THE IMPORTANCE OF PREY SIZE AND DENSITY IN AN ENDEMIC PREDATOR PREY COUPLE (LEECH ERPOBDELLA-MONTEZUMA AMPHIPOD HYALELLA-MONTEZUMA)

The rate with which E. montezuma captured H. montezuma was significantly influenced by both prey size and prey density with highest capture rates on juvenile H. montezuma at high prey densities. E. montezuma captured 30 times more energy at high prey densities (80 animals l-1) compared to low prey densities (10 animals l-1), and captured nearly 7 times more energy as juvenile prey compared to adult prey at high density regimes. E. montezuma showed a significantly higher capture rate for the pelagic H. montezuma than it did for the sedentary Hyalella azteca. The highly predictable nightly accumulations of H. montezuma in the surface 1.0 m of Montezuma Well, Arizona, may have provided the stimulus for the synchronized nightly migrations by E. montezuma and the development of its very specialized diet. -from Authors