Conspecific scent marks may influence underground site selection by a fossorial reptile.

Conspecific cues often provide social information on habitat quality that is considered when deciding to settle at a specific site. The type of sensory cues useful for this will depend on the environment. For amphisbaenians, reptiles adapted to an underground life with highly reduced sight, chemoreception is especially useful to recognize conspecifics. Here, we first analyzed the lipophilic compounds from precloacal gland secretions of the amphisbaenian Blanus cinereus, showing that there were sex- and size-related variations in the proportions of the three major compounds. Then, we tested in the laboratory whether there was an underground site selection based on conspecific chemical cues (substrate scent marks) in two different contexts. In loose substrates, both male and female amphisbaenians tended to choose first the scent-marked substrates more often when the individual that produced the scent, independently of its sex, was relatively larger than the focal individual. In contrast, inside semi-permanent galleries, males, but not females, chose the scent-marked gallery more often when the scent donor, independently of its sex, was relatively smaller. These results suggest that the proportions of compounds in scent marks may allow amphisbaenians to estimate the body size of the producer and that this information affects their site selection decisions. However, the different substrate-dependent responses suggest a different meaning and usefulness of scent marks depending on the context. Significance statement: The presence of your conspecific in a site may indicate that this is a "quality" site to live in. If you are blind and live underground, smell is one of the best options for detecting conspecifics and assessing how good are your surroundings. Here, we test whether a blind amphisbaenian reptile that spends its life buried in sandy substrates uses conspecific chemical stimuli to choose where to settle. We found that this decision is influenced by the microhabitat type, sex, and the size difference between the individual that sniffs and the producer of the scent. Amphisbaenians seem to detect and assess conspecific traits based on the differences in compounds in their odors. Therefore, using conspecific scent to assess habitat quality may help fossorial animals to live underground. [ABSTRACT FROM AUTHOR]