Channel Island fox population grows from 50 to over 2000 in just 9 years-

There are many species of fox around the world — 37 or so. Those fox with a naturally limited geographic range are likely to become the most quickly threatened by extinction. So it was with the (California) Channel Island Fox, which had always inhabited just the Channel Islands.

This tiny fox (Urocyon littoralis) lived on six of the eight Channel Islands, and as a different sub-species on each of them. Sub-species most often emerge when they are isolated by breeding barriers, and islands are a classic kind of breeding barrier. This fox, perhaps the smallest canid, evolved over the last 10,000 years after the mainland gray fox reached the islands when the Ice Age lowered sea level and came close to forming a land bridge to six of the islands. Presumably the gray fox was able to swim the short Ice Age distance or float on debris to the islands

Once the islands were cut off, the fox began to evolve according to the prey available, and the prey was different on each island. According to the National Park Service, “On San Rosa Island, where food item diversity is high deer mice, Jerusalem crickets, beetles and earwigs are the preferred food. On other Channel Islands, diets included plant items such as fruits from cactus, manzanita, saltbushes and seafigs, as well as insects and deer mice when they are present. Occasionally, foxes foraged along the shoreline for crabs and other marine invertebrates.”

Because the prey was small, the gray fox itself grew smaller and smaller, something called “island dwarfism.” This has been observed in many other species that made it from the mainland to isolated islands.

The Channel fox had no natural predators, but the fox populations went into a steep decline when a predator inadvertently emerged after the 1960s DDT poisoning of the bald eagles in these islands. The bald eagle did not eat the foxes, but it was replaced by the larger golden eagle 30 years later. The golden eagle thrived on the islands’ non-native feral hogs which the bald eagles had ignored. The goldens eating the hogs was, of course, a good thing, but, unfortunately they also ate the small foxes even though they were to the eagles little more than an incidental catch.

Canine distemper virus probably reduced the fox population too.

Recovery of the fox was accomplished by catching the golden eagles. They were not killed, being a protected species themselves. Most importantly the threat of new golden eagles was eliminated ridding the real source of golden eagle nutrition, the fat hogs. Bald eagles were reintroduced later. The bald eagles find their food at sea and in the intertidal zone.

These things accomplished, the fox population has grown from just 55 to estimates as high as 2500 since the fox was listed under the ESA.


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About The Author

Ralph Maughan

Dr. Ralph Maughan is professor emeritus of political science at Idaho State University. He was a Western Watersheds Project Board Member off and on for many years, and was also its President for several years. For a long time he produced Ralph Maughan's Wolf Report. He was a founder of the Greater Yellowstone Coalition. He and Jackie Johnson Maughan wrote three editions of "Hiking Idaho." He also wrote "Beyond the Tetons" and "Backpacking Wyoming's Teton and Washakie Wilderness." He created and is the administrator of The Wildlife News.

54 Responses to A tiny fox shows strong recovery under the ESA

  1. ZeeWolf says:

    Thanks, Ralph…. it is nice to see some uplifting news before I head off to work. This is just more proof that the ESA works and is effective at conserving species that need protection. Are there any immediate plans for delisting, or a timeline for recovery?

  2. Immer Treue says:

    More examples of the phenomenon Island (insular) Dwarfism including the Channel Island Fox.

  3. Ida Lupine says:

    Yes, the ESA does work. Luckily this little guy won’t have humans lining up to kill him once he’s delisted. That’s the difference with a predator such as wolves. How awful about the Bali tiger going extinct in the early 20th century due to perceived threats and jewelry made from him.

  4. Louise Kane says:
    a link to some more facts about the foxes, and some images. The history of the fox is like that of species and the evolution of subspecies in the Galapagos and to a certain extent Mona Island.

  5. mikepost says:

    This is a success story but it involves the hunting to exterpation of all the feral wild pigs on the islands. The lesson there is that removal of all feral critters on public land habitats is a key component of habitat restoration. A serious question is why the bison have not been removed from Catalina Island….too cute is the only answer, certainly not science. They have only been there since the 1920’s as the result of a movie shoot. Serious double standard….then there are those feral horses….

    • Ida Lupine says:

      I think whether the feral horses are native is up for debate. At any rate, they are a large part of our heritage and many believe they should stay, myself included. The bison it is true have their own habitat, and if they were only for a movie shoot they should be relocated. And of course we’re still here. 🙂

      • SaveBears says:


        There is only debate about horses in the minds of those that like to bend genetics, the current horses on the landscape are not native to this environment, plain and simple they need to be removed.

