Hypsiboas rosenbergi Boulenger 1898
Rosenberg's Gladiator Treefrog, Rosenberg's Treefrog
Hypsiboas rosenbergi belongs to a group of frogs known as gladiator frogs. Males have large dagger-like spines and engage in fierce wrestling matches that sometimes results in death of one of the contenders (Kluge 1981).
Species description based on Ibanez et al (1999) and Duellman (2001).
Large, tan to grey treefrogs, with some mottling on the dorsal surface. Thighs with variable darker grey to brown bars. Males and females are similarly sized. Males to 92 mm; females to 95 mm. Males have large thumb spines that are typically covered by a sheath of skin when not in use. Excellent photos of the sheath and spine can be found in Hobel (2008) and Kluge (1981), respectively. An extensive description of the adults acan be found in Duellman (1970) and Duellman (2001).
The dorsal skin ranges from smooth to bumpy. Many specimens have a dark, narrow middorsal stripe.
Ventral surface cream-colored to slightly bluish and granular. Males sometimes have pigmentation on the throat.
Sides often have a number of darker vertical bars, particularly in the area closest to the thigh.
Iris yellowish or light tan above to grey below. Pupil horizontal.
Hands and feet extensively webbed. Webbing ranges in color from brownish-yellow to orange. Toes with large terminal discs.
Breeding is more common during the rainy season (May-November; Kluge 1981, Fouquette 1966); however, males can be heard calling throughout the year. In the Darien, frogs breed during the dry season (Breder 1946). Males call singly or in small loose choruses near marshes, ponds and streams (Kluge 1981). For females, time between reproductive bouts averages 35.8 days, although some females require over 100 days to yolk up a new clutch (Kluge 1981).
Eggs are laid in shallow, mud nests near the edges of streams (Breder 1946, Kluge 1981), which most likely functions to protect them from con- and heterospecific tadpole predators (Heyer et al 1975, Kluge 1981). The small, black eggs are laid as a surface film. Eggs hatch into small black tadpoles starting 40 hours after oviposition (Kluge 1981).
Tadpoles develop in streams or ponds. In larger tadpoles, the body is dark brown and the tail has numerous dark flecks and blotches. The ventral surface is lighter brown. For an extensive description of the tadpole, see Breder (1946). Tadpoles are not distasteful to humans and thus most likely contain few toxic compounds in their skin (Wassersug 1971).
Metamorphosis generally occurs in approximately 40 days (Kluge 1981). Metamorphs are pale green-grey with numerous small dark spots covering the dorsal surface (Kluge 1981, Hobel 2008). Time to maturity is about 1 year (Kluge 1981). Most adults do not survive more than one breeding season (Kluge 1981).
Ecology behavior and evolution
Adults eat small arthropods, including arachnids and orthopterans (Kluge 1981). Tadpoles diet is unknown, although tadpoles are cannibalistic on eggs and smaller larvae (Kluge 1981).
Eggs of Hyla rosenbergi are eaten by con- and heterospecific tadpoles as well as snakes, and probably small mammals, turtles and herons (Kluge 1981, Hobel 1999). Eggs are also killed when nests are disturbed by adult male H. rosenbergi or heavy rainstorms (Kluge 1981). Similar organisms eat adult frogs, as well as caiman and adult Leptodactylus pentadactylus (Kluge 1981).
A series of loud "tonks" ranging from two to five notes (Breder 1925, Duellman 1970, Kluge 1981, Ibanez et al 1999). The call carries over 100 m (Breder 1946). See Kluge (1981) and Hobel (1999) for accounts of courtship, territorial, aggressive and distress calls.
Behavior and communication
Kluge (1981) and Breder (1946) provide detailed descriptions of courtship and mating behavior. Males construct mud nests and call from them to attract females (Breder 1946). Males will also utilize natural puddles or cattle prints as nests (Hobel 1999). In Gamboa, Panama, eggs are also laid on the surface of ponds (Hughey pers. obs.). Females are choosy and leave if they find a nest unsatisfactory.
In Panama, males engage in intense aggressive interactions with other males to defend nests, wrestling with each other until one frog retreats or is killed (Kluge 1980). Once eggs are laid in a nest, males will guard them against intruding males until they hatch (Kluge 1981). However, in Costa Rica, these aggressive and protective interactions were not observed (Hobel 1999). Hobel (2008) suggested that the high availability of nesting sites led to decreased nest guarding and fighting behavior in Costa Rica; however it is unknown whether this is due to genetic differences or plasticity or both.
Taxonomy and systematics
Boana rosenbergi, Hyla rosenbergi
The species is named after W.F.H. Rosenberg, who collected the type specimen (Duellman 1970).
"Cachabé" (=Cachabí), Provincia Esmeraldas, Ecuador (Lynch and Myers 1983)
Habitat and distribution
HabitatHumid, lowland forest to 900 m. Hyla rosenbergi also do well in disturbed areas, including close to human habitations and pastureland.
Columbia, Costa Rica, Ecuador, Panama
Distrubution map (IUCN)
Boulenger, G.A. 1898. An account of the reptiles and batrachians collected by Mr. W.F.H. Rosenberg in western Ecuador. Proceedings of the Zoological Society of London: 107-126, 9.
