Sunday, January 23, 2011

Beefeaters of the Santa Cruz Mountains

Two coyotes working the carcass on the night of Day 2.
After finding both canine and feline tracks around the dead steer, we decided to rig up a wildlife camera to see what predators returned. Wildlife cameras can be placed securely in the field to record wildlife activity over an extended period of time, at night, and in situations where wildlife would avoid locations or modify their behavior if a human observer was present.

On Day 2 of my dead-steer observations, I watched from the backyard with binoculars as ravens landed on the carcass and frequently flew off again throughout the morning.  By high noon, the cattle were peacefully grazing in the Golf Tee pasture near the carcass so I decided it was safe to check the wildlife camera.  When I opened the sheep gate to the Golf Tee, the living cattle looked up and trotted out of view.

Please note:  the remainder of this blog post contains graphic descriptions and photos of a carcass and predators feeding on it.  Do not select "Read More" below if you do not want to see these.  If your curiosity is greater than your gag reflex, press on.

How do ravens keep their feathers clean and glossy
while they are scavenging on a carcass?
The carcass did not seem much different.  The trachea, which had appeared severed in the open thoracic cavity the day before, was now partially pulled out of the body.  The dislodged tongue was gone, and there were white streaks on the black pelt and a few white pellets on the ground - all probably sign from ravens and vultures pecking at and excreting on the carcass.  During the day when large predators are sleeping under cover, vultures and ravens get their turn.  They start on the soft tissues (eyes) and exposed flesh, or wait until the carcass has rotted enough that they can tear open the dissolving skin.

The first day, we only had time to attach a wildlife camera to a tripod
and stake it down.  Because the cows rub on everything,
we later mounted the cameras on T-posts.
Most readily available models of wildlife cameras (also called game or scout cameras) are designed for hunters to spy on the size and habits of deer they want to bag.  As a result, biologists have to adapt the camera settings for smaller animals and in unforested habitat.  Frequent checks on the camera in the first few days may be necessary to confirm the settings are correct for that particular situation, and to closely observe other signs at the site to assist interpreting animal behavior that does not show up on the wildlife camera.

The cows continued to graze the pasture around the steer carcass
and often showed up on the photos.
I opened the camera and impatiently waited for it to indicate whether any photos had been taken the previous night.  As the camera slowly scrolled through its settings, I heard a quiet huffing noise and anxiously looked towards the nearby forest.  Predators might be lurking in the shadowy understory or stretched out on a limb sleeping off a meal as was the mountain lion I saw last February in Los Trancos Open Space Preserve.

Honest guys, I didn't do it.
The next huff was a little louder and seemed to come from behind me.  I whirled around to face a lineup of 48 cattle jostling to get a better view of me.  Perhaps they were just curious, but being nervous on the scene, I assured them, "I didn't kill your buddy.  I'm just trying to investigate."

Coyote visiting the carcass on Day 2 in broad daylight.
Finally, the camera flashed its count - 35 images since we set it up the previous afternoon.  One photo showed a coyote standing at the head of the carcass at 11:40 of Day 2, shortly before I came down the hill, although I was a little suspicious that the time stamp on the camera might not be accurate.  The remaining photos showed ravens on the carcass, cattle grazing around the carcass, and some photos of shadows and the unattended carcass.  No photos were taken at nighttime.

This hard pellet about 2" long showed up near the carcass on Day 8.
I do not know what it is and it was gone by the next day.
I changed some settings in hopes of getting some nighttime photos.  Subsequent photos taken on Days 3 through 8 showed coyotes working the carcass at night, on foggy mornings and occasionally during the sunny part of the day.  Sometimes three coyotes showed up in the same photo.

Look closely to upper right
to see whitish coyote by dark carcass early one morning.
With the short winter days and my reluctance to approach the carcass in dark hours, I was not able to directly observe it on some days.   Every morning, I would check the scene from the backyard by binoculars as soon as the sunrise started leaking over Monte Bello Ridge.  On Day 5, I saw a whitish coyote bending over the carcass and digging.  Two smaller coyotes were lounging in the grass nearby.  I think the larger coyote was trying to loosen a limb to drag into hiding.  As the sun cleared the ridge, the 3 coyotes retreated across the Golf Tee in a westerly direction.  The two smaller ones chased each other and all 3 coyotes would stop every few minutes to rub their muzzles against the grass.  They disappeared into a thick stand of willows.  Shortly afterwards, more than 15 ravens circled the carcass.

Day 9 - the carcass has been dragged and flipped,
providing easy access to large area of fresh meat.
On Day 9, when I checked the carcass at 8 AM, it had been dragged approximately 15 feet downhill and flipped over with fresh signs of feeding on the right hip.  When I checked the photos taken the night before, at 3:00 AM, a coyote had its head buried in the body cavity.

Night before Day 9 - coyote on carcass
Night before Day 9 - relatively small round head,
muscular profile, and round long tail of a mountain lion
3 minutes later, the lion is dragging the carcass downhill.
Click photo if you want to see enlarged version.
At 3:45 AM, a muscular rump appears at the shoulder of the carcass, and three minutes later the head of a mountain lion is clamped onto the middle of the carcass and dragging it to the right.

Large track on downhill side of carcass after busy night of dragging.
In the following days, the carcass would continue to be dragged short distances every few days, and as a  result, the wildlife camera was not aimed at it and did not get photos of predators.  However, there were regular signs of feeding mostly on the rear leg bones.

Bobcat sneaking across the pasture in broad daylight.
When sitting, it looked very much like the brown tufts of grass.
In bright light on Day 15, I watched a bobcat slowly make its way across the Golf Tee towards the carcass.  It would walk a few paces, sit down, look multiple directions, sit more, than move a short distance further.  Before it made it across the Golf Tee, however, my camera bag rolled down the hill and scared the little predator back into the willows.

Miri withstanding the stench and resetting the camera
 after the carcass was moved the night before.
My observations and the wildlife camera confirmed that the following predators and scavengers fed on the steer carcass in the first 15 days of observation:  ravens, coyotes, vultures, a mountain lion, and probably a bobcat.  Large feline tracks observed at the side of the carcass indicated a mountain lion had probably visited early on, and the wildlife camera confirmed that a mountain lion fed on the carcass at least one night.  But does this mean that the mountain lion killed the cow?  Not necessarily.  Several studies have found that mountain lions will scavenge on carcasses killed by other predators or which died from illness or injuries.  After more research, I'll discuss this further in a future post.

Even the living cattle would sometimes sniff the carcass.
See black steer in background with neck outstretched.


  1. This and your bone yard posts are incredible for your descriptions. Very, very interesting!!! I love cam traps for what they capture and have added this post to my virtual collection:

  2. I wasn't sure if the topic was going to gross out readers. life-death-life, ad infinitum. I like the way your site is so well organized.

  3. Awesome post, professor! I am excited to be in your blog, and am willing to be your assistant anytime. I am a better weeder than I am t-post wrangler. Feeling thankful for the cow who fed so many and inspired so much.

  4. I guess I don't get grossed out easily. My mentor had us interns collect road-kill while out doing field work. We used her tiny 2-door Civic and it was a stinky affair, especially in the heat of summer. I imagine it was an odd sight to see a gloved hand holding a dangling, mangled carcass out a car window on old back roads. She'd time the development of the maggots and ID the flies from the carcasses, so she'd have baseline data for when the coroner called. She kept pre-rotted liver in her freezer at the ready to finish rearing any flies she collected from corpses.

  5. Wow, maggot dating. That's impressive!


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