Temporal and environmental influences on long-distance calling by free-ranging maned wolves (Chrysocyon brachyurus)

Acoustic communication is favored at times of day and under weather conditions that allow the most effective sound transmission. Changes in vocal activity due to temporal and environmental factors can add significant information about the function of animals' calls by providing clues about behavioral patterns. Estimating the temporal variation of vocal activity also can be important for conservation when calls are used to infer a species' presence and abundance. The maned wolf (Chrysocyon brachyurus) is a near-threatened species and its conservation efforts could benefit from information gathered using passive acoustic monitoring (PAM), but their vocal behavior pattern in the wild is currently unknown. We investigated the nocturnal pattern of roar-bark sequences by maned wolves in Serra da Canastra National Park (Minas Gerais, Brazil) during 4 months of the breeding season and measured the influence of period of night, weather conditions, and lunar phase on their vocal activity. Roar-barks were more frequently emitted in the first 3 h of the night, suggesting an important social function for these long-distance calls in the beginning of the period of greatest activity of maned wolves. The occurrence of sequences was negatively related to mean wind speed, which suggests that wolves are avoiding moments of poor sound transmission. No sequence was detected when wind speed was above 5.4 m/s, probably due to equipment limitation, masking by wind noise, or absence of vocal activity. Maned wolves also vocalized more during moonlit nights. A better understanding of seasonal variation in vocal activity of maned wolves is required, but our study shows that it is possible to detect behavioral patterns of wild populations of this species only by sound, validating PAM as a tool for the conservation of this threatened carnivore.