Breder, CM, Jr. 1946. Amphibians and reptiles of the Rio Chucunaque drainage, Darien, Panama, with notes on their life histories and habits. Bulletin of the American Museum of Natural History 86: 375-436.
Duellman, WE. 1970. The Hylid Frogs of Middle America. Monographs of the Museum of Natural History University of Kansas.
Duellman, WE. 2001. The Hylid Frogs of Middle America. 2nd ed. Society for the Study of Amphibians and Reptiles, Ithaca, New York.
Faivovich, J, CFB Haddad, PCO Garcia, DR Frost, JA Campbell, and WC Wheeler. 2005. Systematic review of the frog family Hylidae, with special reference to Hylinae: Phylogenetic analysis and taxonomic revision. Bulletin of the American Museum of Natural History: 1-240.
Fouquette, MJ, Jr. 1966. Some hylid frogs of the Canal Zone, with special reference to call structure. Caribbean Journal of Science 6(3-4): 167-172.
Goldberg, SR and CR Bursey. 2008. Helminths from fifteen species of frogs (Anura, Hylidae) from Costa Rica. Phyllomedusa 7(1): 25-33
Hawley, TJ. 2009. The ecological significance and incidence of intraguild predation and cannibalism among anurans in ephemeral tropical pools. Copeia 2009(4): 748–757
Heyer, WR. 1976. Studies in larval amphibian habitat partitioning. Smithsonian Contributions to Zoology 242: 1-27.
Heyer, WR, RW McDiarmid and DL Weigmann. 1975. Tadpoles, predation and pond habitats in the tropics. Biotropica 7(2): 100-111.
Hobel, G. 1999. Facultative nest construction in the gladiator frog Hyla rosenbergi (Anura: Hylidae). Copeia 1999(3): 797-801.
Hobel, G. 2000. Reproductive ecology of Hyla rosenbergi in Costa Rica. Herpetologica 56(4): 446-454.
Hobel, G. 2008. Plasticity and geographic variation in the reproductive ecology of gladiator frogs, particularly Hypsiboas rosenbergi. In: Weissenhofer, A, Huber W, & M Klingler. 2008. Geography of the Golfo Dulce region. Biologiezentrum der Oberösterreichischen Landesmuseen, J.-W.-Klein-Straße, Linz, Austria.
Ibañez, R, AS Rand, and CA Jaramillo. 1999. Los anfibios del Monumento Natural Barro Colorado, Parque Nacional Soberanía y areas adyacentes. Mizrachi, E. and Pujol, S.A., Santa Fe de Bogota.
Ibañez, R, F Solís, C Jaramillo, and AS Rand. 2000. An overwiew of the herpetology of Panama. In: Johnson, JD, RG Webb, and OA Flores-Villela. Eds. Mesoamerican Herpetology: Systematics, Zoogeography and Conservation, pp. 159-170. The University of Texas at El Paso, El Paso, Texas.
Kluge, AG. 1979. The gladiator frogs of Middle America and Colombia - a reevaluation of their systematics (Anura: Hylidae). Occasional Papers of the Museum of Zoology of the University of Michigan: 1-24.
Kluge, AG. 1981. The life history, social organisation and parental behaviour of Hyla rosenbergi Boulenger, a nest building gladiator frog. Miscellaneous Publications of the Museum of Zoology University of Michigan: 1-170.
Lynch, JD. 2006. The tadpoles of frogs and toads found in the lowlands of northern Colombia. Rev.Acad. Colomb. Cienc. 30(116): 443-457.
Martin, AA and GF Watson. 1971. Life history as an aid to generic delimitation in the family Hylidae. Copeia 1971(1): 78-89.
Morales, M, A Ortiz, E Toral, and J Regalado. 2002. Monitoreo del aprovechamiento forestal con especies indicadoras de herpetofaunaen el Chocó ecuatoriano, Esmeraldas, Ecuador. Componente de monitoreo biológico, Proyecto SUBIR-CARE. Informe Final Fase III, pp. 104-161. EcoCiencia, Quito, Ecuador.
Santos-Barrera, G, J Pacheco, F Mendoza-Quijano, F Bolaños, G Cháves, GC Daily, PR Ehrlich & G Ceballos. 2008. Diversity, natural history and conservation of amphibians and reptiles from the San Vito Region, southwestern Costa Rica. Revi. Biol. Trop. 56(2): 755-78.
Savage, JM. 2002. The Amphibians and Reptiles of Costa Rica: A Herpetofauna between two Continents, between two Seas. University of Chicago Press, Chicago.
Seibert, EA, BH Lillywhite, and RJ Wassersug. 1974. Cranial coossification in frogs: relationship to rate of evaporative water loss. Physiological Zoology 47(4): 261-265.
Taylor, EH. 1954. Additions to the known herpetological fauna of Costa Rica. University of Kansas Science Bulletin 35: 257-270.
Thornton, WA. 1964. The frog Hyla rosenbergi in Colombia, South America.Herpetologica 20(3): 188-191.
Wassersug, RJ. 1971. On the comparative palatability of some dry-season tadpoles from Costa Rica. American Midland Naturalist 86(1): 101-109.