FIF 2023 Research Grant to Help Count Island Spotted Skunks

Friends of the Island Fox received a record number of grant applications this year. Funds were awarded to two projects. Today we highlight:

Desirae Thomaier a masters student in Biological Sciences at Cal Poly San Luis Obispo. 

 

Island foxes share their habitat with island spotted skunks on Santa Cruz and Santa Rosa Islands. When island fox numbers declined due to golden eagles, island spotted skunk numbers increased dramatically. As island fox populations recovered, skunk numbers appeared to decline. 

While some researchers have attempted to follow island spotted skunks with radio-tracking collars, the spotted skunks small size and seasonal weight fluctuations make it difficult to effectively use radio collars. Prior studies recommended wildlife field cameras as a way to potentially quantify the number of island spotted skunks on each island.

Thomaier's project–Occupancy modeling of Island Spotted Skunks on Santa Rosa and Santa Cruz Islands–will deploy 60 field cameras across each island for a full year.

Hopefully, this effort will provide a better accounting of island spotted skunks numbers and how they are "responding to very high fox abundance."

Island spotted skunks are nocturnal. Interactions between island foxes and island spotted skunks under the cover of darkness. Thomaier's cameras may also uncover additional information about the interactions between these two island carnivores.

The series of three photos below were taken over the course of 8 minutes.

One spotted skunk followed less than a minute later by an island fox.

Followed 7 minutes later by two island spotted skunks.

One skunk is in the upper left corner with the second skunk right on its heels. (photos courtesy of Channel Islands National Park)

What is the story here? We really don't know. Hopefully, Thomaier's research project will help provide a more accurate count of island spotted skunk populations and shine a light on the complicated relationship between these two island predators.

Island spotted skunks may deserve separate species status. FIF Research Grant 2022 recipient Julia Owen will be presenting at the California Island Symposium this week in Ventura.

Island Foxes, the U.S. Navy, and Island Spotted Skunks

"Date with a Fox" February 2022

Island foxes on San Clemente Island live with an active U.S. Navy Base, while island foxes on Santa Cruz Island live with island spotted skunks.

FIF's February virtual program "Date with a Fox" featured:

Holly Gamblin a biologist with the Institute for Wildlife Studies  on San Clemente Island. Gamblin provided a rare inside-look at the island foxes on the U.S. Navy island. Few civilians have access to San Clemente Island.

 

Research biologist Ellie Bolas shared her masters' thesis studies on the interactions between island foxes and island spotted skunks. Island spotted skunks live only on Santa Cruz and Santa Rosa Islands. Very little is known about the ecology and behavior of island spotted skunks. How do these two small predators co-exist on the islands?

If you missed the program you can watch the video here:

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See past "Date with a Fox" programs

Island Foxes and Island Spotted Skunks Sharing Space On Santa Cruz Island

 (Thank you to our guest blogger Calypso N. Gagorik, MS in Biology, Northern Arizona University)

On the California Channel Islands, the island fox (Urocyon littoralis) has been hypothesized to compete with the smaller-bodied island spotted skunk (Spilogale gracilis amphiala). Recent declines in spotted skunk captures have led to concerns on population viability and what role the foxes may have played in the decline.

(Calypso worked in the field on Santa Cruz Island with fellow researcher Victor Zhang.) 

From 2018–2019, we GPS and VHF collared foxes and spotted skunks living on Santa Cruz Island to assess space use and deployed remote cameras to examine interactions between the two species at spotted skunk den sites. We also explored monitoring tools for spotted skunk detection with emphasis on remote camera placement and use of scent stations.

We found fox and spotted skunk seasonal home ranges were much larger than previously reported on Santa Cruz Island and spotted skunks moved around the landscape differently compared to foxes.  

Spotted skunks showed restricted movement, using less than 50% of their home range over shorter time periods such as a week or month. Foxed moved widely through the landscape covering more than 50% of their home range over the course of a week. During this time, we collected the first photo evidence that foxes may be disturbing resting sites of spotted skunks during the day. We also found that remote cameras placed on drainage bottoms may be more effective in detecting skunks. We discourage the use of scents at camera stations as foxes appear to be monopolizing the stations by repeated marking.

Our knowledge and understanding of spotted skunk ecology are still limited due to the many challenges of studying a cryptic species. We encourage further studies be conducted on spotted skunks, particularly focusing on interactions of foxes and spotted skunks at den sites.

Calypso Gagorik, MS Biology

Read the full thesis: Spacial Use Patterns And Management Recommendations For Two Endemic California Channel Island Mesocarnivores, The Island Spotted Skunk (Spilogale gracilis amphiala) and the Island Spotted Skunk (Urocyon littoralis)

Friends of the Island Fox provided financial assistance to this research project. 

The deadline for the FIF 2021 Research Grant is August 31, 2021 

More Island Fox Research