Romer's treefrog (Liuixalus romeri)

Description

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Romer's treefrog fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Romer's treefrog description

One of the world’s tiniest frogs and the smallest amphibian to be recorded in Hong Kong ^{(2) (3)}, Romer’s treefrog (Liuixalus romeri) was discovered in 1952 in a small, remote cave on Lamma Island. Following the collapse of the cave roof soon after its discovery, Romer’s treefrog disappeared and was presumed extinct for nearly 30 years until it was rediscovered in 1984 ^{(3) (4)}.

This diminutive, well-camouflaged species is generally tan to pale brown, with a dark brown or black X-shaped marking on the back ^{(2) (3) (4)}.

Synonyms

Chirixalus romeri, Philautus romeri.

Size

Length: 1.5 - 2.5 cm ⁽²⁾

Romer's treefrog biology

Romer’s treefrog breeds between early March and September ^{(2) (3) (4)}. The male attracts the female by emitting a metallic, staccato, cricket-like mating call, from a position close to a pool or other water source ^{(2) (3)}. Generally, mating occurs on warm, rainy nights, with the female attaching up to 120 eggs in small clusters to submerged sticks or leaves. The eggs are then fertilised by the male ⁽³⁾. The small, free-swimming tadpoles of Romer’s treefrog metamorphose to adults after four to six weeks ^{(2) (3)}.   

A predominantly nocturnal species, Romer’s treefrog feeds on small arthropods, such as termites, which it captures on the ground ⁽²⁾. 

Romer's treefrog range

Endemic to Hong Kong, Romer’s treefrog is naturally distributed on the four islands of Lamma, Lantau, Chek Lap Kok and Po Toi ^{(1) (2) (3) (4)}. 

The construction of a new airport on Chek Lap Kok in the 1990s led to most of the population of Romer’s treefrog on this island being translocated to eight new sites on Hong Kong Island and the New Territories, including Tsiu Hang Special Area, Tai Lam Country Park and Tai Po Kau Nature Reserve ^{(1) (3)}.

Romer's treefrog habitat

Despite its common name, Romer’s treefrog is typically found on the ground or in low bushes ⁽⁴⁾. This species inhabits forests, plantations and other well-wooded areas, close to water sources such as streams and marshes ^{(1) (2)}.

Romer’s treefrog breeds in temporary pools, marshes, small pools in streams, and ponds ^{(1) (2) (4)}. It has also been known to use man-made excavations, gutters and small water-filled containers ^{(1) (4)}. 

Romer's treefrog status

Romer’s treefrog is classified as Endangered (EN) on the IUCN Red List ⁽¹⁾.

Romer's treefrog threats

Romer’s treefrog is primarily threatened by human disturbance and habitat destruction ^{(1) (2) (5)}, while habitat degradation due to pollution is also a major threat to this species ⁽⁵⁾. The eggs and tadpoles of Romer’s treefrog are vulnerable to predation by the introduced mosquitofish (Gambusia affinis), as well as to predation by other frogs ^{(2) (5)}.

The population of Romer’s treefrog has declined since its rediscovery, partly due to immense pressure on the remaining populations from human development. As a result, Romer’s treefrog became one of the first amphibians to be part of a successful translocation programme ^{(2) (3) (4)}.

The construction of an airport on Chek Lap Kok Island extirpated most of the Romer’s treefrog population there. However, successful translocation of many individuals from the island prior to the airport’s development has meant that the total population size of Romer’s treefrog has been more or less maintained ^{(1) (4)}.

Climate change may also become a significant threat to Romer’s treefrog in future. Climate change has already been implicated in earlier spawning dates and breeding migrations in a number of amphibian species. Climate models also predict that many amphibians will suffer huge population declines or extinctions due to a warmer and more extreme climate. It is also likely that climate change will facilitate the spread of disease, such as the chytrid fungus Batrachochytrium dendrobatidis ⁽⁶⁾.

