Crash . . . splash! From my perch on an old log extending into the center of Lost Lake, I was able to locate the source of the sudden noise. A yearling black bear had crashed through the azalea bushes on the north shore of the lake and was now standing, elbows deep, in shallow water and thick, soft ooze. Gradually she worked her way across the lake, walking gingerly to avoid sinking deeper into the mud. Whenever possible, she stepped on a rotting log and followed it for its length. At last her mucky journey ended, and she was rewarded with tasty blueberries growing along the south shore.

I smiled as I watched the little hear, and thought back on an article I had read in the Yosemite Nature Notes about Lost Lake as it existed in 1923, over fifty years ago. At that time, Ansel F. Hall, Chief Naturalist for the Park Service, had stood on the bank of this little pond, located at the base of Half Dome’s southeast face, and had been impressed with the radical change that had occurred since his last visit, fifteen years earlier. Gone was the shallow lake he had expected to see. “I found the lake to be lost indeed,” he wrote. “In its place was a meadow upon which one could walk dry-shod.” He envisioned that the meadow eventually would be replaced by a forest “in twenty or thirty or fifty years.”

Yet here I sat, more than fifty years later, watching a bear with its belly in the mud, in the middle of Lost Lake. What had happened?

When Mr. Hall wrote his article, he believed he had witnessed the natural process of succession in which a lake becomes filled with stream sediments and slowly is transformed into a meadow. However, Lost Lake is not stream-fed. Its water content fluctuates from ten inches during the spring to wet mud during the fall, due to the rise and fall of the water table. Mr. Hall’s initial visit was in the spring. His last visit was in the fall. I believe that what he witnessed was the annual disappearance of a marshy pond.

In the spring when the water is high, the lake is filled with life. This spring, I flushed three mallard ducks from the rushes. From the air, the blue water is hidden by a thin layer of bright-green vegetation. From a bank, one can see the delicate white blossoms of Buckbean, Menyanthes trifoliata, which cover the marshy water from shore to shore. The insectivorous Bladderwort, Utricularia, can be found tangled among the lake’s vegetation. The melodic calls of the many red-winged blackbirds seem magnified between the walls of Half Dome and Mt. Broderick. Flycatchers flash across the water, snapping up dragonflies and mosquitoes.

Unless the year is very dry, Lost Lake retains a great deal of moisture, even through the fall. My first visit was in September, 1971, and I thought, like Mr. Hall, that I could cross the lake “dry-shod.” I crossed that day, but it was not with dry feet. Lost Lake’s center still contained standing water, and more was concealed under thick, deceptively dry-looking mud.

I wonder how much Lost Lake has really changed since 1910? Is the water shallower? The mud thicker? Does it disappear at an earlier date each year? All the vegetation that grows from the shallow waters must lay down a tremendous amount of debris annually.

Fantasizing, I see myself filling a bucket half-full of water, and tossing leaves into it. The leaves decompose and become a soft, viscid ooze. The water in my bucket is murky, but it is still water. Where can the water go? It cannot disappear; it can only fill the bucket fuller as the falling leaves displace the original level.

When I look at Lost Lake in the fall, I see that last year’s vegetation has totally decomposed. Already, the mat of leaves and stems has been converted to a brown mass. The tracks of mice, deer, and bear are imprinted clearly in the drier portions of the mud. How many leaves does it take to make a cup of this fine ooze? The secret of Lost Lake is locked in this answer.

I can only guess, but I believe that this little marshy lake will exist for many, many years to come.

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