Mammals
TIGERS
TIGER, NO LAUGHING JOKE
How is a tiger's face like your thumb?
ANSWER: The stripes on the tiger's face are like your thumbprint. No
two people have exactly the same thumbprint. And no two tigers have exactly
the same stripe pattern.
It takes a lot of muscle to move a 400-pound body (180 kilograms). And
a tiger's body is packed with muscle. So it can leap 10 yards (9 meters)
over level ground, or jump 15 feet (4.5 meters) in the air. Yet it can move
so gracefully that it doesn't make a sound.
Tigers are big-game hunters. They hunt water buffalo, wild pigs, deer,
and other large animals. Water buffalo weigh more than a ton (900
kilograms). It would take 13 men to move such an enormous weight.
Tigers are also big eaters. In a single year, one tiger must eat about
70 deer or other large animals. That is one reason why tigers hunt alone.
If they lived in big groups, they could never find enough prey to feed them
all.
Many people think that a big, dangerous tiger could easily kill all
the prey it wants. But that's not true. In fact, the life of this big game
hunter isn't easy. Most of the animals it tries to attack get away. It
sometimes goes weeks without eating. And then it may hunt animals that can
be dangerous, even for a tiger.
To get enough food, tigers have to hunt day and night. They often hunt
at night, because that's when deer and antelope are most active. Tigers
also hunt at night because they are safe from humans then.
When it hunts, a tiger usually sneaks close to its prey by hiding
behind trees, bushes and rocks.
Tigers cannot run fast for long distances. So they must get close to
their prey before attacking. On their huge, padded feet, they can creep
silently to within 20 feet (6 meters) of another animal without being
heard. Its rear legs press beneath it, like a pair of giant springs about
to be released.
Then, in a series of explosive leaps, it attacks from behind.
Next, the tiger grabs its prey with its claws and pulls it to the
ground. It bites the animal on the throat or on the back of the neck
The tiger has had a long history; the name tiger itself comes from the
Roman word "Tigris", named after the mighty Mesopotamian Tigris River. The
tiger's closest living relative is the lion, and believe it or not, they
can even be interbred. The male tiger can reach sizes of up to 8-10 feet in
length, with three feet for the tail, the male Siberian tiger can reach
lengths of up to 13 feet with weights up to 750 pounds. Tigers can be found
in a fairly diverse area, from north China and Siberia, to the jungles of
Indonesia, even as far west as Iran and the Caucasus Mountains.
The tiger is a solitary animal, hunting mainly at night. The tiger's vision
and sense of smell are relatively poor; the tiger will rely strongly on its
sense of hearing, moving silently through the brush waiting to ambush its
prey. The tiger's main diet consists of deer, antelope, wild pigs, and
cattle. The man-eaters are all too often the sick and injured, too weak to
hunt and capture wild animals. The tiger would much rather flee rather than
stick around and put up a fight.
Tigers are excellent swimmers and will often rest in pools of water
just to escape the heat, or, will swim from island to island such as in the
Sumatran islands. Tigers are poor tree climbers, often only doing so in
emergencies or when they are young, (and on occasion, just out of
curiosity). The Bengal, or, Indian Tiger is the
SIBERIAN TIGER
The largest of all living tigers lives in the coldest climate; but has
thick fur to keep it warm. Its pale color makes it difficult to spot in
the bleak, snowy landscape of Siberia and also makes it easier to get close
to its prey. There are no more than 200 Siberian tigers living in the
wild.
INDIAN TIGER
The Indian tiger is the most common tiger in the world today. In all,
there are about 2,500 left, and most of them live in India.
Hunting tigers used to be a sport for the rich people of India. But
it wasn't really a sport, because the tigers had little chance of escape.
The hunters rode on elephants, while their servants drove the tigers toward
their guns. Over the years, thousands and thousands of tigers were killed
this way.
SUMATRAN TIGER
Their stripes hide them as they stalk prey in the jungle. How? Their
stripes look like the shadows of tall blades of grass, or like shadows and
light playing across trees.
For a fierce hunter, you'd think that food would be plentiful. Not
true as most attacks fail. There may be weeks without eating.
Some Sumatran villagers believe that the tiger holds magical powers
and that it's very bad luck to kill them.
SUMATRAN TIGER
Tigers are among the most admired and most feared animals in the world.
When we think of tigers, we think of danger. We think of powerful beasts
hiding in the dark jungle. We think of the strong jaws, big teeth, massive
feet, and long, sharp claws of the tiger.
But we also think of beauty. We picture a tiger running swiftly through a
jungle, or plowing through snowdrifts. Its muscles ripple. Its brilliantly
striped orange and black coat gleams like satin. Its steely eyes glare into
the distance as it looks for prey.
This animal is a hunter. In fact, tigers are probably better than any other
land animal at capturing large prey single-handedly. Even so, the life of a
tiger is not easy. Finding food can be difficult, especially for a tiger
that is old or weak.
When they are desperate, some of them may even attack humans. But tigers
also get blamed unfairly for many deaths. Very few people are really killed
by tigers each year. Most tigers run away when they see people. And with
good reason.
What tigers have done to people is nothing compared to what people have
done to tigers. Over the last 200 years, we have almost eliminated them in
the wild. Today, they are one of the most endangered animals on earth.
If humans do not disturb it, a tiger may live 20 years or more. Females
usually live longer than males, because the males live more dangerously.
They often fight among each other. Sometimes one of them is killed this
way, or wounded so badly that it cannot hunt.
It isn't easy for people to tell a male tiger from a female, unless
the female happens to be with her cubs, because only females take care of
the young. Otherwise, the most obvious difference between males and females
is size. Male tigers are much bigger. An adult male Bengal or Indian tiger
usually weighs about 420 pounds (190 kilograms), and from head to rear, it
is roughly seven feet long (2 meters). Females are about a foot shorter (30
centimeters), and they weigh about one hundred pounds less (45 kilograms).
Sumatran tigers are generally smaller than Indian or Bengal tigers. The
biggest tiger ever measured was a male Siberian Tiger. It was over 9 feet
long (2.6 meters) and weighed more than 700 pounds (320 kilograms).
Tigers once roamed over most of Asia. Some trekked over the frozen
north, others climbed the jagged mountains of Central Asia, and many crept
through the steamy jungles of the south. The tigers that lived in these
different places gradually developed into a number of different types, or
races.
Although tigers have been able to live in different climates and
landscapes, they have not been able to live alongside people. In fact,
people have killed so many tigers that two races may already by extinct.
