Soil preference in blind mole rats in an area of supposed sympatric speciation: do they choose the fertile or the familiar?

Animals become adapted to different habitats, which, under some circumstances, may lead to speciation. Such speciation can possibly take place even in sympatry, as has recently been suggested in the blind mole rat Spalax galili surveyed at a microsite where two soil types of ecologically contrasting characteristics, basaltic soil and rendzina soil, abut each other. Such speciation would be possible if mole rats developed reproductive isolation, for example, by means of habitat choice. In our study, we quantified food supply and soil characteristics of 20 blind mole rat burrow systems in both soils at a new microsite and tested the mole rat's soil preference in a T-maze. The basaltic soil was harder and heavier than the rendzina soil, and had higher density and biomass of food, which is comparable to the published data from the only other studied microsite 3.7 km apart. Mole rats preferred to burrow in their familiar soil, when the tested soils were moist. After the soils were dried, both groups of mole rats tended to burrow preferentially in the rendzina soil, nevertheless, this preference was only significant in rendzina-soil mole rats. We propose that after the suppression of olfactory cues mole rats preferred to burrow in soil with lower energetic costs of burrowing. We suggest that soil preference by mole rats is effective mainly in moist soil that releases specific odorous cues, which coincides with mating season and natal dispersal. This preference could also play an important causative role in reproductive isolation of the two blind mole rat populations.