Abstract
BackgroundSpecies recognition, i.e., the ability to distinguish conspecifics from heterospecifics, plays an essential role in reproduction. The role of facial cues for species recognition has been investigated in several non-human primate species except for lemurs. We therefore investigated the role of facial cues for species recognition in wild red-fronted lemurs (Eulemur rufifrons) at Kirindy Forest. We presented adult red-fronted lemurs pictures of male faces from five species including red-fronted lemurs, three closely related species, white-fronted lemurs (E. albifrons), brown lemurs (E. fulvus), rufous brown lemurs (E. rufus), and genetically more distant red-bellied lemurs (E. rubriventer), occurring in allopatry with the study population. We predicted that red-fronted lemurs respond stronger to conspecific than to heterospecific pictures and that females show stronger responses than males. In addition, if genetic drift has played a role in the evolution of facial color patterns in the members of this genus, we predicted that responses of red-fronted lemurs correlate negatively with the genetic distance to the different species stimuli.ResultsRed-fronted lemurs looked significantly longer at pictures of their own species than at those of heterospecifics. Females spent less time looking at pictures of white-fronted, brown and red-bellied lemurs than males did, but not to pictures of red-bellied lemurs and a control stimulus. Individuals also exhibited sniffing behavior while looking at visual stimuli, and the time spent sniffing was significantly longer for pictures of conspecifics compared to those of heterospecifics. Moreover, the time spent looking and sniffing towards the pictures correlated negatively with the genetic distance between their own species and the species presented as stimulus.ConclusionsWe conclude that red-fronted lemurs have the ability for species recognition using visual facial cues, which may allow them to avoid costly interbreeding. If so, sexual selection might have influenced the evolution of facial patterns in eulemurs. Since responses also correlated with genetic distance, our findings suggest a potential role of genetic drift as well as sexual selection in influencing the evolution of facial variation in eulemurs. Because study subjects looked and sniffed towards the presented pictures, red-fronted lemurs might have the ability for multi-modal species recognition.
Highlights
Species recognition, i.e., the ability to distinguish conspecifics from heterospecifics, plays an essential role in reproduction
We presented red-fronted lemurs a color photo of either a conspecific or heterospecific male, i.e., photographs of the closely related white-fronted, brown and rufous brown lemurs, which occur in allopatry, and the more distantly related redbellied lemurs, which occur in allopatry with the study population, but in sympatry with the eastern population of red-fronted lemurs (Table 1)
Females spent significantly less time looking at pictures of white-fronted, brown and red-bellied lemurs than males did, but not at pictures of rufous brown lemurs, which are very similar in facial patterns, and the control (Fig. 2)
Summary
I.e., the ability to distinguish conspecifics from heterospecifics, plays an essential role in reproduction. If genetic drift has played a role in the evolution of facial color patterns in the members of this genus, we predicted that responses of red-fronted lemurs correlate negatively with the genetic distance to the different species stimuli. Several studies have demonstrated the ability of non-human primates to differentiate individuals of their own kin/group from strangers and to discriminate between conspecifics and heterospecifics based on visual cues [2, 21, 31,32,33,34,35]. Chimpanzees (Pan troglodytes) and rhesus macaques (Macaca mulatta) used facial cues in black-and-white photographs presented on a computer screen to discriminate between different individuals [22]. Tonkean macaques (Macaca tonkeana) and brown capuchin monkeys (Cebus apella) were able to discriminate between pictures of conspecific and heterospecific individuals, as inferred by their longer looking time towards pictures of conspecifics [25]
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