Eavesdropping (7 page)

Note the reference to the animals
themselves
. The emphasis is not on the perceptual world of the
typical
worm or butterfly, but on the experience of
this
worm and
that
butterfly. For each animal has its
own personal
Umwelt
, a unique sensory collage that reflects the material—and only the material—that it alone has chosen to ingest. Outsiders may be able to infer the content of this collage by noting the orientation of the animal’s head and body, and especially its eyes, ears, and other sensory receptors. They can then look in the same direction or breathe the same air, and this is exactly what they do.
³

Each of us humans has a personal
Umwelt
too, a perceptual world that includes all the individuals we encounter
in situ
. “When we see other people walking around us,” von Uexküll wrote, putting aside his bubble metaphor for the moment, “they are walking on our stage while we do so on theirs. These stages are never identical, and in most cases are even entirely different.”
⁴

There is an allure to these separate spheres. Something about them intrigues and beckons us, draws us in. We must take to the stage—their stage—but we cannot do so physically. That would burst the bubble. Our only choice is to travel as far as our eyes and ears will carry us, completing the journey with inference and imagination.

For von Uexküll, appreciation of another animal meant entering its “self-world” without becoming a part of it. What does it mean—really mean—to enter the “space” of another; and what kind of space is this? A mental space? An emotional or spiritual space? What are the risks and benefits of “entering”? These will be our questions—our questions about
human beings
—but we will get a huge headstart if we first look at eavesdropping in other forms of life.

In the early 1990s, zoologist Peter McGregor pointed out something that now seems simple and obvious. In the wild, everyone’s sensory equipment is permanently turned to the “on” position. Thus, when Bird A
calls to
or
squawks at
Bird B, these sounds are also
heard by
Birds C, D, E, and F as well as heterospecifics—the members of other species. McGregor referred to this arrangement of signalers and receivers as a
communications network
, to capture
the idea that the signals of isolated individuals usually reach all those who inhabit the same perceptual arena. These other animals, however lowly or primitive they might seem, are exquisitely adapted to their evolutionary environments; and they tend not to do things that would serve no useful purpose. So if they spend a great deal of time observing others, they must be getting something in return. What?

One thing they get is food. If an animal forages on his own, he must personally inspect every promising nook and cranny, a hit-and-miss endeavor that can be tiring. But it is possible to scan a fairly large area visually without roaming around, and when other animals are discovered with something appetizing in their clutches, the observer—merely by sidling up to them—stands to gain far more calories than scanning and sidling consume.

The relative ease of this process is perhaps why “free loaders” and “scroungers” have been given such unappealing names, just as “snoops” and eavesdroppers” have. But as degenerate as they may seem from a puritanical perspective, there is much to admire about such individuals from a cognitive perspective. Species that are devious enough to steal something as coveted as food, and to do so on a regular basis, may be smarter than those that meet their nutritional needs “honestly.” In fact, studies indicate that they have significantly larger brains.
⁵

Another benefit of vigilance relates to safety. By sampling their environment, animals get information about predators, enabling them to take evasive action before it’s too late. The Galápagos islands are home to diverse species, including mockingbirds and marine iguanas. As different as they are, these species have something in common. They are both prey to a third resident—the Galàpagos hawk. When mockingbirds see a hawk, they issue an alarm call, as their species evolved to do, presumably for the sake of other mockingbirds. But iguanas can hear the alarm calls of mockingbirds, and they too run for cover.
⁶
Much the same is true of the African dik-dik, a miniature antelope that goes into alert
mode when it hears the alarm call of the white-bellied go-away bird.
⁷

To survive, iguanas and dik-diks must pay attention to hetero-specifics, whether they be predators or fellow prey, but there is one thing, preeminently, that requires animals to attend exclusively to their own species. It’s sex. If males are to procreate, they must be able to locate willing females. In primates, male senses should also be tuned to the signs of ovulation. When females become sexually receptive, there are visible changes in the genital area. Males must notice these right away, for there will be, at most, a tiny window of opportunity before other males move in.
⁸
In our own species, the female speaking voice becomes more attractive to male listeners when women are able to conceive.
⁹

Females must be vigilant, too. In most species, females are “choosier” than males, and this is adaptive. They have more to lose from a poor choice of mates since they have fewer offspring, and make a larger contribution to infant care. To get a good father for their offspring, and a suitable companion for themselves, females must review the available material very carefully. But how will a superficial scan tell them who the best mate is? In many bird species, brains—especially female brains—may be
pre-tuned
to melodious voices and bodily ornamentation, and helpfully so: vocal ability is linked to testosterone, and thus to sex and territorial defense; and brightly colored feathers are supported by melanin and chromatin, which imply some level of fitness.
¹⁰

Color and music would seem to take us into the aesthetic domain, but in the animal world these properties are strictly functional. By holding out for attractive males, females increase their chances of bagging a good-quality mate, and the benefits may continue past their own lifetime. For any sons that are born are likely to be
more
colorful or melodic than the sons of less attractive fathers. They will easily find a mate and reproduce, passing on their mother’s genes along with their own.
¹¹

In animal communication, there are two arrangements in which the information flows mainly in one direction. In one arrangement, the recipient takes in information merely because he is alert, though he may be unusually sensitive to the threat of predators or out-group challengers, or to the existence of prey. I will use the term “vigilance” for this tendency to look
for something
outside the group. In the other arrangement, attention is selectively focused on members of one’s own group. This inclination to look
at someone
is eavesdropping, and I will refer to it as such, in keeping with the scientific literature on mammals, primates, birds, fish, insects, lizards, and plants.
¹²

