Description
Atelopus senex is a medium-sized frog, with males reaching a snout-to-vent length of 28-32 mm and females 30-43 mm (Savage 2002). This species can be easily distinguished from A. chiriquiensis and A. varius by its prominent glands on the head, dorsum and limbs (Savage 2002).

The head is angular, and longer than it is wide (Savage 2002). It has a narrow, rounded snout with a depression between the canthi (Taylor 1952). The snout projects beyond the lips (Taylor 1952). Nostrils are closer to the tip of the nose than to the eyes (Taylor 1952). The lips are lighter in color and have a distinct medial notch (Taylor 1952). From the eye there is a bony temporal ridge and a distinct post-orbital ridge coming off of it (Taylor 1952). There are no visible tympana (Savage 2002). On the shoulders the suprascapulae form a prominent ridge (Taylor 1952). The body is slender, with long arms and legs (Savage 2002). More than half of the forearm extends past the tip of the snout (Taylor 1952). The fingers are thickened at the base and have terminal pads (Taylor 1952). Thumbs are webbed basally and have brown nuptial pads in the male (Savage 2002). The toes are fully webbed and have small terminal pads (Taylor 1952). The skin has multiple tubercles in the groin region (Taylor 1952). Tubercles are also scattered on the sides of the neck and body as well as on the front surface of the upper arm (Taylor 1952). There are tiny pustules on the dorsum in many individuals, and occasionally spicules on the anterior flanks in larger adults (Savage 2002).

Males may be bluish gray, blue-green, black, or occasionally greenish, and tend to have a uniform ground color (Savage 2002). In males, the parotoid and limb glands are pink to cream-colored (Savage 2002). Females have similar ground coloration but may be patterned. The patterning on females consists of contrasting dark and light areas, with the light areas being cream, lemon, or lime-colored (Savage 2002). For both sexes, the venter is gray, sometimes with a yellow to orange tinge, and may or may not have black markings (Savage 2002).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Costa Rica

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (33 records).

A. senex is known from only three localities in Costa Rica, one in the Volcán Barva region and two on the extreme northern slopes of the Cordillera de Talamanca. It is found associated with streams in high premontane rainforest and lower montane wet forest and rainforest, from 1,280 - 2,040 m in elevation (Savage, 2002)[3049].

Life History, Abundance, Activity, and Special Behaviors
A. senex is a diurnal, stream-breeding frog (Savage, 2002)[3049]. The breeding period is from July to August (Savage 2002). This species of frog has been observed to walk more frequently than hop (Taylor 1952).

Trends and Threats
This species suffered a severe decline in 1987-1988, from which it has not recovered. It is also thought to be extinct in the Volcán Barva region (Savage, 2002)[3049].

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities

Comments
Coloration varies among the three known populations. Frogs from the Volcán Barva region are mostly uniformly colored, while those from the Macizo de Cedral are sexually dimorphic in coloration, and those from the Rio Reventazón drainage area show variability (Savage, 2002)[3049].

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

References

Savage, J. M. (2002). The Amphibians and Reptiles of Costa Rica:a herpetofauna between two continents, between two seas. University of Chicago Press, Chicago, Illinois, USA and London.

Taylor, E.H. (1952). "A review of the frogs and toads of Costa Rica." University of Kansas Science Bulletin, 35(5), 577-942.

Species Account Citation: AmphibiaWeb 2009 Atelopus senex <https://amphibiaweb.org/species/79> University of California, Berkeley, CA, USA. Accessed Feb 2, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 2 Feb 2025.

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