The Bengal tiger is the most common tiger in the world today. In all,
there are about 2,500 Bengal tigers, and most of them live in India. The
Caspian tiger is one that you will only see in pictures. This beautiful cat
is now extinct. The Chinese tiger used to live in most parts of China.
Today, there are fewer than a hundred Chinese tigers in the whole country.
The Siberian tiger is the largest of all living tigers. It also lives
in the coldest climate, but it has very thick fur to keep it warm. And its
pale color makes it hard to see in the bleak, snowy landscape of Siberia.
This makes it easier to get close to its prey. There are no more than 200
Siberian tigers living in the wild.
Sumatran and Javan tigers live on land south of the Asian continent.
Their islands are covered by heavy, tropical jungles. To help them run and
hide in the jungle, these tigers are smaller than other tigers. Today,
there are fewer than 30 Sumatran and Javan tigers left in the wild.
The body of a tiger is like a deadly weapon. It has the quickness and
strength to take down animals twice its size. It has long, razor-sharp
claws for grabbing its prey. And it has enormous teeth, which can easily
kill large animals.
But a tiger is also very quiet. It can sneak up on its prey without
being seen or heard. And its stripes help it do this, because they make it
easier for the tiger to hide. You will also discover another reason why a
tiger's stripes are interesting. You can learn to tell one tiger from
another by its stripes.
Like other cats, tigers usually keel their claws hidden beneath the
fur. This way the claws do not wear down too quickly. And they won't make
noise when the tiger steps on rocks or hard ground. When it wants to use
its claws for grabbing or scratching, the tiger will extend them.
Tigers have longer canine teeth than any other predator. One of these
teeth is at least 10 times longer than the biggest tooth in your mouth.
Using its big canine teeth and its broad, powerful paws, a tiger can kill
its prey with one quick bite.
CUB LIFE
Tigers and other predators play an important role in nature. By
killing deer and other prey, they keep the numbers of these animals under
control. And because of this, the animals that survive are healthier.
If there were no tigers in the wild, the number of prey animals would
grow too fast. At first, they would eat so much that they would destroy
many plants. And then many of these animals would go hungry.
A big, hungry tiger can eat about 100 pounds of meat (45 kilograms) at
one sitting. This is about one fifth of its total weight. That would be
like a 10-year-old human eating 40 hamburgers in one meal. Of course, a
tiger has to eat this much because it often goes several days without
eating anything.
On occasion, a tiger will attack a baby rhino. This can be dangerous
though, because the mother rhino is probably close by. And even a tiger
does not want to make a four-thousand-pound rhino (1,800 kilograms) angry!
If a tiger is hungry enough, it may even attack a bear. But that may
be a big mistake.
Baby tigers look like cute kittens. At birth, they are about 12 inches
long (30 centimeters), and they weigh less than two pounds (one kilogram).
But in a year's time, these "kittens" will be big enough to hunt deer and
buffalo.
A mother tiger usually gives birth to two, three, or four cubs at a
time. This is necessary so that at least one of her cubs will survive. Many
predators attack tiger cubs. To help keep them safe, the mother stays with
her cubs for three or four years. During this time, the young tigers have a
lot to learn from her if they are to hunt and survive on their own.
Animals, unlike man, must either capture prey, or, evade predators. In
order for these animals, such as the tiger, to get close enough to its prey
for the attack, these animals must be able to hide, or blend in with the
background. That way the prey animal does not know that they are there…
The tiger uses what is known as disruptive camouflage, which means
that instead of blending in with it's surroundings, the tiger uses it's
stripes to break it's outline, or familiar shapes into smaller unfamiliar
shapes.
Like all young animals, cubs are full of energy. They spend their days
wrestling, chasing each other, and darting after butterflies. All this
exercise helps prepare them for their first real hunt. And they are ready
for this when they are about six months old.
It's hard to believe that in just six months, a playful little cub
will be a ferocious hunter. By then, it will weigh almost 200 pounds (90
kilograms) and have four big canine teeth for attacking prey.
A female tiger is one of the most loving and caring mothers in the
animal kingdom. She cuddles her babies to keep them warm. She feeds them
and protects them from enemies. For three years or more she looks after
them, teaching them how to hunt and survive in the wild.
This cub is only a few weeks old. In the wild, cubs are usually born
in caves and other protected places. The mother keeps them there and brings
them food for about three months. After that, the cubs are big enough to
follow her as she hunts for prey.
The life of a baby tiger can be dangerous. If a mother leaves her
cubs, even for a short time, they may be attacked by predators. Some of the
animals that like to eat tiger cubs are leopards (left), pythons (below
left), and hyenas (below right).
LEOPARDS
CLOUDED LEOPARD: PRECIOUS CARGO
One chapter in the Zoological Society's clouded leopard story began
early in 1983 with the arrival of a young pair of cats from the People's
Republic of China. The cats were a welcome addition to the Society
collection. Staff prepared a plan to encourage successful breeding, but
unfortunately, tragedy occurred before the plan could be implemented.
In the exhibit, the female was accidentally exposed to a male, which
severely mauled her right foreleg and shoulder. The injury was so severe
that, because of the initial trauma and resulting fast-spreading infection,
amputation of the leg and affected scapula were required to save her life.
The difficult surgery was masterfully conducted. Intensive care was
required for more than two months. The veterinary staff and a hospital team
kept the cat alive through repeated tube-feeding and frequent hands-on
care, despite the cat's aggressive distrust of such treatment. Following
many weeks of this regimen, the cat responded and made sufficient recovery
to allow her return to the leopard exhibit.
A primary hurdle had been cleared -- the female had survived the
injury. Next to be resolved were her adjustments to life on three legs and
finding a method which would allow her reintroduction to the Chinese male.
First, the mammal staff placed the cat in a program designed to help
her grow accustomed to life with three legs. After several months of
satisfactory progress, the staff decided to place her with the male, who
had been kept in a separate but adjoining room. The animals were allowed to
make contact as they chose. To the relief of all, the reintroduction was
successful. The cats proved to be compatible, and, shortly after
reintroduction, breeding took place.
On the morning of April 25, 1984, final proof of the success of a long
and difficult management program arrived-- a litter of two cubs. One cub
did not survive, but the other was taken to the Children's Zoo to be raised
by the nursery staff.
UNIQUE FELINE
The clouded Leopard has intrigued its public, been sought after for
its fur, and mystified those who would try to categorize it. During the
early morning hours of April 25, 1984, a discovery was made which was the
culmination of a saga, which held elements of zoo diplomacy and goodwill,
tragedy and suspense, cooperation and success. The discovery climaxed a
chain of events surrounding this paradoxical cat.