      • Rancher Bob says:

        My grandfather told stories of all the livestock turned loose during the depression. People went broke and just moved. There was no money for feed and they were not worth anything, so people just turned them loose. There were all types of horses roaming eastern Montana after the depression. I would guess the same thing happened in many rural areas.

        • Ida Lupine says:

          RB, I just think it’s impossible to turn back the hands of time completely as far as introduced species are concerned, and don’t we owe an animal that helped us greatly a bit better treatment than getting rid of them when they are of no more use to us? Ugh.

          • Rancher Bob says:

            As long as your beliefs hold true for every species not just those one’s you have a soft spot for, can’t pick and choose.

            • Mark L says:

              I guess I see horses a lot like feral pigs…as long as they are countered by an apex predator without intervention, they have a place in the ecosystem (for better or worse). Withdraw the predator(s), and they have no place either….nobody rides for free, nobody, nobody.

              • WM says:

                ++I guess I see horses a lot like feral pigs…as long as they are countered by an apex predator without intervention, they have a place in the ecosystem (for better or worse).++

                The problem is there NEVER was an apex predator (at least as long as horses have been in the US since the Conquistadors) that could take feral horses or burros in any numbers. There will never be a widely distributed apex predator that will take many feral pigs (now in something like 34 states and growing).
                That means man will have to intercede – except that for the wild horses – there is a huge political problem – the romance of the heritage of the West, and protection of federal law in some parts. Fortunately the new horses on the landscape, released due to economic times, which Ralph mentions, are relatively few, and most(?) are neutered. They don’t procreate that fast, and where not federally protected can be removed or eliminated under state authority or by private action. The feral hogs are yet another matter, with two litters a year, and the huge destruction of agricultural lands, with a price tag, apparently exceeding $1B per year. They learn to be nocturnal and avoid humans.

                USDA Wildlife Services needs to get busy on both problems.

              • WM says:

                Sorry, fact correction/update: Feral hogs confirmed with established populations in 38 states with sightings in 47. Damages estimated at $1.5B, and that was in 2007. And, the numbers keep growing…and growing.


              • Mark L says:

                Jaguars have never had a problem taking down horses and burros (and feral pigs too). They were endemic to the southern US until the 19th century. Yep, not near enough of them to put a dent in either population now…and that’s not likely to change. Heck, wolves and coyotes can take young feral pigs and keep the numbers down through stress on the sow (same argument made in NRM area with elk young numbers by some biologists I think). All that ‘landscape of fear’ stuff does seem to have some effect on frequency and number of young.
                Will an apex predator ‘fix’ a problem population, be it horses burros armadillos (just pick and choosing) or feral pigs? No, but just as people (WS or hunters) will go out and shoot them, other humans will just replace the downed animals (excluding armadillos). This only pads WS employees and politicians pockets and fixes nothing (cause some don’t buy into the same policies). Humans don’t work for free….even hunters that volunteer ultimately ‘pay’ through someone’s administration of the area. And, we tend to hunt seasonally, have jobs, have families, have spouses that want us to watch the kids, etc. I’d rather see pressure from both hunters (or WS) AND predators in a mix than just humans alone.

            • SaveBears says:

              Awe, the pick and choose, which animal is good and which animal is bad?

        • Ralph Maughan says:

          Rancher Bob and all,

          Many horses have been turned loose since the Great Recession began in 2008, adding to the problems and controversy.

          • SaveBears says:


            Yes there has, again, it comes down to pick and choose.

            • Mark L says:

              I agree, and it’s usually up to the owner to ‘buck up’ and act responsibly…good luck on that in both cases. People are weird….as long as we have a viable ‘counter’ to their acts, we have a plan.

          • DLB says:

            I think that may have been the result of legislations that shut down the glue factories. That law became a case study in unintended consequences.

  6. Ida Lupine says:

    The mind boggles. Between Louise’s and Immer’s posts about the state of MI’s wolf hunting, and WM’s post about the resistance to controlling feral hogs, it makes no sense! The MI DNR doesn’t know the impact of hunting, and yet another one is scheduled? Makes a lot of sense!

    I still do believe a healthy population of horses ought to be protected as part of our national heritage, and I will support it. The horses have been in this country long enough for them to be a native part of the landscape, IMO. And are most probably are native. Without the bison, wolf, grizzly and wild horse, bald eagle and California condor, it would be a very ugly country. I don’t know why people don’t care about their heritage. I’d hate to see the West turn into yet another homogenized urban sprawl with no character, broken up only by energy development. To tell you the truth, it’s the big energy companies and land development that really threaten the landscape IMO, and I’d prefer ranchers over that any day, if only they’d be more cooperative.

