Popular Science Monthly/Volume 29/October 1886/Some Peculiar Habits of the Cray-Fish
IN hardly any other order of animals do we find such a diversity of habits as among the crustaceans, that include the crabs, lobsters, shrimps, etc. Some are of the sea, others of the land, and others of either; in fact, there seems to be no condition in life they do not share. They are found in the deep sea, and floating on the surface in the Gulf Stream. Some are luminous, others transparent, or have the faculty of changing color. Certain species live in caves, finding their homes in subterranean streams. Others, again, are found in hot springs or in the icy sludge of the Arctic Ocean, while in the south or Antarctic region we have a group that are attached to the wings of birds, thus leading a roving, migratory life. From this hasty glance at the possibilities of "crab-life," we may expect almost anything and not be surprised.
Some weeks ago I left Chicago for a short trip on the Northwestern Railroad up into Northern Illinois. The trains do not make particularly fast time, allowing the tourist an opportunity to obtain a more than casual glance as they move along. In observing the fields and farms in this region, I was struck with one peculiarity not seen in the East. In almost every small valley, especially where there appeared to be a stream, the ground was raised in mounds from eight to twelve inches high, and from six to twelve inches in diameter. Generally they were flat on top, and in almost every case were grassed over the entire surface. A few of these would not have attracted especial attention; but, as we proceeded north, they grew more frequent, and finally patches were seen, several acres in extent, completely covered by the curious mounds. Later on I took occasion to visit one of these localities, and found the prairie completely covered with them for acres. The majority were along the sides of a sluggish brook that held water scarcely an inch deep, and from here they extended away up the slope, so that the most distant heaps were perhaps two hundred feet away from the stream; and, in some cases observed in other localities, no stream or brook could be found, a low, damp spot being the center from which the mounds seemed to radiate or branch. So vast were the numbers of heaps that I could walk for a long distance by merely stepping from one to another, and not unfrequently they were in such close proximity that walking was difficult: a horse in passing over the field presented a curious appearance, evidently finding it hard work; and a carriage would have been wrenched to pieces or badly strained in a short time. The makers of these mounds or heaps were discovered by digging, and proved to be a genus of the common fresh-water cray-fish; and, though I was familiar with their mound-building habits, their location so far from streams was entirely new, and shows that the little creatures are better adapted to a semi-amphibious life than many of their allies that are considered true water-livers.
In making inquiries and investigations into their habits, I found that they differed from our species of the East in certainly, at times, not requiring water. In other words, they passed a certain portion of the time out of the water, and occasionally they would retreat from it; and when floods came they would leave what would be naturally considered their native element entirely and take to dry land.
In a small river that flows through the prairie north of Freeport, Illinois, I found great numbers of cray-fish close in shore, nearly every stone concealing one or more that were well protected by their almost exact resemblance to the bottom in color. Four or five feet above the level of the water were numerous heaps formed in the black clay mud, and almost every one of these contained a cray-fish that was living in water that must have come from above, as the holes had no connection with the river below. Generally I found the little animal out of water, just within the hole, and upon being alarmed it would drop down. Investigation with a stick would show that there were several inches of muddy water in the bottom. The inmates, having no loop-hole for escape, were quite savage, biting at the intruding stick with their powerful claws, and allowing themselves to be almost lifted from the mound.
It would seem strange to find these animals living in this condition if there were not some rational explanation, and it is evident that too much water is equally as disagreeable to the cray-fish here as, if not more so than, not enough, and the mounds and heaps—above and away from the streams—are in this locality the results of the animals' attempts to obtain a location where they can remain in the water or out in safety. To crawl out upon the open bank of a brook would expose them to numerous dangers; so, to avoid this, they crawl up the banks and burrow into the saturated mud or soil, and at times penetrating from the stream-bed, the earth or mud thrown out forming the mound, an opening or door is generally left at one side or on top. Water collects in the bottom of this burrow, while the upper portion is entirely free, thus enabling the cray-fish to take to the water or not, as it is inclined. These mounds are probably built when the streams rise, the crustaceans leaving the swift current and taking to the higher ground for better security. To show how a flood or over-supply of water will at certain times alarm these little creatures, a gentleman residing in Freeport, Illinois, informed me that not many months ago they had some very heavy rains, that greatly increased the volume of the little river running through the town. The water gradually rose until numbers of quite large trees were submerged, and the stream was almost twice its ordinary width. Such an unusual occurrence naturally attracted considerable attention, and my informant and a number of others visited the trees several times, and when the river was at the highest they presented a strange appearance from a little distance. Their trunks seemed to have changed color from the water up to the branches, and on closer inspection it was found that they were completely incased with cray-fish which covered every available space, crowding upward by hundreds, clinging to the bark and to each other, in some spots packed one upon another four and five deep; every moment added to the throng, new ones emerging from the water, while those above, urged on, crept out upon the branches, and completely covered them, presenting a novel and interesting sight. The animals in many cases retained their positions for several days, and did not seem to be affected by their stay out of water. The occasion, however, was taken advantage of by the people, who came with buckets and brooms and swept them from the trees by hundreds, storing them up for future use. The cray-fish in certain portions of the Western country is a pest to the agriculturist, and the work of these little creatures often greatly increases the labor and expense of breaking up land, especially after the burrows or mounds have stood for many years, the vegetation that has grown upon them often increasing their size to mammoth proportions, comparatively speaking. Some farmers consider, however, that they enrich the land by keeping it open, and in many other ways, and that land with cray-fish-heaps is worth more to the acre from this cause. To the man who plows his land in the old-fashioned way, as many Germans yet do, the cray-fish is a hindrance and a pest. Not the least remarkable feature of the life of this little creature is the fact of its living so far from open streams. In many cases examined by me, no stream or brook was present, a mere bog being the center of attraction. How they had wandered so far from clear running water was a mystery. Scientifically, the cray-fish belongs to the family Astacidæ. About fifteen different genera are known, nearly half being marine, the rest fresh-water forms. The forms most familiar to us are Cambarus and Astacus. The latter is common on the Pacific slope and in Europe, while the former is the familiar form of our Eastern rivers and streams, finding their way into the Atlantic Ocean. In many localities their burrowing habits are productive of great damage; this is especially so in the levees of the Mississippi. In some parts of the South they are valued as food, and they can generally be found at Fulton Market, New York, a few people evidently knowing their delicacy in salads, etc. In Europe they have long been used as food, and so great is the demand for them in France that large farms are devoted entirely to their cultivation and breeding, the industry affording a profitable income. A study of the habits of these creatures will well repay the student, as many of them are very curious and interesting. They differ from many of the .rest of the ten-footed crustaceans in not passing through the various larval stages that characterize the growth of so many of their allies.