Influence of Dry Season and Food Quality and Quantity on Behavior and Feeding Strategy of Propithecus verreauxi in Kirindy, Madagascar

According to optimal foraging theory, herbivores can base food choice mainly on the quality or the quantity of food, or both. Among herbivorous primates, folivorous lemurs living in the highly seasonal environment of Madagascar have to cope with the shortage of high-quality food during the dry season, at least in deciduous forests. We studied (Verreaux's sifaka) in Kirindy, western Madagascar, to understand the influence of dry season and food quality and quantity on behavioral patterns and feeding strategy (qualitative vs. quantitative dietary choice) of a folivorous lemur in a deciduous forest. We followed 7 groups (4 groups/period; 3 individuals/group/month) during 4 periods of the year (wet season: February–March; early/middle/late dry season: May–June; July–September; October–November). We collected samples of plants eaten and examined behavioral and feeding patterns, considering food quality (macronutrients, proteins/fibers ratio, and tannins) and abundance. We found 1) a significant reduction of home range, core area, and daily path length from the wet to the dry season, possibly related to dietary change and 2) a daily period of inactivity in the dry season for energy conservation. Regarding the feeding strategy, Kirindy sifakas showed 1) high variation and selection in choosing food items and 2) a dietary choice based mainly on quality: Kirindy sifakas fed on plant species/families independently from their abundance and tannins represented a feeding deterrent during the dry season. Overall, behavioral and dietary adaptations allow Kirindy sifakas to overcome the shortage of high-quality food in the lean period.     

Sexual signalling in Propithecus verreauxi: male "chest badge" and female mate choice

Communication, an essential prerequisite for sociality, involves the transmission of signals. A signal can be defined as any action or trait produced by one animal, the sender, that produces a change in the behaviour of another animal, the receiver. Secondary sexual signals are often used for mate choice because they may inform on a potential partner's quality. Verreaux's sifaka (Propithecus verreauxi) is characterized by the presence of two different morphs of males (bimorphism), which can show either a stained or clean chest. The chest becomes stained by secretions of the sternal gland during throat marking (rubbing throat and chest on a vertical substrate while smearing the scent deposition). The role of the chest staining in guiding female mate choice was previously hypothesized but never demonstrated probably due to the difficulty of observing sifaka copulations in the wild. Here we report that stained-chested males had a higher throat marking activity than clean-chested males during the mating season, but not during the birth season. We found that females copulated more frequently with stained-chested males than the clean-chested males. Finally, in agreement with the biological market theory, we found that clean-chested males, with a lower scent-releasing potential, offered more grooming to females. This "grooming for sex" tactic was not completely unsuccessful; in fact, half of the clean-chested males copulated with females, even though at low frequency. In conclusion, the chest stain, possibly correlated with different cues targeted by females, could be one of the parameters which help females in selecting mates.     

Berenty 2006: Census of <Emphasis Type="Italic">Propithecus verreauxi</Emphasis> and Possible Evidence of Population Stress

We provide a survey of a folivorous lemur, Propithecus verreauxi (sifaka), in the Berenty Reserve, southern Madagascar. Higher densities of folivores in small patches occur in either high-quality food areas or in less disturbed refugia. The skewness of sex ratio, which in lemurs is often male-biased, can be critically exacerbated in population stress. We predicted that sifaka would show higher densities in areas where protein-rich food is abundant (prediction 1a) and in refugium areas (prediction 1b). Owing to increased competition by brown and ring-tailed lemurs and decreased food production by tamarind trees, we expected an extremely male-biased sex ratio (prediction 2). In November–December 2006, we counted and sexed 206 adult/subadult sifaka (49 groups) during daily walks in different forest zones (Ankoba secondary forest, to the north, Malaza gallery/scrub areas, and spiny forest, to the south). Sifaka may have decreased in the gallery forest to concentrate in Ankoba (in a sort of out-of-Malaza). The area contains protein-rich food (prediction 1a confirmed). Sifaka are proportionally more concentrated in the spiny area than in the degraded scrub forest (prediction 1b confirmed). The sex ratio is extremely male biased, possibly due to either high sifaka density, in Ankoba, or food availability reduction, in Malaza (prediction 2 confirmed). The sifaka population seems to be under stress: researchers need to resume demographic studies, interrupted in Berenty in the mid-1980s, to preserve in situ a species that is difficult to protect ex situ.     

Do wild brown lemurs reconcile? Not always

Post-conflict behaviour has been widely investigated in anthropoid primates but not extensively in prosimians. Here, we report the reconciliation pattern of a 14-individual group of wild brown lemurs (Eulemur fulvus) in the Berenty gallery forest (South Madagascar). We found that reconciliation occurs only in the non-feeding context and that it works in reducing the risk of renewed aggression. Thus, reconciliation would provide an immediate positive feedback that is probably independent of the quality of the relationship between opponents. Reconciliation may also be a hic-et-nunc mechanism, needed to avoid conflict spreading across group members, possibly leading to social disruption.     

