Brachycephalus are among the smallest terrestrial vertebrates in the world. The genus encompasses 34 species endemic to the Brazilian Atlantic Rainforest, occurring mostly in montane forests, with many species showing microendemic distributions to single mountaintops. It includes diurnal species living in the leaf litter and calling during the day, mainly during the warmer months of the year. The ecology of the vast majority of the species is unknown, particularly their advertisement call (AC), which has been described only for seven species of the genus. In the present study, we describe the AC of Brachycephalus albolineatus, a recently described microendemic species from Santa Catarina, southern Brazil. We analyzed 34 advertisement calls (ACs) and 554 notes from 20 individuals of B. albolineatus, recorded between 5–6 February 2016 in the type locality of the species. We collected five individuals as vouchers (they are from the type series of the species). Eight individuals we recorded 2–4 times. Brachycephalus albolineatus have a long advertisement call of 40–191 s (mean of 88 s) composed of 7–26 notes (mean of 14 notes) emitted at a rate of 6–13 notes per minute (mean of 9 notes per minute) and at a dominant frequency of 5–7 kHz (mean of 6 kHz). Advertisement calls are composed of isolated notes and note groups (two notes involved in each particular note group); the former is composed by one to three pulses and the note groups by two or three pulses in each note. Most ACs present both isolated notes and note groups, with a few cases showing only the former. Note groups are emitted invariably in the last third of the AC. Most isolated notes escalate their number of pulses along the AC (1 to 2, 1 to 3 or 2 to 3). Note duration of isolated notes varies from 0.002–0.037 s (mean of 0.020 s) and duration of note group vary from 0.360–0.578 s (mean of 0.465 s). We show that there is intra-individual variation in several parameters [(1) duration and rate of the AC; (2) number of pulses and notes, as well as of isolated notes and note groups, per AC; and (3) in dominant frequency]. Individuals apparently expend progressively more energy along their emission of the AC because the AC normally escalates, incorporating note groups and pulses per note. Individual variation analysis also demonstrated that less structured ACs (i.e. with notes with fewer pulses) are not fixed individually and can represent temporal variation. It is possible that isolated notes and note groups could have distinct purpose, perhaps territorial defense and mating, respectively. Recently, it was demonstrated that B. ephippium and B. pitanga are insensitive to the sound of their own calls. However, these species usually call above the leaf litter and belong to a distinct group that B. albolineatus, who call only under the leaf litter. It is possible that species of the genus that only call underneath the leaf litter still retain their hearing capacity.
Advertisement call of Brachycephalus albolineatus (Anura: Brachycephalidae)
