Fecundity and Cougar Kittens

Posted by Mark Elbroch of Panthera in Cat Watch

Two of four 3-week old kittens born to F47, an adult female mountain lion in northwest Wyoming. Photograph by Mark Elbroch / Panthera.
Two of four 3-week old kittens born to F47, an adult female mountain lion in northwest Wyoming. Photograph by Mark Elbroch / Panthera.

F51, an adult female mountain lion currently followed by Panthera’s Teton Cougar Project, has given birth to three litters in three years, which as far as we know, is something of an anomaly. F51 immigrated into our study area from some unknown place and we started tracking her at the very start of 2011, just before she gave birth to her first litter (5 kittens!). In fall 2012, she separated from her kittens when they were 14 months old, and then she gave birth to three kittens, just 16 months after her first litter. Wolves killed two kittens from her 2012 litter when they were very young, and when her last remaining kitten was just nine months old, they went their separate ways. We were completely baffled as to why such a young mountain lion was on her own (typically kittens disperse at about 18 months in our study area), but the answer revealed itself a month later. Just ten months after her 2012 litter, F51 gave birth to four new kittens in 2013. Absolutely amazing, and completely unexpected.

Watch the video below of F51′s 2013 litter when we discovered them (unexpectedly, during routine filed work looking for mountain lion kills). They are two days old.

Fecundity. I’ve always liked the sound of the word, and how it feels when I say it. According to Merriam-Webster’s Collegiate Dictionary, fecundity means “fruitful in offspring.” For biologists, fecundity is a measure of how fruitful is a species. It’s also essential knowledge in understanding species ecology and creating effective conservation plans for species that need support. For wildlife researchers, quantifying fecundity is something of a holy grail, because it requires such a significant time and energy investment, a quest if you will.

What information is needed to determine fecundity for an animal, you might ask? First, we need to know how many offspring are born at a time. Is it typically one offspring, like humans, or twins like pronghorn? Second, we need to know how often a single female gives birth. Females of many species give birth every year, or several times a year, in cases such as meadow voles and cottontail rabbits. Last, we need to know how long females typically live in a population to estimate how many times she might give birth during her lifetime. Seems so simple!

Now let’s consider mountain lions. Cougars are cryptic carnivores that earn a living by remaining invisible to their prey. They live like shadows on the landscape, weaving in between us, often unseen. They wander vast areas as they hunt and survive, making it challenging to predict where they are at any given point in time. Mountain lions are difficult to see on a normal day, but especially tricky to see when giving birth. And mountain lions live eight to 12 years, and sometimes longer (except in hunted populations). So how do we go about finding cougar dens, documenting the length of time between cougar litters, and determining the average length of time a female cougar survives in the wild?

F51, an adult female mountain lion wearing a satellite GPS collar, and 2 of her 4 kittens born in 2013. (Photograph by Mark Elbroch / Panthera)
F51, an adult female mountain lion wearing a satellite GPS collar, and 2 of her 4 kittens born in 2013. (Photograph by Mark Elbroch / Panthera)

It would be a near impossible task, if not for technology that allows us to follow mountain lions in the field—I’m talking about the collars researchers place on animals. Modern GPS collars allow us to not only pinpoint the location of an animal, but to do so in near-real time, because GPS locations are transferred through satellites to computers in our dingy field offices.

But let’s jump to what we’re learning on the Teton Cougar Project, one of few long-running projects on mountain lions. Unfortunately, many research projects are short—typically the length of a MS or PhD program—and thus determining fecundity for a species like mountain lions is impossible. Projects like the Teton Cougar Project are so special because they are so rare.

Over 13 years, we’ve visited the natal dens of 18 different females to document litter size, and recorded inter-birth durations for nine females for which we documented two to three consecutive litters. Here, in the Southern Yellowstone Ecosystem in northwest Wyoming, female mountain lions give birth to an average of three kittens (range two to five) on average every 27 months (range 10 to 39 months). It’s amazing how so much work and so many miles hiked can be summarized in just a sentence or two.

F51 is certainly our most “fruitful” female to date. Follow F51 and other mountain lions on facebook.


