Fab Four: Beetles, Big Cats, Bears and Biodiversity
December 5, 2018
December 5, 2018
In our new paper, published in Oecologia, we highlight the ecosystem engineering role of pumas for beetle communities. Here, we emphasized that pumas provide crucial carcass "habitat" for beetle species during important life history events.
As the sun rose on that calm, spring day in the Bridger-Teton National Forest, crystals of ice covered my tent and eyelashes. The night before, I had finished an 1,800-mile car drive from Pittsburgh to the Tetons. I had never been to the Tetons, nor had I spent much time in a tent, but here is where I would call home for the next six months. I was a graduate student under Dr. Melissa Grigione at Pace University, developing a project with Panthera's Mark Elbroch that would examine the importance of pumas (also known as mountain lions) to beetle communities. It was my first day in the field with Panthera's Teton Cougar Project.
I hiked into the forest the follow morning with Panthera's Connor O'Malley, marching towards some unknown animal killed by the puma we call F61. We had left to investigate after the GPS collar on F61 confirmed she had finished eating and vacated the area. While we were walking to the kill, Connor briefed me on F61, sharing stories of the athleticism and toughness by this legendary cat. I started to smell the carcass as we got closer; it resembled the smell of a wet dog, but more pungent. My heart began to race; I knew it was time.
After some searching, we discovered it: a fresh mule deer carcass sprawled next to the Gros Ventre River. F61 had dragged the carcass over the distance of a football field to its final resting place. I dug into the cold soil surrounding the carcass and began to place my insect traps into the ground. I sat next to my trap for a few minutes, and it didn't take long to see that it was working. One after the other, beetles of different colors and shapes funneled into my traps as they approached the carcass to feed: some flew, some walked, some ran. We were witnessing the linkage between pumas and beetles immediately.
Over the course of six months I hiked daily into the backcountry to collect beetles from carcasses left by pumas in the northwestern Wyoming wilderness. Not a bad life! But there were some speed bumps along the way. On twelve different occasions, a Grizzly or black bear had visited a site, and ate all of the beetles in the collection cups. One time we even saw a grizzly was feeding at the carcass as Panthera's Anna Kusler and I approached the site. The bear ran off after leaving behind claw marks on the aspens as a reminder that we're never alone in the forest.
Other animals also got in the way of my beetle collection. One American robin in particular would watch beetles enter the traps then swoop down for a snack. A curious squirrel took baths in a particular trap each week immediately after I finished setting them up. At another site, a red fox defecated atop the collection cups.
Challenges occurred after I had collected the beetles as well. I'd sit for hours well into the night in a tent outside of the office, huddled under a desk lamp counting beetles on large metal trays. At one point, one of my glass Mason jars filled with smelly beetles and alcohol exploded in the office from pressure (Michelle, the TCP manager, was not too happy). However, we kept plugging away and eventually finished the project.
In the end, we collected 24,209 beetles belonging to 215 individually unique beetle species. Some of these species were predators and came to the carcasses to feed on other beetles. Others came to court partners, lay eggs, and hide their young. Some species came quickly, using their large bodies to monopolize space at the fresh carcasses. A few specialist beetles came months after the puma produced the carcass, as they would eat the hide and fur from the carcass as well as raise their larval young once all of the other beetle species had left. Others would compete with flies, eating their competitors’ larvae as a source of energy to support their own offspring. The different ways the beetles contended with the carcass were endless, and strangely enthralling.
This study shows us how pumas act as ecosystem engineers, which are animals that create or modify habitat in ways that increase biodiversity (beavers are the classic example). This is the first example of an apex predator being one. Pumas play a crucial, and possibly unique, role in providing carcass ‘habitat' for many beetle species in the Greater Yellowstone Ecosystem. Even after months have passed since a cat leaves its kill, beetles are still using the carcasses for habitat. If we can understand the importance of pumas for food webs and provisioning of resources for other species, we can better understand just how important it is to conserve their populations in their natural habitats.