High frequency/ultrasonic communication in a critically endangered nocturnal primate, Claire's mouse lemur (Microcebus mamiratra)

Abstract

The critically endangered Claire's mouse lemur, only found in the evergreen rain forest of the National Park Lokobe (LNP) and a few lowland evergreen rain forest fragments of northern Madagascar, was described recently. The present study provides the first quantified information on vocal acoustics of calls, sound associated behavioral context, acoustic niche, and vocal activity of this species. We recorded vocal and social behavior of six male-female and six male-male dyads in a standardized social-encounter paradigm in June and July 2016 at the LNP, Nosy Bé island. Over six successive nights per dyad, we audio recorded and observed behaviors for 3 hr at the beginning of the activity period. Based on the visual inspection of spectrograms and standardized multiparametric sound analysis, we identified seven different call types. Call types can be discriminated based on a combination of harmonicity, fundamental frequency variation, call duration, and degree of tonality. Acoustic features of tonal call types showed that for communication, mouse lemurs use the cryptic, high frequency/ultrasonic frequency niche. Two call types, the Tsak and the Grunt call, were emitted most frequently. Significant differences in vocal activity of the Tsak call were found between male-female and male-male dyads, linked primarily to agonistic conflicts. Dominant mouse lemurs vocalized more than subdominant ones, suggesting that signaling may present an honest indicator of fitness. A comparison of our findings of the Claire's mouse lemur with published findings of five bioacoustically studied mouse lemur species points to the notion that a complex interplay between ecology, predation pressure, and phylogenetic relatedness may shape the evolution of acoustic divergence between species in this smallest-bodied primate radiation. Thus, comparative bioacoustic studies, using standardized procedures, are promising to unravel the role of vocalization for primate species diversity and evolution and for identifying candidates for vocalization-based non-invasive monitoring for conservation purposes.

Proximity-based vocal networks reveal social relationships in the Southern white rhinoceros

“…As dyads displaying high aggressive interaction rates showed respectively high Hiss call rates, it might be concluded that group members producing high Hiss rates are more aggressive and therefore more dominant than group members producing lower Hiss rates. This would fall in line with similar findings in other mammalian species where dominant group members exhibit higher call rates than subdominant ones (e.g., 65 – 69 ). Additionally, high defensive interaction rates showed a trend in predicting high Pant rates.…”

Evolutionary significance of the variation in acoustic communication of a cryptic nocturnal primate radiation (Microcebus spp.)

“…Arthropods were naturally available when they entered the cage. Observations were conducted between 6 p.m. and 9 p.m. for three consecutive nights (procedure matches to Hasiniaina et al, 2018). The observer sat 2–4 m in front of the cage wearing a dimmed headlamp while observing the animals.…”

“…Recorded files were audio‐screened with Audacity 2.2.2 and Batsound Pro 4.2. Across all studied species, the most common vocalization exchanged during agonistic conflicts was the so‐called Tsak call, recognizable by a uniform inverse U‐shaped frequency contour in the spectrograms (Hasiniaina et al, 2018; Zimmermann, 2010; Figure 2). Our analysis focused on this call type.…”

Sources of variation in social tolerance in mouse lemurs (Microcebus spp.)

“…All animals were released after 1 week at their individual capture point after the end of the last night of observations. Such a temporary stay of wild mouse lemurs in cages has been employed in several previous experimental studies and adverse effects were not observed neither on the individual nor on the population level (e.g., [24, 51, 80–83]).…”

“…The social encounter experiments were conducted in cages of about 1 m 3 that were equipped with four wooden bars and two sleeping sites (Fig. 8, [80]). Cages were placed in the forest close to the research camp but > 1 km away from the capture sites.…”