Common Names: Caucasian Toad (English), Kavkazskaya Zhaba (Russian)
Synonyms: Bufo colchicus Eichwald, 1831 ; Rana caucasica Pallas, 1814 ;

Taxonomic Note:
Until recently this was considered to be a subspecies of Bufo bufo. Orlova and Tuniyev (1989) recognized three subspecies based on morphological characters; Litvinchuk et al. (2008) reported that molecular evidence does not support this division. These latter authors treat B. verrucosissimus as a valid species only tentatively and suggest genetic comparisons with common toads from the Caucasus and the Mediterranean to resolve this issue (Litvinchuk et al. 2008). Litvinchuk et al. (2008) also assign specimens from southern Azerbaijan (and by implication those from Iran) formerly included within B. verrucosissimus to their newly-erected B. eichwaldi.

Red List Assessment

Assessment Information

Assessor(s): IUCN SSC Amphibian Specialist Group,

Contributor(s): Ananjeva, N.B., Kuzmin, S., Rastegar-Pouyani, N., Tarkhnishvili, D., Anderson, S., Bowles, P., Tuniyev, B., Aghasyan, A., Tuniyev, S., Iskanderov, T., Ugurtas, I., Orlov, N.L., Papenfuss, T., Stöck, M., Nilson, G. & Litvinchuk, S.

Assessment Rationale

Listed as Vulnerable on the basis that its population has declined by at least 30%, and possibly by nearly 50%, over the last three generations (24 years), based on measures of population density, declines in the species’ area of occupancy and the extent and quality of suitable habitat, and the effects of introduced species, and because the threats to this species are not reversible and have not ceased.

Reasons for Change

Distribution

Geographic Range

This toad inhabits the Caucasus regions of Azerbaijan, Georgia, Russia and northern Turkey (where it has previously been confused with B. bufo spinosus – Litvinchuk et al. 2008). In Azerbaijan, it occurs continuously along the southern slopes of the Great Caucasus Ridge, and extends along the Kuban River as far as Khurdzhinovo Village (Iskanderov 2009; S. Litvinchuk pers. comm. November 2010). Records from Russia’s Chechnya region require further verification, and it is not present in Dagestan (Mazanaeva 2000). It is replaced by B. eichwaldi in the Talysh Mountains and around the coast of the Caspian Sea (Litvinchuk et al. 2008). It has an altitudinal range from sea level to 3,000 m asl (Iskanderov 2009), and an estimated extent of occurrence of 45,000 km².

Elevation / Depth / Depth Zones

Elevation Lower Limit (in metres above sea level): 0

Elevation Upper Limit (in metres above sea level): 3000

Map Status

Map Status: Done

Biogeographic Realms

Biogeographic Realm: Palearctic

Occurrence

Countries of Occurrence

Population

In Azerbaijan the Caucasian toad occurs in small populations. The species occurs at its highest densities (12-20 individuals/ha) in yards and gardens, and is less common in natural forest (10-12 individuals/ha in Hirkan National Park) (Iskanderov 2009). Comparison of these densities, obtained in 2006, with data from 1989 suggests that population densities in Azerbaijan have fallen by as much as 50% in natural habitats (from 30-40 animals/ha in mixed forest) over the past 27 years as a consequence of declines in habitat quality (Iskanderov 2009). Population densities are low (3-5 individuals/ha) in heavily modified landscapes; based on the extent of habitat loss and the presumed impacts of invasive species throughout its range, the global population may have declined by more than 30% over the past 25 years, as has been suggested for the closely-related Talysh toad (B. eichwaldi). (S. Litvinchuk pers. comm. November 2010).

The population is considered to be severely fragmented, as suitable forest-edge habitat is surrounded by human-modified habitats and these toads are highly site-philopatric (T. Iskanderov pers. comm. February 2011). Although there is no evidence that fragmented subpopulations are genetically isolated, their geographic isolation and pressures on remaining habitat fragments indicate that these are at strong risk of extinction (T. Iskanderov pers. comm. February 2011). Four subpopulations in northern Azerbaijan – from Ismaily, Qabala, Oguz and Shaki – are assumed to be already extinct (T. Iskanderov pers. comm. February 2011).

Population Information

Habitats and Ecology

This is a terrestrial species of mountain coniferous, mixed and deciduous forests, from floodplains to the sub alpine belt. The toad prefers wet, shaded sites in forests, bush lands, their edges and glades. It is also known from a variety of modified habitats, including vegetable gardens, hay meadows, parks and residential areas (Iskanderov 2009). It has a preference for damp, shaded microhabitats with abundant invertebrate prey, including leaf litter, rodent burrows, and beneath stones or logs (Iskanderov 2009). Spawning occurs in clear, still or slow-flowing water, mainly in brooks, springs and small rivers, but also in puddles, ponds, lakes and seepage pools. Animals reach reproductive maturity at 3-4 years old, when they measure 6-7 cm in length (Iskanderov 2009). In common with the related Talysh toad, generation length is presumed to be 5-8 years.

IUCN Habitats Classification Scheme

Life History

Breeding Strategy

Systems

System: Terrestrial, Freshwater

Use and Trade

General Use and Trade Information

There are no reports of this species being utilized.

Threats

Destruction and fragmentation of forests, driven by logging, overgrazing and land clearance for agriculture and settlement, has intensified in recent years (Iskanderov 2009). Because of its specialized habitat requirements, this species is particularly susceptible to anthropogenic threats, and it is rare or absent in areas subject to logging or grazing (Iskanderov 2009). The few human-modified habitats in which this species thrives, such as vegetable gardens, are typically temporary in nature (Iskanderov 2009). Toads appear to be especially sensitive to water pollution at their breeding sites, with the species being lost from areas with even low levels of contaminants (Iskanderov 2009). The recent spread within the Caucasus of the North American Raccoon (Procyon lotor) has resulted in population declines in the Caucasian toad, which is easily caught by predators.

Conservation

This toad is listed in the Red Data Books of Azerbaijan and Russia (and in the Red List of Krasnodar Region and Adygea in particular). It has been recorded from several nature reserves in Georgia, Russia and Azerbaijan, and in two Russian national parks. Outside these areas, the species occurs in localized and seemingly isolated subpopulations (Iskanderov 2009). No species-specific conservation measures are in place, and despite ongoing research in Azerbaijan no successful captive breeding has taken place (Iskanderov 2009). Population reintroduction has been proposed for this species (Iskanderov 2009). Further research is needed into the identity and distribution of members of the B. bufo species group, and into effective husbandry of this species.

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