This cat has behavioral and physical traits typical of the small cats,
genus Felis, and the big cats, genus Panther. A paradox to taxonomists and
zoologists, it has been assigned to its own genus, Necrfelis, and is
considered a bridge between the two larger genera. A relationship to the
extinct saber toothed cat has even been suggested, based on the physical
characteristic of having, in proportion to body size, the longest canines
of all living felines. Its canine structure is also similar to that of the
saber-toothed cat.
The clouded leopard has a body size ranging from 24 to 42 inches (616-
1,066 mm) Its tail adds another 21 to 36 inches (550-912 mm) of length.
This leopard's weight falls between 35 and 50 pounds (16-23 kg). Its fur is
grayish brown to tawny yellow and has dark markings in a variety of shapes,
which seem to form cloudlike patterns.
The clouded leopard was once believed to be exclusively arboreal and
nocturnal. Recent observations in captivity and in the wild indicate,
however, that it may be considerably more terrestrial and diurnal than
previously thought. It is believed to prey upon birds, young buffalo,
cattle, deer, goats, monkeys, pigs, and porcupines. The species is
difficult to manage in captivity because of a tendency to be highly
aggressive toward other species and humans. The exceptionally long canine
teeth can easily inflict mortal injury. True to its paradoxical reputation,
however, some cats may become extremely affectionate toward humans, even
permitting and seeking physical contact.
NORTH CHINESE LEOPARD
This leopard is so rare that humans almost never see it in the wild.
It roams the forests and mountain meadows of northern China and Korea.
It makes its home in a great tangle of fallen trees and shrubs. When
it kills smaller animals it devours them right away. But when it comes to
larger prey, like deer and wild goats, the leopard drags the animal home to
save for several meals.
Don't be scared. The teeth of this snarling leopard won't hurt you.
On the contrary. It's the snow leopard that should be afraid. Its
relatives in the wild are in constant danger from poachers who want to
shoot them for their pelts and teeth.
Even though shooting leopards is illegal, it's considered "good
business." That's because some people still wear leopard fur coats, and
others believe that leopard teeth earrings and necklaces have special
powers.
SNOW LEOPARD: COLD WEATHER CAT
The shy, nocturnal and virtually unknown Snow Leopard is classified
with the big cats, but shares some small cat characteristics, for example
it doesn't roar and it feeds in a crouched position.
The Snow leopard has to contend with extremes of climate and its coat
varies from fine in summer to thick in winter. The surfaces of its paws are
covered by a cushion of hair, which increases the surface area, thus
distributing the animal's with more evenly over soft snow and protecting
its soles from the cold.
Snow leopards are solitary except during the breeding season, (January
to May), when male and female hunt together, or when a female has young.
One to four young are born in spring or early summer in a well-concealed
den lined with the mother's fur. Initially, the spots are completely black.
The young open their eyes at 7-9 days, are quite active by two months, and
remain with their mother through their first winter
Snow leopards are extremely rare in many parts of their range due to
the demand for their skins by the fur trade. Although in many countries it
is now illegal to use these furs, the trade continues and the species
remains under threat.
SNOW LEOPARD
They live in the snow-covered mountain peaks of Central Asia. How
high do these Asian Mountains rise? They reach 20,000 feet in altitude.
The snow leopard's long, thick fur keeps it warm even in the frosty
air, and its creamy white and gray color camouflages it in the snow.
Because humans are fond of turning its beautiful coat into coats for
themselves, the species is on the brink of extinction.
HYENS
SPOTTED HYENA
This hyena is also known as the "laughing" hyena. Sometimes a hyena
lets out a cry that resembles a wild human cackle.
Did you know that a hyena can gorge up to 33 pounds of meat extremely
fast? It needs to eat fast because as many as 50 other hungry hyenas may
be next to it, noisily feeding on the same piece of meat. Scientists have
seen 38 hyenas devour a zebra in 15 minutes, leaving only a few scraps
behind.
The hyena is famous for eating animal parts that other meat-eaters
won't touch. You might even see it stamping and biting on an ostrich egg,
trying to eat it. After devouring everything in sight, the hyena spits out
the horns, hooves, and bone pieces, ligaments and hair. If there are
leftovers, it buries the meat in a muddy pool. The hyena's good memory
leads it back to the hidden food when it's hungry again.
The spotted hyena hunts at night. Hyenas were once thought to be just
scavengers (animals that eat the meat left behind by predators). But now we
know that they're very good at finding their own food, too.
Hunting together in large packs, hyenas have a very effective way of
catching their favorite food. One hyena scares a herd of wildebeest, looks
for the weakest member of the herd, and then begins a chase. The other
hyenas join in the attack, and a wildebeest feast is soon ready.
If you've ever heard the expression "laughing hyena" and wondered
where it came from, it was inspired by the strange, laughter-like sound
hyenas make when they're being attacked or chased.
EATING HABITS
True hyenas have thickset muzzles with large ears and eyes, powerful
jaws and big cheek teeth to deal with a carnivorous diet. They walk on four-
toed feet with five asymmetrical pads and nonretractile claws. The tail is
long and bushy (less so in the spotted hyena). Spotted hyenas will eat
almost anything, but in the wild much of their food comes from mammals
heavier than 44 lb. which they mostly kill for themselves. The frequency of
hunting depends on the availability of carrion; spotted hyenas will loot
the kills of other carnivores, including lions. Group feeding is often
noisy, but rarely involves serious fighting. Instead, each hyena gorges
extremely rapidly on up to 33 lb. of flesh. Pieces of a carcass may be
carried away to be consumed at leisure or, occasionally, stored underwater.
It seems that the success of spotted hyenas is ensured through
individual and cooperative hunting and sharing of food between adults.
Cooperation also extends to communal marking and defense of the territory,
in which both sexes play a similar role, whether or not they are related.
Competition within the clan can, however, be intense. The system of
communication shows adaptations, which reduce aggression and coordinate
group activities. Such competition probably provided the selection pressure
whereby females evolved their large size and dominant position, which in
turn relates also to levels of testosterone in the blood that are
indistinguishable from those of the male. Thus female spotted hyenas are
able to feed a small number of offspring alone and protect them from the
more serious consequences of interference by other hyenas, particularly
unrelated males.
WHY THEY LAUGH
Hyenas are often called "solitary," a label which obscures the fact
that their social systems are among the most complex known for mammals.
Spotted hyenas employ elaborate meeting ceremonies and efficient long-range
communication by scent and sound. Even when moving alone, spotted hyenas
maintain some direct contact with their fellows. They respond to sounds,
which are only audible to humans with the aid of an amplifier and
headphones.
