I awoke one September day with autumn in my blood. The academic year had just begun with its comfortable, addictive commotion –anxious, hormonally charged faces, the smell of new books, the ring of cash registers, and the chatter of new acquaintances and old friends. But as soon as classes were over, I headed north toward Stanley, just east of the Sawtooth Mountains.
My visit caught the Sawtooth Valley in mid-autumn stride. Aspen touched by early morning frost clattered against the backdrop of the Salmon River. A raven quorked on high afternoon thermals. Within minutes of stepping out of the car, I decided to climb along a familiar ridge to get a better view of the Sawtooths and distance myself from the ranch and the road.
With hunting season still a week away, a herd of elk lolled high above on the sage-covered hillside. I chugged slowly up the ridge, pausing every few hundred yards to catch my breath. Alerted by a Clark’s nutcracker scolding from a solitary pine, the elk slid behind the summit and disappeared into the forest. When I arrived at the top, slightly dizzy from the thin air and the view, a hilltop cairn formed by outthrust chunks of decomposing granite offered a nice resting spot. I sat there for several minutes soaking in the last few drops of summer in the valley.
A makeshift flagpole stuck in the rocks had been toppled by the wind, and I decided to set it right again and secure it with some fence wire wrapped around rock anchors. As I picked up one of the rocks, my hand and arm were soon awash in ladybugs, scurrying and nipping at my salty skin. Confused, I gingerly replaced the rock and tried another stone nearby. Again, I was greeted with an agitated crimson swarm –a third rock, a fourth, and several more. The significance finally dawned on me: I had stumbled across a ladybug hibernation site.
Underside of rock with hibernating ladybugs.
Energized by my incredible luck, I raced back down the ridge to share my find with the couple who lived on the ranch at its base. Betty and Craig had settled there in the 1950s and for more than twenty years he was a trapper and a hunting and fishing guide, mostly for wealthy clients who came over from Sun Valley to get a taste of the Idaho backcountry. As always, they were eager to have a visitor.
“Saw your car go by. You already been climbing up on the hill?” Craig asked, noticing my sweaty clothes.
“Yeah, and you won’t believe what just happened up there …what I found up on top!”
“Did you find my ladybugs?” he grinned.
I must have looked like an idiot. My incredible discovery wasn’t such big news after all… we sat down to tea and didn’t talk about the ladybugs again.
When I got back to campus, I realized that serendipity had opened a window on one of nature’s most durable and precious secrets. Craig had undoubtedly come across the ladybugs on a fall hunting trip at least twenty years ago, but how much longer had this hibernation site been there? And how do ladybugs find their way to this site each fall and why this site in particular?
For the next six years, I studied the ladybugs, trying to learn from these gentle creatures nestled in their rocky home. I collected ladybugs in winter and studied their tolerance to cold and to freezing, monitored their arrival at the cairn in fall and their dispersal in spring. Oddly enough, winter aggregations on ‘ladybug hill’ include two different species: Hippodamia sinuata –sometimes called the 9-spotted ladybug– and H. caseyi, found in far fewer numbers. A single cluster of beetles may contain between several dozen and a few hundred individuals. There must be a definite survival value in the communal gathering of large numbers of beetles at this location, although it is still not clear what that might be.
The ladybugs aggregate under rocks and in crevices beneath thin crust of snow. As cozy as this sounds, the nests are not warmed by the metabolic heat of huddling ladybugs. Their metabolic heat production is kept to a bare minimum for survival, because one of the greatest challenges that over wintering ladybugs face is making their limited fat reserves last through eight months of hibernation. Accordingly, temperature readings under uninhabited rocks are indistinguishable from the temperature profiles in the nest itself.
The cairn itself sits exposed on the shoulder of a hill overlooking the Sawtooth Valley, home to Stanley, Idaho –one of the coldest spots in the country. Winter winds on the ridge top can be quite strong and I have often needed to dig a snow shelter to make working there bearable. But regardless what I feel standing up there on the exposed, gusty hill and despite the fact that we have been taught that the temperatures on a mountain top are usually colder than those at lower elevations, the ladybug nests are actually some of the warmest places in the valley.