Feeding Patterns and Dietary Profile of Nocturnal Southern Woolly Lemurs (Avahi meridionalis) in Southeast Madagascar

Folivory has evolved in all primate radiations but the relative importance of resource quantity and nutritional quality of food is controversial. To understand how food abundance and different nutrients affect a folivorous diet, we investigated food composition of the leaf-eating lemur Avahi meridionalis. From June to December 2004, we conducted 26 nights of focal observation (256.1 h) in Sainte Luce pluvial littoral forest (southeast Madagascar) and recorded feeding behavior of 4 radiocollared individuals. Within the subjects’ home ranges, we recorded vegetation characteristics (morphospecies, phenology, diameter at breast height) and sampled food and nonfood items for chemical analyses. A. meridionalis did not eat fruit but only leaves and flowers and did not base their choice on food abundance. Adult leaves eaten were higher in easily soluble protein than adult leaves that were not consumed. The subjects ate young leaves and flowers as soon as they became available. These young leaves contained the same concentrations of soluble protein, higher concentrations of crude protein, and lower concentrations of acid detergent fiber and sugar than mature food leaves. A. meridionalis ate leaves with condensed tannins, alkaloids, and intermediate concentrations of polyphenolics. Contrary to previous studies that considered Avahi spp. a specialist, A. meridionalis acted as leaf-eating generalists with moderate selectivity, based on nutritional quality and tolerance of a wide array of plant secondary metabolites. This illustrates the dietary flexibility within a single genus of primates that seems to be driven by environmental constraints rather than morphological or physiological adaptations.     

When play is a family business: adult play,hierarchy, and possible stress reduction in common marmosets

Easy to recognize but not easy to define, animal play is a baffling behavior because it has no obvious immediate benefits for the performers. However, the absence of immediate advantages, if true, would leave adult play (costly but maintained by evolution, spanning lemurs to Homo sapiens) unexplained. Although a commonly held view maintains that play is limited by stress, an emergent hypothesis states that play can regulate stress in the short term. Here we explored this hypothesis in a captive family group of New World monkeys, Callithrix jacchus (common marmoset). We observed six subjects and gathered data on aggressive, play, and scratching behavior via focal (6 h/individual) and all occurrences sampling (115 h). We found that play levels were highest during pre-feeding, the period of maximum anxiety due to the forthcoming competition over food. Scratching (the most reliable indicator of stress in primates) and play showed opposite trends along hierarchy, with dominants scratching more and playing less than subordinates. Finally, scratching decreased after play, whereas play appeared to be unrelated to previous scratching events, symptoms of a potential stressful state. In conclusion, both play timing and hierarchical distribution indicate that play limits stress, more than vice versa, at least in the short term.     

Inter-sexual multimodal communication during mating in wild geladas: the leading role of females

Female primates can emit vocalizations associated with mating that can function as honest signals of fertility. Here, we investigated the role of mating calls and visual signals in female geladas (Theropithecus gelada). Because females have a central role in the gelada society and seem to solicit sexual interactions, we answered whether they emit vocalizations in conjunction with gazing to increase mating success probability. Before and during copulations, females can emit pre-copulation calls and copulation calls. For the first time, we identified a new female vocalization emitted at the final stage of copulations (end-copulation call), possibly marking the occurrence of ejaculation. We found that longer pre-copulation call sequences were followed by both prolonged copulations and the presence of end-copulation calls, thus suggesting that females use pre-copulation calls to ensure successful copula completion. Moreover, we found that different combinations of female vocal types and gazing had different effects on male vocal behavior and motivation to complete the copula. The analysis of the vocal and visual signals revealed a complex inter-sexual multimodal chattering with the leading role of females in the signal exchange. Such chattering, led by females, modulates male sexual arousal, thus increasing the probability of the copula success.     

Bonobos Protect and Console Friends and Kin

Post-conflict third-party affiliation has been reported to have different functional meanings, one of them being consolation. Here, we tested the main hypotheses that have been put forth to explain the presence of this phenomenon at a functional level in the bonobo: Self-Protection Hypothesis, Victim-Protection Hypothesis, Relationship-Repair or Substitute for Reconciliation Hypothesis, and Consolation Hypothesis. By analyzing the data collected over 10 years, we investigated what factors affected the distribution of both spontaneous third party affiliation (initiated by the bystander) and solicited third party affiliation (initiated by the victim). We considered factors related to the individual features (sex, rank, age) of victim and bystander, their relationship quality (kinship, affiliation), and the effect that third party affiliation had on the victim (such as protection against further attacks and anxiety reduction). Both spontaneous and solicited third party affiliation reduced the probability of further aggression by group members on the victim (Victim-Protection Hypothesis supported). Yet, only spontaneous affiliation reduced victim anxiety (measured via self-scratching), thus suggesting that the spontaneous gesture – more than the protection itself – works in calming the distressed subject. The victim may perceive the motivational autonomy of the bystander, who does not require an invitation to provide post-conflict affiliative contact. Moreover, spontaneous - but not solicited - third party affiliation was affected by the bond between consoler and victim, being the relationship between consoler and aggressor irrelevant to the phenomenon distribution (Consolation Hypothesis supported). Spontaneous affiliation followed the empathic gradient described for humans, being mostly offered to kin, then friends, then acquaintances. Overall, our findings do not only indicate the consolatory function of spontaneous third-party affiliation but they also suggest that consolation in the bonobo may be an empathy-based phenomenon.