Renal Morphology of Sympatric Suiforms: Implications for Competition

We assessed the ability to conserve water in collared peccaries ( Tayassu tajacu ) and feral hogs ( Sus scrofa ) by comparing renal morphology in free-ranging populations living sympatrically in southern Texas. These ecologically similar species coexist in a hot, semi-arid environment in which ability to conserve water may provide a competitive advantage. Kidneys of collared peccaries had relatively larger and thicker medullae and presumably a greater capacity to concentrate urine than feral hogs. Renal indices of peccaries were similar to values predicted by allometric functions, whereas indices of hogs were smaller than predicted. Renal mass in hogs, when scaled by (body mass)0.85, was larger than that of peccaries. Indices of renal function from this study were greater than values reported previously for these species. Geographic variation and adaptation during growth may play a role in renal morphology. Genetic constraints probably control large-scale differences, constraining feral hogs to being less suited to water-stressed environments. Results were consistent with predictions that peccaries should have a competitive advantage over hogs in xeric environments with minimal surface water because of ecophysiology. However, a suite of environmental, behavioral, and functional factors appears to control competitive interactions between native peccaries and introduced hogs.