|
|
MARINELAND OF FLORIDA - THE WAY IT WAS
CAN AN OCTOPUS BE TRAINED ?
One of the most intriguing research
projects in the brief history of the laboratory has been a study of how well
the octopus "remembers". The results of this research, conducted
by Paul H. Schiller of the Yerkes Laboratories of Primate Biology, were published
in The Journal of Comparative Physiological Psychology under the title: Delayed
Detour Response in the Octopus. Were it not for the fact that the Marine Studios
biologists had so successfully maintained adult octopuses alive in captivity,
Schiller would not have had a long enough interval to conduct his study of
this odd animal with his capable tentacles and 360-degree vision. He had poor
luck with his first experiment, which consisted of placing a crab under one
of two inverted cans. The four octopuses participating in this problem first
had an opportunity to study the crab under one of two transparent cups which
were then replaced with the cans. After the cans had been substituted the
octopuses were for short periods restrained from approaching them, the question
being, how long would they remember which can covered the bait? All four scored
very badly. They lifted the cans indiscriminately, sometimes both together,
and seemed to have no idea whatever of what they were about. Schiller next
designed an ingenious box, rather like the ground floor of a dwelling, with
a front door, a hall and a room on either side of the hall. Each room had
a window adjacent to the front door. In the experiment a crab was placed in
a glass beaker and put, for example, in the room to the right of the front
door. The octopus could look through the window and see the food, but in order
to get at it they had to enter the front door, pass down the hall and turn
to the right at its far end. Would the octopuses, while going down the hall,
remember which room the crab was in and make the correct turn? Schiller first
familiarized them with the glass beaker and gave them practice in extracting
crabs from it. He wanted to make sure that they
recognized it for what it offered-food. The octopuses. weighing roughly two
pounds, their bodies measuring five inches and their tentacles twelve, were
next turned loose on the box. upon looking through the window they saw the
crab in the glass beaker and tried in vain to reach it by getting through
the window. Failing in this they then went through the door. Schiller at first
left out the partitions between the hall and the rooms so their only problem
was gaining entrance. When they had learned this much he replaced the partitions.
After relatively few attempts they became quite competent in making the right
turn- in fact they almost never failed. Upon entering the door they often
faced the wall of the room in which they had seen the crab and side-stepped
down the hall until they reached the far door. To prevent them from orienting
themselves this way, Schiller put another door with a hole in it at the far
end of the corridor. While squeezing through this they could no longer remain
oriented toward the bait. However their percentage of correct turns was still
high. Schiller next placed at the end of the hall a solid door to delay the
octopuses temporarily so that he might determine how long they could remember
which way to turn. He found that if the delay was under forty seconds they
rarely failed to make the correct turn. If the interval was longer than a
minute they were much less successful, and if delayed tow or three minutes
they became completely confused. If conditions were normal they were nevertheless
able to retain the lesson learned here over a period of weeks, for when exposed
to the problem again after a long interval they solved it rapidly. The common
Atlantic octopus used in the experiment is one of more than a hundred species
and is brought to the Studios from the rocky floor of the Atlantic several
miles offshore. In the sea his eight tentacles usually provide motive power
but if pressed he can proceed by jet propulsion and further confound his predator
by ejecting an inky, smell-deadening smokescreen. In his powerful tentacles,
horny beak and poisonous "saliva" the octopus has formidable weapons.
A crab trapped by one of the suction cups arranged in double rows on each
tentacle finds himself drawn inexorably inward towards the mouth where the
eight arms converge. The crab's struggles quickly cease apparently owing to
toxic "saliva". The bite of even a small octopus leaves humans with
a painful, enduring wound like a bee sting or the jab of a hot pin. Profuse
bleeding and pain subside within an hour but the wound may be extremely sensitive
for weeks. Whether the bite of one of the great Pacific octopuses, with its
tentacle spread of twenty-five feet would be fatal is not known for no one
has ever been bitten by one. Scientific literature about the cephalopod group,
to which both the octopus and squid belong, does not contain a description
of a giant living squid, since no fishing or research ship has ever captured
one. However, the imprint of his adhesive cups, the size of an elephants foot,
have been found on the skin of sperm whales, and his ugly beak in their stomachs.
Were it not for the fact that some few dead giant squids washed up on the
shore of Newfoundland and North Europe during the nineteenth century, science
would have little authentic description of these legendary creatures .
{Home} {History} {Photos} {Links} {Visitor's Memories} {Contact}
