Iberian frog (Rana iberica)

Spanish: Rana Patilarga
GenusRana (1)
SizeLength: 4 - 7 cm (2) (3)

The Iberian frog is classified as Near Threatened (NT) on the IUCN Red List (1). This species is also listed as Vulnerable in the Spanish Red Data Book (1) (2).

The upperparts of the highly aquatic Iberian frog (Rana iberica) are usually reddish-brown (2) (3), although they can sometimes be ochre.  The skin of this species may be smooth or slightly granulated, with dark or whitish marks and a black v-shaped pattern on the back. A dark stripe extends from the nostrils to the eyes, and a thin white stripe is present along the upper lip (2).

The underparts of the Iberian frog are whitish to reddish, while the throat is heavily pigmented with dark grey and has a pale central line (2) (3). The long hind limbs of the Iberian frog are patterned with dark, transverse bars (2) (3), and the fully webbed hind feet enable this species to swim in fast-flowing streams (2) (3).

Male Iberian frogs lack vocal sacs, but do develop nuptial pads during the breeding season, which are growths on the thumbs that are used to grip the female during amplexus (2). Female Iberian frogs are larger than the males (2) (4).

Individuals from lowland and montane populations differ in size, with adult frogs in the high-altitude populations growing faster than those from the lowlands (5).

The tadpoles of the Iberian frog are brown or sometimes reddish on the upperparts, with whitish and golden marks. The undersides are greyish, and the intestines are visible through the skin. Tadpoles of this species can grow up to 50 millimetres in length and have a well-developed dorsal fin (2).

As its name suggests, the Iberian frog is endemic to the Iberian Peninsula (2), where it is mainly found in the northern part of Portugal and north-western and central Spain (1) (2) (6).

Although this species is widely distributed in the north-western parts of Spain, the few isolated populations of the Iberian frog towards the east of the country become more scattered (2), reaching as far as the Basque Country (1) (2) (6).

The Iberian frog is an aquatic species, and is usually found close to rivers, streams, lakes and marshes, particularly in shady areas with plenty of vegetation (1) (2) (6). These water bodies are often found within such terrestrial habitats as woods, moors, meadows and areas with low scrub (1) (6).

Some montane populations of the Iberian frog are known to inhabit glacial lakes (2), and in the northern part of its range it has been recorded down to sea level, along slower flowing rivers (1) (6). This species occurs up to elevations of 2,425 metres (1) (6).

The Iberian frog generally breeds in shallow, stagnant bodies of water (1) (6), or areas with slow running water (2).

Juvenile Iberian frogs are mostly diurnal, whereas adults tend to be nocturnal. However, within populations of this species in central Spain, adults may also be active during the day. Across most of its range, the Iberian frog is active throughout the year, although montane populations are inactive during part of the winter (2).

Timing of the breeding season depends on the location, with Iberian frogs in the lowlands breeding from November to March, and those inhabiting mountainous regions breeding between March and May (2).

The Iberian frog mates at night (2), usually in streams (5). Mating begins with the male following the female while emitting a low call, which carries on throughout the start of amplexus. During mating, the female may also emit vocalisations (2). Male Iberian frogs do not possess vocal sacs, which are present in males of many frog species to amplify the mating call, but instead may have glands which produce pheromones to attract females (5).

Depending on its size, the female Iberian frog will lay between 192 and 445 eggs in rounded masses, either attached to vegetation or beneath it. Development of the larvae lasts approximately three months (2).

The Iberian frog tends to feed mainly on aquatic prey (5), and eats a wide variety of invertebrates. Larger individuals are able to eat larger prey, and as the Iberian frog grows it becomes able to eat hard-bodied prey including beetles (2).

Despite being common in some parts of its range, the Iberian frog is declining rapidly in other areas, particularly in Spain (1) (2) (6).

There are many threats to the Iberian frog, including habitat loss through deforestation and intensification of agriculture (1) (2) (6), increasing pressure from tourism development (1) (6), and disturbance as a result of human recreational activities (1) (7).

Both natural and introduced fish species are known to predate upon the Iberian frog tadpoles (8), and introduced predatory mammalian species have also been reported to affect populations of this frog species (1).

The Iberian frog is listed on Appendix II of the Bern Convention (9), as well as on Annex IV of the EU Habitats Directive, which means that it is in need of strict protection (10). In Spain, the Iberian frog is protected by national legislation, and can be found in two Natural Parks: Parque Natural del Gorbea and Parque Natural de Izki (1) (6). It is also listed as Vulnerable in the Spanish Red Data Book (1) (2) (6).

As part of conservation efforts for the Iberian frog, there have been some reintroductions of captive-bred individuals in central Spain (1).

Recommendations for reducing the effects of human disturbance on populations of the Iberian frog include setting up buffer areas stretching from the stream to a distance of at least 2.5 metres, and reducing the numbers of visitors to such areas (7). Further suggested conservation measures include the removal of predatory fish from certain key areas, with the aim of recovering habitat and improving connectivity between different populations of the Iberian frog (8).

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  1. IUCN Red List (November, 2011)
  2. AmphibiaWeb - Rana iberica (November, 2011)
  3. Gibson, C. (2010) Wild Animals. Dorling Kindersley Ltd., London.
  4. Monnet, J-M. and Cherry, M.I. (2002) Sexual size dimorphism in anurans. Proceedings of the Royal Society of London B, 269: 2301-2307.
  5. Wells, K.D. (2007) The Ecology and Behavior of Amphibians. University of Chicago Press, Chicago.
  6. Stuart, S.N., Hoffmann, 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.
  7. Rodríguez-Prieto, I. and Fernández-Juricic, E. (2005) Effects of direct human disturbance on the endemic Iberian frog Rana iberica at individual and population levels. Biological Conservation, 123(1): 1-9.
  8. Bosch, J., Rincón, P.A., Boyero, L. and Martínez-Solano, I. (2006) Effects of introduced salmonids on a montane population of Iberian frogs. Conservation Biology, 20(1): 180-189.
  9. Council of Europe: Bern Convention (November, 2011)
  10. EU Habitats Directive (November, 2011)