How Desert Rodents Overcome Halophytic Plant Defenses

Feeding behaviour of Tympanoctomys barrerae, a rodent specialized in consuming Atriplex leaves

“…T. barrerae would use not only the lower incisors but the bundles of stiff hairs as well. The latter anatomical structures are located on either side of the mouth and have been reported as unique to T. barrerae (Mares et al, 1997).…”

“…This species exhibits a low population density and a patchy distribution restricted to salt basins and sand dunes (Ojeda et al, 1996). T. barrerae has become highly specialized in consuming the leaves of halophytic plants, and has evolved several morphoecological adaptations to a desert life style (Mares et al, 1997;Ojeda et al, 1999).…”

A desert octodontid rodent, Tympanoctomys barrerae, uses modified hairs for stripping epidermal tissue from leaves of halophytic plants

“…Tympanoctomys barrerae also has chisel-shaped incisors but, in addition, extending from the palate and occluding with the lower incisors are two bundles of stiffened vibrissae (referred to here as bristle bundles) that vibrate to remove the epidermis from the leaves. Observations of living specimens (Mares et al, 1997b) indicate that this unique apparatus is a much more efficient method of leaf-stripping than that described for D. microps using incisors alone (Kenagy, 1973).The following anatomical study deals specifically with Tympanoctomys barrerae. This is a rare and poorly known octodontid rodent.…”

“…Those that do live in these areas often have special adaptations. A particularly interesting example is the relationship between the halophytic plant, Atriplex (saltbush), and the desert rodents that are specialized to feed on its leaves (Mares et al, 1997b). Atriplex lives in salt flats.…”

“…But such high salt loads are toxic to mammals and would require more water than that provided by the leaves to maintain osmotic balance. Adaptations for overcoming this problem have been described by Mares et al (1997b) in three phylogenetically unrelated species of desert rodents: the chisel-toothed kangaroo rat (Dipodomys microps, family Heteromyidae) of the Great Basin Desert of North America, the fat sand rat (Psammomys obesus, family Muridae) of the Sarah Desert of North Africa, and the red vizcacha rat (Tympanoctomys barrerae, family Octodontidae) of the Monte Desert of Argentina. At least two of the three (D. microps and P. obesus) have evolved kidneys that excrete very concentrated urine, thus eliminating the excess salt taken in with the Atriplex leaves.…”