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Aggressive Behavior in a Centrolenid Frog, With Comments on Territoriality in Anurans

1976; Herpetologists' League; Volume: 4; Issue: 32 Linguagem: Inglês

1938-5099

William E. Duellman, Alan H. Savitzky,

Ecology and Vegetation Dynamics Studies

Centrolenella griffithsi (Coin) & e exhibit aggressive behavior consisting of grasping one another with the forelimbs while suspended from vegetation. Aggressive behavior and territoriality are well developed in certain species having specialized reproductive modes that require limited resources. FROGS of the genus Centrolenella are small delicate species. Characteristically males call at night from vegetation overhanging streams, and eggs are deposited on vegetation over water. Observations on several South American species and reports by McDiarmid (1975) on some Central American species reveal that males have calling sites that are utilized on succeeding nights and that egg clutches are deposited on or near the leaf used as a calling site. McDiarmid and Adler (1974) reported on territorial behavior in Centrolenella HERPETOLOGICA 32:401-404. December 1976 This content downloaded from 157.55.39.116 on Sun, 18 Sep 2016 06:02:11 UTC All use subject to http://about.jstor.org/terms 402 HERPETOLOGICA [Vol. 32, No. 4 viridissima [= fleischmanni] and Centrolenella valerioi. In these species the intrusion of a male at the calling site of another male evoked a series of responses by the resident male, consisting of (1) an encounter call, (2) jerky motions, and (3) axillary clasping. These encounters resulted in the intruder twisting away and departing from the calling site of the resident. We report here a different kind of apparent territorial behavior in Centrolenella griffithsi (Goin). Observations were made on the nights of 9 and 10 April 1975 at a stream 9 km SE of Tandayapa, Provincia Pichincha, Ecuador. This locality is at an elevation of 2150 m on the Pacific slopes of the Cordillera Occidental of the Andes. The area supports cloud forest and contains many streams and many more rivulets. Cliffs with continuously dripping water support an abundance of ferns. Centrolenella griffithsi were very numerous on vegetation over the stream and on ferns on the cliff. In many cases calling males were no more than 50 cm apart. On 9 April two males were found dangling from a fern overhanging a rivulet; an egg clutch was present on the same frond. The frogs were grasping one another belly to belly, each with the forelimbs wrapped about the other's neck. One frog was holding onto the fern with both feet, whereas the other was holding on with one foot; the other hind limb was folded against the body in a resting position. The frogs repeatedly flexed and extended their outstretched hind limbs so as to move their bodies up and down. The frogs were collected subsequent to the original observations on their position. On 10 April a male was accidentally frightened from a perch 2 m above the stream; it jumped to a fern 1.5 m above the water. The fern was occupied by a calling male. Almost immediately the resident and the intruder were dangling by their feet from an horizontal herbaceous stem 10 cm below the fern. The position FIG. 1.-Grappling & e of Centrolenella griffithsi, drawn from photograph. of the frogs was the same as those observed the night before except that each frog grasped the stem with both feet (Fig. 1). During the following 5-6 min each frog periodically flexed one leg causing the pair to swing laterally. Subsequently the frogs simply hung from the stem for another 5 min, after which time they were collected. At the initiation of the second confrontation there was no audible change in the call of the resident. If there was a change This content downloaded from 157.55.39.116 on Sun, 18 Sep 2016 06:02:11 UTC All use subject to http://about.jstor.org/terms December 1976] HERPETOLOGICA 403 it most likely was not noticed due to the large number of calling males in the immediate vicinity. Two different calls were traced to males of C. griffithsi. The most commonly heard call consisted of two short notes, whereas less frequently a single note was heard. Possibly the single note is a territorial call or, in using the terminology of McDiarmid and Adler (1974) an encounter call. The occurrence of scores of high-pitched peeps every minute precluded accurate determination of which individual was producing what kind of note. The only other Centrolenella found along the stream is a much larger species with a distinctly different call.