In many ecosystems, a well-balanced yet delicate relationship exists between predators and their prey. Like two dancers anticipating each other’s moves, predator and prey often find themselves entangled in a sophisticated battle for survival, and whoever adapts to the other first holds the advantage. Prey often find ways to avoid, deceive or confront their carnivorous counterparts, and predators find new ways to hijack their defenses. As a result, this never-ending brawl often shifts favor to one side or the other for a variety of reasons that researchers are still trying to pin down.
Aaron Wirsing, professor of environmental and forest sciences at the University of Washington, and a team of scientists from different backgrounds, specialties and locations published an over 20-year collaborative effort in Ecology Letters to better understand this balance and, in doing so, unravel how predators impact whole habitats and species. “Work like this is a testament to the value of collaboration, teamwork and long-term research,” says Wirsing.
The study sheds light on predator-prey interactions from marine to terrestrial ecosystems, vertebrates to invertebrates, and demonstrates Wirsing’s “ecology without borders” research approach. Wirsing proposes that non-consumptive predator effects (NCEs) can be important drivers of shifts in a system’s equilibrium. NCEs can occur both directly or indirectly and are heavily dependent on not only the danger a prey perceives in its immediate surroundings, but also their capacity to avoid it or even fight back. A good example of a NCE is how mule deer and white-tailed deer, when exposed to grey wolves, choose terrain on which they graze based on how well they are able to escape if a wolf shows up. This, in turn, could have a cascading effect on the terrain’s plants, whose growth and propagation can hinder or benefit depending on how much the deer graze in that chosen area.
These anti-predator behaviors, however, do not apply to all animals. For instance, we don’t see them as much in moose, likely because these large animals are capable of directly engaging with a couple of wolves and are unfazed by their presence.
The setting in which predator and prey interact can play an important role in shaping patterns of defensive behavior, as illustrated in another example between tiger sharks and bottlenose dolphins. Turns out, the clarity of the water — or turbidity — can play a role. In the absence of turbidity, or in clearer water, researchers found dolphins are more timid in their activity, as sharks, being prominent visual hunters, dominate the system. In murkier waters after a heat wave, dolphins are more relaxed and freer to search for food thanks to the cover provided by seagrass, which coupled with echolocation allows them to navigate shallow banks and detect sharks without much visibility. Similarities between the wolf and shark case studies point to generalities in the ways prey can adapt their behavior when confronted by the danger of predation, regardless of ecosystem type and species groups.
Wirsing hopes that the concepts presented in this new review paper will allow researchers to develop behavioral models that will help predict the environmental impact of predators in a given system. From a conservation standpoint, these insights offer not only a powerful tool to illustrate the effects of potential ecological disasters like predator extinctions, but also show the importance of successful habitat restoration efforts. By successfully predicting the effects of introducing or removing certain predators in a given ecosystem, researchers will be able to calibrate the impact of their conservation efforts.
Collaboration from researchers all over the spectrum of the field is also a vital aspect of this work, according to Wirsing. “Having ongoing discussions and engaging in a constant cross pollination of ideas with other likeminded researchers, often results in a more general understanding of natural systems,” he says. This open exchange of information between specialists provided the study with a broader pool of expertise to draw ideas from and allowed its authors to compare and study NCEs with a much wider context.
Wirsing’s assessment of predator-prey interactions not only establishes an important framework for predicting the impact a predator can induce in an ecosystem, but also expands the current understanding of how ecological and environmental context interact with how prey species respond to risk. This work also emphasizes the importance of understanding species’ natural history, encouraging future researchers to dive deeper into the study, modeling and predicting many of the hidden patterns found in nature. Understanding how the creatures that surround us, big or small, shape our world will ultimately give us a stronger chance at restoring what has been lost, preserving what still remains and sustaining ourselves because, as Wirsing passionately puts it, “we’re not separate from nature. We are of nature”.
