Wieteke Holthuijzen, MSc Student

Hide and Seek: Uncovering the ecological impacts of invasive house mice on Midway Atoll
Sometimes field work gets messy... Wieteke working with a Laysan Albatross chick on Midway Atoll NWR. Photo credit: Greg Joder

Sometimes field work gets messy... Wieteke working with a Laysan Albatross chick on Midway Atoll NWR. Photo credit: Greg Joder

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My research interest lies in the nexus of nature and human presence, especially of seemingly remote flora and fauna that are still affected by human activities. I seek to study the interactions and relationships among abiotic and biotic factors of islands; the threats that face these unique ecosystems (including invasive species, anthropogenic impacts, and climate change); and how to maximize island ecosystem recovery. Specifically, I am interested in understanding the comprehensive influence of introduced house mice on Midway Atoll National Wildlife Refuge (NWR) and develop methods that restore ecological functioning. 

 

Islands are critical areas for biological conservation because they house a disproportional amount of the world’s biodiversity. However, island ecosystems are globally imperiled due to threats posed by invasive mammal introductions. Invasive house mice have ecosystem-altering ramifications on islands upon introduction through depredation of seeds, plants, invertebrates, and even seabirds. Mice impact island species’ distributions, densities, and persistence which in turn alters or disrupts nutrient cycles, symbioses between species, and other ecological processes. Mice can be eradicated from islands, but a critical uncertainty remains regarding island ecosystem response to such conservation interventions. This information is essential because it allows for novel questions about the direct and indirect impacts of mice to be tested. 

 

In December 2015, U.S. Fish and Wildlife Service (USFWS) biologists and volunteers discovered house mice attacking adult nesting Laysan and Black-footed Albatrosses at Midway Atoll NWR, part of Papahānaumokuākea Marine National Monument. Mice attacks have been documented at other islands and on other seabirds, but never at Midway Atoll NWR on adults, incubating albatrosses. House mice are not native to Midway Atoll NWR and were inadvertently introduced to the atoll decades ago. Curiously enough, mice have coexisted among millions of seabirds nesting on the ground, in burrows, and in trees at Midway without obvious conflict—until now. Working with Island Conservation, USFWS is proposing to protect seabirds on Midway Atoll NWR by completely removing the invasive house mouse from the atoll, which is necessary to protect the largest albatross colony in the world as well as 29 other species of birds that rely on this unique Refuge. Collaborating with USFWS, Island Conservation, and the Young Lab at UC Santa Barbara, my graduate work will focus on the broader ecological monitoring  of the mouse eradication on Midway Atoll NWR and quantifying the impacts of mice pre-/post-eradication on island flora and fauna. 

 

On Midway Atoll NWR, removing mice could consequently aid and greatly increase the rate of recovery of various ecological processes, functions, and dynamics more efficiently than current labor-intensive restoration techniques by hand (such as spraying weeds or hand-planting native plants). This eradication presents a unique opportunity to design and implement a pre- and post-control study to understand the comprehensive influence of mice on islands and develop methods that restore ecological functioning. Working collaboratively with eradication practitioners and USFWS, we will employ novel DNA metabarcoding and stable isotope analyses to ascertain mouse diet on  Midway Atoll NWR and consequently use those data to guide ecological monitoring to determine the impacts of mice before and after eradication. Through this project, we will develop new methods for mouse diet analysis that will feed into a predictive framework that identifies the potential ecological effects of mouse eradications and guide future, successful island restoration efforts.

Helping to raise orphan White Terns on Midway Atoll NWr... and helping them figure out the careful act of taking-off and landing. Photo credit: Narongkorn Tassananggulla

Helping to raise orphan White Terns on Midway Atoll NWr... and helping them figure out the careful act of taking-off and landing. Photo credit: Narongkorn Tassananggulla