Trace element intake via soil ingestion in pronghorns and in black-tailed jackrabbits

Abstract

Soil ingestion ratios were estimated for 2 primary herbivore species utilizing a sagebrush ecosystem in southeastern Idaho to determine the relative importance of soil and vegetation pathways in trace element ingestion and to make predictions of the importance of these pathways for toxic and radioactive elemental intake. The mean (mean and 95% CI) soil intake rates for pronghorns (Antilocapra americana) and black-tailed jackrabbits (Lepus californicus) were 48.7 (45.0-52.7) and 9.7 (9.0-10.6) g/day, respectively, with seasonal peaks occurring in spring (March-May) and in fall (August-October). We did not determine whether soil intake resulted from direct soil ingestion or soil attachment to ingested forage. Soil comprised 5.4% and 6.3%, respectively, of the pronghorn and jackrabbit total dry matter intake. Relating trace element concentrations in soil and vegetation to the daily soil and forage intake rates permitted an estimate of the importance of these 2 ingestion pathways. For both pronghorn and jackrabbits, the estimated percentage of elemental intake attributable to soil was 75% (Na, Fe, V, and F) and 10-50% (Mn, Cr, Mg, Ni, K and Zn).