The use of operant conditioning to study olfactory species discrimination in two mouse lemur species (M. lehilahytsara and M. murinus)

For nocturnal animals, olfactory communication is of high significance. Mouse lemurs, which live arboreal in dispersed social systems, use scent marking behaviours in different contexts. Since up to two mouse lemur species can co-exist in Malagasy forests, olfactory species recognition should be highly beneficial, since it should help to identify and localize potential conspecific mates. It is, however, unknown, whether urinary species-specific signatures are discriminated by mouse lemurs. Therefore, the aim of this project is to test whether mouse lemurs can discriminate between urine samples containing different species signatures. To achieve this, a non-invasive and low-budget operant conditioning setup was established, using a two-way choice arena, in which up to 15 trials were conducted per animal and day. Initially, 45 captive M. murinus and M. lehilahytsara were screened with regard to their learning motivation, the majority of which (80%) did not pass the habituation criteria within the given timeframe. However, all four finally selected test animals (aged 2-6 yrs), two M. murinus (1 male, 1 female) and two M. lehilahytsara (1 male, 1 female), were successfully trained in a 5-step-conditioning process to discriminate conspecific from heterospecific urine odour. They learned to choose correctly the conspecific urine odour over the heterospecific urine odour, requiring the median of 293 trials over the median of 27.5 test days for training. This study demonstrates the functionality of the established setup despite some methodological limitations. We conclude that mouse lemurs can learn to discriminate speciesspecific olfactory signatures by operant conditioning.