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Life History, Abundance, Activity, and Special Behaviors
These frogs can be long-lived and have a potential life-span of at least 15 years (Leenders 2001). Adults are nocturnal and stay in hiding during the day, sheltering in subterranean burrows, beneath logs, in the spaces between tree roots, or under houses (Savage 2002). Juveniles, however, are active during the day and can be found on top of the leaf litter (Savage 2002). This species prefers dimly lit forest (Jaeger and Hailman 1981). At the first sign of dusk, males of this species give off a loud "wrooop" (Leenders 2001). The call lacks pulses (Hero and Galatti 1990). Males are territorial and call sporadically from burrows located underneath a log or rock, often in densely vegetated areas (Leenders 2001).
Mating is believed to take place throughout the rainy season months of May to November (Savage 2002). However, Hero and Galatti (1990) observed that males in the central Amazon region of Brazil began calling immediately after the first substantial rains, in late September, and that calling ceased after two to four weeks. Both calling and breeding take place at the water's edge; it is not known whether the same burrows used for shelter are also used as nest sites (Savage 2002). Amplexus is axillary in this species (Savage 2002). As the male hugs the female under the armpits with his robust forearms, he creates a large foamy mass around the eggs by rapidly moving his back legs through the jelly surrounding the fertilized eggs (Heyer and Rand 1977). This foam nest consists of a frothy mix of sperm, skin secretions, water, and air (Heyer and Rand 1977). Females lay about 1,000 light gray eggs, and the foam nests are constructed in dry cavities or depressions (Savage 2002). These hollows may be natural or possibly excavated by the males (Muedeking and Heyer 1976). Foam nests may be constructed near puddles, temporary pools or in seasonally flooded spots, such that rain washes the larvae out of the nests and into nearby small rain pools (Breder 1946). Alternatively, foam nests have been observed in open depressions at some distance from water, so that tadpoles develop within the nest until metamorphosis (Muedeking and Heyer 1976; Hero and Galatti 1990). In the latter case, Muedeking and Heyer (1976) noted both larvae and eggs in the nests, and inferred that eggs were being consumed by larvae. Leptodactylus pentadactylus larvae are unusually resistant to desiccation for anuran tadpoles, and can survive almost seven days out of water (Valerio 1971). Foam nests also provide protection to larvae from desiccation (Heyer 1969).
Galatti (1992) observed that the strong seasonality in Leptodactylus pentadactylus reproduction in Brazil coincided with arthropod prey availability. He observed two peaks in arthropod abundance, one in late September (when the adults arrived at breeding sites), and the second in January and February, when tadpoles completed metamorphosis into juvenile frogs (Galatti 1992). These peaks did not completely correspond to rainfall, as the first peak in arthropod prey abundance occurred during the late dry season and the second occurred during the wet season (Galatti 1992).
Leptodactylus pentadactylus is able to secrete huge amounts of mucus as an antipredator defense (Savage 2002). In addition to making the frog slippery and difficult to hold, the skin secretions are toxic (Savage 2002). Savage (2002) points out that this toxicity is evident both from direct contact (resulting in human skin rashes and stinging) and indirect contact, from being in the same room when the frog is handled (which results in sneezing and swelling of human eyes and mucus membranes). The residue from these skin secretions is lethal to other frogs which come in contact with it (Savage 2002). Leptodactylus pentadactylus also exhibits defensive behavior, which consists of facing the predator, inflating and elevating the body with all four limbs (Villa 1969; Savage 2002). This has the effect of raising the posterior, glandular surfaces above the level of the head since the hind limbs are longer (Villa 1969; Savage 2002). Initial elevation is followed by repeated raising and lowering of the body (Villa 1969; Savage 2002).
These frogs are opportunistic feeders. Adults consume anything that they can swallow, including bird chicks, snakes, other frogs (particularly dendrobatids, despite their toxicity), and scorpions (Leenders 2001). Tadpoles initially feed on the foam produced by the male, but later will either eat algae (Vinton 1951) or become carnivorous, preying on eggs and tadpoles of their own species or other species (Muedeking and Heyer 1976; Heyer et al. 1975).
Predators on Leptodactylus pentadactylus eggs include the ephydrid fly Gastrops willistoni, which lays its own eggs on L. pentadactylus clutches in Costa Rica and Brazil (Villa et al. 1982). Predators on the adult frogs include coatimundis, snakes, and caimans. When discovered, these frogs often remains still and easily approached. If caught, however, they will emit an extremely loud, high-pitched scream to startle potential predators (Leenders 2001).
Research has shown that these frogs have an accurate visual image of their surroundings, though it is not known exactly what cues they use for orientation (Leenders 2001). Frogs taken from their burrows and displaced over short distances have managed to return to their burrow in a straight line (Leenders 2001).
Adult Leptodactylus pentadactylus are negatively phototactic (avoid light), unlike most anurans (Kicliter and Goytia 1995).