Improving joint species recovery

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? For example, does habitat complexity, or prey availability facilitate joint recovery of competitors? 

  • Which factors are required to facilitate the sustained recovery of multiple species? 

Osprey, credit to Jeremy Cohen

Ecological consequences of intra- and inter-specific variability

Approaches that average population and community responses are important to discerning broad ecological patterns but risk masking inter- and intra-specific variability that may be key to conservation success. In past research I have focused on evaluating how individuals and species vary in their response to threats and management. In future work, my lab will combine state-of-the-art quantitative approaches with field experiments and observations to address key questions including:

  • What are the demographic consequences of intra- and inter-specific variability for threatened species? How can this knowledge guide more effective conservation efforts?

  • Are species responses to threats, climate, and management related to their functional traits? Can we use these to borrow information across species?

Burrowing owls, credit to Eden Ravecca.

Minimizing threats and increasing species resilience in invaded ecosystems

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?

Brushtail possum, edited

Knowledge of these interactions is crucial to mitigating unintended impacts of management efforts, and may provide alternative management approaches, such as removal of invasive prey to reduce impacts of invasive predators. I have strong collaborations with government agencies in Australia and New Zealand that are currently addressing some of these challenges.

Quantitative Conservation Lab       

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