NIGHT FEEDING BY GUPPIES UNDER PREDATOR RELEASE: EFFECTS ON GROWTH AND DAYTIME COURTSHIP

Abstract

The nonlethal effects of predation threat can be pervasive but are also easily overlooked. We investigated effects of predation threat on feeding by guppies (Poecilia reticulata), and how threat-induced temporal shifts in feeding activity affect reproductive behavior and growth. Contrary to the view of the guppy as a “diurnal” species, our observations revealed that guppies free from severe predation threat expand their foraging into the nocturnal period. We found such nocturnal foraging to be as profitable as diurnal foraging, and guppies under threat incurred a substantial growth penalty when predators inhibited night feeding. Denial of night feeding also decreased daytime courtship by males, facultatively duplicating a classical observation comparing courtship intensity in contrasting predator regimes, but providing a novel mechanism for the effect. Our findings support the view that evaluations of predator effects on life histories should consider potential predator-caused alterations in size-specific energetic gain, along with the classical consideration of predator-altered mortality rates. The results of this study show that predation threat can induce a large, facultative shift in the temporal niche and vital rates of a prey species. We discuss some implications of the effect in the broader contexts of predator facilitation, evolution of life histories, and trait-dependent decisions to boost daily intake by expanded feeding times.