Growing Up at Espenberg: Eggstatic About Foxes
Whhhrrrrr! Whhhrrrrr! The engine of the four-seater Maule airplane roared in my ears as we glided 8,000 feet above the Alaskan tundra. Below, I could see tiny white specks-gulls-soaring over the ponds that dotted the scene, stretching to the horizon where the frozen ocean met the treeless plain. Even on this day in early June, the ponds had collections of ice and snow about their edges, and the ocean itself was a gigantic frozen block, rising three feet above the ground where it touched the beach.
An hour later, the Maule, dodging driftwood, touched down on a beach black with sand from a volcanic explosion 50,000 years earlier. We were on the north side of Cape Espenberg, just above the Arctic Circle in the Bering Land Bridge National Preserve, located in northwest
Alaska. This is the area where it is thought that the first humans crossed over to North America. Cape Espenberg is 40 miles from the nearest town, toilet, phone, television, building, or person. As the Maule took off and waggled its wings in a goodbye-and-good-luck gesture, I realized I was to be there, at the mercy of nature, for the next six weeks, with no protection but the thin canvas of the tent in which I was to live. There would be no contact with the outside world but through the small handheld radio (which often didn‘t work), and the AM/FM radio, which received only one station-KOTZ Kotzebue-broadcast from the nearest town (population 2,000), located over 40 miles across the Chuckchi Sea ice.
But that didn‘t bother me.
This was the summer of 1995; I was 10 years old. Since then, I have spent every summer at Espenberg, helping my parents research several species of birds. I have become accustomed to the nights that reach below freezing in mid-July, and the swarms of summer mosquitoes that give no relief when the wind slacks. I have come to love the endless daylight, for the sun does not drop below the frozen waters during the summer months, just as it hardly rises above the horizon during the winter months! At Espenberg, I learned how to identify birds, find their nests, and measure their eggs. We worked with shorebirds: red-necked phalaropes (Phalaropus lobatus), red phalaropes (Phalaropus fulicaria), western sandpipers (Calidris mauri), semipalmated sandpipers (Calidris pusilla), and dunlins (Calidris alpina), as well as waterfowl such as the common eider (Somateria mollissima). I learned how to capture, band, and measure the birds, and how to create interesting meals from the storage boxes of dried and canned foods on which we subsisted. I began as a field assistant and grew into the official camp cook and bird bander. As I became more experienced, Dad would simply hand me a bag of tools, a trap, and a list of birds, and I would set out to catch them on my own.
It wasn‘t enough for my curious mind, however, to only be a part of someone else‘s research. I wanted a project of my own...
One night, about two weeks into my first summer at Espenberg, my father whispered, "Hey, Juliann! Come here! Look at this!" I stepped out of the warm tent, heated by the propane camp stove, and into a magical land of mist. A thick fog covered the cape, leaving only the sparse dunes faintly visible in the swirling world. The sun had dipped low over the ocean and cast its rosy, slanted rays onto the shrouded land, setting the condensed water droplets aglow. Suddenly, a sleek form emerged from the fog, trotting determinedly. Its pointed black nose directed its feet, and its bushy red tail, tipped with white, flicked to keep perfect balance.
The red fox (Vulpes vulpes) trotted silently through camp, passing within 10 feet of us. I was dumbstruck. The fox hadn‘t even seemed to notice us! I thought humans were supposed to be so far removed from the rest of nature as to be terrifying and destructive to it! But the fox did not seem aware of that. At that moment, I had a wonderful epiphany. This fox, passing its life on this remote cape, had never before seen the likes of me. It had never heard the sound of a gun, nor felt the sharp bite of a trap. This fox was free from all the learned fear apparent in wild animals who have encountered the wrath and power of humans.This fox WAS NOT AFRAID! I still revel in this thought.
