Secondary burrow users and indication for possible cache pilferage of Gerbillinae burrows

Abstract Burrowing species are key in many ecosystems because they create niches for species that cannot dig their own shelters. These secondary users rely on existing burrows for protection, particularly in open ecosystems, such as deserts. Although gerbils (subfamily Gerbillinae) are dominant burrowers in the Sahara Desert, their impact on secondary users has not been investigated. We present a field study on secondary use of Gerbillinae burrows, combining surveys and experiments, and examine the cues used to locate burrows. In surveys, we assessed seasonal variation in burrow availability, documented secondary users and their extent of use, and tested whether burrows emit a heat signature that might guide users. In experiments, we used artificial burrows to determine whether potential users rely on thermal, visual or olfactory cues. Surveys revealed that burrow numbers increased as summer progressed and that most secondary users were species capable of digging. Surprisingly, experiments showed that gerbils themselves were most attracted to artificial burrows, suggesting that they may take over conspecific burrows. Moreover, gerbils were drawn only to burrows with freshly dug soil odour and even to plots with disturbed soil but no burrow. Thus, gerbils may frequently act as secondary users, pilfering burrows constructed by other gerbils.