    • Immer Treue says:


      In fairness, I’ve made no comments about MI wolf hunting data (MI has not had a season), but lack of age breakdown from MN and WI wolf seasons. Only one season’s data probably would not yield definitive proof about possible pack disruption, but might shed some light in that direction.

      • Ida Lupine says:

        I wasn’t sure if it was WI or MI. It’s a good point, I think, that you make.

        I hope Ma’iingan is still with us?

    • mikepost says:

      “most probably are native”…Ida, where do you get this stuff. The American feral horse is clear documented genetically as being of European origin and no more distantly than the 1500’s. You have as much of a chance of finding a live native north american horse as you do a live sabre tooth tiger. You normally have some good things to say but when you deny science because it does not suit your emotional attachment to the animal then you are engaging in the same kind of double-speak that the anti-wolf use in their emotional rejection of wolves.

  7. rork says:

    You are helping prove the anti-wolf-hunting forces are full of irrational people who don’t care about anything but cuteness factors.
    Heritage can be used to argue for many terrible things, like dams, killing whales, and many hunting practices that you probably don’t like.

    • Ida Lupine says:

      I don’t agree. The big difference is preserving a life, where whaling and similar practices drives an animal into extinction. Since our electrical power needs have changed, dams that are no longer necessary should be taken down, and that is happening.

      ‘Cuteness factor’ I think is another phrase made up to derail argument in support of wildlife, and I support all wildlife, cute or not. I’m probably one of the few who doesn’t mind spiders, snakes and mice, and I’m not the only one. 🙂

      • Ida Lupine says:

        And bats, which I call flying mice. They’re cute!

      • WM says:


        ++Since our electrical power needs have changed, dams that are no longer necessary should be taken down, and that is happening.++

        While I am for free flowing rivers in many places you do realize that dams do things other than generate electricity (we have an entire system of them on the Columbia and Snake Rivers). Among those other uses are flood control, diversion for irrigation, recreation on the reservoir pools behind the dams, and to achieve flow equalization to assist in meeting municipal and industrial demands. Dams do lots of bad things, but they also may be considered necessities to meet the needs of growing human populations. While we may see some go away as they come to the end of their engineering design life (sedimentation), replacement or augmentation of power sources that decreases need, like on the Snake, I don’t see many large dams, some of which are the worst environmental offenders according to some, going away real soon, the lower Snake dams being a rare exception, if ever implemented.

        • WM says:

          Sorry about the bad grammar/run-on sentence, but you get the idea.

        • Ken Cole says:

          The dams on the main Columbia and lower Snake river do not provide flood protection. They are run-of-the-river dams built primarily for barge traffic.

          Those in Hells canyon are only for power generation and provide little flood protection.

          • WM says:


            Sorry for taking this further off topic, but I think you generalize a bit, perhaps incorrectly. The main stem Columbia does provide considerable flood control storage/diversion with the off-stream complex at Grand Coulee Dam (Columbia Basin Project with its massive reservoirs and canal system), and the way all the run of the river dams on the Columbia are operated as a system for flood control purposes, reserving flood capacity on pools upstream of the dams, pursuant to Corps of Engineers mandate. The COE runs the river (including navigation), though BPA has power generation responsibilities. See this source, specifically pp.33-37 to see how prominent flood control is in the strategy:

            By the way, the 1948 flood at Portland was the leverage the COE needed to throw flood control into their benefit-cost analysis to justify federal funding for continuing expansions and improvements at all the dams built for BPA. I know this because I wrote a paper on it when one of the first EIS’s in the country done under NEPA, for the expansion of Bonneville Dam.

            By default, because the lower Snake dams are also operated by the Corps which specifically has a flood control mandate (and upstream Dworshak Reservoir and Dam on the Clearwater) they are also operated to some degree to attenuate flows for flood control, as well, in concert with other objectives. They would be remiss if they didn’t do this, since they operate nearly all the dams in the system. The Lower Snake dams were designed primarily for peaking power of up to 3000MW. But, as the largest tributary to the Columbia system, it is also likely those dams will continue to get scrutiny for future use with climate change in order to provide additional on-stream storage (small as it might be) to handle those increased of early high country runoff events within the drainage. BPA and the Corps will continue to push that concept to keep them from being removed.

            Overlayed on all this is the complexity of trying to manage the system for fisheries pursuant to continuing federal court decrees and oversight under US v. Oregon.