The fox came to be known affectionately as Scrawny, as its coat was rather ratty and it was skinny as a pencil. I observed Scrawny often, at least twice a week. She would trot through camp, stop and lift her head to the wind, sniff, and then continue on her merry way. One day I was coming back from the outhouse-a hole dug in the sand near camp-and there was Scrawny. I stopped to watch her. She was walking slowly, stopping often to sniff the grass. Then she plopped down, scratched behind her ear, and went to sleep! Five feet in front of me! Another time I saw her crawl into a small hole and lie with her head on her paws.
One of my brother‘s favorite ground squirrels was romping about in the grass next to camp. In a flash, Scrawny was there, her jaws on its neck. Seconds later, the life had been shaken out of the squirrel, and Scrawny was loping off, her neck arched with the weight of her kill. I decided to follow the fox. I knew that if she was carrying her meal off instead of eating it, she must have a den somewhere. So I ran after her, keeping far enough behind so I wouldn‘t interfere. After about a mile and a half, I heard yips, and out ran eight tiny fox pups from several holes in a grassy dune! They scampered up to Mom and licked her face, begging for the food. I watched the interaction between mother and kits for a half hour and then ran back to camp to divulge my secret.
By this time, I was sure I wanted my research to envelope the foxes at Cape Espenberg. I also wanted to work with birds, because I was interested in them, too. The perfect opportunity presented itself, and I prepared to begin my experiment the following summer-1995. Here‘s how it came about...
When we found nests, we marked them with Popsicle sticks, which were placed five to 10 paces away and marked with the distance. However, we found that many nests were destroyed only days after discovery... It is possible to tell who has eaten the eggs by certain clues left at the nest. For instance, jaegers eat the eggs right in the nest bowl, jabbing holes in the shells with their beaks and licking out the insides. Foxes, however, often carry off the eggs, then bury them or bite them in half to devour the insides. Foxes often defecate in the nest bowl. From these clues, we were able to discern that many of the nests had been pillaged by foxes. The question was, Were we leading the foxes to these nests? Had they discovered that the strong scent of humans meant a nest was nearby? I decided to find out.
Before conducting my own study, I conducted some library research and found that numerous other scientists had asked similar questions and performed similar studies. Most of them found that the presence of humans did not make much, if any, difference on the overall predation rate of nests (Willis, 1973; Gotmark, 1984; Nichols, 1984; Galbraith, 1987; Sedinger, 1990; O‘Grady, 1996). A few, however, discovered that predation increased slightly when nesting birds were disturbed (Mayer-Gross, 1997; Salathe, 1987). Crows sometimes used people to find loon nests (Gotmark, 1990), and jaegers, but not gulls, followed researchers to waterfowl nests (Strang, 1980). But what about foxes?With this knowledge in mind, it was time for my research to begin.
Instead of using real nests in my study, I decided to create artificial nests using store-bought chicken eggs. That way I could control various important factors: time exposed, habitat, and human activity. The next summer, I brought three dozen eggs out to Espenberg (two dozen for the project and one dozen for breakfast!). I selected a ridge well away from our main area of activity and set up 24 nests (one egg per nest), 12 on each side of the ridge.The north side was reserved for the experimental nests. I checked these nests every other day and called them two-day nests. Each time I checked these nests, I walked along a distinct path from the stick to the nest and rubbed my hand on each egg to leave my scent, thus leaving as many human markings as possible. The south side of the ridge was used for the control nests. These nests were also marked with Popsicle sticks, but I was careful to leave as few human signs as possible, and only checked these nests every two weeks. They were known as the two-week nests. If there was a significant difference between the number of nests eaten by predators in the two categories, then I would have evidence that we had contributed to the high predation rates.
The eggs were divided into four habitats, mirroring the four main nesting habitats at Espenberg: ridge (dry, many colorful lichens and mosses, hardly any grass), side-of-ridge (also dry, with mosses and lichens, more grasses), marsh (wet, hummocky, long grasses), and side-of-lake (thick, wet moss with very tall grasses). The habitat for each egg was decided by lottery; I drew the placement out of a hat (literally!) to avoid biasing the data. The guidelines were simple: there were 12 nests in both the control and the experimental groups, therefore there would be three eggs in each of the four habitats.There was one final and important feature of the experiment: the artificial nests were meant to mimic waterfowl nests. Before waterfowl flush from their nests, they carefully cover the eggs with the nest lining (grass and down). This reduces predation by hiding the eggs from view. It was important that I likewise cover the eggs in my artificial nests; they would otherwise be instantly devoured by patrolling jaegers (who constantly scour the land from a bird‘s-eye view, looking for anything bright and egg-like to eat).
