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 and Island Spotted Skunks

On two of the Channel Islands, island foxes share their ecosystem with island spotted skunks.

The island spotted skunk is smaller than the island fox, and even more elusive. Because the skunk is primarily nocturnal, few people encounter them and, until recently, little was known about them.

When the island fox faced near-extinction on Santa Rosa and Santa Cruz Islands in 2000, people took note of the island spotted skunk for the first time. The first counting of island spotted skunks occurred when they were captured during island fox counting.

When the island fox population was low, the population of island spotted skunks soared. This gathering of spotted-skunk and island-fox cake pops, illustrates the overwhelming number of spotted skunks to island foxes. 

By 2014, however, the foxes were overtaking the skunks in reproduction and survival; island fox numbers almost equaled the estimated number of spotted skunks. As island foxes continued to increase across Santa Rosa and Santa Cruz Islands, the island spotted skunk population continued to decline dramatically. (Or at least, the number of island spotted skunks captured during island fox counting has declined.)

The gathering of cake pops–compiled by researchers Juliann Schamel and Angela Guglielmino–demonstrates how drastic the population shift has become.

What we don't know is: Why? Why have island spotted skunk numbers declined so much? What is the normal population relationship between these two species? Are island foxes out-competing island spotted skunks or is something else at play?

In the past few years, researchers have begun looking into the life and behavior of the island spotted skunk. FIF contributed support to researcher Ellie Boas to supply batteries for the first trap cameras that were put out to capture images of island spotted skunks. Researchers continue to try to capture images of island foxes and spotted skunks interacting, but it has been a challenge.

2020 opened with an important meeting of biologists, wildlife veterinarians, researchers, and invested organizations and institutions to pursue inquiry into the island spotted skunk. Following the example of the Island Fox Conservation Working Group and the successful conservation efforts for the island fox, the group will work to solve questions and develop action plans.

Friends of the Island Fox sends a resounding "Yip, Yip" to the newly formed Island Spotted Skunk Conservation Working Group. 

May we all work together to understand the important relationship between these two unique island species.