In a system with alternate prey, predator population may:
Alternative prey can maintain or increase predator numbers even while the principal prey declines because the predator’s energy intake depends on the total accessible resource base. Generalists may switch toward the alternative, and reproduction or survival supported by that food can offset losses caused by scarcity of the main prey. In a multispecies growth equation, positive contributions from alternative prey can keep predator per-capita growth above mortality. Predator abundance is therefore neither necessarily constant nor unaffected by the main prey’s decline. This subsidy can have an im
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 14