Facilitation between herons and smallmouth bass foraging on common prey

Abstract

Understanding how multiple predators affect one another and their shared prey is an increasingly important goal for ecologists examining predator-prey dynamics and food-web structure. In a field experiment, we examined the outcome of interactions between terrestrial and freshwater predators foraging for the same prey in two temperate North American streams. We used a factorial design to examine the combined foraging effects of herons and smallmouth bass on striped shiners and central stonerollers. We found that there was facilitation between the two predators, resulting in risk-enhancement for the prey species, with particularly pronounced effects on the smallest (<70 mm) size classes. Facilitation is the least well-documented predator-predator interaction and has not been quantitatively demonstrated for freshwater and terrestrial predators.Our results indicate that bass may gain a net benefit from the presence of wading birds such as herons and egrets, and that concerns about the negative effects of birds on fish stocks through competition may be unwarranted.

Facultative predation and scavenging by mammalian carnivores: seasonal, regional and intra‐guild comparisons

“…Nevertheless, facilitation remains the least well‐documented relationship between carnivores (Steinmetz et al. ). What are the consequences for the coexistence of carnivore species in seasonally variable environments?…”

Experimental Removal and Recovery of Subtidal Grazers Highlights the Importance of Functional Redundancy and Temporal Context

“…Only the simultaneous removal of both grazers triggered a transient increase in cover of sessile invertebrates. Such non-additive effects have been observed in field experiments conducted in terrestrial [40] , [41] , freshwater [42] , [43] , and marine [44] , [45] habitats. In our case, we evaluated the magnitude of the non-additive response in the context of three years of seasonal variation.…”

Fish ladders: safe fish passage or hotspot for predation?

“…Turtles were also observed, but the importance of fish in its omnivorous diet is unknown -although fishermen usually The high prey density along the Lajeado fish ladder and the expected state of exhaustion from overcoming the flow was one of the possibilities suggested by Agostinho et al (2007c) to explain the abundance and permanence along the ladder of some migratory and large piscivorous catch turtles using fish baits. Additive and/or emergent effects are expected in such situations (Griffen, 2006;Steinmetz et al, 2008), especially given the apparent concentration of different predator groups with diverse predation strategies and behaviours. In the case of additive effects, the risk of fish being consumed increases with complementary predatory activity, as the fish are exposed to different types of predators (e.g., opportunistic, ambushing, and chasing predators).…”