Charity is thought to be unlikely in the wild because if animals put
themselves out for others, with no benefit to themselves, they generally
do not survive or reproduce as successfully as selfish members of their
species. As a result, fewer of their ‘do-gooder’ genes are passed on to
successive generations, and in the course of time natural selection weeds
out the altruistic behaviour.

Tony Williams of Queen’s University, Ontario, studied the lesser snow
goose (Chen caerulescens caerulescens) in the wild, and found that more
than 13 per cent of families contain a fosterling.

He wondered whether the adoptive parents were reaping benefits from
their behaviour. From previous studies, he knew that large families of geese
dominate smaller ones when competing for food, enabling goslings in larger
groups to grow faster. So adopting young might give a family strength in
numbers.

To see if this could explain adoption, Williams first checked whether
lone goslings were insinuating themselves into family groups without the
knowledge of adult birds. But he found that young, inexperienced parents
were no more likely to adopt than older birds. Also, strays joined families
long after the age at which young birds can be individually recognised by
their parents. So the adult geese were not adopting strays by accident.

He then looked at how much extra work adoption caused the parent geese.
The answer was very little – the time the parents spent looking out for
predators was no greater for large families than for small ones. Also, goslings
feed themselves, so the fosterlings needed no feeding by adults.

Williams concluded that the benefits gained by adopting extra young
easily outweighed the costs usually linked with this sort of altruism, so
the behaviour could become relatively common.

In comparing the size of adopting and non-adopting families, Williams
found that adopting families, not surprisingly, became larger thanks to
the picking up of strays. The benefits of this meant that parents which
adopted were three times as likely to return to the breeding ground the
following year, suggesting that they obtained more food to help them survive
the winter.

Claudia Feh and Jeanne de Mazieres of the Tour du Valat Biological Station
in Arles studied the way a herd of Camargue horses (Equus caballus) groomed
each other. They found that time and time again the horses directed their
attention to the napes of each other’s necks (Animal Behaviour, vol 46,
p 1191).

To determine if this spot was special to the horses, the researchers
chose eight adults and eight foals which were used to being handled by
people, and recorded the animals’ heart rates with a stethascope during
grooming.

The researchers first rubbed a spot low on the shoulder, which the horses
did not touch themselves when grooming each other. This failed to change
the heart rate, but when they scratched the horses on the nape of the neck,
the heart rate slowed by about 10 per cent.

Feh and Mazieres believe that their results show that grooming is about
more than hygiene. By calming animals, it may help dispel social tension.
In primates, for example, grooming often takes place after fights. The
result also adds to evidence that grooming has physiological effects on
the body. Again in primates, grooming causes he release of endorphins, the
natural opium-like substances produced by the brain. Finally, it shows that
vets who use acupressure at the nape of the neck to calm nervous horses
are doing exactly the right thing.

Klaus Vestergaard of the Royal Veterinary and Agricultural University in
Frederiksberg in Denmark, Jaap Kruijt of the University of Groningen in the
Netherlands and Jerry Hogan of University of Toronto set out to find the
reason for the hens’ savage behaviour, which may result in death.
Vestergaard suspected it might have something to do with dustbathing, which
he had observed earlier in free hens. To stop their plumage becoming too
greasy, the birds peck at the ground, then squat in the dirt to shimmy and
shake, working the dust particles into their feathers.

In a laboratory, Vestergaard and his colleagues kept two groups of jungle
fowl, the wild relative of the domestic hen. The birds in one group were
reared in large cages with sand and earth on the floor, while the birds in
the other group were reared in similar cages with bare wire mesh floors
(Animal Behaviour, vol 45, p 1127).

The birds reared on sand and earth prepared to dustbathe by pecking the
ground vigorously and raking their bills through it, as if to discover if it
was suitable for bathing. They rarely pecked each other, particularly once
they had started dustbathing.

However, the birds on the bare floors were unable to dustbathe.
Nevertheless, they went through the motions of dustbathing. They warmed up
by pecking the ground. But they often pecked at each other as well. Some
birds would peck frantically, as if somehow stuck in this warm-up phase,
while others would go on to mime dustbathing on the wire mesh floor.

Vestergaard and his colleagues conclude that the savagery of battery hens is
a by-product of their attempts to behave like free birds.

But the reason why birds have long tails may not be as simple as this,
say British zoologists. It depends on the shape of the tail. Although in
some species, tails are long because females prefer them that way, in other
species tails are long for aerodynamic reasons.

Andrew Balmford, Adrian Thomas and Ian Jones of the University of Cambridge
set out to discover if the long tails really are a burden which can be
shouldered only by the fittest males. Using computer models, they calculated
the lift and drag that birds’ tails of different shapes and sizes produced
(Nature, vol 361, p 168).

