Spatiotemporal distribution of individuals as an indicator for the social system of Lepilemur sahamalaza

Abstract

Primate social systems are highly diverse, complicating the classification of particularly elusive species that are difficult to observe. The spatial distribution of individuals over time is a critical indicator for the social organization and long-term studies are important to establish patterns of social interactions. In recent years, species of the cryptic, nocturnal sportive lemurs of the genus Lepilemur were found to live in pairs in which a single male and a single female share and defend a mutual home range. The present study aimed to forward research into this underrepresented genus by determining the social organization and structure of the Sahamalaza sportive lemur, L. sahamalaza. We collected 773.15 hr of behavioral and GPS data during a period of 10 months (between 2015 and 2016) on 14 individuals: eight females and six males. There was no evidence of pair-specific home range use as intra-and intersexual home range overlap was high. No pattern of social interactions between focal individuals could be distinguished despite high range overlap.Individuals met and interacted infrequently, resulting in an interaction rate of 0.32 interactions/hr. Sleeping associations between adult individuals were never observed.While both sexes had access to multiple potential mating partners, range sizes or ranging distances did not increase in mating periods. Overall, the social system of Sahamalaza sportive lemurs exhibits aspects of a solitary social organization and structure with potential for the polygamous mating system. These findings underline the importance of detailed social ecology studies that can provide the basis for understanding potential environmental influences on social system variability of closely related species.

Sahamalaza Sportive Lemur, Lepilemur sahamalaza, Vocal Communication: Call Use, Context and Gradation

“…High intrasexual differences were detected: only 4 of the 10 radio-collared females contributed to the recorded vocalisations, whereas 6 out of 8 radio-collared males did so. The prevailing social system of Sahamalaza sportive lemurs has been described as "solitary" [Seiler et al, 2015a;Mandl et al, 2019] but little is known about the social structure and dominance hierarchies in the population. Differences in calling behaviour may reflect differences in dominance hierarchy as individuals that hold higher ranks were found to call more frequently and for longer periods [Fischer et al, 2004;Bolt, 2013].…”

“…Duetting, as found in Milne Edwards' sportive lemurs, L. edwardsi, mainly functions as a form of territorial defence or to strengthen pair bonds [Méndez-Cárdenas et al, 2008;Snowdon, 2017]. While no pair bonds have been discovered to date [Seiler et al, 2015a, Mandl et al, 2019, duetting cannot be ruled out with confidence as it was impossible to assess the social relationship of all calling individuals in this study, so there might be an undiscovered underlying, possibly kinship-related, group structure [Geissmann and Mutschler, 2006;Torti and Gamba, 2013]. Calling bouts can also serve to establish "dear enemy" relations between neighbours to avoid costly fights [Wich et al, 2002;Tripovich et al, 2008] and to regulate spacing between individuals sharing the same area as was suggested for other nocturnal primates [Fichtel and Hilgartner, 2013].…”

“…observation]. In addition, although playback experiments have shown indications for differing call functions [Seiler et al, 2015b], it has been difficult to connect calls with context due to this species' solitary social organisation [Seiler et al, 2015a;Mandl et al, 2019]. With the overall goal to elaborate on existing information by recording calls year-round, including the wet season, we determined four study objectives: 1 Describe all recurring call types over the course of a year On average, nocturnal primates show smaller vocal repertoires than diurnal species (mean repertoire size: 8.7 [see Marler, 1965;Macedonia and Stanger, 1994;Stanger, 1995;McComb and Semple, 2005]).…”