Brazilian Poison Frog

Ranitomeya vanzolinii is a small frog with adults measuring from 16.7-19 mm. Males observed in pairs with females had a mean size of 17.0 +/- 0.6 mm, while paired females had a mean size of 18.6 +/- 0.7 mm (Caldwell, 1997). This species was first described by Myers (1982), who noted that R. vanzolinii can be identified by its coloration, which is consistent between localities separated by hundreds of kilometers and 1200 m in elevation. The body has pale yellow rounded to elongated spots on a black background. Limbs show fine blue reticulation over a black background, sometimes extending onto the digits or palms and soles. In most specimens a few pairs of dorsal spots are connected by pale lines, but spotting is the predominant pattern. The head is narrower than the body. In lateral profile the snout is rounded, obtuse, or sloping; in dorsal profile, the snout is truncate. Nares are located laterally on the snout, near the tip. The tympanum is present and either circular or vertically elliptical in shape, but is concealed posterodorsally. Teeth are lacking. Adult males have well-developed vocal slits. Hands are relatively large (75-90% of head width). The first finger is shorter than the second when adpressed. Fingers (except for the first finger) have considerably expanded discs, with the discs being at least twice the width of the fingers. The tubercles on the hand lack pigment and thus appear prominent. A large outer metacarpal tubercle is present on the median base of the palm, as well as a smaller inner metacarpal tubercle on the base of the first finger, and one or two subarticular tubercles on each finger. The hindlimbs are moderately long, with the adpressed heel reaching the eye or tympanum (Myers, 1982). Other dendrobatids also have similar reticulation on the limbs and similar hand structure (Adelphobates quinquevittatus, Ranitomeya fantastica, Ranitomeya reticulatus). However, these three dendrobatid species have different patterning on the dorsum, with lines, reticulation, or uniform coloration being present. In contrast, Ranitomeya vanzolinii is the only one with rounded spots on the dorsum and thus can be easily distinguished. (Myers, 1982).

Spotted Poison Frogs occur in east-central Peru and the adjacent part of Brazil (Myers, 1982). They are generally found in primary lowland Amazonian rainforest, in the upper drainages of the Ucayali and Juru� rivers (Myers, 1982; Caldwell and De Oliveira, 1999). However, there is one record of this species from 1300 m elevation at Tsioventeni, between Rio Ucayali and the headwaters of Rio Pachitea (Myers, 1982). Adults are found mainly in the lower understory (less than 6 m above the forest floor), while individuals found in leaf litter tend to be juveniles (Caldwell and De Oliveira, 1999).

Ranitomeya vanzolinii is primarily arboreal as an adult, preferring perches mostly up to 2 m high but occasionally as high as 6 m above the forest floor. Frogs of this species found in the leaf litter are mostly juveniles (Caldwell and De Oliveira, 1999). Ranitomeya vanzolinii form pair bonds and exhibit biparental care, in which males and females remain in pairs to care for their young and feed them. Both pair bonding and biparental care are unusual for anurans. Ranitomeya vanzolinii is the only frog species so far for which pair bonding has been observed in the wild. During the course of a two-month study, pairs generally appeared to be monogamous, with females remaining within the territories of their mates (Caldwell and De Oliveira, 1999). However, Caldwell and De Oliveira (1999) did observe one male consorting with two females within his territory. Males vocalize frequently, both in defense of their territory and to communicate with females through both advertisement and courtship calls (Caldwell, 1997; Caldwell and De Oliveira, 1999). Following courtship and fertilization, a clutch consisting of one to several fertilized eggs is deposited inside a small tree hole containing water, above the cavity's waterline. The tree holes are quite small, with the average size being 3.0 x 1.7 cm and 17.9 cm deep. Primarily holes in saplings and woody vines are used, with preferred cavities located about 1.2 m above the forest floor. The cavities contain very little water, less than 18 ml on average. No sunlight enters the tiny openings, precluding algal growth in the water of the treehole. The diminutive size of the openings also means detritus and macroinvertebrates such as mosquitoes are not found in the water. Hence there is no source of food for tadpoles in the treeholes (Caldwell, 1997; Caldwell and De Oliveira, 1999). Tadpoles are reared singly. If the parents deposit more than one fertilized egg in the treehole, the additional tadpoles are not allowed to fall in the water, where they might be consumed by a sibling. Instead, on hatching, a tadpole crawls onto the male's back and is transported individually by the male parent to another treehole containing water. A few days later the male guides the female to the new treehole containing their tadpole, using vocalizations (Caldwell, 1997). When the pair enters the cavity, the frogs court, with the male continuing to call during courtship. Parents remain in the treehole for 2-3 hours. Periodically during this time the female submerges her posterior half into the water, with the male calling more softly and sometimes also entering the water alongside her. When the female is in the water, the tadpole apparently communicates with her by approaching her vent and making rapid swimming movements. Presumably this signals the female to deposit an unfertilized egg for the tadpole to consume (Caldwell and De Oliveira, 1999). The majority of eggs deposited for larval consumption are unfertilized (Caldwell, 1997). Tadpoles are not fed every day. The parents return at approximately five-day intervals (with a range of 1.73-8.5 days) to court each other and feed the offspring (Caldwell, 1997). Females deposit 1-2 eggs at each feeding (Caldwell and De Oliveira, 1999). Tadpoles have serrated jaw sheaths, facilitating tearing of the outer egg envelope. The yolk of the unfertilized egg is consumed by the tadpole but the outer egg jelly capsule is not. (Caldwell, 1997; Caldwell and De Oliveira, 1999). Adults hunt during the day and their diet consists mainly of tiny ants and mites. (Caldwell and Summers, 2003). This species appears to be present at high density in the region where it is found, with male territories often adjacent to one another (Caldwell and De Oliveira, 1999).

This species is not threatened. It is abundant in the region where it is found (Caldwell and De Oliveira, 1999).

Ranitomeya vanzolinii, also known as the Brazilian poison frog or spotted poison frog, is a species of frog from the family Dendrobatidae. It is found in the Amazonian rainforests of Brazil and Peru, and possibly Bolivia.