Allobates carajas
Advertisement calls. SVL of captured recorded males ranged between 17.6–18.5 mm (average 17.7 mm, n = 5). By inspecting the waveforms and spectrograms of calls of ten males recorded in Carajás, we identified four types of temporal arrangement of notes (Fig. 11). In Serra Sul, notes were emitted either grouped in discrete trills (n = 2 males) or continuously, separated by regular silent intervals (n = 1 male). At Trilha do Lago, most recorded males (n = 3) emitted isolated notes, separated by long, irregular silent intervals. In this location, two other males emitted notes continuously, but notes were separated by short, irregular silent intervals. A sixth male emitted notes grouped in trills, but turned to a continuous regular call at the end of the recording. A single male was recorded at N1 Trail while emitting notes arranged in trills.
Considering all recordings, notes had an average duration of 0.04 ± 0.01 s (range 0.02–0.06 s) and were emitted at an average dominant frequency of 5101.9 ± 236.1 Hz (range 4752.8–5384.9 Hz). Notes had an ascending frequency modulation (Fig. 12). Average lower frequency of notes was 4655.1 ± 199.9 Hz (range 4402.3–4937.9 Hz) and average upper frequency of notes was 5418.8 ± 232.6 Hz (range 5107.3–5742.0 Hz). In average, notes occupied a frequency bandwidth of 763.7 ± 1129 Hz (range 533.1–920.0 Hz).
When notes were emitted continuously (n = 5 males), silent intervals between notes was extremely variable, ranging between 0.22–3.40 s (mean 0.76 ± 0.62 s; n = 100 silent intervals). When arranged in discrete trills (n = 4 males / 23 trills), trills were formed by 4–22 notes (mode = 8 notes) and their duration ranged between 1.49–7.05 s (mean = 4.38 ± 1.61 s). Trills were emitted between irregular, generally long silent intervals, ranging between 3.03–17.95 s (mean 7.22 ± 3.60 s). Silent interval between notes within a trill ranged between 0.24–0.91 s (mean 0.40 ± 0.14 s; n = 69 silent intervals).
Comparison with advertisement calls of other species.
Advertisement calls of A. caeruleodactylus, A. magnussoni, A. masniger, A. nidicola, and A. subfolionidificans are formed by a single note, emitted continuously between irregular (A. caeruleodactylus, A. subfolionidificans) or regular (A. magnussoni, A. masniger, A. nidicola) inter-note silent intervals, not arranged in discrete note trills. Dominant frequency of notes in A. carajas is lower than that of notes in calls of A. caeruleodactylus (dominant frequency 5.54–6.64 kHz) (Lima & Caldwell 2001). Note duration in calls of A. carajas is generally longer than that in calls of A. magnussoni (note duration 0.047– 0.104 s). Additionally, A. magnussoni frequently emits calls formed by note-pairs (Lima et al. 2014). Silent interval between notes in the continuous calls of A. nidicola and A. masniger are always regular, ranging between 0.206– 0.315 s and 0.253–0.425 s, respectively (Caldwell & Lima 2003; Kaefer et al. 2012). Continuous calls of A. carajas can not be distinguished from those of A. subfolionidificans by their spectral or temporal parameters, overlapping in all measurements (Lima et al. 2007).
Some Allobates species alternate between two types of advertisement calls, emitting notes continuously or arranged in bouts or trills. When emitting trills of notes, silent interval between notes of A. carajas is longer than that in trills of A. marchesianus (0.12–0.21 s) (Caldwell et al. 2002b).
Continuous calls and note trills of A. carajas overlap in temporal parameters with those of A. olfersioides, however, notes in calls of A. olfersioides occupy a narrower frequency bandwidth (frequency bandwidth range 0.08–0.41 kHz) (Forti et al. 2017). Dominant frequency of notes in calls of A. carajas is lower than that of notes in calls of A. sumtuosus (dominant frequency 5.60–6.48 kHz) (Simões et al. 2013a).
Advertisement calls of some Allobates species are constituted exclusively by note trills. However, in comparison to A. carajas, note trills are generally longer and formed by a larger number of notes in calls of A. bacurau (call duration 6.92–11.07 s, 60–81 notes) (Simões 2016). Trills of A. crombiei (Morales, 2002) are formed by a larger number of notes, emitted between much shorter silent intervals (25–59 notes, interval between notes 0.045–0.069 s) (Lima et al. 2012). Note trills and silent interval between notes within a trill are shorter in calls of A. grillissimilis (trill duration 0.12–0.30 s, interval between notes 0.010–0.043) (Simões et al. 2013b). Minimum trill duration in A. carajas (1.49 s) only slightly overlapping with maximum trill duration in A. trilineatus (trill duration 0.97–1.55 s). Minimum interval between notes in trills of A. carajas (0.24 s) much longer than maximum interval between notes in A. trilineatus (0.07–0.09 s) (Grant & Rodríguez 2001).
Advertisement calls of A. flaviventris Melo-Sampaio, Souza & Peloso, 2013, and A. hodli are emitted as trills of note-pairs or couplets, not as trills of single notes (Simões et al. 2010; Melo-Sampaio et al. 2013; Lima et al. 2014). Advertisement calls of A. femoralis (Boulenger, 1884) and A. myersi (Pyburn, 1981) are emitted as trills of three, four, six or eight notes (Amézquita et al. 2006; Simões & Lima 2011).
Note trills of A. carajas more closely resemble those of A. brunneus, A. goianus, A. paleovarzensis, and A. tinae, overlapping in all call parameters. However, in general, notes in trills of A. goianus are shorter and emitted between shorter silent intervals (note duration 0.030–0.051s, interval between notes 0.020–0.048 s) (Carvalho et al. 2016). Notes in trills of A. paleovarzensis are split by generally shorter silent intervals and emitted with a lower dominant frequency (interval between notes 0.065–0.266 s, dominant frequency 4.05–4.93 kHz) (Lima et al. 2010). Note trills of A. tinae are generally formed by a small number of notes (2–9 notes) (Melo-Sampaio et al. 2018). Additionally, the ability to emit continuous calls is not reported for A goianus, A. paleovarzensis or A. tinae. Continuous calls or note trills of A. brunneus can not be distinguished from those of A. carajas. However, notes emitted in continuous calls of A. brunneus are always regularly spaced, with silent intervals between notes varying between 0.35–0.42 s (Lima et al. 2014). [1]