Calls audible to the unaided human ear include whoops, fast whoops,
yells and a kind of demented cackle that gives this species its alternative
name of laughing hyena. Whoop calls, in particular, are well-suited to long-
range communication as they carry over several kilometers; each call is
repeated a number of times, which helps the listener to locate the caller,
and each hyena has a distinctive voice. Infant hyenas will answer the pre-
recorded whoops of their mothers, but not those of other clan hyenas.
LIONS
AFRICAN LION: FAMILY CATS
Lions are among the most admired animals on earth. Their strength and
beauty, combined with their bold nature, have fascinated people for ages.
In fact, the lion has often been called the "king of the beasts." And when
you see a big male lion, with its magnificent main and proud walk, it's
easy to understand why. Lions really do look like kings.
But lions don't always lead the easy lives of kings. They often need
to work hard to survive. Lions are meat eaters, or carnivores, so they must
hunt other animals for food. And sometimes prey is hard to find. When food
is scarce, a lion may go for days without eating.
Lions are members of the big cat family, which includes tigers,
leopards, and jaguars. The main difference between the big cats and all
other cats is that generally big cats can roar but cannot purr. Other cats
can purr but cannot roar.
The lion is one of the biggest cats in the world. Only the Siberian
tiger is larger. A male lion may be 9 to 10 feet long (3 meters) and can
weigh 500 pounds (227 kilograms) or more. Female lions are smaller. The
average female is 7 to 8 feet long (2 l/2 meters) and weighs 270 to 350
pounds (140 kilograms).
Lions are different from most other cats in that they live in groups
called prides. They hunt together, guard their territory together, and
raise their young together. Lions that live in groups can catch more food
than a single lion can. And they can protect themselves better. Also, lions
that are born into groups have a large family to care for them.
There are two different kinds, or subspecies, of lions: the African
and the Asiatic. Most of the lions in the world today are African lions.
These animals live on the grassy plains of Africa. The few Asiatic lions
that remain live on a small wildlife preserve in India. There were once
many other kinds of lions in the world but all of these are now extinct.
Lions sometimes climb high up into trees to rest on their branches and
escape the biting insects below.
The body of a lion is made for catching prey. Most of the time, lions
try to get very close to their prey before they attack it. Then they make a
big leap and grab the prey. To help them get close without being seen,
lions have golden-brown coats that blend in with the land around them. And
to help them leap, they have strong muscles in their legs. A lion can leap
35 feet (10.5 meters) through the air in a single jump.
Lions do most of their hunting at night, so they have wonderful
hearing and eyesight to help them find prey in the dark. Their hearing is
so sharp, they can hear prey that is more than a mile away. Lions can turn
their ears from side to side to catch sounds coming from almost any
direction. When a lion is moving through tall grass, it may not always be
able to see its prey -- but it can always hear it. The eyes of lions are
the biggest of any meat-eating animal. Like the eyes of other cats, they
are specially made for seeing at night.
Lions often work together when they hunt. By doing this, they increase
their chances of getting food. A lion that hunts alone may have a hard time
catching prey.
Most of the hunting is done by a team of females. They divide the job
among them, with each female doing part of the work to catch the prey. Some
of the females scare prey animals and make them run -- while other females
lie in ambush to grab the fleeing animals.
The extra strength of a male is sometimes needed to bring down larger
animals, like wildebeest or buffalo. And larger animals are the best prey,
because they provide more meat.
No matter how good a lion is at hunting, it misses more prey than it
catches. Sometimes lions will go for days without eating. If lions can't
find enough of their regular prey, they will eat smaller animals like hares
and tortoises -- and even porcupines.
When they can, lions get their food by taking it away from other
animals. This is often easier than hunting. In some parts of Africa, much
of the food that lions eat is taken away from hyenas. When food is really
scarce, lions will eat almost anything they can find -- including snakes,
locusts, termites, peanuts, fruit, and rotten wood.
Baby lions are called cubs. And like most baby animals they need lots
of loving care. A lion cub is totally helpless at birth. It is blind and
can barely crawl. And it weighs less than 5 pounds (2 kg).
Cubs are born in-groups called litters. Usually, there are three cubs
in a litter. But sometimes there are as many as five. For the first few
weeks of their lives, the cubs stay hidden in a safe place away from the
pride. Then their mother brings them out to join the "family."
In a pride, all of the females help take care of the cubs. When one
mother is away hunting, the other lions feed and watch over her young. But
sometimes, all of the adults join the hunt. Then the cubs are hidden in the
tall grass or among the rocks.
A cub is born with dark spots all over its body. Some people think
that the spots may make it harder for predators to see the cubs when they
are hidden.
A mother lion carries her babies in her mouth -- just like a
motherhouse cat. To keep predators from finding the cubs, she moves them to
a new hiding place every few days.
AFRICAN LION: FUTURE
Asiatic lions are endangered, and African lions have less living space
than in times past. This is because people are taking away their homes, or
habitats. The human population in Africa and Asia is rapidly growing, and
people are turning more and more land into farms and ranches. This means
that the lions have less food to eat and so it is harder for them to live.
Fortunately, wildlife organizations throughout the world are working
hard to save the lions' habitats. And governments in both Africa and India
have set aside special land where lions can live in safety.
AFRICAN LION: THE MANE CAT
Most experts agree that a lion will attack a human only if provoked.
But the experts also suggest that knowledge of the warning signs are
mandatory for anyone who travels by foot in the bush. An angry lion will
drop to a crouch, flatten its ears, and flick its tail tip rapidly from
side to side. Low grunts and growls can often be heard; and just prior to a
charge, the tail is jerked up and down. While these warning signs are
important, it is perhaps of greater importance that a lion can bolt from a
crouch and travel 40 yards in less than 2.7 seconds.
The lion is the largest of the African cats, weighing up to 200
kilograms (440 pounds). Of the big cats, only the tiger is of greater size.
The mane of a male lion is the most distinguishing characteristic of the
species, although a small percentage of lionesses also have manes. The mane
adds to the apparent size of a male lion, and it is believed that the mane
provides added protection during male-to-male combat. The mane begins to
develop at about one year of age but remains short and scraggly until the
male is three or four years old. Another physical characteristic of lions
is the tuft of long hairs at the end of the tail. This black tassel occurs
in both males and females. Often, when females have cubs or are being
courted by males, the tail tassel is carried high above the ground.
Researchers believe that this behavior allows cubs or males to maintain
visual contact with the female when she moves through dense vegetation.