Elk, It’s What’s for Dinner… In Winter

Posted by Mark Elbroch of Panthera in Cat Watch

F61, an adult female mountain lion, standing over the carcass of an adult cow elk she successfully killed at the tale end of last winter. (Photograph by Mark Elbroch/Panthera)
F61, an adult female mountain lion, standing over the carcass of an adult cow elk she successfully killed at the tale end of last winter. (Photograph by Mark Elbroch/Panthera)

It’s akin to a light switch; it’s that stark. One day mountain lions inhabiting the Southern Yellowstone Ecosystem are predominantly killing mule deer, and the next day they all switch to killing elk. And then they kill elk for five to five and a half months before they switch back to deer.

It happens on a slightly different date each year. In 2013, it was November 14th, two weeks earlier than in 2012. There hasn’t been a deer killed by the cats we are tracking as part of Panthera’s Teton Cougar Project since that date, and we don’t expect we’ll find a deer killed by a project cougar until May. Nowhere in their vast geographic distribution do cougars exhibit such distinct summer and winter diets as in our study area.

Ungulate (a fancy word for a “hoofed mammal”) migrations, driven by the seasonal availability of forage that sustains them, result in large-scale redistributions of resources for carnivores. In response, carnivores adapt their foraging behaviors in systems with migrating prey.

In summer, carnivores in North America are quick to seize opportunities presented by the birth pulse of numerous, vulnerable, young ungulates. Whereas in winter, carnivores take advantage of the numerous ungulates struggling to survive harsh weather on lesser-quality forage and suffering poorer health. In the Southern Yellowstone Ecosystem, cougars do something more. Not only do local mountain lions follow trends in changing prey vulnerability, but they also track changing prey numbers.

M80, a young male cougar, practicing his choke hold on a mule deer fawn carcass. (Photograph by Mark Elbroch/Panthera)
M80, a young male cougar, practicing his choke hold on a mule deer fawn carcass. (Photograph by Mark Elbroch/Panthera)

Through November and December each year, thousands of elk descend upon the National Elk Refuge and surrounding Bridger-Teton National Forest and Grand Teton National Park lands in northwest Wyoming (as well as thousands of tourists to ride in sleighs drawn by sturdy horses to view them, but cougars generally steer clear of the tourists). Recent winter elk counts in the area number around 11,500 animals. This boon in prey numbers for local mountain lions coincides with the migration of mule deer out of our study area into the flat lands surrounding Jackson, WY and further south. Thus, it is not surprising that cougars here switch their focus from deer to elk with the Christmas season.

Cougar populations across North and South America are primarily non-migratory and hunt non-migratory prey. Nevertheless, where mule deer exhibit seasonal migrations, some cougars follow, exhibiting seasonal ranges themselves; other cougars remain in winter deer range through the summer, where deer persist, but at lesser numbers (Pierce et al. 1999, Cooley et al. 2008). In contrast, cougars here remain relatively stationary as ungulates migrate across the Southern Yellowstone Ecosystem, and kill different prey in different habitats in different seasons.

As they hunt through the year, mountain lions in the Southern Yellowstone Ecosystem also distribute a wealth in carcasses for scavengers, decomposers and floral communities, in more diverse locations than they would if ungulates didn’t come and go. Thus ungulate migrations in the Southern Yellowstone Ecosystem are not just vital to the dynamic health of the area, but a cornerstone piece needed to understand why local cougars do what they do throughout the year.

For those who are interested, click here to read our research paper on this subject. And please follow our work on Facebook.

3Pierce BM, Bleich VC, Wehausen JD, Bowyer RT (1999) Migratory patterns of mountain lions: implications for social regulation and conservation. J Mamm 80: 986-992.

Cooley HS, Robinson HS, Wielgus RB, Lambert CS (2008) Cougar prey selection in a white-tailed deer and mule deer community. J Wildl Manage 72: 99-106.

