Saturday, February 5, 2011

Predator in the Middle - What Happened

If you saw this on a drive down a quiet country road, what would you think?

Press "Post a Comment" below to share your thoughts.

----------------------------------------------- A Followup: ---------------------------------------------
A few days ago, I invited readers to share their thoughts about the above photo. Responses here and ones I otherwise received speculated this situation was the result of humans persecuting animals, a giant shrike or other predator taking advantage of a barbed wire fence, even witchcraft (see comment section below).  Let me share the specific facts as I heard them, biological facts as I've learned them, and unmask this story of predators.

That is a bobcat carcass hanging on a barbed wire fence.  I did not stage that photo.  It is exactly how I found it.

A few days ago, a ranger told me he was driving around the curve at the Alpine Road corral and was surprised to see a very large bird flush off the road.  It was dragging a spotted carcass in its talons and having a hard time getting airborne.  As it swooped over a steep road bank, it barely cleared a barbed wire fence and the carcass snagged on the top strand. The dark bird kept flying without its payload, and the ranger assumed it would come back later for its dangling meal.

Large bird flying over Dipper Ranch in December
He was certain the bird was a golden eagle because of its large size and overall dark color. I was not surprised to hear that a golden eagle was seen in the neighborhood.  On December 23, I was washing dishes and heard a red-tailed hawk screaming so loudly, I figured I'd better investigate.  I headed outside wiping my hands on my apron (not really), and looked up to see a red-tail hawk chasing a large dark bird.  Compared to the red-tail, this bird was huge.  It made a few wide turns over the farmyard with slow beats of its solid wings without once acknowledging the irate hawk.  I hurriedly pulled out the camera I always keep in my apron pocket and got a few blurry photos before it steered its bulk towards Devil's Canyon, then Monte Bello Ridge.  My cross-canyon neighbors tell me they see golden eagles fly into Devil's Ridge in the springtime and they think the eagles might be checking the cliffs.  I briefly considered tossing my house cats out in the yard to attract the magnificent bird back (a moment of premonition?).

White patch on golden eagle's right shoulder
By color and size, I was pretty sure the large bird flying over my kitchen was a golden eagle, and checking my photos later, I could make out the characteristic golden color of its lower nape.  This eagle had a distinct, white semi-circle on its right shoulder (lesser secondary coverts).  In January, another ranger saw a golden eagle on a deer carcass (probably roadkill) in Russian Ridge Open Space Preserve.  I checked his early morning photos and that bird appeared to be a different eagle since it did not have a white shoulder patch.  It did have some white streaks in its underwings and was possibly a subadult. Golden eagle sightings are occasionally listed on the Peninsula Birding Group for the Santa Cruz Mountains including recent sightings of a "hatch-year" and two adults.

Another blurry photo of the large bird
After assessing the ranger's Alpine Road eagle report as reliable, I impatiently worked through a dayload of meetings.  The ranger told me about this incident two days after he witnessed it, and I wasn't sure there would be any signs left.  When I finally got down to the Alpine Road corral late that afternoon, I found the spotted carcass hanging on a fence high above the road just as the ranger had described it.

I speculated the bobcat had been hit by a car and the golden eagle was feeding on the roadside carrion.  It also occurred to me that this could be the remains of a bobcat I had seen 4 days earlier on the Dipper Ranch cautiously sneaking towards a steer carcass.  The family of 3 coyotes who frequently showed up on the wildlife cameras I installed at the steer carcass, or even the mountain lion that dragged the heavy carcass one night, might have decided to eliminate the smaller bobcat as competition for carrion which can be an important food source in the winter before the grassland herbivores start popping out meals on tiny hoofs and paws.  In either case, I assumed the golden eagle scavenged the bobcat and did not originally kill it.