Fortunately for us, it is also an excellent way for humans to maintain
visual contact.
LION: NO LONGER KING
You may have believed that African lions are the kings of the jungle.
Well, that's just not true. But the reason isn't because lions aren't the
lordly animals that you thought them to be; it's just that lions don't live
in the jungle. They live in the open savannas in Africa, which are grassy
plains with a few scattered trees.
Lions, of course, are big cats, but they're different from tigers,
leopards and other big cats because they are very social animals. They live
in a group called a "pride," which can have as many as 35 lions in it.
Adult female lions, or lionesses, and cubs make up most of each pride,
although two or three adult males live in it, too.
Hunting is how the lions get their food. They eat animals such as
zebras, gazelles, hartebeests, gnus and even buffalo. Lionesses do most of
the hunting but when it comes to eating, the adult males get their share
first.
Lions often hunt together. A couple of lions may chase the prey and
herd it toward other lions hiding in the grass. Then the hiding lions leap
out and ambush the prey.
When lions eat, they often eat a whole lot of meat all at once. It's
possible for a wild lion to eat up to 40 pounds of meat at one sitting. But
then it may fast for several days and not eat anything. While it's fasting,
the lion may be very, very lazy and just sleep a lot ... until its time to
eat again.
If you've ever heard the roar of a lion, you know what a thundering
sound it is. It's very possible for a lion's roar to be heard five miles
away if the wind conditions are right. Lions often roar just after the sun
goes down.
Male lions have manes around their necks. A young male will start to
grow a mane when he's about a year old. It's believed that the mane helps
protect the neck areas of males when they fight with each other.
Baby lions are called cubs. A lioness will usually have three or four
cubs in an area protected by rocks or brush. Many animals are born with
their eyes closed, but it's possible for a lion cub to be born with its
eyes open. The cubs are very playful and love to wrestle and stalk each
other. Lionesses often care for each other's cubs, which is a little bit
like baby-sitting.
Although African lions aren't an endangered species, there's a lion
subspecies that lives in Asia that is very rare and endangered.
So remember: While you may not be able to call a lion the king of the
jungle, there's certainly no reason you can't call him the king of beasts.
ASIAN LION
In the past, you could find hundreds of thousands of these lions in
the Middle East and Asia. Now, they number only 180, living on a small
wildlife preserve in India. Like the African lion, they've suffered from
the destruction of wild lands and from over hunting.
Once, people thought that Asian lions had shorter manes than African
lions, but that's not the case. Both can have either long or short manes.
WOLVES
COYOTE: PLACE IN THE FOOD CHAIN
Every animal on earth lives by eating some other living organism --
plant or animal. The sequence of eaten and eater is called a food chain.
The ultimate source of the energy contained in food comes from the sun. It
is stored in the grass, and passed on to the grasshoppers. The alligator
lizard, which eats the grasshopper, is the next link in the food chain. It,
in turn, is eaten by a roadrunner, which then falls victim to the coyote.
The coyote is called an ultimate consumer because nothing hunts it for
food.
But this food chain is a closed circle, the final link -- coyote --
being fastened to the first -- the grass. When the coyote dies, its
chemicals are broken down by bacteria and returned to the soil, where they
nurture more plant growth.
Like many wild dogs, the coyote is usually active at night, when it
can hunt safely. You can often see a coyote in the early evening and
morning, as it goes to and from its nighttime activities.
Coyotes can run as fast as 40 miles per hour, and at slightly slower
speeds, they can run for miles. If a coyote can stay close to its prey, it
has a good chance of getting a meal.
DHOLE
In hunting style, the dhole is like the hyena. It hunts in a pack with
other dholes, whining, barking and whistling as they go. Whistling usually
means that the hunt is unsuccessful, and the pack should reassemble for
another try.
It is almost impossible for a single dhole to kill a deer, but five to
twelve dholes can manage it together. After the kill, dholes compete for
the morsels by eating very fast. A dhole can chew up almost nine pounds of
meat in an hour.
Strong, wise, brave -- all these words describe the gray wolf. But
another word needs to be added to the list: endangered.
Two hundred years ago, the gray wolf roamed throughout North America.
But many of them were shot by European settlers and pioneers, who were busy
cutting down the wolves' forest home for houses and towns. Those wolves
that remained found fewer deer, moose and beaver to eat.
Today, the gray wolf continues to feel the impact of an expanding
human population. That, and the popular belief that wolves shouldn't live
near humans, continues to threaten their presence on our planet.
GRAY WOLF
Did you know that the gray wolf is the largest member of the dog
family? Apart from man, it once was the most widespread mammal outside the
tropics. As humans move into its habitat, the wolf had to move out.
Did you know that after humans, wolves may be the most adaptable
creatures of all? They're able to live in a wider variety of climates and
habitats than most other animals and can survive on many different kinds of
food.
BEST LEFT UNPROVOKED
Wolves prey on many species in the north -- musk ox, caribou, moose,
deer, hares and even rodents. These carnivores are among the most maligned
of all animals, victims of false myths and legends and systematic programs
of extinction. They are accused of attacking humans and destroying entire
herds of domestic animals. But their depredations of livestock are less
severe than often claimed. And unprovoked attacks by healthy wolves in
North America on humans are unknown. Those recorded from Europe's Middle
Ages are thought to have been by rabid animals or hybrids.
The world will be a far lonelier place if the last wolf dies. As
biologist Ernest P. Walker wrote in his book, MAMMALS OF THE WORLD, "The
howl of the wolf and coyote, which to some people is of more enduring
significance than superhighways and skyscrapers, should always remain a
part of our heritage."
.
PRIMATS
APES: FUTURE
The future of apes is up to us. All of the great apes are already on
the endangered species list, and all of the lesser apes are as well.
Scientists who have studied them agree that all great apes will soon die
out in the wild unless steps are taken now to protect them.
Gorillas and orangutans appear to have no natural enemies, and
chimpanzees have very few. Gibbons, because they move so fast and live so
high up in the trees, are safe from any animal. Nothing could threaten any
of the apes with extinction until man started hunting them, capturing them,
and destroying the wild lands in which they live.
Today, hunting of apes is against the law everywhere, and there are
strict regulations controlling the capture of wild apes. But illegal
hunting and trapping continues. And the greatest threat of all -- the
destruction of wild lands -- grows greater every day. Tropical forests are
being cut down faster today than ever before ... at the rate of one acre
every second, according to a recent report. At this incredible pace, the
homes of many wild creatures -- including apes -- are simply disappearing.
