Thursday, January 25, 2024

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


Monday, January 22, 2024

Island Fox Gets a Health Check - Part 3

Welcome guest blogger Jessica Sanchez, wildlife veterinarian and FIF Board Member. She's explained how island foxes are captured annually in Part 1 and shown how a fox's body condition is evaluated in Part 2. But an island fox health check includes additional health measures.

We check the foxes for ectoparasites such as ticks, fleas, mites, and lice. We comb their fur to find fleas, and pay special attention to their ears, armpits, and belly area–where lice and ticks are often found. 

Ticks are collected so we can identify the species and test them for viruses or bacteria they might be carrying. Since ticks can feed on multiple hosts in their lifetime, testing the ticks tells us about what diseases the island spotted skunks, deermice, and other island species might be exposed to as well. 



We take a look in the fox's ears using an otoscope, just like the doctor uses to examine your ear canal. On Santa Catalina Island, where ear mites introduced by feral cats have been associated with ear tumors, foxes are treated with a topical medication to kill ear mites and reduce inflammation in the ear canal.

We collect blood from the jugular vein. This is used to test for exposure to disease, genetic analyses, and to look at other health parameters like liver and kidney function.

One of the most important steps is to administer vaccinations. A subset of the population is vaccinated every year for rabies and canine distemper virus. Neither disease is currently found on the Channel Islands, but we vaccinate as a preventative measure after the Santa Catalina Island foxes almost went extinct due to the introduction of canine distemper in 1999–2000. Vaccinations ensure that if there is ever an outbreak of either disease, at least the vaccinated foxes will survive to repopulate the island. (FIF's efforts to provide vaccine for island foxes in 2023)

A subset of foxes also gets radio collared. 


These collars are small, less than 5% of their body weight, and do not interfere with the foxes going about their daily life. Collars serve multiple purposes, allowing us to track the size and location of home ranges, monitor survival, and find dead animals quickly so their carcasses can be sent for necropsy ASAP to identify the cause of death. 

Most of the radio collared foxes are unvaccinated "sentinels," meaning if a disease outbreak occurs, they are not protected and may get sick, but their deaths will be detected via the change in their collar signal so we can recover the bodies for necropsy. Without collared animals, we would not know foxes were dying and would not be able to find the carcasses to get more information about the cause. Monitoring mortalities also gives us information on trends in other causes of death, such as internal parasites or being hit by cars, so we can address those threats as well.

Foxes are released after their workups and immediately run off! - Jessica Sanchez


In Part 4, Jessica details what happens when an island spotted skunk is unexpectedly caught during island fox health checks.

Friday, January 19, 2024

An Island Fox Gets a Health Check - Part 2

Welcome guest blogger Jessica Sanchez, wildlife veterinarian and FIF Board Member. In Part 1, she explained how island foxes are captured annually. Now, she'll take us through an island fox health check.

As biologists and veterinarians, we carefully remove the fox from the box trap, being sure not to get their tail caught in the door!

Island foxes are blindfolded to help keep them calm and reduce stress. Foxes do not have any natural predators on the Channel Islands so they are very brave, but they can still be stressed from handling by humans. Exams are quick and we do our best to be quiet and efficient. Island foxes are not sedated, so they can be released immediately and return to life as normal ASAP.

The health exam begins with an examination of teeth.

We open their mouths very gently so we can see the upper premolars. The wear on these teeth allows us to classify each animal into an "age class." Age classes range from 0 (pups born that year) to 4 (very old foxes with worn teeth). The pups also have serration on their incisors that have not yet worn smooth. Although age classes are not an exact age–and can vary by island, diet, and habitat (rougher food and sand wear teeth faster)–they give us a semi-standardized guide for assessing how old the population is overall. (more on using teeth to age island foxes)

We can also identify the pups of the year (less than a year old) by their appearance. They start out darkly colored and slowly transition to their adult gray/rufous/white. By the time we catch them during the summer/fall season, they look like mini-adults but with a rounder, fluffier shape.

