Hipposideros larvatus

behaviour · bio.acousti.ca

Ontogenetic Development of Isolation Calls Newborn bats emitted many types of isolation calls, including DFM, AFM, UFM, short or long constant frequency (CFs and CFl), short broadband noise bursts (BNBs), and different noise burst com- binations: NB-DFM, NB-AFM, and NB-UFM. The oscillograms and spectrograms of isolation calls are shown in Fig. 1 and the duration, Fpeak, composi- tional structure, and occurrence frequency of isola- tion calls are shown in Table 2. The three monosyllables (DFM, AFM, UFM) were found in the adult vocal repertoire. As pups matured, entropy and duration of DFM and AFM monosyllables did not change significantly (see Ta- ble 3 — LMMs, all P > 0.05). The entropy of UFM monosyllable changed slightly but significantly, and duration decreased significantly (entropy, P < 0.001, slope = 0.00030; duration, P < 0.05, slope =-0.02886). Parameters associated with frequency (Fpeak, F1/4, Fcenter, F3/4, Fmin, Fmax, bandwidth) in- creased significantly for each of the three isolation call types (LMMs, P < 0.001). Sex had no signifi- cant effect on any LMM (all P > 0.05). Euclidean distances between DFM, AFM, and UFM of pups and adults decreased during develop- ment (Fig. 2). Thus, monosyllables of isolation calls gradually changed during ontogeny, becoming more similar to the corresponding adult vocal repertoire. We found that DFM, AFM, and UFM of isolation calls remained part of the adult vocal repertoire. Individual Signature in Isolation Calls The DFA demonstrated that the UFM syllables encoded an individual signature which was statisti- cally significant (Fig. 3). The DFA classified 71.2% of calls to the correct individual (Table 4), which was significantly higher than expected by chance (10%; binomial test: P < 0.001). Echolocation Call Features and Development with Age The first early echolocation calls were recorded four days post-partum. The Fpeak was located in the third harmonic (the third harmonic frequencies 85.13 ± 0.67 kHz and second harmonic frequencies 57.07 ± 0.71 kHz, respectively), but transferred to the second harmonic (61.13 ± 1.26 kHz) within the first week of birth. The ontogenetic development of echolocation calls is depicted in Figure 4a (‘A’ rep- resents an adult echolocation call), with interval and duration of calls decreasing (Fig. 4b and 4c), and Fpeak and BFM increasing (Fig. 4d and 4e) with age. Significant differences existed in the echolocation calls of 40-day-old pups and adults (PMANOVA, d.f. = 1, F =15.729, P < 0.01). No significant differ- ences were apparent in temporal (interval and dura- tion) call parameters between 40-day-old pups and adults (independent sample t-test, for interval, t = 1.692, P = 0.093 > 0.0125; for duration, t = 1.899, P = 0.060 > 0.0125, number of calls = 140), but significant differences were found in spec- tral (Fpeak and BFM) call parameters between 40-day- old pups and adults (Mann-Whitney U-test, all P = 0.000 < 0.0125, number of calls = 140).

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