Coyote scavenging on steer carcass
and trying to locate sound of shutter clicking on wildlife camera
Slipping into my recently acquired dead-wildlife detective mode, I sensed something odd about the bobcat carcass.  The front legs and back pelt were undamaged and attached to the stripped yet fully articulated backbone.  The rear legs and tail were gone.  Between the front legs hung a solid, bloody bulk and the ribs were snapped off at different lengths.  I looked around in the nearby bushes and hollows to see if I could find more of the carcass but I didn't find any guts, other bones, or any type of digging or recent soil disturbance.  I returned to the carcass and eventually recognized the stubs of ears and nostrils on the unfurred bulk hanging between the legs which turned out to be a partially defleshed skull. Despite my attempt to be an objective observer, I was feeling creeped out as the sun set, so I took a stick and loosened the torn body from the fence and gently wrapped it around the base of a T-post where the predators could finish their meal out of eyesight from the road.

I spent the next few days reflecting on the sad fate of the bobcat, its beautiful lifeless paws, and decided to learn more about golden eagles.  Since they are large birds admired by some, despised predators to others, and they range across North America, Asia, northern Africa and Europe, they have been frequently studied.  Golden eagles are top predators and many were previously killed in rural western states because of the belief that they took large amounts of livestock.  Although their diet varies by location, in most places, their prey primarily consists of rabbits and ground squirrels.   Lagomorphs (rabbits, hares and pikas) represented 85% of the diet of nesting golden eagles studied in Northern California, and 87% and 91% in similar studies in Utah and Colorado (Bloom and Hawks).  A dense population of golden eagles in the Altamont Pass area near the city of Livermore, California, eat primarily California ground squirrels (Santa Cruz Predatory Bird Research Group).  Golden eagles also hunt deer, coyote, snakes, frogs, fish, other birds and will feed on carrion.  

They have been known to take small domestic livestock such as lambs and calves.  In the same Northern California study, the remains of livestock found in golden eagle nests in a rangeland area were less than 1% of their total diet.  Over the six-year study period, the remains of 3 total calves were found in the nests (20 average nests were checked each year) and at least one was determined to be collected as carrion because it contained crushed bones that were too big for golden eagles to smash.  The researchers found sheep wool in the nests, were not able to determine the number of sheep collected, but their estimated biomass represented a small fraction of other prey items consumed.  

Shooting or even collecting feathers from bald and golden eagles is illegal unless you have received permission as a Native American for religious purposes, for some scientific purposes, or if authorized by the Secretary of Interior for the protection of wildlife or agricultural interests under certain circumstances.  If convicted of a violation under the Bald and Golden Eagle Protection Act, you can be fined $5000 to $10,000 and imprisoned up to two years for each incident, and additionally lose your permit to graze domestic livestock on federal land.  The golden eagle was added to the Eagle Protection Act in 1962 because "Whereas the population of the golden eagle has declined at such an alarming rate that is is now threatened with extinction; and Whereas the golden eagle should be preserved because of its value to agriculture in the control of rodents."

The fence did it.
So, back to the photograph of the bobcat carcass hanging on the barbwire fence.  This incident was not a barbaric human persecuting a predator, or the ubiquitous coyotes.  Ironically, it was a formerly persecuted top predator consuming a mesopredator.  If I hadn't received the first-hand reliable eye-witness account, I am not sure how I would have interpreted the gory remains.  As I continue to read about golden eagles, I realize I probably misinterpreted the scene by assuming the golden eagle was a scavenger in this situation.

It was while reading an account of eagle-feeding habits on the Internet Center for Wildlife Damage Management, that I realized how chillingly close their description was to what I saw on the fence:  
"Eagles skin out carcasses, turning the hide inside out while leaving much of the skeleton intact, with the lower legs and skull still joined to the hide. On very young animals, however, the ribs often are neatly clipped off close to the backbone and eaten. Eagles frequently do not eat the breast bone, but some clip off and eat the lower jaw, nose, and ears. Quite often, they remove the palate and floor pan of the skull and eat the brain."  

