Silky sifaka (Propithecus candidus) "zzuss" vocalizations: sexual dimorphism, individuality, and function in the alarm call of a monomorphic lemur

Response of diademed sifaka (Propithecus diadema) to fosa (Cryptoprocta ferox) predation in the Betampona Strict Nature Reserve, Madagascar

Large-bodied mammals living in fragmented habitats are at higher risk of extinction, and such risk can be influenced by ecological factors such as predator-prey system dynamics. These dynamics can be particularly complex for conservation management when one endangered species preys on another endangered species in an isolated or poor-quality habitat. Here we describe predation events observed over 19 months that involved two threatened species: the largest carnivore in Madagascar, the fosa (Cryptoprocta ferox), and three groups of diademed sifaka (Propithecus diadema) in the Betampona Strict Nature Reserve. This site is a 22 km2 low-altitude rainforest that is surrounded by agricultural land and isolated from larger forest corridors. We aim to (1) assess the behavioral changes of P. diadema in response to fosa attacks and identify any antipredator strategies that they adopted, and (2) quantify the frequency of fosa attacks and the predation impact on the sifaka population. We report five direct observations of fosa predation attempts (one successful), the discovery of a dead sifaka with evidence of fosa predation, and the disappearance of three individuals. We describe the observed attacks and compare the sifaka activity budgets and movement patterns before and after the events. To escape the predator, sifakas fled short distances, hid, and remained vigilant. The impact of predation, combined with low reproductive rates and potentially high inbreeding of this isolated diademed sifaka population, could affect the survival of this species in Betampona. Given the compounding effects of habitat isolation and high hunting pressure, community-specific conservation strategies should incorporate predator-prey dynamics via longitudinal monitoring of predator and prey population densities and quantifying the predation pressure between them.

Comparative Analysis of the Vocal Repertoires of the Indri (Indri indri) and the Diademed Sifaka (Propithecus diadema)

Strepsirrhine vocalisations are extraordinarily diverse and cross-species comparisons are needed to explore how this variability evolved. We contributed to the investigation of primate acoustic diversity by comparing the vocal repertoire of two sympatric lemur species, Propithecus diadema and Indri indri. These diurnal species belong to the same taxonomic family and have similar activity patterns but different social structures. These features make them excellent candidates for an investigation of the phylogenetic, environmental, and social influence on primate vocal behavior. We recorded 3 P. diadema groups in 2014 and 2016. From 1,872 recordings we selected and assigned 3814 calls to 9 a priori call types, on the basis of their acoustic structure. We implemented a reproducible technique performing an acoustic feature extraction relying on frequency bins, t-SNE data reduction, and a hard-clustering analysis. We first quantified the vocal repertoire of P. diadema, finding consistent results for the 9 putatively identified call types. When comparing this repertoire with a previously published repertoire of I. indri, we found highly species-specific repertoires, with only 2% of the calls misclassified by species identity. The loud calls of the two species were very distinct, while the low-frequency calls were more similar. Our results pinpoint the role of phylogenetic history, social and environmental features on the evolution of communicative systems and contribute to a deeper understanding of the evolutionary roots of primate vocal differentiation. We conclude by arguing that standardized and reproducible techniques, like the one we employed, allow robust comparisons and should be prioritized in the future.

Factors affecting call usage in wild black-and-white ruffed lemurs (Varecia variegata) at Mangevo, Ranomafana National Park

Vocal communication is an important modality for group-living primates inhabiting dense forest habitats that can hinder visual and olfactory signals. Nevertheless, research on primate vocalizations has historically focused on a narrow subset of haplorhine taxa; comparatively few studies have been focused on strepsirrhines, despite facing similar ecological and social challenges. Ruffed lemurs (Varecia)-a taxon known for their raucous calls-are rainforest specialists that exhibit strong fission-fusion dynamics and communally rear large litters of young. However, surprisingly few studies have examined Varecia vocalizations in the wild, meaning virtually nothing is known about the call types or how they facilitate their unique social and reproductive strategies. Our goal for this study was to examine how various contextual factors such as weather, behavioral state, and subgroup size and composition affected vocal activity across call types in wild black-and-white ruffed lemurs. We conducted focal follows on 31 individuals (two communities) in Mangevo (Ranomafana National Park) from May-August 2019 to record behavioral and vocal activity. We distinguished 11 call types, although three (hum, roar-shriek, chatter) constituted the majority of vocal activity. Calling rates were consistent throughout the day, but decreased with high rainfall. We found sex- and subgroup-specific differences in call usage, likely related to female dominance and subgroup composition, respectively. We identified behavioral contexts that some call types were consistently given in; this can be used to help infer call function. This study provides some of the first quantitative analyses of ruffed lemur vocal communication and lays the groundwork for more systematic hypothesis testing in future studies.

Peafowl antipredator calls encode information about signalers

Animals emit vocalizations that convey information about external events. Many of these vocalizations, including those emitted in response to predators, also encode information about the individual that produced the call. The relationship between acoustic features of antipredator calls and information relating to signalers (including sex, identity, body size, and social rank) were examined in peafowl (Pavo cristatus). The "bu-girk" antipredator calls of male and female peafowl were recorded and 20 acoustic parameters were automatically extracted from each call. Both the bu and girk elements of the antipredator call were individually distinctive and calls were classified to the correct signaler with over 90% and 70% accuracy in females and males, respectively. Females produced calls with a higher fundamental frequency (F0) than males. In both females and males, body size was negatively correlated with F0. In addition, peahen rank was related to the duration, end mean frequency, and start harmonicity of the bu element. Peafowl antipredator calls contain detailed information about the signaler and can potentially be used by receivers to respond to dangerous situations.