Most endangered of the apes are the mountain gorillas. Today, there
are less than 500 in Central Africa.
And the other apes are not much better off. Nobody is really sure how
many pygmy chimpanzees or bonobos survive in the jungles south of the Congo
River -- but it is probably less than 10,000. There are fewer than 5,000
orangutans still alive in scattered areas of Borneo and Sumatra. And the
numbers of lowland gorillas and chimpanzees are declining rapidly.
Fortunately, there are people who are trying to save the magnificent
apes. In Central Africa, governments are working to protect the last
remaining homes of mountain gorillas. They have even organized guards that
patrol the borders of gorilla preserves to keep the gorillas safe from
hunters. The World Wildlife Fund and other groups are raising money to buy
land and make sure that it will never be taken away from gorillas,
chimpanzees, orangutans, and gibbons. And scientists everywhere are
studying the apes to find new ways to help them.
BONOBO OR PYGMY CHIMPANZEE
Biologists who have studied the behavior of these animals say they are
the smarter of two species of chimpanzees. Their hair is parted at the
middle and wisps out to the sides of the head, giving them an obvious
physical distinction from the common chimpanzee.
Both species of chimps are intelligent. They belong to the select
animals that make and use tools. You might see a chimp defend himself with
a tree branch, or take a twig and turn it into a useful devise for
gathering or eating foods. Chimps also communicate with many gestures and
vocalizations.
People may feel especially drawn to chimps because of some similar
behaviors. Young chimps laugh when they're tickled. Bonobos quarrel over
food, but hug and kiss to make up.
BONOBO: WORKSHOP IN CONSERVATION
The bonobo or pygmy chimpanzee, is one of only four living species of
great apes. The other three species, the gorilla, orangutan, and common
chimpanzee, have received far greater attention until now. Not even
recognized as a separate species until 1929, the bonobo still remains much
of a mystery in its native habitat, the central rain forests of Zaire.
Often confused with the common chimpanzee, the bonobo is only slightly
smaller but has a more graceful, slender body; the head is smaller but the
legs are longer than those of common chimps. The most outstanding physical
difference is the bonobo's hairstyle, an attractive coiffure of long black
hairs neatly parted down the middle. To the experienced eye, the difference
between the chimpanzee and the bonobo is as great as the difference between
a leopard and a cheetah.
The bonobo is as rare in zoos (there are less than 80 in captivity
worldwide) as it is in the wild (estimates range from 5,000 to 20,000). In
1989, the entire San Diego Zoo group of 11 animals was relocated to the
Wild Animal Park.
No effective conservation plan for the bonobo could be developed
without firsthand knowledge of the only country that is home to this
critically endangered ape. International conservation projects are as much
a people issue as an animal issue; therefore, the needs of the local
Zairian people must be taken into account. Political, cultural, and
economic problems are just as important to consider as the biological needs
of the species we are attempting to save. For these reasons, the San Diego
Bonobo Workshop continually emphasizes the need for an international
cooperative effort with the people and government of Zaire.
In light of the increasing awareness of the need to preserve the
world's biodiversity, it is quite surprising how little attention Zaire has
received. The extent and variety of the biological resources in Zaire's
forest ecosystems is matched by few other tropical countries. After Brazil,
Zaire has the second largest tropical forest in the world. Despite this
fact, Zaire is among the last of the countries in the tropical forest belt
without a comprehensive program to protect its tropical forest. Programs
like the one developed at the San Diego Bonobo Workshop will be
instrumental in obtaining funds from organizations like the World Bank to
protect the bonobo and its forest habitat.
THE GORILLA SUBSPECIES
Three subspecies of gorillas are currently recognized. Almost all zoo
gorillas are western lowland gorilla (Gorilla gorilla) native to west
African nations such as Cameroon, the Central African Republic, Gabon,
Nigeria, and Rio Muni. The total population of western lowland gorillas is
estimated to be between 30,000 to 50,000 individuals, and they are
classified as threatened by the IUCN (International Union for Conservation
of Nature and Natural Resources). Studying these gorillas in the wild is
extremely difficult, because their preferred habitat is dense jungle.
A very few eastern lowland gorillas (Gorilla gorilla graueri) native
to eastern Zaire, live in zoos. Mbongo and Ngagi, the two "mountain
gorillas" who lived at the San Diego Zoo in the 1930s and 1940s, would now
be classified as eastern lowland gorillas. These gorillas are considered
the largest subspecies on average, and generally have blacker hair than
western lowland gorillas. They number approximately 3,000 to 4,000 and are
classified as endangered.
No mountain gorillas (Gorilla gorilla beringei) exist in captivity,
but these are the most-studied gorillas in the wild. They live in the
mountainous border regions of Rwanda, Uganda, and Zaire. Only about 600
individuals exist, in two separate populations, and they are classified as
endangered. Mountain gorillas are distinguished physically by their large
size and extra-long, silky black hair. A number of skeletal differences
exist between the three subspecies as well.
It would be interesting to see if DNA sequence comparisons could help
us understand the phylogenetic (evolution of a genetically related group as
distinguished from the development of the individual organism)
relationships of the gorilla subspecies. This could help anthropologists
understand the mechanisms and rates of primate evolution. It could also be
important if gorilla populations ever become so critically depleted that
interbreeding of different subspecies were contemplated. At CRES, we are
comparing DNA sequences from gorillas of all three subspecies. Only a few
gorillas have been tested so far, but to date it appears that the
relationships between the subspecies generally follows the geographic
location of populations.
Western lowland gorillas have a large range, and many DNA sequence
differences exist between different individuals of this subspecies. Western
lowland gorillas are separated by 600 miles from eastern lowland gorillas,
and substantial sequence differences exist between the two groups as well.
The eastern lowland and mountain gorilla populations are found relatively
close together, but they have been isolated from each other for an unknown
amount of time. They are presently separated by substantial geographic
barriers: portions of the Rift Valley and a variety of mountain ranges.
However, we find much less genetic difference between the eastern lowland
gorillas and the mountain gorillas than there is between certain western
lowland gorillas. The distinct physical differences between eastern lowland
and mountain gorillas probably reflect recent adaptations to their
respective habitats -- lowlands versus mountains -- and not a distant
genetic relationship.
