A Nose for Identifying a Species

Last December, Friends of the Island Fox worked with The Nature Conservancy and Working Dogs 4 Conservation on a project to see if a specially trained dog could track down island spotted skunk dens and scat. (See Moose the conservation working dog)

courtesy of TNC and WD4C

 

In the initial project, Moose used his specially trained nose to locate 11 scat samples. Two scat samples were also found by humans. The samples were sent to the Genetics Lab at UC Davis and Friends of the Island Fox helped fund the genetic testing of the samples. How well did Moose do identifying island spotted skunk scat from island fox scat?

Moose: 9 out of the 11 scats came from island spotted skunks. 1 sample was too degraded for DNA analysis (it might have been skunk) and 1 sample was island fox scat. 90% accurate!

Humans: 1 of the 2 scats came from an island spotted skunk, the other was island fox. 50% accurate!

 

Obviously, Moose is better than humans at detecting island spotted skunk scat.

island fox scat

The next questions: 

• Is there enough quality DNA in a scat sample to determine the identity of an individual island spotted skunk?
• It would cost $7,000 to develop island spotted skunk genetic markers to determine individuals. Can enough scat be located to establish a population estimate and would it be fiscally feasible to count the population this way?

 

The other information obtained from the scat samples pertains to diet. Island spotted skunk scat was compared with island fox scat. Stay tuned for more on metabarcoding.

Why do we need to count island spotted skunks?

Conservation Working Dogs and Zoos Helping Wildlife

photo courtesy of TNC and WD4C

 

Meet “Moose” a hard-working canine with the nonprofit organization Working Dogs for Conservation (WD4C).

Moose recently completed a tour of duty on Santa Cruz Island as part of a multi-organizational effort to find a better way to gather information on island spotted skunks.

Island spotted skunks only live on Santa Rosa and Santa Cruz Islands. As island foxes recovered on these islands, island spotted skunks seemed to have declined. There is concern for these rare little skunks and a lack of understanding about their relationship with island foxes. Do island foxes directly impact island spotted skunks? Do they compete for similar resources?

Friends of the Island Fox has supported several research investigations into this relationship:

• C. Gagorik and V Zhang: "Examining habitat use and movement patterns of island foxes and island spotted skunks on Santa Cruz Island”
• J. Schammel: Dietary overlap and change between island foxes and island spotted skunks on Santa Rosa Island
• J. Owen: Genetic relationships of spotted skunk subspecies
• D. Thomaier: Occupancy modeling of island spotted skunks on Santa Rosa and Santa Cruz Islands using field cameras 

In 2024, the question arose about western spotted skunks in captivity that might participate in research studies as a control for island spotted skunks. FIF’s Education Director, Keri Dearborn, did an internet search and found “Boo” a female western spotted skunk at the Sequoia Park Zoo. Boo and her two brothers had been orphaned when they were very young. Though they were rescued, they became imprinted on humans and couldn’t be returned to the wild. Boo was living at the Sequoia Park Zoo in Eureka and her two brothers were at the Turtle Bay Exploration Park near Redding.

 

While Thomaier’s field cameras have documented island spotted skunks, to-date identifying individual skunks in images has been very difficult. Island spotted skunks push off radio collars and typically avoid capture.

Lara Brenner, Island Scientist with The Nature Conservancy, had been working with a conservation dog to sniff out invasive Argentine ant colonies on Santa Cruz Island. Could a conservation working dog locate island spotted skunk dens? Finding scat and dens would be less invasive than capturing skunks and might open up a whole new way to determine their numbers.

Moose gets suited up for work

 

Moose had experience tracking grizzly bears and locating their dens. Could he do the same job for tiny island spotted skunks? Protocol for a test was put in place. Because island foxes are susceptible to canine diseases and because island foxes can be a source of disease for dogs, Moose was up-to-date on all of his vaccinations.

The two zoos collected soiled bedding and feces from the three western spotted skunks. The fragrant material was sent to a WD4C training location in Montana, where Moose learned to identify spotted skunk scent. Would the western spotted skunk scent be close enough to the island spotted skunk scent for Moose to be successful?

 

Toward the end of 2024, Moose and his handler traveled to Santa Cruz Island. Moose “hit the ground running,” Brenner says. As a conservation working dog, he wears a special harness with bells and a GPS locator. Brenner explains that the GPS locator “is so that we can record his tracks and understand [his] search effort… i.e. how far does Moose have to go and how long does he have to sniff before he finds a skunk?”

On the first day, Moose signaled his handler that he’d found an island spotted skunk den. 

Working the hillsides with a canine nose, detection dogs are more efficient than people and have a higher success rate locating a target species. Over three weeks, Moose found several den sites, including this one with an island spotted skunk at home, and 12 scats.

Island spotted skunk in den (courtesy of TNC)

Can DNA from the scats identify individual island spotted skunks? Can genetic meta-barcoding of scat samples identify specific dietary items for island spotted skunks and island foxes? We’re just at the tip of learning how working dogs like Moose can contribute to island conservation?

courtesy of TNC and WD4C

 

This project is a multi-institutional collaboration between Sequoia Park Zoo, Turtle Bay Exploration Park, The Nature Conservancy, Working Dogs for Conservation, and Friends of the Island Fox. The biggest credit goes to the four-footed collaborators: the three western spotted skunks who are helping their wild counterparts and a very talented working dog named Moose.

Unexpected Creatures During Island Fox Counting - Part 4

Welcome guest blogger Jessica Sanchez, wildlife veterinarian and FIF Board Member. She's explained how island foxes are captured annually in Part 1, shown how a fox's body condition is evaluated in Part 2, and demonstrated health procedures preformed on island foxes during an annual health check in Part 3. As she explains, she might be out capturing island foxes, but they aren't the only animals she encounters.

