Big Cat Week: Dark Beaches, Big Cats

National Geographic Emerging Explorer Gregg Treinish and his team at Adventurers and Scientists for Conservation bring us stories from around the world about adventuring with purpose. Here, ASC naturalist guide Nikki Mann reflects on jaguars, sea turtles and their interactions during her recent scouting trip to Costa Rica. Be sure to check out Big Cat Week and the Cause an Uproar initiative for more on these amazing felines.

By Nikki Mann

We spent hours and hours walking a tropical beach in Santa Rosa National Park, Costa Rica…

In the dark…

Without headlamps.

As the surf pounded the beach to my left, invisible and insistent, I tried to decide if I looked weak—or, really, if I looked like the weakest of our group.

This is a worry I often have while doing physically demanding work in remote locations, but in Costa Rica, it was not the opinion of the four other guys I was concerned about.

It was the opinion of the jaguars.

This image, captured by photographer Alonso Sánchez of ACR Wildlife Photography on a beach less than a mile away, is what we were hoping to see—a jaguar eating a sea turtle. Although jaguar tracks appeared on the beach almost nightly, the cats remained invisible shadows. (Alonso Sánchez of ACR Wildlife Photography)

The huge cats were on the beach with us. We’d just found tracks—called huellas in Costa Rica—made less than 20 minutes ago, after our last walk down the sand looking for turtle tracks.

The big male jaguar had been there.

Cat biologist Juan Carlos Cruz Diaz (Photo by Nikki Mann)

He probably was still there, too, watching us from the thicket of mangrove trees only a dozen feet away. These massive, rare, and relatively polite cats were the reason cat-biologist Juan Carlos Cruz Diaz and his friend, wildlife photographer Alonso Sánchez, were spending their vacation at a remote research station in Santa Rosa National Park, on the north Pacific coast near the Nicaraguan border.

We traveled to this place via rental car, bus, a 1975 Land Rover with no seat cushions, and our own two feet, backpacking the final two miles through a lightning storm. Although the beach itself is only a half-mile strip of sand sandwiched between charcoal cliffs, it is known as the best place in Costa Rica to see jaguars.

“The only jaguar I’ve seen was like for just three seconds, right here,” Juan Carlos had said earlier that day when we arrived at the open-air research station. This statement, coming from a biologist who has studied jaguars in Costa Rica for the past six years, is telling.

Jaguar populations and behavior are not well understood. Secretive night hunters, they live in remote, densely forested places. Although Juan Carlos has camera traps set up literally all across the country, and has seen photographs and videos of various jaguars, he never gets to see the cat he works so hard to protect.

Jaguar tracks new-1
A large male jaguar left these tracks at 1:00 a.m., less than 15 minutes after we walked here. (Photo by Nikki Mann)

Jaguars in Costa Rica suffer from a number of pressures, among them habitat loss, slow regeneration rates, and being shot by ranchers for killing livestock. Possibly the most devastating impact to overall population numbers is illegal poaching of many of the big cat’s prey species like the agouti, a rodent the size of a house cat, and the peccary, a wild pig.

As though it will help me see in the dark, I wipe my glasses, fogged from the humidity of this “dry” forest, which received more rain this afternoon than my home state usually gets in an entire month.

I am reminded of another key prey species as the putrid smell of rotting flesh assaults my nose. The only resident researcher at this remote biological field station, a short, muscled Nicaraguan named Wilbert, clicks on his flashlight, briefly scanning the dense growth for the orange eye-shine we hope to see. The beam casts eerie shadows on the corpse of a hollowed-out Olive Ridley sea turtle shell and its punctured skull.

dead olive ridley
The leftovers of a jaguar meal, an Olive Ridley turtle carcass (Photo by Nikki Mann)

This particular skeleton is a leftover from arribada, another rarity in Costa Rica. Last Wednesday, five days before our arrival, 28,000 turtles came up on this beach to nest.

There are only two beaches in Costa Rica where arribada occurs, and the jaguars know it. Tonight, they hunt with only four or five turtles arriving, mainly the smooth-shelled Olive Ridleys, or possibly one of the flashier green turtles.

Even though I knew we were going try to see jaguars at night, nothing prepared me for the actuality of walking in almost total blackness and being watched by a 200-pound-plus killing machine—a predator with excellent night vision and and no fresh turtle kills since last week.

Although the jaguars hunt near the high tide line, I wasn’t tempted to stray closer to the ocean. The third interesting set of huellas we saw in the sand that night was made by one of the saltwater crocodiles patrolling the ocean, also looking for sea turtles.

Juan Carlos, Nikki and Jeff
Juan Carlos, Nikki and Jeff (Photo by Jeff Wohl)

Juan Carlos turned on his headlamp to follow the drag tracks of a crocodile’s spiny tail through the sand. “Probably three meters,” he said, guessing the size of the animal. “Going back and forth from the swamp.”

I did some mental math. Three-point-three feet to a meter times three meters was a nine-and-half-foot “log” with teeth that, walking in the dark without a headlamp, I could accidentally step on.

This is what adventure scientists do on vacation. And we love it.

Nikki Mann and her partner in adventure, Jeff Wohl, have been ASC guides for three years. When they aren’t working in field biology or teaching natural history, they can be found planning their next epic trip. Learn more about Adventurers and Scientists for Conservation Guided Science Outings at

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Meet the Author
Gregg Treinish founded Adventure Scientists in 2011 with a strong passion for both scientific discovery and exploration. National Geographic named Gregg Adventurer of the Year in 2008 when he and a friend completed a 7,800-mile trek along the spine of the Andes Mountain Range. He was included on the Christian Science Monitor's 30 under 30 list in 2012, and the following year became a National Geographic Emerging Explorer for his work with Adventure Scientists. In 2013, he was named a Backpacker Magazine "hero", in 2015, a Draper Richards Kaplan Entrepreneur and one of Men's Journal's "50 Most Adventurous Men." In 2017, he was named an Ashoka Fellow and in 2018 one of the Grist 50 "Fixers." Gregg holds a biology degree from Montana State University and a sociology degree from CU-Boulder. He thru-hiked the Appalachian Trail in 2004. Read more updates from Gregg and others on the Adventure Scientists team at Follow Adventure Scientists on Instagram @adventurescientists, on Facebook @adventurescientists, and on Twitter @AdvScientists.