Trends in Ecology & Evolution
ReviewPredation landscapes influence migratory prey ecology and evolution
Section snippets
Predators and migratory prey
Animal migrations (see Glossary) are spectacular phenomena where concentrated and conspicuous animal movements often result in striking predator–prey interactions across the migratory life cycle (Figure 1). Predators influence prey ecology and evolution through an integrated process of mortality risk, set by predator communities and habitats, followed by prey perception of risk, which informs their antipredator responses, which further reduce mortality, all balanced by the underlying tradeoff
Predation landscapes for migratory prey
Geographic variation in predator communities and habitat features lays the foundation of mortality risk (sometimes called ‘danger’), which is conveyed to migratory prey through predator cues, allowing an antipredator response, which further lowers resulting mortality risk [1,2]. We consider a predation landscape as the two measurable components of this integrated process: spatially variable mortality risk after the modifying influence of responses (risk landscape) and migratory prey
Risk landscape
Mortality risk varies across the migratory life cycle due to variation in predator communities and habitat features. Migrants often experience high mortality in the migration corridor from conspicuous migratory movements and groups and an obligation to traverse exposed habitats [19,26]. Predator behavior also contributes to spatial patterns of risk. Predators may track migrants along the corridor, as when wolves (Canis lupus) follow migrating caribou (Rangifer tarandus) or when free-tailed bats
Perception of risk
Migrating prey encounter varied and unfamiliar predator cues, challenging accurate perception of risk. As migrants travel along the migration corridor, they continuously encounter unfamiliar environments [3,30]. Even if migrants know the area from prior migrations, they have less information about local risk than animals living in a well-known home range [31]. Furthermore, environmental risk cues likely vary in meaning (risk versus safety) or reliability across the heterogeneous migratory
Response landscape
Prey decide how to respond to risk cues based on individual traits affecting vulnerability and other demands requiring energy. Energetic demands of migration can compete with costs of antipredator behavior. For migrants, costs of antipredator behavior can include immediate energetic costs from engaging in an antipredator response (e.g., flight) or immediate opportunity costs from spending time avoiding predators instead of other activities that benefit fitness (e.g., refueling, traveling,
Ecological and evolutionary consequences
The unique migratory challenges related to mortality risk, perception, and antipredator responses each vary across the migratory life cycle, which drives ecological consequences connected across space and time, depending on where responses and risk occur [49]. Antipredator responses in the migration corridor can alter arrival timing, which may affect growth, survival, or reproductive success at destinations [40,50]. Mortality in risky corridors can affect population demography [26]. High rates
Humans change the risk landscape
Humans alter predator populations and can broadly shift the magnitude of mortality risk across the landscape [60]. Humans introduce non-native predators, which increases risk in new spatial patterns. Climate change also affects predator distributions and risk. Warming spring temperatures caused elderberry (Sambucus racemosa) to flower early and drew brown bears (Ursus arctos) away from migratory salmon (Oncorhynchus nerka) streams [61]. Native top predators, including marine mammals, birds, and
Humans change the response landscape
Human activities can modify the ability of migratory prey to detect and process cues, thereby altering the response landscape. Noise and light pollution can be major challenges for migratory prey as they frequently travel through human-modified landscapes [69]. When migratory songbirds arrived at stopover habitats near simulated traffic noise, some species avoided noisy areas altogether presumably because noise impeded their ability to detect predators and therefore increased mortality risk.
Restoring predation landscapes
To restore healthy predation landscapes for migratory prey, the most sustainable and effective conservation strategies involve habitat restoration because altered habitats are often the ultimate cause of changes that either favor or harm natural predator populations and alter prey vulnerability [7,81]. Protecting key habitats along common migratory routes (e.g., flyways, swimways) can benefit populations of co-migrating predators and prey through increased abundances and more naturally
Concluding remarks
Migratory prey face unique challenges related to predation, presenting ecological constraints and tradeoffs that result in diverse ecological and evolutionary outcomes. To overcome the challenges of responding appropriately to variable and unfamiliar predator cues, migratory prey across taxa utilize social information and learning. The required cognitive mechanisms, the sources of information they use, and the relative importance among cues remain key areas for future research (see Outstanding
Acknowledgments
This paper began as discussions held at the 2019 American Fisheries Society-The Wildlife Society joint meeting. K. Kobayashi generously helped design the figures. This work was supported by a Delta Science Fellowship (funded by the State Water Contractors and California Sea Grant), UCSC Hammett Fellowship Award, the AFS J Frances Allen Award to M.C.S, and the NOAA Cooperative Institute for Marine Ecosystems and Climate. We appreciate the very thorough and constructive feedback from three
Declaration of interests
No interests are declared.
Glossary
- Antipredator response
- any response by a prey animal that reduces mortality risk (e.g., flee, travel in a group, change coloration).
- Fitness rewards
- outcomes of activities that increase an individual’s lifetime reproductive success (e.g., the acquisition of energy from foraging).
- Migration
- animals engaging in persistent directional movement to a new location that repeats cyclically. Applies over any spatial or temporal scale and repetition can occur within or across generations [7,98]. Inclusive of
References (103)
Landscapes of fear: spatial patterns of risk perception and response
Trends Ecol. Evol.
(2019)What explains variation in the strength of behavioral responses to predation risk? A standardized test with large carnivore and ungulate guilds in three ecosystems
Biol. Conserv.
(2019)Energy landscapes and the landscape of fear
Trends Ecol. Evol.
(2017)- et al.
Predicting predator recognition in a changing world
Trends Ecol. Evol.
(2018) School level structural and dynamic adjustments to risk promote information transfer and collective evasion in herring
Anim. Behav.
(2016)- et al.
Novel predation opportunities in anthropogenic landscapes
Anim. Behav.
(2018) Light pollution is a driver of insect declines
Biol. Conserv.
(2020)Survival, dispersal and early migration movements of captive-bred juvenile eastern loggerhead shrikes (Lanius ludovicianus migrans)
Biol. Conserv.
(2010)Birds’ gap-crossing in open matrices depends on landscape structure, tree size, and predation risk
Perspect. Ecol. Conserv.
(2020)Evaluating the efficacy of predator removal in a conflict-prone world
Biol. Conserv.
(2018)