Predator-prey interactions in complex communities

Disentangling predator-prey interactions and restoring functional ecological relationships

Large apex predators are being driven towards extinction at an alarming rate: due to their unique biology, these carnivores are often the first species to succumb to anthropological pressures. When predators go extinct, we lose not only the species itself, but also the ecological relationships between that species and other members of its community (a process known as “trophic downgrading”).

The relationships between predators and prey play an important role in structuring ecological communities, with predators influencing the dynamics of their prey in ways that cascade through ecosystems to affect processes such as productivity, biodiversity, nutrient cycling, disease dynamics, carbon storage, and more. It is becoming increasingly important to understand these trophic connections in order to conserve functional ecological relationships or predict the ecosystem-wide consequences if these interactions disappear.

Predators shape ecosystems by modifying the dynamics of their prey directly and indirectly. Directly, predators reduce the number of prey by consuming individual prey animals. Fewer prey translates into decreased impact on their community. Indirect pathways operate when predators induce risk-mitigating behaviors in prey, changing where and how prey interact with their landscape. Due to the logistical challenges of observing or experimentally manipulating large, wide-ranging species, we have a poor understanding of how these pathways operate in natural systems. One of the primary issues faced by researchers examining at these relationships is the complexity of natural communities. In nature, prey have to handle risk from multiple predators simultaneously and predators have to compete with each other for access to prey. We often resort to studying predator-prey pairs in isolation, but by disregarding significant interplay among multiple predators and prey, mechanisms that drive community dynamics can be obscured.

Lion Center team member Dr. Meredith Palmer is using a combination of camera trap surveys, radio collar data, and experimental manipulations performed across Africa to unravel predator-prey relationships in complex communities. She is working in some of the last remaining areas with intact carnivore guilds as well as parks and reserves which have lost top predators or are actively trying to restore complete predator communities. Disentangling the multiple pathways by which predators affect prey in intact systems will enable us to predict how adding or removing predators might influence prey dynamics and ecosystem functioning in these degraded systems. Her work will not only shed light on the complicated web of interactions tying large mammal communities together, but will have important implications for ongoing conservation efforts.