Life History, Abundance, Activity, and Special Behaviors
In wet forest stream habitats, the frogs are dispersed in and along streams. They can climb and are found up to 3 meters above ground, perching on large moss-covered boulders near waterfalls and along the banks of streams. In contrast, in dry forest stream habitats the frogs are smaller (2/3 the size), distributed mainly over the forest floor, and occur only up to 1.5 meters above ground. The population density of Panamanian Golden Frogs is higher in dry forests than in wet forests (Poole 2006).
Female frogs move into the forests in the late dry and early rainy season (February-March) and return to streams to breed in the late rainy and early dry season (November-January) (Karraker et al. 2006). Males tend to stay in streams year-round establishing territories and waiting for the females to return (Poole 2006). Male frogs perch on rocks in or along the banks of streams and waterfalls, and they defend their territory by semaphoring (hand-waving, plus an unusual form of foot-raising--not foot-flagging, and reorientation) (Lindquist and Hetherington 1996; Lindquist and Hetherington 1998a; Lindquist and Hetherington 1998b). Males also vocalize, but prefer semaphoring over vocalization, apparently due to the noisiness of waterfalls and stream flow in their natural habitat (Lindquist and Hetherington 1996). Females also semaphore in this species, as they do in the related species Atelopus varius (Lindquist and Hetherington 1998a; Crump 1988). There is a male-favored gender bias, resulting in the majority of males being single, and thus all females encountered in streams are amplexed (Poole 2006). Amplexus can last from a few days to two months in captivity (Poole 2006).
Oviposition occurs in wider stream sections along shallow margins, where the water runs quickly and there is slightly lower canopy closure, during periods of lower water flow (Karraker et al. 2006). The mean depth of preferred streams in Karraker et al.'s (2006) study was 16.5 ï¿½ 15.7 cm, and the mean stream velocity was 0.34 ï¿½ 0.15 m/s, with a mean water temperature of 23.4ï¿½C ï¿½ 0.8ï¿½C. A single string of cream-colored eggs is attached to a rocky stream substrate, which is most often large (such as a boulder or bedrock) (Karraker et al. 2006). Selection of larger substrates in confined channels may reduce the risk of eggs being washed downstream in late rainy season storms (Karraker et al. 2006). The single strand is looped back upon itself, forming two or more layers of eggs in a loose, elongated mass (Karraker et al. 2006). Average clutch size is 370 eggs (ranging from 202-623), with an average ovum diameter of 1.8 mm (Karraker et al. 2006). Clutches are usually found within 2 m of the stream border and are evenly distributed between riffle and run habitats; they are generally placed 1.1 ï¿½ 1.3 m apart, implying communal oviposition (Karraker et al. 2006). It has been suggested that if this is communal oviposition, it may occur in Atelopus zeteki in order to distribute the risk of predation and to accommodate a lack of suitable oviposition sites (Karraker et al. 2006). In captivity, the embryonic development ranged from 7-11 days at 22.0ï¿½C and averaged 8.9 ï¿½ 1.3 days (Detroit Zoo unpublished cited in Karraker et al. 2006).
Tadpoles are commonly found resting on top of stones and stream gravel at the edges of shallow pools below cascades (Lindquist and Hetherington 1998). Their coloration is similar to the color of the sand, which is the predominant surrounding substrate (Karraker et al. 2006). They may live anywhere along the stream where water pools, as long as the pool is directly connected to flowing channels. They prefer water depths of 5-35 cm (Lindquist and Hetherington 1998b). The development of the larvae takes place with the onset of the wet season, and the possession of a large ventral adhesive disk allows the larvae to remain attached to objects on the bottom of the stream against the torrential current (Savage 1972). However, Karraker et al. (2006) observed that the ventral suctatorial disc of newly hatched Atelopus zeteki larvae is either undeveloped or not yet functional immediately upon hatching. It is not known at what point the disc acquires functionality.
Juveniles were always observed within 2 m of the stream (Lindquist and Hetherington 1998b). Interestingly, although adult males are territorial and do not allow conspecifics other than gravid females to approach, Lindquist and Hetherington (1998b) observed subadults in close proximity and sometimes even touching adult males. However, as soon as significant rainfall began, all juveniles vanished from open streamside areas used by adult males. Lindquist and Hetherington (1998b) hypothesized this might be due to rain triggering territorial defense behavior in adult A. zeteki males.