A recent study (H e t h et al. 2002) challenged the idea of “blind” foraging in herbivorous underground dwellers by showing that subterranean rodents of several species use olfaction to discriminate between soils in which plants had or had not been growing. Here we address additional questions about odour-based foraging underground. We tested responses of Zambian mole-rats (Cryptomys anselli and C. kafuensis) to putative carrot kairomones using tunnel T-mazes. Mole-rats distinguished peat moistened with hydroponic as well as filtered hydroponic “carrot water” from peat moistened with distilled water. Furthermore, mole-rats detected carrot kairomones that percolated over the course of a week through the soil to a distance of 30 cm. These results demonstrate that 1) Attractiveness of soil is given by contents of primary root kairomones not caused by microbial activity in planted soil. 2) Carrot-kairomones are water-soluble molecules of less than 0.6 μm diameter. 3) Carrot-kairomones diffuse around the plant, making plants detectable from a distance.
We studied the inner ear of Ctenomys talarum, a small solitary subterranean rodent distributed in the southern region of Buenos Aires Province (Argentina) using standard staining techniques. The inner ear of this subterranean rodent is characterized by a long basilar membrane, a higher density of cochlear receptors in the apical region of the basilar membrane and a gradual increment of the width of the triad of outer hair cells from the base towards the apex. These anatomical features of the cochlea of C. talarum can be interpreted as biomechanical specializations to enhance low-frequency sound reception.