LION-TAILED MACAQUES: BACKGROUND
The macaques, a genus of some 13 to 20 species (there is disagreement
among taxonomists on the actual number), are found in North Africa and
throughout southern Asia from Afghanistan to Japan. The most familiar form
is the rhesus monkey, which is often seen by tourists in the towns and
cities of India. Fossils dating to six million years indicate that the
macaques originated in northern Africa and once roamed over Europe as far
north as London. These earlier macaques were not very different in
appearance from the Barbary monkeys that survive today in Morocco, Algeria,
and on Gibraltar. However, once the Macaques reached Asia, at least by
three million years ago, they diversified into a variety of forms. Few are
as distinctly different as the lion-tails, with their black coats, silver
facial ruffs, and strongly arboreal habitats. Lion-tails are one of the two
macaque species that are listed as in danger of extinction, but we may
realistically expect the Tibetan, Formosan, and Sulawesian species to fall
into that category before the year 2000.
Their geographical range snakes along the slope's and highest crests
of the Western Ghat Mountains where, today, the forest is reduced to about
one percent of the total land cover. Like its captive counterpart, the wild
living lion-tail was ignored by primatologists until well into the 1970s.
Although opinions vary, most would agree that the wild population today
numbers between 2,000 and 5,000 individuals. Initial field reports indicate
that wild lion-tails prefer to spend about 99 percent of their time in the
trees. Like other macaques, their diet is dominated by wild fruits, but
includes a variety of flowers, leaves, buds, grasses, insects, and even a
few nestlings of birds and mammals. One of the more interesting forms of
feeding reported by Dr. Steven Green of Miami University involves a simple
form of tool use. In order to protect their hands while feeding on stinging
caterpillars, lion-tails have been seen to pluck large tree leaves and lay
them over the caterpillars before pouncing on them.
In the wild state, lion-tail groups average about 20 individuals,
usually with more than a single adult male present. Males are larger than
females by about a third and are typically ranked relative to one another
in a social hierarchy. Males usually emigrate from their natal group to
join another during the early stages of adulthood. Being macaques, lion-
tails are intensely social and are highly aggressive toward unfamiliar
individuals. Preliminary work on our captive population indicates that much
of the behavior between group members is dependent upon one's relationship
to a small number of female-headed lineages. It is possible to have up to
four living generations within each matriline and four or five matrilines
within a group. Dominance relationships among and within matrilines play a
crucial role in the everyday life of females and their offspring, as they
do for adult males. One's social position determines access to essential
resources such as food, perches, and social partners.
LION-TAILED MACAQUES: FUTURE PLANS
This highly endangered primate has been exhibited at the San Diego Zoo
since 1923. In 1979, the existing population of three males and three
females was relocated to the Primate Research Pad for concentrated study of
their reproductive biology. Within the next decade their reproductive
cycles were characterized, as were their sexual and social behavior,
parturition and infant rearing, and various other aspects of the captive
experience. Nearly a dozen scientific papers from these studies have been
published in peer-reviewed journals or as book chapters.
BY 1989 the Zoo's captive population had grown to 38 individuals. This
same year the program undertook a significant change in direction. Seven
individuals, including five born at the Primate Research Pad, were released
into a state-of-the-art exhibit in Sun Bear Forest. Although these
individuals are no longer under study, it was knowledge gained over the
previous decade that contributed to the design of an exhibit facility
which, by anyone's criteria, is an outstanding success.
A second troop of 11 individuals was simultaneously relocated to the
newly constructed 3/4-acre breeding kraal at the Wild Animal Park. It is
this population which will be a major research focus during the next five
years. This troop has been exempted from Species Survival Plan management,
a program of the American Association of Zoological Parks and Aquariums,
providing freedom to pursue several interesting lines of inquiry. One of
these has to do with the impact of traditional management regimes on
certain life history parameters. The second investigation will pursue
experiments designed to prepare the troop for reintroduction to suitable
habitat in India in five to seven years.
The lion-tailed macaque is by nature a highly social mammal. Group
members are organized in a social hierarchy that appears to remain stable
over many years. Individual troops are highly xenophobic. This trait,
combined with natural aggressiveness, results in potentially fatal conflict
when new individuals are introduced. In the wild state, males will leave
their natal troop at sexual maturity and join a new one. Females remain in
their natal troops throughout their lives.
Transfer by males is accompanied by a substantial amount of
aggression, but is presumably a necessary event to preclude inbreeding.
These natural attributes of wild troops would seemingly have profound
implications for the transfer of individuals, especially of females,
between zoological institutions to satisfy genetic and reproductive
objectives.
It is relevant to ask if the ongoing disturbance of the social order
through frequent inter-institutional transfers might negatively impact on
such parameters as infant mortality, female fecundity, and perhaps even the
neonatal sex ratio. Our kraal group has been together for the past 24
years, the only social disturbances having been the replacement of breeding
males. We have learned how to integrate new males into groups with a
minimum of social upheaval. We therefore have a unique opportunity to
compare findings from our relatively undisturbed population with those from
more traditionally managed populations in other zoos over the next several
years.
Preparation of this same troop for reintroduction to the wild has two
components. The first entails a number of experimental procedures designed
to "teach" natural foraging, avoidance of predators (including humans), and
appropriate social cohesiveness. In addition, the troop must be routinely
evaluated for any pathogens that would pose a hazard to the existing wild
population.
The second component is evaluation of potential release sites in the
wild. The area selected for a test-case reintroduction must not only be
protected from human activity, but must contain adequate food and shelter
to insure the long-term survival of the troop. CRES anticipates working
closely with Indian colleagues on this aspect.
NIGHTTIME IS THE NORM: LABOR AND BIRTH IN THE LION-TAILED MACAQUE
Lion-tailed macaque neonates (newborns) are born with black fur, and
their faces, hands, and feet are pink and hairless. Their characteristic
silver manes do not begin to grow in until the babies are several weeks
old, and their faces gradually acquire the black pigmentation of adults.
When the lion-tailed macaque breeding and management program began at
the CRES primate facility more than ten years ago, little was known about
the gestation, labor, and delivery of infants in this species. There was
extensive documentation of parturition in some other macaques, but no
comparable data were available on the much rarer lion-tailed macaque. How
long is the normal gestation length? At what time are births most likely to
occur? How long does labor last? What factors indicate that there may be a
delivery problem requiring veterinary intervention? Answers to these and
other important questions were needed in order to ensure the best captive
management procedures and to maximize the breeding success for this
species.
The primary reason these data had not been collected previously is
that most new infants were usually discovered in the morning, after the
keepers arrived at work. We began collecting data on each lion-tailed
macaque birth by setting up 24-hour "birth watches" that began several days
before the dam was due to deliver. Conception dates were determined
partially through hormone data from daily urine samples, and also by
keeping careful track of menstruation, sex-skin swellings, and mating
episodes. Parturition-date predictions were based on the 168-day gestation
length documented for the rhesus macaque. However, because this is an
average length, we began our observations about ten days before the due
date in order not to miss the early deliveries.