Tails come in three main shapes. Tails which are triangular in flight,
such as the house martin’s, have shallow forks when closed. Other birds
such as the pheasant have tails with a long tapering extension beyond the
widest point. Still other tails have narrow streamer-like extensions – either
paired, as in the swallow, or single, as in the pintail duck.

The zoologists’ computer simulation showed that long tails with a shallow
fork are no burden at all. The amount of lift provided by a tail depends
on its widest span. When a bird’s tail feathers are lengthened, making a
wider triangle, the bird gets far more lift than drag in flight, so such
designs help birds to fly. Because such a tail helps both males and females
equally, the difference between the sexes should be far less marked than
in birds with other types of long tails. This is just what the Cambridge
zoologists found when they examined birds in museum collections.

However, long streamers and tapered extensions are a real drag. They
do not make a tail wider, so they provide no extra lift; they serve only
to make flying harder work. Such tails could be explained by the ‘good genes’
idea, because a male would have to be strong and healthy to carry this type
and still live a successful life. If the argument is true, these tails should
be a characteristic of males.

The zoologists did not have access to enough museum species to test
this idea for tapered tails. However, they measured museum specimens with
long paired streamers and found that the longer a species’ tail extensions,
the greater their development in the male relative to the female.

But could the idea explain the evolution of both these tail-types from
their very beginnings? Balmford’s group thinks not. Short streamers do not
create much drag because they are so narrow. They would not hinder a bird’s
flight, and so even the puniest male should be able to sport them with ease.
This is a problem for the ‘good genes’ idea. Balmford and his colleagues
believe that in their earlier stages these useless ornaments cannot have
been preferred by females as a sign of quality, so they must have begun
to evolve for another reason. The earliest streamers may have attracted
females for a different reason. Females may have tended to opt for the most
eye-catching of potential mates, for example.

So, for whatever reason, some long tails are sexy. But this does not
mean males should really handicap themselves in the name of sex appeal.
When long tails do not help in flight, the maximum tail length is limited
because at some point they become a serious burden, even for the best males.
This limitation should be particularly evident in species with tapering
rather than streamer-like extensions, because such tails produce the most
drag. Among the museum specimens, tapering tails were indeed shorter than
streamers.

Daniel Povinelli from Yale University and Kathleen Parks and Melinda
Novak from the University of Massachusetts trained pairs of macaques to
carry out complementary parts of a single task. They then tried to get each
macaque to do the other’s job. They found that the macaques were clueless.
Each seemed to have no mental picture of its partner’s role (Animal Behaviour,
vol 44, p 269).

Povinelli’s group trained four rhesus macaques (Macaca mulatta) to work
with human partners for a reward such as a biscuit. Food was hidden in one
of three containers. One partner could see where it was hidden but could
do nothing to retrieve it. The other partner could draw the containers within
reach by pulling on a handle, but could only pick the right one if its partner
pointed to it.

Povinelli trained two monkeys as ‘pointers’ for their human partners
and two as ‘retrievers’. Then came the crucial part of the experiment. The
monkeys swapped roles with their human partners.

In their new roles, the macaques showed no sign of having understood
or absorbed the nature of their human partner’s job, even though they had
watched their partner many times. They were flummoxed and had to be trained
from scratch to do the job competently.

Earlier research by Povinelli and his colleagues has shown that in this
role-swapping test, chimpanzees differ from monkeys. They are able to pick
up their partner’s behaviour. So, like people, chimpanzees can learn by
watching other animals.

This difference between monkeys and apes fits in well with previous
research findings. Chimpanzees, gorillas and orang-utans all realise that
their image in a mirror is themselves, whereas macaques do not. Also, previous
experiments in which Povinelli has been involved have shown that chimps
and humans, but not macaques, are aware that individuals can know different
things (New ÐÓ°ÉÔ­´´, Science, 8 December 1990).

Apes seem to have a concept of themselves as distinct from other individuals.
They also seem to be aware of what they are doing or are able to do, and
aware of how their actions resemble or differ from those of others. They
also seem to be able to put themselves in another animal’s position, imagining
what it does and what it knows.

In contrast, macaques are not sufficiently self-aware to spot the link
between their own movements and those of a reflection in a mirror. Nor do
they register the differing abilities and roles of others in a way that
lets them emulate them in the future.

Adult chinstrap penguins react to their chicks’ demands for food by
turning on their heels and running away. So the unfortunate chick must catch
up or starve.

A team of biologists led by Javier Bustamante of the Experimental Biology
Station in Seville studied a colony of chinstrap penguins on Deception Island
in South Shetlands, Antarctica. They found there may be good reason for
the penguin parents to give their chicks such a hard time. By testing their
offsprings’ sprinting abilities, parents could be deciding which one to
give food to (Animal Behaviour, vol 44, p 753).

