AMPHIBIAWEB
Incilius fastidiosus
family: Bufonidae

© 2010 Division of Herpetology, University of Kansas (1 of 1)
Conservation Status (definitions)
IUCN (Red List) Status Critically Endangered (CR)
CITES No CITES Listing
Other International Status None
National Status None
Regional Status None

 

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Description
Bufo fastidiosus is a small toad, with males ranging from 43-52 mm and females from 40-60 mm. Its head is wider than it is long, and the skin on the upper surface of the head is co-ossified to the skull. The eyes are of moderate size and the iris is brown. The tympanum and middle ear are lacking. This toad has massive, elevated, light-colored canthal, supraorbital, postorbital, and bulbous supratympanic cranial crests. In contrast, the parietal crest is weak. The parotoid gland is smooth and oblong, and its size is about two-thirds the area of the eyelid. There is a well-developed broad temporal plate which exhibits exostosis (bony growth) continuous with the supratympanic crest. Dorsal surfaces have large and small smooth warts and a single distinct series of smooth lateral warts. The venter is strongly tuberculate. The upper surface of the tibial segment has massive pointed warts. Limbs are short, especially the hind limbs. The hands and feet have fleshy pads with webbed fingers and toes, and they lack definite subarticular, accessory palmar, or plantar tubercles. Finger II is longer than finger I. The inner metatarsal tubercle is elliptical, the outer tubercle is elongate and larger than the inner, and no tarsal fold is present (Savage 2002).

The dorsal ground color of adult toads is brown to black, nearly uniform in color or with red, rusty, or pink warts and tubercles. A light mid-dorsal stripe is usually present; there are no transverse dark limb bars. Ventral coloration is brown to black and mottled with lighter pigments (Savage 2002).

Males have no vocal slits or sacs. They lack an advertisement call but do have a weak release trill. Adult males have hypertrophied forelimbs and a discrete light nuptial pad on the thumb (Savage 2002).

Bufo fastidiosus larvae are small, reaching a total length of 15.99 mm at stage 36. The body is ovoid and the mouth is anteroventral. The snout is rounded in a dorsal outline and directed dorsolaterally. Nostrils and eyes are dorsal with the nostrils slightly closer to eyes than snout tip. The spiracle is lateral and sinistral, and the vent tube is medial. The tail and fins are moderate in size, with a small caudal fin that is subovoid to round at the tip. The larval oral disk is medium and emarginated. Beaks and 2/3 rows of denticles are present. The upper jaw sheath is moderately wide and finely serrated, with the medial section forming a straight line and the lateral processes abruptly tapering posterolaterally. The lower jaw sheath is about equal in width to the upper, also finely serrate, and strongly V-shaped. Body coloration is a uniform chocolate brown, with a dark gray venter. Caudal musculature is dark olive brown, and the fins are a translucent olive brown with dark speckles. (Lips and Krempels 1995)

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Costa Rica, Panama

 

View distribution map using BerkeleyMapper.
Bufo fastidiosus is found in premontane and lower montane rainforest zones on the slopes of the southern Cordillera de Talamanca of Costa Rica, and on the Atlantic slope of immediately adjacent western Panama. It occurs at 760-2100 m above sea level (Lips and Krempels 1995).

Life History, Abundance, Activity, and Special Behaviors
These toads are diurnal and may be fossorial during much of their adult lives. Lips and Krempels (1995)[3905] reported that adults were seen along the Rio Coton from Feb.-June 1992, and gravid females were present from Feb.-May. Adults appeared along the stream immediately after an increase in precipitation. Additional adults were excavated from leaf litter (Aug. 1991) at densities of five and ten adults per two 8x8 m plots, and juveniles were found along the rocky shores of Rio Coton throughout the year (Lips and Krempels 1995).

Males typically position themselves along the edges of 5-15 cm deep seepage pools. Males do not call (they lack vocal sacs) but give a release trill and vibration when handled. Males amplex any toad encountered but immediately release other males, presumably as a response to the release trill and vibration (Lips and Krempels 1995). Bufo fastidiosus undergoes inguinal amplexus, where the male clasps the female around her pelvic region and rests his feet on her thighs. This position is maintained for several hours (Graybeal and de Queiroz 1992). Upon arrival at the pools, females are immediately amplexed by 2-10 males, forming balls of toads in the pools. Females remain limp and immobile while males vie for amplexus (Lips and Krempels 1995). Lips and Krempels (1995) reported that three dead females were found after the peak of the breeding period, apparently drowned by the weight of amplexing males.

Females deposit their eggs in small pools formed after heavy rains during the late dry to early wet season (April-May). The eggs are black and yellow, and they are laid during the day in long single strands. Small indentations between the eggs give the strands a rosary-like appearance. The strands are not usually attached to vegetation, but when desiccated they stick to emergent plants and branches. Eggs are large, and clutch size is about 80-90 eggs per female. Two envelopes encase each egg, a thick outer one and an inner vitelline membrane that is barely distinguishable. There are no partitions between eggs. In the lab, hatching took place by stage 17 (day 4-5) and metamorphosis in 60-70 days (Lips and Krempels 1995).

The tadpoles are well camouflaged against the silt substrate of pools, and the larvae aggregate in groups near the bottom of the small pools in areas of flowing water. The reason for this aggregation may be a behavioral response or a result of the small pool size (Lips and Krempels 1995). Bufo fastidiosus also exhibits a defensive posture in which all four feet are planted, the pelvic region is elevated, and the head is lowered. This position is similar to one used by Osornophryne percrassa (Graybeal and de Queiroz 1992).

Trends and Threats
Bufo fastidiosus has experienced a severe population decline of over 80% over the last three generations, and may now be extinct. The species was once abundant in Costa Rica, but is now difficult to find in Costa Rica and Panama. Probable reasons for the decline include habitat loss, habitat quality reduction, and the impact of pathogens (possibly chytridiomycosis) (IUCN 2006).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Disease

Comments

A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).

References

Graybeal, A., and de Queiroz, K. (1992). ''Inguinal amplexus in Bufo fastidiosus with comments on the systematics of bufonid frogs.'' Journal of Herpetology, 26(1), 84-87.

IUCN, Conservation International, and NatureServe. (2006). Global Amphibian Assessment: Bufo fastidiosus. [Internet]. www.globalamphibians.org. Accessed 12 October 2007.

Lips, K.R., and Krempels, D.M. (1995). ''Eggs and tadpole of Bufo fastidiosus Cope, with comments on reproductive behavior.'' Copeia, 1995(3), 741-746.

Savage, J. M. (2002). The Amphibians and Reptiles of Costa Rica. University of Chicago Press, Chicago and London.



Written by Christin Hong (cmhong AT berkeley.edu), Museum of Vertebrate Zoology; University of California, Berkeley
First submitted 2007-10-24
Edited by Kellie Whittaker (2009-11-02)

Species Account Citation: AmphibiaWeb 2009 Incilius fastidiosus <http://amphibiaweb.org/species/167> University of California, Berkeley, CA, USA. Accessed Oct 20, 2017.



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Citation: AmphibiaWeb. 2017. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 20 Oct 2017.

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