The birth watch involved round-the-clock observations at 15-minute
intervals during successive, 4-hour shifts. Observations were recorded by
keepers, technicians, and trained volunteers. As soon as any signs of
straining or birth fluids were noted, continuous notes were kept and each
subsequent contraction or birth-related event was timed and recorded.
Behavioral indications of impending labor included restlessness and manual
exploration of the vaginal area. Although these signs eventually proved
reliable, we used the first, clear contraction as the starting point for
measuring the duration of labor. (In human terms, this is equivalent to
second-stage labor. The usual criterion of first-stage labor, cervical
dilatation, cannot be observed in the wild primate unless restraint is
used.) During actual labor, several straining postures were noted; most
common were variations of squatting postures and arched-back stretches.
The first birth was to an experienced mother (this was her third
delivery) and was documented on videotape. After nearly 8 full hours of
labor and 188 contractions, the dam gave birth to a healthy, female infant.
These initial observations led us to believe that a labor of this duration
was not a basis for concern; however, we soon learned that this was far
beyond the average labor length and number of contractions common for this
species.
Over an 8-year period, we were able to collect data on 18 births from
8 different mothers in our colony. Our program has provided some valuable
information about species-typical birth patterns that we can now use to
direct management decisions. We found that the average length of labor to
expulsion of the fetus was about 2 hours and 15 minutes, and the shortest
labor was only 50 minutes total. The female that required eight hours to
deliver in the first case observed then delivered her subsequent infant in
only a little over an hour! Although our sample is still small, it would
appear that, on the average, first-time mothers have longer and more
difficult labors.
Our study determined that the average number of contractions to
delivery for lion-tails was 54. The female with the longest labor also had
the largest number of contractions (454). In her next delivery, the infant
arrived after only 14 contractions, the lowest number recorded during the
entire birth study. Based on the average number of contractions seen in 17
successful deliveries, and one ending in stillbirth, contraction
frequencies approaching 75 to 100 in number may serve as a warning that
intervention will be necessary.
The average length of gestation for 14 pregnancies in our colony was
169.5 days, with a range of 163 to 176 days. This is very similar to what
has been reported for other macaques. Our observers quickly discovered that
those who watched during the 7 to 11 P.M. shifts were the most successful
at being present when births occurred: labor began between the hours of
7:15 P.M. and 3:15 A.M. in every case but one. The exception was one first-
time mother that began straining in the early afternoon. This female had a
difficult labor, and a dead fetus was later removed by cesarean section
after 8 hours of straining and 193 contractions. All the other births
resulted in live offspring and occurred between the hours of 8:05 P.M. and
6:28 A.M. Based on previous primate birth records, daytime births are not
the norm and may indicate an increased risk to both fetus and dam.
Expulsion of the placenta always took place within about 20 minutes
after parturition, and usually it was immediately consumed by the mother.
In a few cases, first-time mothers carried the placenta around for several
hours, along with the infant, until it could be removed by keepers.
Whenever possible, a sample of the placenta is saved for analysis by Zoo
pathologists, who check it for abnormalities. After delivery, the mothers
carefully lick the birth fluids off their infants, and the neonates begin
nursing within a few hours. Each and every female in the study provided
excellent maternal care immediately following parturition.
The lion-tailed macaque breeding colonies are now located in the Sun
Bear Forest exhibit at the Zoo (one adult male and six females) and in a
large, off-exhibit kraal at the Wild Animal Park (one adult male, two
juvenile males, one infant male, and ten females). Together these represent
the largest captive group of lion-tailed macaques in the world -- about 20
percent of the total captive population. Eight years of patient monitoring,
birth watches, record keeping, and evaluation have brought us a long way in
the breeding and captive management of this macaque species.
ZOONOOZ, May, 1990 "Nighttime Is the Norm: Labor and Birth in the Lion-
tailed Macaque," by Helena Fitch-Snyder, Animal Behavior Specialist/CRES
and Donald Lindburg, Ph.D. Behaviorist/CRES.
MORE ON IGUANAS
The environment in which a lizard lives may determine how easily its
scent marks can be located by other lizards. Both desert iguanas
(Dipsosaurus dorsalis )and green iguanas (Iguana iguana) possess femoral
glands on the underside of the hind legs. They use pheromone secretions
from these glands to mark their territories. Desert iguanas live in
extremely hot and arid habitats, whereas green iguanas live in humid
tropical forests. Because these two species of lizards live under such
different environmental conditions, it is not surprising that the way their
pheromone signals are transmitted differs.
Desert iguanas have scent marks that are nonvolatile, which means that
they evaporate very slowly into the atmosphere. These marks are also
extremely resistant to chemical breakdown at high temperatures. The low
volatility and thermal stability of desert iguana scent marks ensures that
they persist under harsh desert conditions, a necessary quality if they are
to be used effectively for territory marking. Although these
characteristics make scent marks more durable in desert environments, they
pose a problem for desert iguanas attempting to detect them if the marks
are not volatile; they may be difficult or impossible to locate using
smell. Desert iguanas avoid this problem by combining a unique type of
visual signal with their scent marks.
One striking property of desert iguana scent marks is that they
strongly absorb ultraviolet light. Although these wavelengths are invisible
to human eyes, they appear dark to animals able to see ultraviolet light --
much as ultraviolet-absorbing honey guides on flowers look black when UV-
sensitive camera film is used to view them. Recent studies have shown that
desert iguanas are able to see long-wave ultraviolet light, and they may
use this adaptation to detect scent marks from a distance. After scent
marks are localized using visual cues, desert iguanas can approach and
investigate them in more detail through tongue-flicking. Although it is not
known to occur in mammals, visual sensitivity to ultraviolet light has been
shown in certain insects, spiders, fish, frogs, and birds. The ability of
desert iguanas to detect ultraviolet light may help them solve some of the
problems associated with finding scent marks in a desert environment.
In contrast to those of desert iguanas, the scent marks of green
iguanas contain a variety of volatile chemical compounds, and they do not
absorb ultraviolet light. Behavioral studies indicate that green iguanas,
unlike desert iguanas, can detect these scent marks by smell alone. Because
the chemical components of green iguana scent marks remain active and
transmit well under the humid conditions of tropical forests, green iguanas
do not appear to need a visual cue in order to locate scent marks. Research
on both iguana species demonstrates how the environment in which animals
live can influence the nature of the communication signals they employ.