        • zach says:

          Let’s hope the Klamath is up there, also.

      • JB says:

        “‘Cuteness factor’ I think is another phrase made up to derail argument in support of wildlife…”

        Okay, ask yourself if you feel the same way about preserving other types of non-native, feral livestock. Perhaps you could be the new ‘Wild Horse Annie’ — but for cows? 😉


        It’s interesting to me that no one has mentioned other non-native species that are purposefully maintained (e.g., pheasant). When I’ve queried about this in the past, some have pointed out that pheasant hunting (in some states) drives license sales and so is a boon to conservation. So would y’ll be supportive of feral horse preservation if the feral horse lovers were ponying up (pun intended) $$ for conservation?

        The problem with principles is that they’re great…until they’re not.

        • WM says:

          purposely maintained invasive species… chukars, Or in the aquatic ecosystem, the rainbow trout.

          The problem with invasive livestock (usually not feral if cattle or sheep) is that they have economic value in the marketplace. Wild horses and burros do not; all they do is consume grasses that otherwise might be utilized by other wildlife, or domestic livestock (did I mention they have economic value in the marketplace), AND importantly these horses and burros continue to grow in numbers through procreation and lack of a predator that targets them. This, then, requires expenditure of federal tax dollars to round-up, remove, feed, pen and provide veterinary care, for the purpose of trying to sell them off, or research scientific ways to reduce their numbers, through methods of birth control. Railroads, and what are now antique steam engines and out of date narrow track, are also part of the heritage of the West. And, if we are candid, they probably contributed far more to its development than horses. Should we continue to seek their preservation? At least they don’t increase in numbers, or eat grass, when left on their own. 😉

          • Ida Lupine says:

            Steam engines are not living things. Have we become such a throw-away society that we no longer distinguish between the non-living and the sentient? It makes no difference what the percentage is, horses have contributed to human progress greatly.

          • JB says:


            Reading between the lines, the principle that underlies your response seems to be: “if an exotic animal has economic value, then it we should preserve/conserve it.” I do not doubt that their economic value is the reason why we have so many livestock on western landscapes (though I would point out that they’re costs are not being fully monetized); however, I don’t agree that economic value is a sufficient reason to allow non-native species to continue to exist on the landscape.

            I’m very dubious of those who would rely solely on a species’ economic value as justification for their existince , while deriding others for focusing on other types of value (symbolic, for instance). We have modified landscapes across the US with purposeful introduction of species. All of these species CHANGE the ecosystem…

            • WM says:


              I don’t have a problem “conserving” invasive species that do not have perceived economic value, if there are other redeeming values of sorts that provide justification, like small populations of feral horse/burro (as Ida suggests). What I have a problem with is the costly obstructionist efforts that continue to allow their numbers to grow at substantial cost, while degrading range conditions. And please do not equate the criticism of that with any support for economic value invasive cattle/sheep on public lands. I am just saying that is the way it is, and why there is greater support for one and not so much the other.

        • ZeeWolf says:

          JB – In response to your query: My set of values is to have wild flora and fauna consist of native and indigenous species regardless of their economic value. I do not want feral cats, horse, cattle, hogs and etc… nor do I want cheatgrass, russian olives, houndstongue, canadian thisles and all the other non-native flora going feral or becoming naturalized upon the landscape.

          I am not against having domesticated animals and plants being used for husbandry and such, but they should be properly contained and not allowed to go feral. But when it comes to my wildlands, I prefer to see the species that are naturally occuring.

          The Channel Island fox population was recovered (or is in the process of being recovered, as the case may be) partly due to the control and removal of non-native species. I would wager that there exists numerous other threatened and endangered species whose recovery would be assisted by control of non-natives species that directly or indirectly compete for the same habitat.

          I am not “against” any species and do appreciate them all but only in thier native habitat or properly cared for and contained if they happen to be domesticated.

          • Ida Lupine says:

            I’m being overrun by wild raspberries, or wineberries I think they are called. I think they are edible, I hope the wildlife likes them. Autumn olives are beautiful, and smell heavenly. Their fruit has more nutritional value (lycopene) than tomatoes. Tomatoes I don’t believe are native either. Shall we get rid of them?

            • Ida Lupine says:

              Cheatgrass I think isn’t well adapted to our native prairies and is a big fire hazard. Asian carp brought in to clean up the Mississippi is getting out of hand and causing trouble (whose bright idea was that, anyway?), and zebra mussels brought in by shipping vessels. We should also make illegal the importation of exotic birds and animals as pets. I read somewhere that we have more tigers in captivity in the US than there is in the entire wild. And now that I think about it, about those zoos….another relic from previous eras that has no use in modern society, except if you consider the only way to save an endangered species.

