Red-fronted lemurs can recognise their own species in photographs.

Many species of lemur have distinctively patterned faces with variously coloured beards, muzzles and cheeks. Red-fronted lemurs (Eulemur rufifrons) have a dark muzzle and a reddish-brown head, with golden eyes.

A study by researchers from the German Primate Centre in Göttingen, published in the journal BMC Evolutionary Biology, suggests that the facial patterns of closely related lemur species could have a functional role in species recognition and mate selection. The study found that when red-fronted lemurs were shown photos of their own and closely related species, they spent significantly more time looking at the former than the latter.

Recognising one’s own species before mating sounds like a no-brainer. It is important to avoid going through the costly waste of time of mating with the wrong animal, thereby producing hybrid offspring.

The scientists made their findings by visiting the Kirindy forest of western Madagascar and showing wild red-fronted lemurs headshots of their own species and of three closely related ones (white-fronted, brown and rufous brown lemurs), as well as the more distantly related red-bellied lemur.

The heads were isolated against a grey background. A white circle on a grey background was used as a control.

All the photos were presented to the wild lemurs so that the each animal was seeing them at “face-height”. Each lemur was only shown one photo at a time, with two days elapsing before the next was displayed.

The researchers found that the level of interest shown in the photos appeared to correspond with the amount of genetic relatedness: the closer the species pictured, the more time the lemurs spent looking at the photos.

Lead author Hanitriniaina Rakotonirina says, “We were surprised to find that the animals appear to be able to differentiate among closely related sister species. For example, males of the rufous brown lemur and the red-fronted lemur are difficult to distinguish by the human eye. However, we found that lemurs seem to be able to do it.”

Other cues besides visual may be at work. The authors found that red-fronted lemurs also spent more time sniffing at pictures of their own species than pictures of other species. Rakotonirina notes that this “cross-modal recognition appears to play an important role for species recognition; an interesting subject to study in the future.”