Romer's treefrog conservation

Romer’s treefrog is one of three amphibian species listed under the Hong Kong Wild Animals Protection Ordinance, which prohibits the hunting, wilful disturbance, possession, sale or export of this species ^{(2) (3) (4)}. A major population stronghold for Romer’s treefrog, Ngong Ping in Lantau, has been designated a Site of Special Scientific Interest ^{(1) (2)}. Many of the key sites for this species on Lamma Island fall within a Conservation Area ⁽²⁾.

A comprehensive captive breeding programme for this species began in 1992, when the population of Romer’s treefrog on Chek Lap Kok was imminently threatened by the construction of a new airport. Extensive collections were made from the island, and the rescued frogs were maintained in a breeding and management programme at The University of Hong Kong. Thirty individuals were also sent to Melbourne Zoo in Australia, to establish a second breeding population ^{(1) (3) (4) (5) (7)}. 

The aim of the captive breeding programme was to maintain a breeding population of Romer’s treefrog which could be released back into suitable sites the wild. In 1993 and 1994, adult frogs and tadpoles from captive populations were relocated to eight new sites. Seven out of the eight areas where this species was introduced still harbour significant populations of Romer’s treefrog ⁽³⁾, and an ongoing monitoring programme records the success of the introduced populations each year during the breeding season ⁽⁵⁾.  

A large population of Romer’s treefrog in Sok Kwu Wan has also been the focus of concerted conservation action, with the Department of Agriculture, Fisheries, and Conservation, the University of Hong Kong and the Kadoorie Farm and Botanical Garden working together to protect the species from slope stabilisation work which threatens to destroy its habitat ^{(1) (3)}.

Find out more

Find out more about Romer’s treefrog:

• Department of Agriculture, Fisheries, and Conservation - Romer’s treefrog (May, 2011)
  http://www.afcd.gov.hk/english/conservation/con_fau/con_fau_rom/con_fau_rom_gen/con_fau_rom_gen_eco.html

Find out more about amphibian conservation:

• Amphibian Ark:
  http://www.amphibianark.org/

Authentication

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Glossary

Arthropod

A very diverse phylum (a major grouping of animals) that includes crustaceans, insects and arachnids. All arthropods have paired jointed limbs and a hard external skeleton (exoskeleton).

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Fertilisation

The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.

Metamorphosis

An abrupt physical change from the larval to the adult form.

Nocturnal

Active at night.

Spawning

The production or depositing of large quantities of eggs in water.

Translocation

The movement of a species, by people, from one area to another.

References

1. IUCN Red List (May, 2011)
   http://www.iucnredlist.org/
2. Department of Agriculture, Fisheries, and Conservation - Romer’s treefrog (May, 2011)
   http://www.afcd.gov.hk/english/conservation/con_fau/con_fau_rom/con_fau_rom_gen/con_fau_rom_gen_eco.html
3. Karraker, N. (2009) A Rare Frog Species found on Lamma Island - Romer's Tree Frog: A Lamma Icon. Blog post, Blogspot.com. Available at:
   http://lam-ching.blogspot.com/2009/06/rare-frog-species-found-on-lamma-island.html
4. Banks, C.B., Lau, M.W.N. and Dudgeon, D. (2008) Captive management and breeding of Romer’s tree frog Chirixalus romeri. International Zoo Yearbook, 42: 99-108.
5. David Dudgeon Staff Profile, The University of Hong Kong - Romer’s treefrog (May, 2011)
   http://www0.hku.hk/ecology/staffhp/dd/Philautu.html
6. Stuart, S.N., Hoffman, M., Chanson, J.S., Cox, N.A., Berridge, R.J., Ramani, P. and Young, B.E. (Eds.) (2008) Threatened Amphibians of the World. Lynx Edicions, Barcelona, Spain, IUCN, Gland, Switzerland and Conservation International, Arlington, Virginia.
7. AmphibiaWeb: Zoos play a vital role in amphibian conservation - Romer’s treefrog (May, 2011)
   http://amphibiaweb.org/declines/zoo/index.html#romeri