Deer carcass fed on by coyotes with evidence of
gnawing, canine punctures in scapula, and pulled hair
I went back through my photos of the bobcat carcass on the fence and realized why the carcass had seemed so odd to me - it was too clean for a carcass fed on by coyotes.  Thin bones that coyotes usually crunch and scrape were still intact and picked neatly clean.  I had also never seen a carcass with skin pulled back over curved surfaces rather than ripped open and torn free.  Because it was hanging on a fence out of the reach of coyotes for two days, this gruesome sight which we found emotionally upsetting and imagined the cruel actions of humans was actually a near perfect visual representation of how large avian predators eat. 

In eulogy of the bobcat, I want to recognize its status as a mesopredator - a mammalian carnivore of medium size, sometimes with highly adaptive behaviors.  Some ecologists have theorized and found many potential examples that as apex predators are eliminated by humans, out of fear, competition for food, or through alteration of habitat, this may result in an increase in the predators the next size and trophic level down in that ecosystem (Praugh et al.).  One might assume that the elimination of apex predators would result in an increase in prey species (e.g. deer), however, if the removal of top-predator competition allows the subsequent rise of mesopredators, and these are more efficient at reproduction and predation, then the overall amount of prey may actually be reduced in the absence of large apex predators.

Just as I would recommend a rancher not assume livestock was killed by a particular predator until evidence is carefully examined, so I recommend we not assume humans are always responsible for the death of wildlife.  There are a lot of predators out there and they've gotta eat.  Let's learn more about predator ecology before we tumble into emotional skewering of either wildlife predators or human predators.

The new fencelines have barbed strands (green) on the top to hold cattle
and unbarbed strands (silver) on the bottom for the wildlife to pass under.
See also:

Golden EagleAquila chrysaetos, The Birds of North America - Online, Cornell University.

Food Habits of Nesting Golden Eagles in Northeast California and Northwest Nevada, Peter Bloom, California State University - Long Beach, and Stephen Hawks, Bureau of Land Management, 1982.

The Rise of the Mesopredator, Laura R. Praugh, et al., Bioscience, October 2009.


  1. I would be horrified and assume it was a human demonstrating typical predator-hatred. I sometimes used to come across shot and maimed coyotes when I worked in the Sacramento area, and this appears to be the same thing. Also, I want this poor creatures remains to be taken down where they can decompose in peace. If you tell me where it is, I will go do it.

  2. I removed the carcass from the fence shortly after I found it. I did not photograph (nor am I sharing this) to shock but to share some relevant info. Thank you for sharing your thoughts and concern.

  3. I've seen old photos of similar ... instances. Coyotes, and fox that had run afoul of a farmer who had finally had it with losing sheep, chickens, etc. It also reminds me of much more recent pictures of the rabbit fencing in Western Australia. Dingos and other critters get hung up in it while trying to go over, through or under. Strangely, you almost never see rabbits tangled in it. Was the carcass a bobcat? Young cougar? I can't quite tell... Its a cat of some sort...

  4. My first thought was there must be a mutant, super-sized shrike in your area. I first heard about the shrike's behavior of impaling and storing insects and other small prey on thorns or barbed wire from fellow blogger biobabbler, but I couldn't find her post to reference. In all seriousness, I'm guessing a turkey vulture or a condor left the remains of this bobcat carcass on the fence.
    ps - Rolled out of my chair laughing at your great pun to my last comment. Thanks!

  5. I agree with tierramor. I'd think some (in my view) awful creature killed a bobcat, is vilifying them (in my view unjustly), and this is a barbaric expression of their view of what I think is an amazing creature. NOT to mention lots of livestock are killed by DOGS but dogs are seldom blamed--people go straight to coyotes, etc.

  6. That really makes my blood boil. I understand a farmer/rancher's anger over predation, but weather causes much more livestock death.
    I really wonder about humans.

  7. Great information! A predator, not scavenger. (And, I didn't intend to imply a turkey vulture or condor would act like a shrike. I figured, like you did, that it couldn't quite get up off the ground to clear the fence with such a heavy load which was caught in the barbs.)