Hunters or Hunted? Wolves vs. Mountain Lions

Posted by Mark Elbroch of Panthera in Cat Watch

F109, a six-year-old cougar, nursing three three-week-old kittens. She wears a Vectronics satellite collar which allows researchers to follow her movements in near real time and study the secret lives of mountain lions. Photograph by Mark Elbroch/Panthera
F109, a six-year-old cougar, nursing three three-week-old kittens. She wears a Vectronics satellite collar which allows researchers to follow her movements in near real time and study the secret lives of mountain lions. Photograph by Mark Elbroch/Panthera

Wolves are coursing, social predators that operate in packs to select disadvantaged prey in open areas where they can test their prey’s condition. Mountain lions are solitary, ambush predators that select prey opportunistically (i.e., of any health) in areas where slopes, trees, boulders, or other cover gives them an advantage. Thus, wolves and cougars inhabit and utilize different ecological niches, allowing them to spatially and temporally coexist; nevertheless, in the absence of wolves, cougars utilize areas traditionally assumed to be the sole dominion of coursing wolves. This suggests that where wolves are sympatric with cougars, wolves limit mountain lions.

In fact, wolves kill mountain lions. This has never been disputed. Wolves are considered the dominant competitors in most interactions between the species. Take for instance, the Hornocker Institute study of mountain lions in Northern Yellowstone led by Dr. Toni Ruth, in which researchers discovered the remains of three mountain lions killed by wolves. What is contentious is the idea that mountain lions might kill wolves.

Look carefully for the mountain lion in the background, pushed off its kill by a large wolf caught on remote camera. Photograph courtesy Teton Cougar Project/Panthera
Look carefully for the mountain lion in the background, pushed off its kill by a large wolf caught on remote camera. Photograph courtesy Teton Cougar Project/Panthera

Liz Bradley, a Montana Fish, Wildlife and Parks wolf biologist, reports that she has discovered five wolves killed by mountain lions in three years—all bearing the characteristic canine punctures in their skulls betraying the identity of the perpetrator. Some dispute her claims and point out that wolves fight each other too, especially adjacent packs, and that they also attack the head; skeptics believe a canine puncture in a wolf skull could be made by another wolf just as easily as a mountain lion.

The Teton Cougar Project operates in the Southern Yellowstone Ecosystem, and is one of very few long-term studies of mountain lions. Since the start of the project, wolves have trickled into the area, established territories and reproduced. In 2001, U.S. Fish and Wildlife Service surveys estimated that there were about 10 wolves in our study area, and that number steadily increased to as high as 91 in 2010. To date, we’ve documented five lions killed by wolves, all kittens, and all less than six months old while they were still relatively slow to climb and less than fully coordinated. But it was just last October that we finally documented the contrary. For the first time, a mountain lion we were tracking killed a wolf.

She’s a particularly feral mountain lion, F109, an adult female with three three-month-old kittens. All cougars are feral, of course, but there’s something unique about F109. She has “crazy” eyes, and always wanders the most rugged, inhospitable terrain. She was near impossible to catch in the first place. She’s a survivor.

We can’t tell you exactly what happened, but we can describe what we deciphered from the clues left behind in the snow. F109 was up high traversing steep, barren slopes, where we expected there was little game. Nevertheless, her location data indicated that she’d stopped and we suspected she’d made a kill. We slogged up the mountain to investigate, the ground bare of snow adjacent the road, but as deep as our thigh in the high bowl where she lingered. The entire area preceding her position was a mosaic of wolf tracks and trails. A wolf pack made up of adults, subadults and pups had criss-crossed the area, leaving barely a patch of snow without their sign.

Perhaps the wolves had challenged F109, or perhaps just one of them wandered too close to her kittens, or perhaps a pup felt like exploring on its own—trying to decipher the absolute pandemonium of tracks was beyond us. Whatever the circumstances, F109 captured and killed a pup born this year just above the chaos of wolf activity. By this time (November), wolf pups are sizable, their skulls larger than those of coyotes. We discovered the signs of struggle, the telltale blood in the snow, and the pup’s remains beneath a lonely subalpine fir: a pile of coal black fur, bone shards from the legs, and the skull, skinned but completely intact. F109 and her kittens had consumed the pup completely.

4Thus far, our research has supported exactly what everyone  expected: Wolves dominate mountain lions in most encounters. But, this recent exchange is particularly exciting. No longer can we say that wolves dominate mountain lions in all encounters. What circumstances led to F109 turning the tables, we do not know. Perhaps F109’s predecessors served as naïve intermediaries relearning to coexist with a dominant competitor, a species absent since 1926, when the last wolf was killed in Yellowstone National Park. Perhaps F109 is evidence that lions learn quickly and adapt, and that mountain lions will successfully coexist with wolves in the Yellowstone Ecosystem for generations to come.