Plants? Yes, plants. When attacked by herbivores, some plants send an SOS signal—a bouquet of volatile chemicals. These chemicals attract the natural predators or parasitoids of the herbivores, who eavesdrop on the plants. In some cases, neighboring plants—no more exotic than lima beans—have also been caught eavesdropping.
¹³
These “bodyguards” then release their own concoction, sympathetically, in what one biologist has called “a botanical cry for help.”
¹⁴

Whether eavesdropping is practiced under the leaves, or by the leaves themselves, there are indications that it played a role in the evolution of communication systems. In fact, there are suggestions that the ability to send and receive signals may have co-evolved. Biologist John Endler has proposed that in evolution, signals were designed so as to increase the fitness of the
senders
. But there was a delicate balance that had to be achieved, for it would have been necessary to maximize the reception of conspecifics—the evolutionarily “intended”
receivers
—while minimizing interception by potential predators.
¹⁵

Endler’s hypothesis is appealing, for it combines with other evidence to suggest that eavesdropping—far from being a trivial thing or, in our species, a “naughty” thing—played a significant role in evolution, shaping the neural control and processing systems that are now used for communication. Ancient eavesdropping, it would appear, contributed to the design of modern brains.

Information about all of these things that animals care about, from food and predators to sex and fitness, is in the public domain, available to individuals who are generally alert to the possibility of certain events. It is critical to survival and reproduction and, as public information, it can be intercepted with little risk or effort. Are animals that acquire material which benefits them in the moment, or their offspring in the future, supposed to pretend that they didn’t see it?

That would be tantamount to genocide. Signals and displays are in a species’ repertoire for a reason. They met millions of years of ancestral needs, and continue to do so today. The ornamental and behavioral displays of males provide information to observers, who use it to make adaptive choices. The probability that this information will be ignored approaches zero. In fact, some biologists believe that it was the perceptual appetites of females that caused the appearance of male traits in the first place.
¹⁶

All of these cases of eavesdropping are
one-on-one
. One eavesdropper is focused on one
individual
. It is true, of course, that the eavesdropping may have been inspired by a third animal. The eavesdropper may also be able implicitly to relate what he sees to some feature of his own life—certainly, as we will see, this is possible in our own species. But as we saw with Margaret Browne,
one-on-two
eavesdropping is also common, and in these arrangements the spotlight is on an interaction, or a
relationship
, between two (or more) individuals. What kinds of relationships do animal eavesdroppers favor?

Most involve sex or dominance. These desiderata go by different names, but they are as entangled in the wild as they are in Harlequin novels. In many species, females base their choice of mates partly on fighting ability, and in primates, aggressive and dominant males typically produce more offspring than subordinate ones.
¹⁷
Sex and dominance also converge in some songbird species, where dominant males use their voices to shout down male competitors. Other males, who eavesdrop on these slanging
matches, avoid the winner later on, but female eavesdroppers do just the opposite. They approach this warrior, and more: they sexually display to him.
¹⁸
This makes good biological sense, for a winner is exactly what they need. He will defend his territory and fight, successfully, for everything else that his family requires.
¹⁹

But what if a female has set her sights on a male that
looks
like a suitable mate but has never fought in her presence? Should she take the plunge, trusting her own evaluation, or wait until a fight breaks out, with the risk that some other female will enter the scene in the meanwhile? In many species, the females experience no such conundrum. They select a convenient male and proceed to mate with him. Then, at some point during the act, they emit a loud copulation cry. Most or all of the unmated males in the group hear this, and treat it as a challenge. They hurry to the spot, descend on the male, and begin fighting with him—and each other. The best fighter is the last one standing, and he is the one that is “chosen” by the female.
²⁰

There are connections between sex and aggression in our species, too. In men, a single hormone, testosterone, promotes both, and women favor males with physical and behavioral characteristics that are correlated with high levels of testosterone. Men with low-pitched voices have more testosterone than others, sound more dominant and attractive, have sex more often—and with more different partners—and father significantly more children.
²¹
Men with large shoulders and hips, and a large shoulder-to-hip ratio, have more testosterone than other men, and women like these physical features too.
²²

Sex and dominance are also linked in human cultures. Romantic bestsellers rarely if ever feature gentle heroes.
²³
According to romance novelist Doreen Malek, women prefer to read and fantasize about “a strong, dominant aggressive male brought to the point of surrender by a woman.” There is no sense of triumph, she wrote, in “winning against a wimp.”
²⁴

Under the leaves, the criteria used in mate selection are the “standards” that evolved. They may appear somewhat fixed, but there is room for environmental influence. In a surprising range of species, from guppies to quail, females put aside innate preferences for certain male features when they see other females consorting with males that lack these qualities, or have different attributes.
²⁵
This is especially true when the female “model” is older than the eavesdropper.
²⁶

Males also base their courtship tactics on what is going on around them. In song sparrows, eavesdropping males will literally “change their tune” if they pick up the telltale signs of sexual competition. In an experiment carried out in Denmark, audio recordings of male courtship calls were played to see how mated males would respond. Predictably, they increased their own courtship behavior. They did so, it was assumed, in an effort to outshine their imagined rival, and to avoid being cuckolded.
²⁷

If eavesdropping can help an animal get a mate, or dodge an unwinnable fight, it may also produce a perceptual experience in and of itself. Rui Oliveira and his colleagues in Portugal put two male cichlid fish in chambers that were separated by a partition. For three days these solitary “actors” were viewed, without their knowledge, by other male cichlids on the other side of a one-way window. Then the partition was removed. Predictably, the actors instantly began a fight for dominance. What they experienced is unknown, but it must have been exciting to the audience, for their testosterone levels were elevated by the fight, and they remained high for some time afterwards.
²⁸
Sporting events do much the same thing to men.
²⁹