacks webbing on the toes (3) (4). The body of the Santa Cruz dwarf frog is brownish, with a dark stripe along the sides (3).

Until recently, the Santa Cruz dwarf frog was known only from a single location, at Horto Florestal de Santa Cruz, in the state of Rio de Janeiro, Brazil (1) (5) (6). However, it was recently recorded at a second location, at Serra do Mendanha, in Rio de Janeiro state. This species had also previously been collected from another area at Barro Branco, but is now believed to be extinct there (2).

The Santa Cruz dwarf frog inhabits the Atlantic forest region of Brazil. It is thought to have originally occurred in primary forest, but extensive habitat destruction means it is now found only in disturbed, secondary forest (1) (2).

Santa Cruz dwarf frogs are usually found near ponds within forest, and have been recorded at elevations close to sea level and at around 130 metres above sea level (1) (2).

Very little information is available on the biology of the Santa Cruz dwarf frog. Like other Physalaemus species, it is likely to lay its eggs in a foam nest (1) (3) (4) (7), which is produced by mucus secretions from the female that are kicked into a foam by the male (7). The foam nest is laid on the surface of shallow, temporary pools (1) (7), and may be attached to those other females, creating large egg masses which are less likely to dry out (7). The males of Physalaemus species call to attract females, usually while floating in water (4).

The Santa Cruz dwarf frog has a small population and a very limited range, and is currently threatened by habitat loss (1) (2). The Atlantic forest of Brazil has been largely destroyed by deforestation, agriculture, plantations, urbanisation, infrastructure development and wildfires (6) (8), and Brazil’s amphibians may also face threats from disease, invasive species and climate change (6) (9).

In addition to various forms of human disturbance, such as urban expansion, the forests inhabited by the Santa Cruz dwarf frog are being converted to eucalyptus plantations and to agriculture (1) (2). This species is listed as Endangered on the list of threatened Brazilian fauna (10).

The Santa Cruz dwarf frog is found in the Florestal Nacional Mario Xavier protected area, but this site needs improved management and protection (1). The new location at which this species was found is partially within the Parque Natural Municipal da Serra do Mendanha, but the areas the Santa Cruz dwarf frog probably inhabits are still under threat (2).

Recommendations for the conservation of Brazil’s amphibian species include better habitat protection, environmental education, captive breeding programmes and further research (6). More information may be needed on the distribution, biology and ecology of the Santa Cruz dwarf frog before more specific conservation action can be taken for this little-known amphibian.

Find out more about conservation in the Atlantic forest:

• Conservation International: Biodiversity Hotspots - Atlantic Forest: 
  http://www.biodiversityhotspots.org/xp/Hotspots/atlantic_forest/Pages/default.aspx
• WWF: Atlantic Forests: 
  http://wwf.panda.org/about_our_earth/ecoregions/atlantic_forests.cfm
• SOS Mata Atlântica:
  http://www.sosmatatlantica.org.br/
• The Nature Conservancy:
  http://www.nature.org/wherewework/southamerica/brazil/work/art5080.html
• World Land Trust:
  http://www.worldlandtrust.org/projects/brazil.htm