Credits: Cat Watch


The Patient Photography of Steve Winter

Posted by Lauren Ward of NG Staff in Explorers Journal

Photography by Steve Winter/National Geographic
Photography by Steve Winter/National Geographic

National Geographic wildlife photographers have often recounted the painful waiting period that comes with getting the perfect shot. Countless hours are spent sitting within the stuffy confines of a blind or perched behind a crop of tall grasses, camera lens at the ready, waiting for the animal to stalk past.

Photographer Steve Winter has spent his career photographing big cats — everything from the elusive snow leopard to mountain lions in the Hollywood hills. Steve has done his fair share of waiting.

Think several hours is a long time to wait for a photo? Try 14 months. Steve’s latest project in Griffith Park rendered many stunning new images of unseen urban wildlife captured against the nighttime Los Angeles cityscape. The pièce de résistance came when Steve’s team photographed the holy grail of L.A. fauna, a mountain lion called P-22 prowling its midnight trail right next to the Hollywood sign.

watch the video

Steve’s photos are evocative. For Angelenos especially, the sight of a cougar elicits a sense of local pride in a city generally thought to be picked clean of its native species. But what may be even more remarkable is the planning, preparation, and technology that went into bringing this photo to life. Camera traps were place in strategic areas within the park that had the best view of Downtown.

“The single hardest thing about working in this park is finding locations where you see urban wildlife and the city…You have to see that you’re in downtown L.A. You don’t want to think you’re in Downtown L.A., you want to know you’re in Downtown L.A.,” explains Steve.

With help from National Geographic’s Remote Imaging engineers, Steve has recently developed the next generation of highly specialized video camera systems currently in Griffith Park equipped with infrared detection and external lights.


Here’s how it works: A camera trap is placed on the trail (1). The external lights (2) are connected via wire to the camera trap. A beam-break sensor (infrared trip wire) (3), once tripped, will wirelessly send a signal to the camera trap to turn on. The camera trap then begins recording for a predetermined time.

“After fourteen months, everything came together- the lighting, the composition, and I got the image I dreamed of: P-22 with the Hollywood sign,” marvels Steve.

What’s more, Steve’s work has contributed to a growing body of knowledge on the health and population size of mountain lions in Southern California. Click here to interact with a map of greater Los Angeles that illustrates how cougar survival rates can be lower in an urban jungle than in areas where they’re hunted.

Full National Geographic Magazine Article: Ghost Cats


Steve’s new book, Tigers Forever: Saving the World’s Most Endangered Big Cat, encapsulates the beauty and fragility of tigers in Sumatra and Myanmar. In its infancy, the book began as three unique stories born from Steve’s travels between several tiger hotspots in Southeast Asia- a journey that took place collectively over the course of 10 years.

With only 3,200 individuals remaining in the wild, Tigers Forever begs the question, do we care if tigers walk the Earth?  In this sense, Steve’s photography has become more than a portfolio of pretty pictures, but also a testament to what we still have the power to save.

Ten percent of profits earned from each book goes to on-the-ground field research supporting tiger conservation throughout Asia. Check out Tigers Forever here.

(Related: Steve Winter’s Journey to Tigers Forever)

Big Cat Week 

Big Cat Week is right around the corner. A week dedicated to nature’s fiercest felines, we’re celebrating these magnificent creatures by rounding up a team of big cat experts like Steve Winter for our next Google+ Hangout on Tuesday, December 3rd at 12:30 p.m. EST (5:30 p.m. UTC). And don’t forgot to tune into Nat Geo WILD for a week of non-stop big cat programming beginning November 29th.

How to Participate in the Hangout

You can be a part of the Cause an Uproar and our Google+ Hangout. Send in your questions for these National Geographic Explorers and they may be asked on air. Submit your questions by…

  • Uploading a video question to YouTube with hashtag #bigcats
  • Posting a question on Google+ or Twitter with hashtag #bigcats or
  • Commenting directly on this blog post

Follow National Geographic on Google+ or return to this blog post to watch the Google+ Hangout Tuesday, December 3rd at 12:30 p.m. EST (5:30 p.m. UTC).

Other Hangouts From National Geographic:

Hangout With Buzz Aldrin and Conrad Anker
Hangout With Explorers on All Seven Continents