Animal Letusimulants

— The feigning of death by certain animals, for the purpose of deceiving their enemies, and thus securing immunity, is one of the greatest of the many evidences of their intelligent ratiocination. Letusimulation (from letum, death, and simulare, to feign) is not confined to any particular family, order, or species of animals, but exists in many, from the very lowest to the highest. It is found even in the vegetable kingdom, the well-known sensitive plant being an interesting example. The action of this plant is, however, purely reflex, as can be proved by observation and experiment, and is not, therefore, a process of intelligence. The habit of feigning death has introduced a figure of speech into the English language, and has done much to magnify and perpetuate the fame of the only marsupial found outside the limits of Australasia. “ Playing ’possum ” is now a synonym for certain kinds of deception. Man himself has known this to be an efficacious stratagem on many occasions. I have only to recall the numerous instances related by hunters who have feigned death, and have then been abandoned by the animals attacking them.

I have seen this habit in some of the lowest animals known to science. Some time ago, while examining the inhabitants of a drop of pond water under a high-power lens, I noticed several rhizopods busily feeding on the minute buds of an alga. These rhizopods suddenly drew in their hairlike filaria and sank to the bottom, to all appearances dead. I soon discovered the cause in the presence of a water-louse, an animal which feeds on these animalcules. It likewise sank to the bottom, and after looking at the rhizopods swam away, evidently regarding them as dead and unfit for food. The rhizopods remained quiet for several seconds, and then swam to the alga and resumed feeding. This was not an accidental occurrence, for twice since I have been fortunate enough to witness the same wonderful performance. There were other minute animals swimming in the drop of water, but the rhizopods fed on unconcernedly until the shark of this microscopic sea appeared. They then recognized their danger at once, and used the only means in their power to escape. Through the agency of what sense did these little creatures discover the approach of their enemy ? Is it possible that they and other like microscopic animals have eyes and ears so exceedingly small that lenses of the very highest power cannot make them visible ? Or are they possessors of senses utterly unknown to and incapable of being appreciated by man ? Science can neither affirm nor deny either of these suppositions. The fact alone remains that, through some sense, they discovered the presence of the enemy, and feigned death in order to escape.

There is a small fresh - water annelid which practices letusimulation when approached by the giant water-beetle. This annelid, when swimming, is a slender, graceful little creature, about one eighth of an inch long and as thick as a human hair ; but when a water - beetle draws near, it stops swimming, relaxes its body, and hangs in the water like a bit of cotton thread. It has a twofold object in this : in the first place, it hopes that its enemy will think it a piece of wood fibre, bleached alga, or other non-edible substance ; in the second place, if the beetle be not deceived, it will nevertheless consider it dead and unfit for food. This example of letusimulation I have repeatedly seen, and any one may observe it with a glass jar, clear water, a water-beetle, and several of these annelids. The annelid is able to distinguish the beetle when it is several inches distant, and the change from an animated worm to a lifeless thread is startling in its exceeding rapidity.

Many of the coleoptera are letusimulants. The common tumble-bug, which may be seen any day in August rolling its ball of manure, in which are its eggs, to some suitable place of interment, is a remarkable letusimulant. Touch it, and at once it falls over, apparently dead. Its limbs become stiff and rigid, and even its antennæ are relaxed and motionless. You may pick it up and examine it closely. It will not give the slightest sign of life. Place it on the ground and retire a little from it, and in a few moments you will see it erect one of its antennæ and then the other. Its ears are in the antennæ, and it is listening for dangerous sounds. Move your foot or stamp upon the ground, and back they go, and the beetle again becomes moribund. This you may do once or twice, but the little animal, soon finding that the sounds you make are not dangerous, scrambles to its feet and resumes the rolling of its precious ball.

Some animals feign death only after exhausting all other means of defense. The bomdardier beetle, or stink-bug, has on the lateral margins of its abdomen certain bladder-like glands which secrete an acrid, foulsmelling fluid. It has the power of ejecting this fluid at will. When approached by an enemy, the bombardier presents one side to the foe, crouching down on the opposite side, thus elevating its battery, and waits until its molester is within range. It then fires its broadside at the enemy. If the foe is not vanquished, as it generally is, but still continues the attack, the bombardier topples over, draws in its legs, and pretends to be dead. Many a man has acted in like manner. He has fought as long as he could ; then, seeing the odds against him, he has feigned death, hoping that his opponent would abandon him and cease his onslaughts. I have seen ants execute the same stratagem when overcome either by numbers or by stronger ants. They curl up their legs, draw down their antennaæ, and drop to the ground. They will allow themselves to be pulled about by their foes without the slightest resistance, showing no signs of life whatever. The enemy soon leaves them, whereupon the cunning little creatures take to their feet and hurry away.

The most noted and best known letusimulant among mammals is the opossum. I have seen this animal look as if dead for hours at a time. It can be thrown down any way, and its body and limbs will remain in the position assigned to them by gravity. It presents a perfect picture of death. The hare will act in the same way on occasion. The cat has been seen to feign death for the purpose of enticing its prey within grasping distance of its paws. In the mountains of east Tennessee (Chilhowee) I once saw a hound that would “ play dead “ when attacked by a more powerful dog than itself. It would fall upon its back, close its eyes, open its mouth, and loll out its tongue. Its antagonist would appear nonplused at such strange conduct, and would soon leave it alone. Its master declared that it had not been taught the trick by man, but that the habit was inherited or learned from its mother, which practiced the same deception when hard pushed.

Most animals are slain for food by other animals. There is a continual struggle for existence. Most of the carnivora and insectivora prefer freshly killed food to carrion. They will not touch tainted meat when they can procure fresh. It is a mistake to suppose that carnivora prefer such food. The exigencies of their lives and their struggle for existence often compel them to eat it. Dogs will occasionally take it, but sparingly, and apparently as a relish, just as we eat certain odoriferous cheeses. But carnivora and insectivora would rather do their own butchery ; hence, when they come upon their prey apparently dead, they will leave it alone and go in search of other quarry, unless they are very hungry. Tainted flesh is a dangerous substance to go into most stomachs. Certain ptomaines render it sometimes very poisonous. Long years of experience have taught this fact to animals, and therefore most of them let dead or seemingly dead creatures severely alone.