chapter  17
35 Pages

Predator–Prey Interactions

ByMichael R. Heithaus

CONTENTS 17.1 Introduction .................................................................................................................................. 488 17.2 Elasmobranchs as Prey................................................................................................................. 488

17.2.1 Predators of Elasmobranchs............................................................................................ 488 17.2.2 Avoiding Predators.......................................................................................................... 488

17.2.2.1 Habitat Use....................................................................................................... 489 17.2.2.2 Activity Levels and Patterns ............................................................................ 490 17.2.2.3 Hiding and Crypsis .......................................................................................... 490 17.2.2.4 Group Formation.............................................................................................. 490 17.2.2.5 Vigilance........................................................................................................... 491 17.2.2.6 Deterrence and Defense................................................................................... 491 17.2.2.7 Flight ................................................................................................................ 492

17.2.3 Apparent Competition..................................................................................................... 492 17.3 Elasmobranchs as Predators......................................................................................................... 492

17.3.1 Diets of Elasmobranchs and Optimal Diet Theory ........................................................ 493 17.3.2 Finding Prey .................................................................................................................... 494

17.3.2.1 Habitat Use....................................................................................................... 494 17.3.2.2 Search Patterns................................................................................................. 497 17.3.2.3 Activity Levels and Patterns ............................................................................ 497

17.3.3 Capturing and Consuming Prey...................................................................................... 498 17.3.3.1 Stalking and Ambush ....................................................................................... 498 17.3.3.2 Prey Herding and Manipulation ...................................................................... 499 17.3.3.3 Prey Debilitation .............................................................................................. 499 17.3.3.4 Benthic Foraging.............................................................................................. 500 17.3.3.5 Batch Feeding .................................................................................................. 500 17.3.3.6 Ectoparasitism .................................................................................................. 500 17.3.3.7 Scavenging ....................................................................................................... 500 17.3.3.8 Group Foraging ................................................................................................ 501

17.3.4 Competition ..................................................................................................................... 501 17.3.5 Foraging Trade-Offs ........................................................................................................ 502

17.3.5.1 Foraging-Safety Trade-Offs............................................................................. 502 17.3.5.2 Foraging-Reproduction Trade-Offs ................................................................. 504 17.3.5.3 Intraguild Predation ......................................................................................... 504

17.3.6 Variation in Feeding Strategies and Tactics ................................................................... 505 17.3.6.1 Ontogenetic Variation....................................................................................... 505 17.3.6.2 Inter-and Intraindividual Variation ................................................................. 505

17.4 Regulation of Elasmobranch Populations.................................................................................... 505 17.5 Role of Elasmobranchs in Marine Ecosystems ........................................................................... 506

17.5.1 Density-Mediated Effects................................................................................................ 507 17.5.2 Behavior-Mediated Effects.............................................................................................. 509 17.5.3 Community Consequences of Elasmobranch Predation ................................................ 510

17.6 Summary....................................................................................................................................... 512 References .............................................................................................................................................. 512

17.1 Introduction Predator-prey interactions play a central role in the behavior, ecology, and population biology of most taxa and are critical in community dynamics. For elasmobranchs, most studies focus only on their role as a predator. This is an important oversight as most species are both predator and prey, at least for periods of their life history. In this chapter I place predator-prey interactions in the rich theoretical framework that has developed over the last several decades, from both a behavioral and a trophic perspective. Rather than compiling an exhaustive list of predator-prey interactions, I develop a framework for these interactions highlighting relevant elasmobranch examples. While there have been intriguing studies, there is much work to do and I hope that this chapter will help stimulate studies based on hypothesis testing that will help answer unresolved issues in the behavior and ecology of elasmobranchs.