I continued this experiment for four years, during the summers of 1995, 1996, 1997, and 1998. Each summer the experiment lasted about four weeks, thus allowing me to check the two-week nests halfway through, and again at the end of the experiment. The results from the first two years supported my suspicion that foxes were finding the nests as a result of our nest-marking scheme: a substantially higher proportion of the two-day nests were eaten (see Figures 1 and 2, chi-square test, P 0.005) . One day I even witnessed Scrawny come loping down the ridge, stop to sniff a marker, turn, walk right down my path, remove the egg from the nest and take it a short distance away, and then commence to devour it! It was like magic, but not a magic that I wanted to be responsible for. As a result of my experiments, we decided to check real nests less often. When we found a nest, we would float the eggs (a technique for determining nest initiation date based upon egg density), and then not return until just before the estimated hatching date. We also began placing the markers farther away (15 to 20 paces rather than five to 10).
However, an interesting thing happened in the final two years of my study. The number of nests eaten in the two categories was essentially the same (see Figures 3 and 4, chi-square test, P 0.5) ! Interestingly, these same years Scrawny was not seen and was presumed dead (foxes don‘t live forever!). From this I have hypothesized that Scrawny may have been a major source of the nest robbing. The fox population was down altogether that year, so that could also be the explanation. However, we continued our more careful practices to prevent training any Scrawny grandchildren!
If I could continue this project in the future, with an unlimited budget, I would place time-lapse cameras by each artificial nest, thus enabling me to actually see who eats the eggs. This would allow me to determine more confidently what percentage of eggs is taken by foxes compared to other predators, such as jaegers and ground squirrels. I did try this in the summer of 1999, but I had only one camera, and to my chagrin, that egg was never eaten!
Across the cape, in the south dunes, resided a den of arctic foxes (Alopex lagopus). These foxes were even more passive than the red foxes. They could often be spotted curled in a ball by their den, amidst arctic poppies and flowering coltsfoot, basking in the chilly arctic sunlight. When my brother and I approached them with a telephoto lens to capture them on film, they took no notice. In fact, they were so lethargic we were afraid they were sick, but they had a large litter of black, roly-poly kits every year to prove their vitality.
There are not many places on this earth where arctic foxes and red foxes den so close to each other, so I asked, What do these two species of foxes eat? Do they compete for the same food source? I hypothesized that they probably didn‘t according to the competitive exclusion principle: if they did use the same foods, one of the species should be outcompeted if food was in low supply. However, the more basic question remained: what did they eat?
There were two ways to resolve this question. First, I could observe the diet as it was devoured. This seemed nearly impossible, since I need sleep once in a while! Second, I could observe the diet in its more condensed, immobile form-after it had been consumed and processed. In other words, I could look at the indigestible remains in their feces! Yuck! But... that‘s what biology is all about. So... I plugged my nose, and, armed with a garbage bag, latex gloves, and 100 small paper bags, Mom and I visited both dens and carefully collected 50 fox scats per species. Upon returning to Fairbanks, Alaska (where I live), my father, who is a biology professor at the university, sterilized the scats so I wouldn‘t get any fox-related diseases (fox feces often contain the eggs of a tapeworm that can develop into tumor-like growths in humans). Mom and I spent many hours hovering over a microscope, carefully picking apart the scats with tweezers and determining the percentage of every part of its contents. We compared what we found to a reference collection of known teeth, bones, and hair.