When they go hunting in the sea, chinstrap penguins (Pygoscelis antarctica)
leave their young in groups known as creches. On their return, they may
either disgorge a fish immediately, or make their chicks chase them for
it. The feeding chases can last for a minute or more. Sometimes, a tenacious
chick gets a meal but at other times it is left behind hungry.

A parent may force its chick to chase to encourage it to explore the
area outside its creche. Or the parent may be luring the chick away from
the creche in order to feed it in a place where there are no competing chicks
from other families. Alternatively, an adult may simply be reluctant to
feed a chick as it approaches independence.

If any of these reasons are correct, feeding chases should occur regardless
of the size of a brood. But this not what the Spanish zoologists found.
Lone chicks were usually fed immediately whereas chicks with a sibling were
far more likely to be put through their paces. In families with two chicks,
chases were four or five times as common and lasted much longer. These chicks
had to run for about two minutes to get a meal, compared with 20 seconds
for a lone chick.

Bustamante believes this shows that in a family of two, parents are
reluctant to give all of their food immediately to only one of their offspring.
So feeding chases may help parents to decide the best way to distribute
their food between two young.

One possible explanation is that making the chick run reveals whether
it is hungry enough to be persistent, or alternatively, whether it is strong
and healthy enough to keep up the chase. Or it may be that the feeding chases
are used to separate the siblings, so that the chicks do not compete with
each other for the meal. This would reduce the amount of food dropped and
wasted in a squabble.

Bustamante and his colleagues found that chases did seem to separate
pairs of chicks, so that only one was fed at any one time. On 27 occasions
when both siblings were present, the chick that ran for the greatest time
was fed most often in 20 instances. But chasing was just as frequent and
just as prolonged when only one of the two chicks was present, which sometimes
happened if only one noticed that a parent had returned from fishing. So
the idea that the chases are designed to reduce competition between siblings
cannot be correct.

However, even if only one chick was present, the parent with two offspring
must decide how much food to part with. Should it be kept aside for the
absent sibling? Or should a young bird that seems very hungry be given a
complete meal, regardless of its sibling? Because feeding chases occur even
when only one of the two young is present, this suggests that parents are
always putting their young to the test before they part with any fish. Perhaps
a chick that runs fast is proving itself hungry, and a deserving case.

In another species of penguin, the Adele, chicks do indeed run faster
when they are hungrier. But another possibility is that parents favour chicks
that are strong. This would be a good strategy if there was not enough food
to feed two offspring properly. By concentrating on the strongest, the parents
could ensure that at least one chick does well in hard times.

It has long been known that in many species of macaque, animals that
lose fights will vent their frustration on subordinate macaques. One possible
reason for this could be that it diverts the aggressor’s attention to a
new target. Another is that it could be a way of seeking the aggressor’s
approval-for instance, if the attacked individual is one whom the aggressor
often puts in its place.

Clearly, neither of these reasons explains why a macaque should turn
on one of its aggressor’s relatives. To discover the reason for this behaviour,
Filippo Aureli of the University of Rome and his colleagues studied a group
of 37 Japanese macaques (Macaca fuscata) at Rome Zoo.

The scientists found that a defeated macaque was particularly likely
to exact this form of revenge when the aggressor was so dominant that the
defeated animal was unable to fight back. Usually, the macaque in turn chose
a victim that was vulnerable-often a young animal.

Revenge alone is an unlikely explanation for this behaviour. When a
macaque attacks a fellow macaque, it takes a big risk because of clan loyalties
within the troop. The attacker risks being set upon by its victim’s relatives,
who may even retaliate against the attacker’s kin.

The risks entailed probably explain why this sort of behaviour is not
very common. In fact, Aureli and his colleagues saw a rival’s relatives
being picked on in only 2 per cent of fights. But the scientists say that
in some circumstances the behaviour might offer rewards which outweigh the
dangers of retaliation.

The circumstances in which victims attacked their aggressor’s kin had
two distinguishing features. First, in more than half of these cases (54
per cent), the vengeful macaque joined in a group attack against the unfortunate
target; this minimised the chances of it being subjected to any counterattack.
Secondly, the majority of cases (74 per cent) occurred brazenly, within
sight of the former aggressor.

Aureli thinks this boldness reveal the function of such ‘kin-directed
revenge’. If an aggressor is forced to witness a group attack on one of
its more vulnerable relatives, it may in the future think twice before attacking
its former victim (Animal Behaviour, vol 44, p 283).

Attackers often use considerable cunning to get near their victim without
arousing any suspicion. They may feign indifference by barely glancing at
him, digging casually in the sand or pretending to collect handfuls of pebbles.
But the moment their victim ejaculates, they jump him, hitting, biting and
tugging at his fur.

What possible motive can there be in this bizarre form of aggression?
To get an answer, B. Drukker and colleagues at the University of Utrecht
spent three years studying a colony of stump-tailed macaques (Macaca artoides).
They observed more than 70 animals and more than 600 cases of harassment
during sex (Animal Behaviour, vol 42, p 171).