We also catch island spotted skunks, although this has become rarer in recent years.

You know you have caught a skunk even before you get to the trap because...

1. of the smell
2. they ball up all the grass and vegetation in the trap to make a cozy little nest for themselves
   

If you're lucky, they will still be asleep in this nest when you approach the trap the next morning. All of this gives you time to pause and carefully plan your approach to getting them out of the humane box trap. 

Skunks also get a microchip for identification and we take a tiny 2–3mm biopsy of the ear, with a special cartilage snip device, for genetic testing. Then they receive a thorough exam. (similar to island foxes) We try to handle the little skunks carefully so they don't spray us–this is for our benefit and theirs as it can take up to a couple of weeks for skunks to regenerate their spray and they need it to defend themselves. 

Currently, island spotted skunks are not vaccinated, though researchers are investigating options to potentially do so in the future.

Island spotted skunks aren't the only surprise that might be found in a box trap set out for island foxes. See what else Sanchez has found:

 

An island scrub-jay!

The final steps of a long day catching island foxes are to wash off any skunk spray and/or fleas, check yourself for ticks, enjoy a beautiful sunset, and get a good night's sleep before doing it again the next day! - Jessica Sanchez

Part 1 - capturing island foxes

Part 2 - Health Check: body condition

Part 3 - Health Check: veterinary procedures

 

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:

To participate in FIF's "Date with a Fox" in May - join our donor list or subscribe to our e-newsletter.

See past "Date with a Fox" programs

Investigating the Relationship Between Island Foxes and Island Spotted Skunks

Islands typically support few terrestrial, or ground-living, carnivores due to the challenges of traveling over water to arrive on islands. On Santa Cruz and Santa Rosa Islands we have the rare occurrence of  two insular carnivores: the island fox and the island spotted skunk (Spilogale gracilis amphialus).

How the skunk got to the islands remains unclear, yet evidence has shown they have existed with the foxes for at least 7,000 years. (Fox arrival on the islands)

The spotted skunk and island fox are rivals, competing for the same resources in the form of aggression and predation. Averaging 3–4 lbs on the northern islands, the island fox is the larger and more dominate species. Island spotted skunks are about half the size. However, there is little understanding of when and where these two species interact.

In 2020, Friends of the Island Fox provided some funding to aid in a better understanding of the activity pattern of skunks and foxes on Santa Cruz Island. (More on FIF Research Grants)

Modern Global Positioning Satellite (GPS) collar technology can now capture additional information from wildlife that was not previously accessible–including accelerometers, which measure the forces of active movement. In this study, several foxes and skunks were fitted with GPS and accelerometer enabled collars to map the movement of each species with the aim of revealing the environmental factors that are most important in driving the fox's activity, such as changes in temperature, reproduction, and/or competition.

Researcher Calypso Gagorik with island spotted skunk

Calypso Gagorik, the project's principle investigator, says: "Given that the spotted skunks are strictly nocturnal, the chance of fox-skunk encounters may be entirely driven by changes in daily fox activity patterns."

skunk radio collar

The map below shows the GPS data points of one spotted skunk and one island fox that have overlapping home ranges. (Red dots represent island fox locations and Blue indicators are island spotted skunk locations. Skunk locations are taken less frequently because the batteries on their collars are considerably smaller. Each GPS location mark requires battery use.) What still needs to be analyzed is whether the fox and skunk were active at the same time of the day.

 

The importance of this research according to Gagorik, is "if foxes and skunks utilize similar area, but are active at totally different times, then the chance of interspecific interactions may actually be quite low." In other words, an island fox might visit a water source during the day, while the island spotted skunk might drink from the same location at night.

Researcher Victor Zhang with spotted skunk

Previous accelerometer data that was collected in 2019 have informed Gagorik and, fellow researcher, Victor Zhang "that the timing of daily fox activity varies greatly across the year, and the current analyses (completion summer 2021) will aim to reveal the environmental factors that are most important in driving changes in fox activity timing." Island foxes may be hunting prey at night during the winter and feeding on fruit during the day in summer. Gagorik adds, "Knowledge of these relationships will allow us to better predict the behavioral responses of both species to environmental change, as well as generate new knowledge on fox and skunk ecology." (Calypso Gagorik, email communication).

Previous data has shown that foxes occupy a flexible niche within the island community. They possess the ability to take advantage of the various habitat types, which make up the Channel Islands. On the other hand, the island spotted skunk may have a more specialized niche driven by fox activity.

Friends of the Island Fox is committed to research that will expand understanding of island fox biology and behavior. The more we know about island foxes the better we will ensure a future for both species.

 

"Examining temporal niche and movement patterns of the island fox (Urocyon littoralis) and the island spotted skunk (Spilogale gracilis amphiala) on Santa Cruz Island, CA" was investigated by Calypso Gagorik and Victor Zhang in conjunction with Northern Arizona University and under the supervision of The Nature Conservancy.

FIF is accepting applications for our 2021 Research Grant thru August 31, 2021

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.

Fox Foto Friday - Foxes and Spotted Skunks

How can we enter the world of the island fox and the other animals that live on the Channel Islands without disturbing their natural behavior? One way is with strategically placed movement-activated cameras.

Researchers found an area with evidence of island fox activity. Evidence like tracks and scat. They positioned the special camera and left it to document the animals that walked past. Not only was an island fox using this area of Santa Rosa Island, so were the two spotted skunks, pictured below. Both were using the area at night.

Notice that the dates on the two images are months apart. Still, images like these are helping to provide information to better understand the interactions between species and the species themselves. Island spotted skunks are considered solitary creatures, yet the image captured two together. The biologists titled this image a "rumble." What brought these two skunks together? Territorial dispute? Mating season? There is so much to learn about the lives of island foxes and their neighbors.