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1. Octopus: The Ocean’s Intelligent Invertebrate:
A Natural History, Jennifer A. Mather, Roland
C. Anderson and James B. Wood (Timber
Press, 2010)
Who knows humanity who only human knows?
We understand ourselves better by looking at
other animals, but most other animals are not
as remarkable as the octopus.
These eight-armed invertebrates are much
more closely related to oysters, limpets and
ship-worms than they are to fish, let alone to
mammals, but they lead fully active lives and
seem fully conscious creatures of strong and
even unsettling intelligence.
Octopuses are molluscs, or “soft ones” (the
same Latin root is found in “mollify”), with no
internal skeleton and no rigid structure. Unlike
some of their relatives, however, they do have
brains. And more than one brain apiece, in a
sense, because their arms are semi-
autonomous. They don’t really have bodies,
though, which is why they belong to the class
known as Cephalopoda, or “head-foots”.

2. Squid and cuttlefish, which are also covered in
this book, are in the same class but do have
more definite bodies, because they swim in
open water rather than, like octopuses, living
on the sea-floor. Another difference between
the groups is that octopuses don’t have
tentacles. Their limbs are too adaptable for
that:
Because the arms are lined with suckers along the
underside, octopuses can grasp anything. And since the
animal has no skeleton, it can flex its arms and move them
in any direction. The arms aren’t tentacles: tentacles are
used for prey capture in squid, and these arms, with their
flexibility, are used for many different actions.
(“Introduction: Meet the Octopus”, pg. 15)
Octopuses would be interesting even if we
humans knew ourselves perfectly. But one of
the interesting things is whether they could be
us, given time and opportunity.
That is, could they become a tool-making,
culture-forming, language-using species like
us? After all, unlike most animals, they don’t
use their limbs simply for locomotion or
aggression: octopuses can manipulate objects
with reasonably good precision.

3. I used to think that one obstacle to their use of
tools was their inability to make fine
discriminations between shapes, because I
remembered reading in theOxford Book of the
Mind (2004) that they couldn’t tell cubes from
spheres.
The explanation there was that their arms are
too flexible and can’t, like rigid human arms
and fingers, be used as fixed references to
judge a manipulated object against. But this
book says otherwise:
[The British researcher J.M.] Wells found that common
octopuses can learn by touch and can tell a smooth cylinder
from a grooved one or a cube from a sphere. They had
much more trouble, though, telling a cube with smoothed-
off corners from a sphere… They couldn’t learn to
distinguish a heavy cylinder from a lighter one with the
same surface texture. (ch. 9, “Intelligence”, pg. 130)
The problem isn’t simply that their arms are
too flexible: their arms are also too
independent:
Maybe the common octopus could not use information
about the amount of sucker bending to send to the brain and
calculate what an object’s shape would be, or calculate how
much the arm bent to figure out weight. Octopuses have a
lot of local control of arm movement: there are chains of
ganglia [nerve-centres] down the arm and even sucker

4. ganglia to control their individual actions. If local
information is processed as reflexes in these ganglia, most
touch and position information might not go to the brain
and then couldn’t used in associative learning. (Ibid., pg.
130-1)
Or in manipulating an object with high
precision and accuracy. An octopus can use
rocks to make the entrance to its den narrower
and less accessible to predators, but that’s a
long way from being able to build a den. It is a
start, however, and if man and other apes left
the scene, octopuses would be a candidate to
occupy his vacant throne one day.
But I would give better odds to squirrels and to
corvids (crow-like birds) than to cephalopods.
Living in the sea may be a big obstacle to
developing full, language-using, world-
manipulating intelligence. The brevity of that
life in the sea is definitely an obstacle: one
deep-sea species of octopus may live over ten
years, which would be “the longest for any
octopus” (ch. 1, “In the Egg”). In shallower,
warmer water, the Giant Pacific
Octopus,Enteroctopus dofleini, is senescent at
three or four years; some other species are
senescent at a year or less. Males die after
fertilizing the females, females die after

5. guarding their eggs to hatching. In such an
active, enquiring animal, senescence is an odd
and unsettling process. A male octopus will
stop eating, lose weight and start behaving in
unnatural ways:
Senescent male giant Pacific octopuses and red octopuses
are found crawling out of the water onto the beach [which
is] likely to lead to attacks by gulls, crows, foxes, river
otters or other animals… Senescent males have even been
found in river mouths, going upstream to their eventual
death from the low salinity of the fresh water. (ch. 10, “Sex
at Last”, pg. 148)
Female octopuses stop eating and lose weight,
but can’t behave unnaturally like that, because
they have eggs to guard. Evolution keeps them
on duty, because females that abandoned their
eggs would leave fewer offspring. Meanwhile,
males can become what might be called
demob-demented: once they’ve mated, their
behaviour doesn’t affect their offspring. In the
deep sea, longer-lived species follow the same
pattern of maturing, mating and senescing, but
aren’t so much living longer as living slower.
These short, or slow, lives wouldn’t allow
octopuses to learn in the way human beings
do.