Drukker and colleagues found that the macaques were not harassing others
in order to gain sexual attention themselves. Females at the most fertile
stage of their reproductive cycle were no more likely to make attacks than
animals that were less sexually motivated.

The zoologists wondered whether the aggression was aimed at stopping
offspring being conceived. Adults might benefit from this by reducing the
number of other parents’ young competing with their own offspring. Juveniles
might also be helped if their mother was prevented from producing rival
siblings.

But the researchers found that the attacks almost always occurred after
eja-culation, and hardly ever in time to pre vent it. Also, the juveniles
who were still dependent on their mothers were far less likely to be involved
than adolescents that were fully weaned and independent.

The team also rejected the idea that harassment is a means for females
to assess the ‘staying power’ of potential mates. For one thing, males as
well as females acted as the harassers. And the aggression did not stop
mating. It neither inhibited ejaculation nor reduced the length of time
a pair sat locked together afterwards.

This left only one possible motive for the harassment: revenge. The
macaques, they reasoned, were retaliating for aggression received in the
past. It makes sense to attack when your opponent is temporarily distracted.

This explanation accounted for several features of the behaviour. Females
are never attacked, while dominant, aggressive males are particularly likely
to be the victims.

Females, the smaller and lighter sex, continue to use this rather unsporting
form of aggression into adulthood. Males, on the other hand, stop when
they have reached their full size and weight, as if when they are more equally
matched, they do not have to save their retaliation until their opponent
is helpless.

Prospective fathers of a species of mediterranean blenny (Aidablennius
sphynx) are given a trial sample of eggs to look after. When a female returns
a day or two later, she will not mate with the male if the eggs have gone
(Animal Behaviour, vol 43, p 865).

Sarah Kraak and Eric van den Berghe studied the blenny both in the wild
and in the laboratory. The biologists placed glass tubes in the rock crevices
where males nested, to serve as artificial nests. The males took to the
tubes, often guarding them for months on end.

Kraak and van den Berghe counted the eggs in these tubes every day.
They found that males with tubes that were initially empty attracted very
small deposits of less than 10 eggs. But if a male successfully retained
one of these clutches, his nest was usually filled with hundreds of new
eggs within the space of a few days. But if the ‘test clutch’ disappeared
within a day, the nest was very unlikely to receive a further batch of
eggs.

But were the females really testing the male’s parental quality? The
researchers were unable to see whether the large clutches were laid by the
same females that had laid the ‘trial egg’. But they were able to see that
an individual female would return to a nest she had visited after a gap
of a few days. And in the laboratory, they found that females did discriminate
against seemingly careless fathers.

Kraak and van den Berghe also gave the females a choice between males
with empty nests and males who had started off with large clutches which
were then ‘raided’ by the biologists. They found that the females greatly
preferred the males with nothing in their nests. These males may not have
had a test run, but at least they were not proven bad fathers.

A relative of the crow, the white-winged chough (Corcorax melanorhamphos)
is unable to rear its young without help. At least four adults are needed
to raise a bird to the age when it fledges. As a consequence, groups grow
very slowly, and new recruits are valuable for the vital help they provide
to breeding pairs.

Robert Heinsohn of the Australian National University carried out a
study of white-winged choughs. Having ringed the birds so that he could
distinguish individuals, he observed fledglings spending time in groups
other than their own on a total of 14 occasions. Although on three of these
occasions the fledglings returned to their families, in five cases the young
birds stayed in their new flock. On all other occasions Heinsohn lost track
of the birds.

Sometimes, the kidnapped bird stayed with its kidnappers on what appeared
to be a long-term basis – on three occasions, for more than a year. Heinsohn
observed all three birds helping at the nests of their kidnappers: as if
they had been kidnapped with a view to their becoming helpers when they
matured.

Heinsohn saw the transfer of the young bird on four occasions. Sometimes
it occurred during ‘display battles’ between opposing groups of choughs.
Larger groups commonly harass smaller ones, often destroying eggs and nests.
But later in the season, when the young have left their nests, aggression
takes the form of display battles, with the groups of birds lining up on
opposing branches to call and shake their white-tipped wings and fanned
tails at each other. During a confused melee of battling birds, Heinsohn
twice observed birds moving from their own groups to another.

However, this was not the only situation in which birds transferred.
The other two transfers Heinsohn observed took place when fledglings were
being actively sought out by adults from the rival group. The adults displayed
or preened at them, and the fledgling promptly changed flock.

Heinsohn believes that kidnapping may have two advantages if the fledgling
stays with the new group to adulthood. First, it brings new blood into the
group. Secondly, and more importantly, it increases the number of helpers
at the nest and so improves the chance of successful reproduction.