Little rodent, big appetite: Researchers identify the dietary impacts of invasive mice on the Farallon Islands

On an island 30 miles off the coast of San Francisco, a group of mice are packing an ecological wallop much larger than their small statures would suggest. The conclusions of the study were led by LSU Associate Professor of Oceanography and Coastal Sciences Michael Polito. Today's study was published in PeerJ.

Southeast Farallon Island is home to the largest seabird breeding colony in the contiguous United States and is part of the Farallon Islands National Wildlife refuge. During the 1800s or early 1900s, house mice were accidentally introduced to the island. About 50,000 house mice live on the island, which is roughly the size of two football fields. The proposed plan by the US Fish and Wildlife Service to eradicate mice from the South Farallon Islands was supported by the study.

A better understanding of mouse abundance and diet is what the research team discovered.

There was a lack of data on what mice were eating on the island prior to this research.

Scientists used a technique called stable isotope analysis to study the diet of mice.

"As far as I know, mice are what they eat," he said.

The availability of native seabirds, salamanders, insects and vegetation on the island was related to the seasonal abundance of introduced mice.

They conclude that mice are highlyomnivorous and opportunist eaters whose population numbers and diet change dramatically throughout the year in response to changes in food availability and seasonal climate. When the mouse population is low, they eat mostly plants. When the number of mice increases, they eat more native insects and seabirds. In the fall, when the mouse population is high, they compete with the Farallon arboreal salamander, a species found only on the islands, for food. There is a decline in mouse numbers during the winter.

Studies have found that the presence of mice on the islands attracts migratory birds, such as the burrowing owl, which then prey on rare native seabirds. Invasive mice have an outsized impact due to the nature of the environment.

"Native plants and animals can't leave the island to get away from the mice, and these plants and wildlife never had to evolve defensive behaviors against rodents in the way that mainland species have."

The researchers concluded that mice have a wide range of influences on the island.

"Our study provides the latest and most comprehensive understanding of mouse diet and the impacts they're having on the native community," said Pete Warzybok, a co-author of the paper. The findings make a strong case for the eradication of the mice in order to restore the Farallon Islands.

More information: Michael J. Polito et al, Population dynamics and resource availability drive seasonal shifts in the consumptive and competitive impacts of introduced house mice (Mus musculus) on an island ecosystem, PeerJ (2022). DOI: 10.7717/peerj.13904 Journal information: PeerJ Citation: Little rodent, big appetite: Researchers identify the dietary impacts of invasive mice on the Farallon Islands (2022, September 22) retrieved 22 September 2022 from https://phys.org/news/2022-09-rodent-big-appetite-dietary-impacts.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.