Water Bears in Crater Lake
By C. Warren Fairbanks, Assistant Park Naturalist
One day in early August, 1954, Ranger
Naturalist John Rowley and I were prowling about the base of Wizard
Island, situated near the west end of Crater Lake. This was an important
hunting expedition. Extensive and careful preparations had been made
before starting the trip. First, adequate provisions had been secured by
making arrangements, well in advance, with the dining hall for a supply
of sandwiches and various suitable accessory food items -- it was to be
an all day trip.
After checking the supplies, we stowed
them carefully, along with other gear, into pack sacks. These in turn
were loaded into a conveyance that carried us to the Rim Village, which
was as far as we could travel by motor vehicle. The remainder of the way
to Crater Lake had to be negotiated on foot. Upon unloading at the Rim,
therefore, we shouldered our packs and headed down the Lake Trail -- a
trek of 1.6 miles.
On this particular day we took our
time. In addition to being rather heavily loaded with essentials, we had
brought along various pieces of photographic equipment in order to make
a complete pictorial record of our operations. Consequently, we stopped
now and then to capture with lens and film interesting features and
events along the way.
At the bottom (of the trail, not the
lake), we obtained a boat with outboard motor -- previously arranged
for, to be sure. As quickly as possible, yet without undue haste, we
loaded our gear into the boat for the one and one-half mile voyage to
Wizard Island -- the water being a little too cool for comfortable
swimming, especially with full field pack -- and took off, after the
motor finally started, of course.
Upon reaching the island, we picked up
other equipment which had been cached there during a preliminary
exploratory mission and, now completely outfitted, set course for the
shore of Fumarole Bay, chief base of operations.
Fully half a day had been consumed in
this phase of our venture, so, reaching our destination, we sat down to
devour our repast. All the while, excitement of anticipation for the
hunt kept mounting within us. It was even difficult to make ourselves
take the time to properly dispose of paper sacks and milk cartons for
return to a suitable trash repository before heading out. In fact, John
Rowley, younger and more impetuous, and having seen some sign which
suggested the presence of game, set off along shore while still munching
a sandwich. This he held firmly in his left hand while using his right
to aid his progress along the rough and steep terrain.
I was not long in following, however.
Presently, initial excitement having been replaced by the steadier verve
of actual search for the prey we were working the area methodically as a
well-accustomed team, leaving no stone unturned in the effort to exhaust
all possibilities for finding their lairs. Then, having examined the
original site thoroughly, we returned to the boat to seek other likely
spore.
Finally, and much later, each of us
sighted and drew fine bead -- first I, then Mr. Rowley -- on fair game.
There, caught squarely in the centers of the fields of our respective
hundred-power scopes, were two water bears -- the first ever reported to
be seen in Crater Lake. Mine was so nearly hidden by lush green
vegetation that I could just barely (no pun intended) make out his --
or, more probably, her -- outline. Ranger Naturalist Rowley's, on the
other hand, was lumbering along nearly always in the open. No triggers
were pulled, however -- park regulations do not permit action.
We had, of course, returned to the
laboratory, and our " scopes" were microscopes. Water bears are very
small animals. Although the largest of them are a little over one
twenty-fifth of an inch in length, most tardigrades, as they are known
to students of zoology, are only about half that size or less (Pennak,
1953). Actually, they are not very well known, even to the zoologist.
The name of this animal means "slow walker," and the clumsy lumbering
way in which he gets around is very suggestive of his common name --
water bear.
Since he has four pairs of short stumpy
legs, some people consider him to be a rather distant cousin of the
spider, while others place him in a completely separate division of the
animal kingdom. Be his relationships as they may, these two specimens
proved to be a very interesting find. To our inexperienced eyes, they
appeared to belong to the genus Macrobiotus, although this has
not been definitely determined. The one which came under my microscope
was taken from the bottom of Fumarole Bay. It was collected with a mass
of filamentous green algae (simple green plants) that was lifted with a
plant grapple (Fairbanks and Rowley, 1954) from a depth of twelve feet.
The other specimen, oddly enough, came from rotting wood lying in water
along the nearby shore of the island.
Even though water bears are little
known, they are reportedly very abundant in various aquatic and
semiaquatic habitats (Pennak, 1953). Frequently they are found on masses
which are intermittently wetted by rain or splashings from streams. The
animals have the ability to shrink up and become inactive when
conditions such as insufficient moisture make active existence
impossible. In this way they are able to remain alive in a state of
minimum activity, which can persist as long as there are food reserves
available within their bodies.
Tardigrades feed mostly upon plant
cells, from which they extract the fluid contents by a sucking action.
They also may be cannibalistic to a certain extent. In the main,
however, they should be classed as converters which make the food
substances manufactured by plants available to other animals. They, in
turn, are preyed upon chiefly by certain protozoans and by roundworms (Pennak,
1953). Therefore, they form one link in the food chain which always
begins with the green plant and which leads ultimately to some large
animal.
It might be correctly inferred that the
"hunting expedition" mentioned above was not organized to track down the
water bear. To be exact, we, were searching for other forms of life. The
find, however, was one of considerable interest because it brought to
light a little-known animal which had not previously been reported as
part of the fauna of Crater Lake National Park.
Literature Cited
Fairbanks, C. Warren, and John R.
Rowley. 1954. Tribute to the clarity of Crater Lake. Nature Notes
from Crater Lake 20:34-36.
Pennak, Robert W. 1953. Fresh-water
Invertebrates of the United States. New York, The Ronald Press. ix,
769
