Thursday, May 16, 2024

What is Island Fox Density?


Density is a term used in biology to express the number of individual living things in a given area. Biologists use a defined area size–ie. a square meter, square kilometer or square hectare–to quantify density. 

A square kilometer is equivalent to the footprint of Disneyland in southern California and a square hectare is equivalent to a professional baseball field.

Understanding how many island foxes are living in a square kilometer is part of the calculation for estimating the size of an island-wide population.

At the recent Island Fox Conservation Working Group Meeting, land managers reported on the island fox density for their islands. There was a noticeable difference between northern and southern islands.

Northern islands are reporting considerably higher island fox density. The causes for this are not completely clear. Northern islands may benefit from less extreme weather–higher average rainfall and more moderate summer temperatures–which support diverse prey and plant food for island foxes. Northern islands also have fewer impacts from humans; Catalina Island and the two Navy islands, San Clemente and San Miguel, have roads and cars that cause the highest percentage of fatalities for island foxes. 

High density, however, can have a downside. Catalina Island has been stable for the past 10 years with a density around 9 foxes per sq km. The island with the highest density in 2023–14 foxes per sq km–was also the smallest, San Miguel Island. When density increases, individual island fox territory decreases. A smaller territory means a smaller area to find food. High density can push some individuals into habitats with fewer quality resources. San Miguel's resources are less diverse than the larger islands and there are fewer options for foxes when drought or other weather extremes occur.


When island foxes are living closer to each other, the possibility of disease moving rapidly through a population also becomes heightened. Parasites can spread more easily.

Understanding population density is important for calculating risks to populations and making informed conservation decisions. 

Friday, May 10, 2024

Date With A Fox - Island Fox Research with Juliann Schamel and Dr. Alexandria DeCandia

Friends of the Island Fox's Virtual Program on current island fox research.

"Date With A Fox"

with guests Juliann Schamel and Dr. Alexandra DeCandia

from Tuesday, April 30th

The April program highlighted current findings on island fox diet and microbiome. Microbiome investigations can help us understand how island foxes and island spotted skunks are using resources in the island ecosystem. Dietary investigations analyzing stable isotopes in whisker samples are revealing changes in island fox diet as their population size recovers and potential resource competition with island spotted skunks. 

Both research presenters are past recipients of Friends of the Island Fox Research Grants.




Dr. Alexandra DeCandia is an Assistant Teaching Professor in the Biology Dept. at Georgetown University and works with the Center for Conservation Genomics at the Smithsonian's National Zoo and Conservation Biology Institute. Her work has been published in Molecular Ecology and she is currently working on a joint project with Juliann Schamel supported by Friends of the Island Fox.


Juliann Schamel is a Biological Science Technician working with island foxes at Channel Islands National Park and a graduate student in ecology and conservation at the University of Aberdeen, Scotland. Her work has been published in PLOS ONE and she presented a poster on island fox and island spotted skunk dietary overlap at the California Island Symposium. 

Informed conservation decisions for island foxes and island spotted skunks depend on scientific knowledge.

Friends of the Island Fox is currently 

accepting applications for our 2024 FIF Research Grant.

Subscribe to the FIF bi-monthly e-newsletter for invitations to upcoming "Date with a Fox" presentations.