              I should say that I may complain about Ken Salazar and the Interior Dept. and the Administration lot, but one thing I am grateful for is his America’s Great Outdoors Rivers Initiative (one for each state), and getting rid of those great monuments to humanity that also may be beyond their useful life and need to be removed, or upgraded for efficiency with modern technology, or are dangerous. Improving the quality of our iconic rivers and water, restoring fish, help meet our obligation to our native people, and creating jobs and recreation.

            • rork says:

              Where have you seen invasive tomatoes.
              Crops are rarely a problem. They don’t compete,

          • JB says:

            “I am not “against” any species and do appreciate them all but only in thier native habitat or properly cared for and contained if they happen to be domesticated.”

            Hi Zee:

            I generally agree with what you’ve written. However, there are always exceptions. For example, I’m fully supportive of the introduction of a variety of non-native species that provide much of our current food supply. 🙂

            Again, one of the persistent problems is that there do not appear to be any principles that always hold, making us appear unprincipled in our approach to conservation.

            • ZeeWolf says:

              JB – In reference to your reply, I will reference a quote from my earlier post:

              “I am not against having domesticated animals and plants being used for husbandry and such, but they should be properly contained and not allowed to go feral.”

              Thus, I feel that I am in agreement with your statement:

              “I’m fully supportive of the introduction of a variety of non-native species that provide much of our current food supply”

              For example, let’s take a look at one particular plant that is commonly grown throughout the United States, say tomatos. According to the Wikipedia article on tomatos, they orginated in Mexico and spread througout the world after Spanish colonizaton of that part of the world.

              According to my value set, I take no issue nor have qualms having tomatos grown in Colorado, where I live. I enjoyed them for lunch, have helped to tend them in a neighbor’s garden (for which I will reap the rewards) and in general enjoy the variety in my diet (variety being the spice of life and all that).

              Now, that being said… I don’t want to see tomatos growing wild outside of garden space. I would be kind of ticked to see them growing feral in my favorite location to revel in the glory of nature, where I enjoy the panoply of native species.

              Your last parapgaph is well stated and I believe accurate. Other words that come to mind: undisciplined, thoughtless, capricious, “willy-nilly”…

        • Ida Lupine says:

          I have thought often about the disparity between non-native animal and plant species that we plan to keep because they are useful to us, and which ones we want to ‘get rid of’ because they are no longer any use to us. So it really is a matter of pick and choose, but not from the side you would think. How about those GMOs messin’ up the landscape.

          I’m not the type of person who wouldn’t practice what I preach.

      • rork says:

        ” and I support all wildlife, cute or not”
        You are talking as if the horses have no costs for other animals. That’s not how existential game-theory works. How do you feel about the plants they eat, and endanger, or the native wildlife they displace. I call bullshit.
        I’ve seen estimates of how many plants have been made extinct by horses, but can’t find them easily.

        • Ida Lupine says:

          It all pales next to the displacing humans do and have done, and will continue to do.

  8. Snaildarter says:

    Not to mention of the real cause which was DDT.

    Introduced mammals species are not as big a problem as the smaller things globalization keeps bringing us. Good bye American Chestnut, Eastern Hemlock, now Ash trees are on the hit list, red buds, elms the list goes on and on.

  9. Mark L says:

    Tomatoes are native (MesoAmerica). I think as we ‘go along’ with the native vs. invasive we need to look almost holistically at ecosystems instead of doing the pick and choose most do on larger mammals. There’s a lot of good in some invasives as they create as much as they destroy i.e. Complaints about coyotes in the southeast US are almost always because they have predated upon an invasive that a human has put a value upon. They are ironically our homeland defense, for the most part.

  10. Snaildarter says:

    Personally I’d like to see mega fauna return to the western hemisphere. Hippos, Rhinos and elephants are missing. Our eco-system seems unnatural and incomplete. There should be an America cheetah to chase pronghorn. Early human migration to the new world seems the obvious culprit in the extinction of many key species. Of course we can’t even get the bubbas to accept the return of wolves so this is just a pipedream.


July 2013


‎"At some point we must draw a line across the ground of our home and our being, drive a spear into the land and say to the bulldozers, earthmovers, government and corporations, “thus far and no further.” If we do not, we shall later feel, instead of pride, the regret of Thoreau, that good but overly-bookish man, who wrote, near the end of his life, “If I repent of anything it is likely to be my good behaviour."

~ Edward Abbey