We found an array of tidbits inside the scats, including sand and parts of birds, berries, bones, eggshell, seashell, insects, fur, seals, ground squirrels, and voles. Both species of foxes seemed to be consuming mainly ground squirrels, eggs, birds, and berries. The only real difference between species was the few insect and seashell remains in the red fox scats (which weren‘t found in the arctic fox scats) and the small amount of vole remains in the arctic fox scats (not found in red fox scats). For the most part, the two species seemed to have similar diets (see Figures 5 and 6) . From this, I concluded that food was apparently not a limiting factor for the foxes at Cape Espenberg, for neither species had been outcompeted by the other.
In the future, I would like to attach transmitters to the foxes. This would allow me to follow their daily routine, and see where they go and what they do. I am interested to find out if the foxes intrude into each other‘s territory (if the red foxes go to the south dunes and vice versa). Red foxes are supposed to be the dominant species, but we observed more arctic fox activity in the north dunes-red fox territory-than we did red foxes in the south dunes-arctic fox territory. This could be because we spent much more time in the north dunes (where we camped). With transmitters on the foxes, it might be possible to answer these queries!
I last left Espenberg on June 28, 2001. It was a hot day (for Espenberg), and the mosquitoes were having a picnic on our hands, faces, and basically any exposed body part. We had to haul all our gear-food, tents, toiletries and all-through hip-deep marsh out to a lake in the middle of the cape, where we were picked up by a float plane. As the plane roared to take off, bouncing over the shallow waves, I gazed out over the vast stretch of arctic tundra where I had grown up. Next year I would be off to college, and I didn‘t know when, if ever, I would see my beloved Espenberg again. Espenberg is a place where the very dirt is alive and wriggling, where the land and water and fire and sky come together to create a fascinatingly living world. I wanted something to remember it. Then I spotted a reddish object in the distance, moving trippingly across the tundra. It stopped, lowered its head, and sniffed the ground. In my mind‘s eye, I imagined it lifting its head to show the alabaster, rounded form of an ancient chicken egg in its jaws, stained a slight brown by its long hibernation underground. I closed my eyes as the plane lifted from the sparkling sapphire waters and banked hard to the left, setting a direct course for Kotzebue. Years of memories flashed before my sealed lids, and with the thrum of the motor in my ears and the cape fading behind me, I opened my eyes, reached into my day pack, pulled out my journal, and began to write...
Whhhrrrrrrrrr! Whhhrrrrrrrrr! The engine of the four-seater Maule airplane roared in my ears as we glided 8,000 feet above the Alaskan tundra...
Galbraith, H. "Marking and visiting Lapwing Vanellus vanellus nests does not affect clutch survival." Bird Study 34 (1987): 137138.
Gotmark, F. "Do field observers attract nest predators and influence nesting success of common eiders?" Journal of Wildlife Management 48 (1984): 381387.
Gotmark, F. 1990. "Predation of artificial and real arctic loon nests in Sweden." Journal of Wildlife Management 54 (1990): 429432.
Mayer-Gross, H. and H. Crick. "The effect of observers visiting the nests of passerines: an experimental study." Bird Study 44 (1997): 5365.
Nichols, J. and H. Percival. "Observer visitation frequency and success of mourning dove nests: a field experiment." Auk 101 (1984): 398402.
O‘Grady, D. and D. Hill. "Nest visitation by humans does not increase predation on chestnut-collared longspur eggs and young." Journal of Field Ornithology 67 (1996): 275280.
Salathe, T. "Crow predation on coot eggs: effects of investigator disturbance, nest cover and predator learning." Ardea 75 (1987): 221229.
Sedinger, J. "Effects of visiting black brant nests on egg and nest survival." Journal of Wildlife Management 54 (1990): 437447.
Strang, C. "Incidence of avian predators near people searching for waterfowl nests." Journal of Wildlife Management 44 (1980): 220224.
Willis, E. "Survival rates for visited and unvisited nests of bicolored antbirds." Auk 90 (1973): 263267.
Copyright © 2002 American Museum of Natural History.
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Supplement a study of biology with an activity drawn from this winning student essay.
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- Have them research further whether human interference attracts predators, reporting on what they learn. If desired, you can have them start with the references cited at the end of the essay.
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