Reproduction can be assessed in the females by examining their abdomens. A female who has not had pups that year will have white fur on her belly, with no mammary/nipple development (left, below). A female nursing pups will have the hair licked away from her nipples, the surrounding hair will be stained red from the saliva of the puppies, and her mammary tissue will be large and well developed from producing milk (right, below).

We do a thorough exam, assessing body condition and checking for any injuries. We check each foot to make sure they have no injuries to their claws, which are semi-retractable. Island foxes and grey foxes are unique among canids in that they can rotate their wrists, allowing them to grip and climb trees. (more on the island fox's ancestor, the grey fox)

Foxes often have grass awns or other debris stuck in their eyes, so we clean these out and remove any gunk that has accumulated. - Jessica Sanchez

In Health Check Part 3 - Jessica will detail the specific health measures taken for island foxes.

Part 4 - Other species encountered during health checks

Tuesday, January 16, 2024

How Do Biologists Capture Island Foxes?

Meet guest blogger, FIF Board Member, Jessica Sanchez. 

Sanchez is a wildlife veterinarian and epidemiologist who's been working with Channel Island foxes since 2006. She started her career managing the captive breeding and wild fox monitoring program on Santa Cruz Island. For her master's degree, she researched social interactions among island foxes, and modeled vaccination and monitoring methods to prevent and detect disease outbreaks. She is currently a consulting veterinarian for island foxes across the Channel Islands, providing medical care and advising on biosecurity and fox health research.

Every year, island managers and biologists conduct island-wide capture of wild island foxes to monitor the population size, reproduction, and health of individuals. This is done using the same locations every year, so direct comparisons can be made and trends identified. (counting island foxes)

The first step is finding a safe location to place a box trap–somewhere with flat ground, so it won't roll. It has to be out of the direct sun and wind, away from water with no risk of flooding, and where we can use vegetation to cover and disguise the capture device.


We capture foxes using wire, humane, live box traps; the very same ones used to capture feral cats. There is a "treadle plate" at the back that is attached to the door with a stiff wire. When the animal steps on the treadle, the door closes behind them.

We disguise the wire bottom by covering it lightly with grass or other vegetation. This also provides a comfortable bed for the fox to spend the night. We attract the fox with a small cup of fox-safe food at the very back, past the treadle. The fox must enter far enough to trigger the door and close it behind itself. An aromatic scent is also spread on a branch above the box trap–this scent travels longer distances than the smell of the food and attracts the fox to the area.

We cover the box trap with vegetation so the island fox is shaded and protected from any other animals that might come poking around. Then, we leave it overnight and return to check it first thing in the morning.

Sometimes, animals will try to get to the bait without going inside. This trap was disturbed by ravens! Ravens are extremely smart and will learn that the brightly colored "flagging" we put on trees to mark locations means there is an easy meal nearby.

If a fox is in the box trap, we first weigh both the trap and the fox. Once the fox is released, we subtract the weight of just the trap to calculate the fox's weight. An adult island fox will weigh between 1.5–3 kg, or 3–6 lbs, with foxes being slightly different sizes on different islands (largest on Santa Catalina, smallest on Santa Cruz).

We carefully remove the fox from the trap, being sure not to get their tail caught in the door!

The first thing we do once we have the fox in hand is scan it for a microchip tag, just like the ones used in dogs and cats. This tells us that the fox has been previously caught. The microchips are small implants, the size of a grain of rice, and are inserted under the skin near the shoulder blades using a needle.

The microchip provides lifelong identification of an individual so we can track its history–the locations it was captured, its age, any injuries, whether it had offspring, vaccines administered, any blood test results, and radio-collar frequencies.  - Jessica Sanchez

See F257's multi-year story.

The microchip can also alert the biologist that the captured fox has already had a health check that year. If so, it is immediately released.


If not, the island fox will receive a full health check. Follow as Jessica provides an island fox with a Health Check Part 2 - body condition. 

Health Check Part 3 - Preventative care 

Other species encountered during health checks