6. The most important part of human learning is,
of course, central to this book and this review:
language. Cephalopods don’t have good
hearing, but they do have excellent sight and
the ability to change the colour and patterning
of their skin. So Arthur C. Clarke (1917-2008)
suggested in his short-story “The Shining
Ones” (1962) that they could become
autodermatographers, or “self-skin-writers”,
speaking with their skin. The fine control
necessary for language is already there:
Within the outer layers of octopus skin are many
chromatophores – sacs that contain yellow, red or brown
pigment within an elastic container. When a set of muscles
pulls a chromatophore sac out to make it bigger, its color is
allowed to show. When the muscles relax, the elastic cover
shrinks the sac and the color seems to vanish. A nerve
connects to each set of chromatophore muscles, so that
nervous signals from the brain can cause an overall change
in color in less than 100 milliseconds at any point in the
body… When chromatophores are contracted, there is
another color-producing layer beneath them. A layer of
reflecting cells, white leucophores or green iridophores
depending on the area of the body, produces color in a
different way: Like a hummingbird’s feathers, which only
reflect color at a specific angle, these cells have no pigment
themselves but reflect all or some of the colors in the
environment back to the observer… (ch. 6, “Appearances”,
pg. 89)

7. “Observer” is the operative word: changes in
skin-colour, -texture and -shape are a way to
fool the eyes and brains of predators. The
molluscan octopus can adopt many guises: it
can look like rocks, sand or seaweed. But the
champion changer is Thaumoctopus mimicus,
which lives in shallow waters off Indonesia. Its
generic name means “marvel-octopus” and its
specific name means “mimicking”. And its
modes of mimicry are indeed marvellous:
This octopus can flatten its body and move across the sand,
using its jet for propulsion and trailing its arms, with the
same undulating motion as a flounder or sole. It can swim
above the mud with its striped arms outspread, looking like
a venomous lionfish or jellyfish. It can narrow the width of
its combined slender body and arms to look like a striped
sea-snake. And it may be able to carry out other mimicries
we have yet to see. Particularly impressive about the mimic
octopus is that not only can it take on the appearance of
another animal but it can also assume the behaviour of that
animal. (ch. 7, “Not Getting Eaten”, pg. 109)
But octopuses also change their skin to fool the
eyes and brains of prey.
The “Passing Cloud” may sound like a martial
arts technique, but it’s actually a molluscan
hunting technique. And it’s produced entirely
within the skin, as the authors of this book

8. observed after videotaping octopuses “in an
outdoor saltwater pond on Coconut Island”,
Hawaii:
Back in the lab and replaying the video frame by frame, we
found how complex the Passing Cloud display is. The
Passing Cloud formed on the posterior mantle, flowed
forward past the head and became more of a bar in shape,
then condensed into a small blob below the head. The
shape then enlarged and moved out onto the outstretched
mantle, flowing off the anterior mantle and disappearing.
(ch. 6, “Appearances”, pg. 93)
It’s apparently used to startle crabs that have
frozen and are hard to see. When the crab
moves in response to the Passing Cloud, the
octopus can grab it and bite it to death with its
“parrotlike beak”. They “also use venom from
the posterior salivary gland that can paralyze
prey and start digestion” (ch. 3, “Making a
Living”, pg. 62). But a bite from an octopus
can kill much bigger things than crabs:
Blue-ringed octopuses, the four species that are members of
the genus Hapalochlaena, display stunning coloration. Like
other spectacular forms of marine and terrestrial life, they
have vivid color patterns as a warning signal. These small
octopuses pose a serious threat to humans. They pack a
potent venomous bite that makes them among the most
dangerous creatures on Earth. Their venom, the neurotoxin
tetrodotoxin (TTX) described by Scheumack et al in 1978,

9. is among the few cephalopod venoms that can affect
humans. A variety of marine and terrestrial animals
produce TTX [including] poisonous arrow frogs [untrue,
according to Wikipedia, whichrefers to “toads of the
genus Atelopus” instead], newts, and salamanders… but
the classic example, and what the compound is named
after, is the tetraodon puffer fish. The puffers are what the
Japanese delicacy fufu is made from. If the fish is prepared
correctly, extremely small amounts of TTX cause only a
tingling or numbing sensation. But if it is prepared
incorrectly, the substance kills by blocking sodium
channels on the surface of nerve membranes. A single
milligram, 1/2500 of the weight of a penny, will kill an
adult human… Even in the minuscule doses delivered by a
blue-ringed octopus’s nearly unnoticeable bite, TTX can
shut down the nervous system of a large person in just
minutes; the risk of death is very high. (“Postscript:
Keeping a Captive Octopus”, pg. 170)