  8. My son guessed 'giant shrike' in addition to others with shrike comments. He is studying aeronautical engineering and the Shrike Commander is a small twin piston engine airplane used by the US Coast Guard and Mexican Air Force.

  9. You say: "Let's learn more about predator ecology before we tumble into emotional skewering..." Fair enough - BUT, realize that a photo image hits one differently than seeing something in real life. Both in habitat work and in rescuing feral cats, I've dealt with wounded or dead animals, animals who've been shot or hit by a car. When you are face to face with it, you put on your big-girl pants and your detective hat to figure out what happened, and how you can help. But when you are at home in front of a computer, it's different because you are passive. I think our society has so many overwhelming images in the media of violence to animals or humans that many people shut down. Others (like me, I am the first to admit it), hyper-react. Your suggestion for reasoned research before emotional response is a fair one. Probably (hopefully?), in the field, many of us would do just that.

  10. I have very mixed feelings about this post. I expected people to be surprised, but I didn't expect people to be so angry. In retrospect, I should have posted the backstory right away with the original photo so that the biological merit would have been obvious up front. I apologize for not being more aware and sensitive of how that photo might affect people. I keep thinking about the golden eagle picking away at its meal and how basic that is to life but we often don't see it. On the Dipper Ranch blog, I try to share the natural events I witness on a small piece of land so that others can be there too. Making the ecological connections is very real to me but maybe I need to work more on how I share it. I am grateful for your advice.

  11. In my flight test class my Professor was showing us a video of a GPS controlled glider that a few students had built years previously. While testing the finished glider, the professor managed to capture a video of a golden eagle making a quick attack towards the aircraft. He claimed that it attempted to hit the glider with a rock it carried in its talons, and indeed, you can see a small dark shape falling from its claws towards the glider as it attacks.

    Personally, I am of the opinion that it was not a rock but a small rodent that it was forced to drop before it attacked; however, I'm not sure I want argue about it with my professor.

  12. per Reed: maybe that was a bunny bomb. As my friend says, "The bunnies always bite the dust." She was referring to those TV nature shows.

  13. Cindy, I believe your post was perfectly reasonable, in-line with what other nature bloggers post, and educational about golden eagles. Please, don't let internet bullies change what or how you write. Don't ever apologize; it's YOUR blog, after all.

  14. I'm glad you posted a follow-up on what actually happened to the bobcat.The fact that it was most likely a Golden Eagle never would've crossed my mind. I knew they went for smaller prey (sometimes larger), but for whatever reason it never occurred to me that that smaller prey might be a predator in and of itself. And I very much appreciate the logical follow through. I have to admit that the first thing that came to mind was that it was the work of an angry human. Where I live we see a lot of stupid human behavior, many times just because they thought it was fun. Being backed right up again Tahoe National Forest, people from everywhere come and try to get away with everything they can.

    People make assumptions on what they know. The most common knowledge of seeing a carcass like that strung on barbed wire... well, they know human behavior much more intimately than that of wild creatures. They're going to assume it was someone with a tweaked set of needs. And tierramor is right. We've been almost trained to either shut down, or over-react. Hence the anger. Not your fault. Just social training. ;)

  15. Super points, Kristine, and nicely said. @Cindy, I don't think anyone was angry at YOU, but most of us with a reasonable big heart have a lot of anger and hurt out floating around out there, and seeing some spotted paws hung off a fence will sure make it land quick. It is directed at the ubitiquous THEY who is ruining the world, not at the Cindy who we care for or like to learn from. Just clarifying the difference.

    But it is sweet, also, that you are thinking about how your words and pictures land in us. I think it's a good responsibility to engage with for those of us who create media. What do I want to say? And what will those listening *hear*? And how can I change the first so that the second will conform better with what I am trying to accomplish, or, at the least, help me and my readers smile more in the day and sleep more soundly at night?


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