From habitat use to social behavior: natural history of a voiceless poison frog, Dendrobates tinctorius

Abstract

Descriptive studies of natural history have always been a source of knowledge on which experimental work and scientific progress rely. Poison frogs are a well-studied group of small Neotropical frogs with diverse parental behaviors, distinct calls, and bright colors that warn predators about their toxicity; and a showcase of advances in fundamental biology through natural history observations. The dyeing poison frog, Dendrobates tinctorius, is emblematic of the Guianas region, widespread in the pet trade, and increasingly popular in research. This species shows several unusual behaviors, such as the lack of advertisement calls and the aggregation around tree-fall gaps, which remain poorly described and understood. Here, we summarize our observations from a natural population of D. tinctorius in French Guiana collected over various field trips between 2009 and 2017; our aim is to provide groundwork for future fundamental and applied research spanning parental care, animal dispersal, disease spread, habitat use in relation to color patterns, and intra-specific communication, to name a few. We report sex differences in habitat use and the striking invasion of tree-fall gaps; describe their courtship and aggressive behaviors; document egg development and tadpole transport; and discuss how the knowledge generated by this study could set the grounds for further research on the behavior, ecology, and conservation of this species.

Keywords: Agonistic behavior; Amazon; Courtship; Habitat use; Parental care; Tadpole transport; Treefall.

Figure 1. Colour pattern variation (A–L) within the studied population (as described in Rojas & Endler, 2013) and (M–P) between different populations of the dyeing poison frog in French Guiana (see Noonan & Gaucher, 2006).

(A–F) males, (G–L) females. Lines on the background paper mark five mm. Note the enlarged toe discs in males, but overall larger female body size (for details see Rojas & Endler, 2013). Photo credits: Andrius Pašukonis and Matthias-Claudio Loretto ((A–L) Nouragues Nature Reserve, French Guiana), Antoine Fouquet ((N) Bakhuis, Suriname; (O) Mt. Galbao, French Guiana), and B. Rojas ((M) Mt. Matoury, French Guiana; (P) Mt. Bruyére, French Guiana).

Figure 2. Examples of phytotelmata (pointed at by the arrows with no label) used as tadpole-deposition sites at the studied population.

Some of these become available when a tree falls (A, C, D). Tadpoles of other species can sometimes be found sharing these pools with D. tinctorius tadpoles (D). Color patterns are clearly visible already at metamorphosis (D). Photo credits: Bibiana Rojas (A, C) and Andrius Pašukonis (B, D).

Figure 3. Habitat use in D. tinctorius in relation to sex.

Numbers in the boxes indicate the total number of individuals in each category (N =109). Females are more often associated with open areas of leaf litter, whereas males are more frequently found associated to structures such as fallen logs and buttresses (Z = 2.943, P < 0.001). Asterisks denote significant differences at the 0.05 level. Data collected only in 2010.

Figure 4. Dozens of adult D. tinctorius (pointed at by the arrows) can aggregate at once at a newly formed treefall gap (A).

There are no sex differences in immediate arrival in a newly formed gap (χ²= 0.08 df = 1, P = 0.778), but males are more likely to be found in treefall gaps in the long term ((B) χ² = 11.137, df = 1, P = 0.001). Photo credit: Bibiana Rojas.

Figure 5. Courtship in D. tinctorius.

(A) Example of tactile interactions observed between courting individuals: a female with a forelimb on a male’s head. (B) Waveform and (C) spectrogram of D. tinctorius call recorded from close range (approx. 30 cm) during courtship. The normalized waveform reveals the relative amplitude modulation and the pulsating structure of the call (pulse rate = 154 Hz); the spectrogram (FFT window length = 0.01 s, Gaussian window, frequency range 0–6,000 Hz) show the broadband spectral structure of the call with dominant frequency band centered around 3,150 Hz. Photo credit: Bibiana Rojas.

Figure 6. Clutch development in D. tinctorius in the wild.

(A) Freshly laid clutch of five eggs; (B) The same clutch 5 days later. Note that two of the initial eggs have been infected by a fungus; (D) 15 days after egg laying, two surviving tadpoles are ready to be picked by the male and taken to a body of water where they will continue to develop until metamorphosis; (E) A tadpole attached to the male’s back. (C) A fresh clutch and (F) a male with two tadpoles on his back. (C) and (F) provide scales for size reference. Photo credits: Andrius Pašukonis (A, B, D, E) and Bibiana Rojas (C, F).

Figure 7. Cannibalism in tadpoles of D. tinctorius.

(A) A cannibalistic tadpole with the remainings of its victim; (B) oral apparatus (anterior side up) of a stage 25 (Gosner, 1960) D. tinctorius tadpole. Photo credits: Bibiana Rojas (A) and Eva K. Fischer (B).

Figure 8. Tadpole transport in D. tinctorius.

A male (A) and a (exceptional) female (B) with tadpoles on their back (indicated by white arrows). (C) Most individuals were found carrying one tadpole, but two and three tadpoles can also be carried at once. Photo credit: Bibiana Rojas.

Figure 9. Images of an agonistic encounter between two male D. tinctorius.

Physical combat involves pressing the opponent against the substrate (with either the forelimbs or the whole body) (A), wrestling (C), and kicking. Occasionally, males also vocalize during fighting, as seen by the inflated vocal sac in the (B). Photo credit: Bibiana Rojas.