Temperature data late Dec 1999-early Jan 2000. On the morning of 1/6/2000 (dotted line), the valley floor (blue) fell to -20F but the ladybug nest (red) was much warmer @ +22F.
A driving January storm on ladybug hill.
On clear winter nights, dense cold air sinks to the valley floor displacing the lighter, warmer air, which rises up the ridge. The temperature difference can be dramatic. One January night, when the valley was -22oF, temperature readings in the cairn were +22oF. That’s a strong incentive for ladybugs to find their way back to the rock pile before winter sets in.
The most intriguing mystery of all, though, is how the ladybugs manage to find their way back to that same hilltop cairn, year after year. The homing process is even more of a puzzle when one considers their life cycle. Over wintering ladybugs arrive at the cairn in September and remain until May, waiting in suspended animation for the return of spring, when they migrate down to the valley floor in May to begin feeding on aphids that drink the juices of the early wildflowers in the alpine meadows. They mate, deposit their larvae and die there. The best estimates are that summer-born ladybugs probably live just a few weeks, so the beetles returning to the ridge top the next fall are two or three generations removed from the spring migrants. Ladybugs are not strong flyers and, in any case, it seems unlikely that any beetles survive the entire summer and lead others back to the cairn. Yet, this cycle of emergence in late May, followed by a few generations summering in the valley and the return of the surviving grandchildren or great-grandchildren to the hibernaculum has repeated itself for years on end.
What drives this unerring migration to the same spot? There are several north-south ridges in this valley, and exposed cairns of decomposing granite sit atop many of them. Yet, season after season, I have found no evidence of ladybugs at these other sites while every fall thousands of ladybugs congregate at the cairn on ladybug hill. To appreciate how ladybugs navigate –what they sense and how they respond– is next to impossible for visually oriented humans. The ladybug’s umvelt, her sensory sphere, might involve some visual cues, but olfaction and chemoreception are probably much more important. Not all of them survive the winter; so is it possible that migrating ladybugs detect the nesting site by the scent of their fallen ancestors and settle in? Or do prevailing thermals give them a lift and then peter out at this particular ridge top, depositing them here in much the same way that the hiking trail led me and Craig and probably others before us to rest on this pile of granite? I still don’t know. I may never know. But the fact that ladybugs manage to return to it decade after decade is remarkable enough to keep me coming back, too.
After observing these ladybugs for five consecutive winters, many of my original questions spawned new lines of inquiry, but most of the answers are still incomplete and few of those are intuitively obvious. True understanding requires patience and durability –a kind of mental staying power that derives from a balance of resolve and resignation –traits that I like to think sustain the ladybugs in the bleakest January. It requires willingness to taking the long view –something that is hard to reconcile with the values of a society in which complex issues are reduced to sound-bites and ‘disposable’ is a good thing. While we seek newer and faster, ladybugs require several generations to make their cyclical migration, which includes several months of just staying put, a reminder that sometimes progress is best made by holding back. And they are satisfied with things that work; their rock pile is safe and reliable and they do not seem to be looking for something better. Nature does not strive for perfect or optimal, only good enough.
Some winters, I would bring a group of students to ladybug hill. They were generally impressed and charmed by the sight of ladybugs in their hibernaculum, and, like me, they had plenty of questions. But for most of them, the enthusiasm was short-lived. I know that by leading them to the site, by sharing this gift with them, I am denying them the same opportunity for discovery that made it precious to me. Still, I suspect that many of these young adults have never contemplated sustained natural processes before, much less been encouraged to make their own detailed observations of species and their natural histories or to appreciate the importance of long-term study of seasonal change and year-to-year variations. They haven’t been given the tools or the skills necessary to make long-term connections –connections that could help them see themselves in a larger context.
The ladybugs have taught me many things but this might be the most important lesson of all: how important it is for us to seek alternatives to the thrill of instant rewards, to slow down and to foster an ethic of attentive patience, forbearance, cooperation, and a respect for the persistent resourcefulness of all living things.
Adapted from Whole Terrain 12:25-27 (2003) Whole Terrain
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