How does a lemur's sense of smell help?

The sense of smell, or olfaction, is highly important to lemurs and is frequently used in communication.] Lemurs have long snouts (compared to the short snouts of haplorrhines) that are traditionally thought to position the nose for better sifting of smells, although long snouts do not necessarily translate into high olfactory acuity since its not the relative size of the nasal cavity that correlates with smell, but the density of olfactory receptors.Instead, the long snouts may facilitate better chewing.

Lemurs generally have a wet nose, orrhinarium, as well as a longer snout than anthropoid primates.

The wet nose, or rhinarium, is a trait shared with other strepsirrhines and many other mammals, but not with haplorrhine primates.Although it is claimed to enhance the sense of smell, it is actually a touch-based sense organ that connects with a well-developed vomeronasal organ(VNO). Since pheromones are usually large, non-volatile molecules, the rhinarium is used to touch a scent-marked object and transfer the pheromone molecules down the philtrum (the nasal mid-line cleft) to the VNO via the nasopalatine ducts that travel through the incisive foramen of the hard palate.

To communicate with smell, which is useful at night, lemurs will scent mark with urine as well asscent glands located on the wrists, inside elbow, genital regions, or the neck. The scrotal skin of most male lemurs has scent glands Ruffed lemurs (genus Varecia) and male sifakas have a gland at the base of their neck, while the greater bamboo lemur (Prolemur simus) and the ring-tailed lemur have glands inside the upper arms near the axilla. Male ring-tailed lemurs also have scent glands on the inside of their forearms, adjacent to a thorn-like spur, which they use to gouge, and simultaneously, scent-mark tree branches. They will also wipe their tails between their forearms and then engage in "stink fights" by waving their tail as their opponents.