Improving joint species recovery

Credit to Jeremy Cohen, Osprey

The rate of species extinctions and declines continues to rise at an alarming rate. Reversing these dire trends with limited conservation funds requires management efforts that lead to effective and long-lasting population recoveries. In collaboration with U.S. Geographical Survey and the National Park Service, we combined nest occupancy and reproductive data in an Integrated Population Model to demonstrate that managing individual nests, scales-up to faster population recovery of bald eagles (Cruz et al. 2018, J. Applied Ecol.). We used hierarchical models and Bayesian variable selection to evaluate the top-down (i.e., recovering bald eagles) and bottom-up factors (i.e., food, weather and nesting habitat) influencing the joint recovery of osprey and great blue herons over 26 years in Minnesota (Cruz et al. 2019, J. Animal Ecol.). The recovery of bald eagles hindered the recovery of ospreys and herons. The ecosystem benefits of returning top predators to ecosystems therefore requires multi-species management. Nonetheless, conservation of terrestrial ecosystems is largely driven by single-species approaches. As part of future research, the lab aims to address key questions including: How are interactions of recovering species mediated by ecosystem-context? Which factors are required to facilitate the sustained recovery of multiple species? ​

Bottom-up benefits of habitat restoration

Habitat loss and modification remain as key drivers of species declines and extinctions worldwide. Restoration efforts aim to reverse these trends with the assumption that if habitat is restored, animals will eventually return too; but this is seldom assessed. Part of the challenge is that survey techniques are costly and time consuming, and are therefore often implemented in areas that are too small to assess impacts of landscape-level habitat change. The lab is currently evaluating how habitat modification at the Morley Nelson Snake River Birds of Prey National Conservation Area has impacted Prairie Falcon foraging decisions (using GPS-GSM transmitters), and the abundance and adaptive capability of their main prey, Piute ground squirrels. We will also validate novel techniques for surveying ground squirrels against estimates of abundance derived from trapping. By understanding how habitat changes have modified predator foraging choices in relation to prey abundance and adaptability, we can guide conservation efforts to ensure that restoration scales up to higher trophic levels and promotes overall ecosystem health. This project is a collaboration between our lab, USGS and the Department of Defense.

Interactions among raptor species

Great Horned Owls are the most common and widespread owl species in North America. They are also dominant competitors and intra-guild predators of other raptors. Our lab will quantify how habitat and anthropogenic disturbance mediate interactions between Great Horned Owls and subordinate species including Mexican Spotted Owls (in the Grand Canyon National Park) and Aplomado Falcons (in Texas). These projects are in collaboration with the National Park Service and The Peregrine Fund.   

Mexican Spotted Owls

Minimizing threats and increasing resilience in invaded ecosystems

Eastern Barred Bandicoot

Invasive species drive species declines and extinctions worldwide. Their impacts are varied depending on the identity and diversity of native species in the system (Cruz et al. 2013 Bio. Conserv.), habitat complexity, climatic conditions, and the presence of other invasive species. For example, increased rabbit numbers support increased numbers of feral cats (Cruz et al. 2013 Plos ONE). Controlling rabbits may thus be more effective than controlling feral cats. Knowledge of how native species respond to invasive species can also guide management efforts. For example, brushtail possums (native prey) responsed to predation risk from multiple invasive predators by travelling closer to trees that they could use as escape routes (Cruz et al. 2013 Behav. Ecol. & Sociobio.). Reduced logging of native forests may therefore indirectly alleviate impacts of foxes and feral cats in this system. The lab will aim to build on previous work to inform efforts that mitigate invasive species impacts and improve native species resilience. Key questions include: Which conditions mitigate invasive species impacts? For example, can increased habitat complexity provide effective refugia against invasive species? How do invasive-native and invasive-invasive interactions influence overall impacts?