Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Amphibia Anura Bufonidae

Scientific Name: Incilius holdridgei
Species Authority: (Taylor, 1952)
Common Name(s):
English Holdridge's Toad
Bufo holdridgei Taylor, 1952
Taxonomic Source(s): Frost, D.R. 2014. Amphibian Species of the World: an Online Reference. Version 6 (27 January 2014). New York, USA. Available at: (Accessed: 27 January 2014).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered D ver 3.1
Year Published: 2012
Date Assessed: 2010-08-03
Assessor(s): NatureServe & IUCN SSC Amphibian Specialist Group,
Reviewer(s): Pascual Cuadras, A. & Angulo, A.
Contributor(s): Bolaños, F. & Chaves, G.
Facilitator/Compiler(s): Young, B.E.
Listed as Critically Endangered because extensive searching within its historical range in 2008–2010 suggests that its adult population size is less than 50 mature individuals.
Previously published Red List assessments:
2004 Extinct (EX)

Geographic Range [top]

Range Description:This species has been recorded on the Volcán Barva, Cordillera Central, Costa Rica, at 2,000–2,200 m asl (Savage 2002). The known historical range is less than 100 km²
Countries occurrence:
Costa Rica
Number of Locations:1
Lower elevation limit (metres):2000
Upper elevation limit (metres):2200
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:It was formerly common in appropriate habitat and during the breeding season at the onset of the rainy season (2,765 males were seen visiting two pools in an eight-day period; Nowak and Robinson 1975). This species was not seen from 1987–2007 despite repeated searching (seven consecutive years of intensive searching to 2007: Héctor Zumbado, Andrés Vaughn, Warren Calvo, Adrián García unpublished data 2007) throughout its range. Nevertheless, the species was subsequently rediscovered in 2009 at two sites 2 km apart with adults, juveniles, and tadpoles (Abarca et al. 2010). Extensive searching has revealed less than five adult toads, and no large breeding aggregations such as were formerly reported for the species, suggesting a population of fewer than 50 adults (Abarca et al. 2010).
Current Population Trend:Unknown
Additional data:
Number of mature individuals:5-50
Population severely fragmented:Unknown

Habitat and Ecology [top]

Habitat and Ecology:This species lives in montane rainforest. It is a fossorial species, and can be found under surface debris within the forest during periods of heavy rain, but otherwise it prefers mossy stream banks during dry periods. It is an explosive breeder that lays its eggs in forest floor pools, as well as in man-made drainage ditches (Savage 2002). Historically the species bred in large aggregations in pools in an open pasture. Subsequently, due to habitat protection efforts, the pastures have begun reverting to forest. A resurvey in 2009 demonstrated that the area formerly covered by pasture was now dense, young secondary forest dominated by oak (Quercus sp.) trees. The suitability of this secondary forest for the species is unknown, as recent sightings have been in more open areas covered with bushes and grasses (Abarca et al. 2010).
Systems:Terrestrial; Freshwater

Use and Trade [top]

Use and Trade:

There are no reports of this species being utilized.

Threats [top]

Major Threat(s): Although not proven, the main cause of the population decline is thought to be chytridiomycosis perhaps in synergy with the effects of climate change. The current reversion of the pastures where the species was original found abundantly to secondary forest may or may not be a threat to this species (Abarca et al. 2010).

Conservation Actions [top]

Conservation Actions: Much of the known range of this species is protected in Parque Nacional Braulio Carrillo, 20 km north-east of the capital of San José. The two sites where the species is known to persist in 2010 are located in the Cerro Dantos and Jaguarundi Refuges, neither of which have the same protection status as a national park. Even with the lower protection status, the forest cover of these refuges remains intact and seemingly not threatened (Bruce Young pers. obs. 2011). More information is needed on this species' natural history and threats.

Classifications [top]

1. Forest -> 1.9. Forest - Subtropical/Tropical Moist Montane
suitability: Suitable  major importance:Yes
5. Wetlands (inland) -> 5.8. Wetlands (inland) - Seasonal/Intermittent Freshwater Marshes/Pools (under 8ha)
suitability: Suitable  
14. Artificial/Terrestrial -> 14.2. Artificial/Terrestrial - Pastureland
suitability: Suitable  
1. Land/water protection -> 1.1. Site/area protection

In-Place Research, Monitoring and Planning
  Action Recovery plan:Yes
In-Place Land/Water Protection and Management
  Occur in at least one PA:Yes
  Percentage of population protected by PAs (0-100):100
In-Place Species Management
In-Place Education
7. Natural system modifications -> 7.3. Other ecosystem modifications
♦ timing: Unknown    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion

8. Invasive & other problematic species & genes -> 8.1. Invasive non-native/alien species -> 8.1.2. Named species (Batrachochytrium dendrobatidis)
♦ timing: Unknown ♦ scope: Unknown ♦ severity: Unknown ⇒ Impact score: Unknown 
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

11. Climate change & severe weather -> 11.5. Other impacts
♦ timing: Unknown ♦ scope: Unknown ♦ severity: Unknown ⇒ Impact score: Unknown 
→ Stresses
  • 1. Ecosystem stresses -> 1.3. Indirect ecosystem effects

1. Research -> 1.3. Life history & ecology
1. Research -> 1.5. Threats

Bibliography [top]

Abarca, J., G. Chaves, A. García-Rodríguez and R. Vargas. 2010. Reconsidering extinction: Rediscovery of Incilius holdridgei (Anura: Bufonidae) in Costa Rica after 25 years. Herpetological Review 41: 150-152.

IUCN. 2012. IUCN Red List of Threatened Species (ver. 2012.2). Available at: (Accessed: 17 October 2012).

Novak, R.M. and Robinson, D.C. 1975. Observations on the reproduction and ecology of the tropical montane toad, Bufo holdrigei Taylor in Costa Rica. Revista de Biologia Tropical: 213-237.

Savage, J.M. 2002. The Amphibians and Reptiles of Costa Rica: A Herpetofauna between two Continents, between two Seas. University of Chicago Press, Chicago.

Citation: NatureServe & IUCN SSC Amphibian Specialist Group,. 2012. Incilius holdridgei. In: The IUCN Red List of Threatened Species 2012: e.T54664A3018206. . Downloaded on 07 October 2015.
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