There are several thousand species of mammals living today, and all
share a set of common characteristics, or are descendant from a previously living
group that already had many of these characteristics. Most mammals live on land
and are terrestrial. Some live on terrestrial structures, but feed in the sky such as
bats, which fly. Some mammals live in water most of their lives, but emerge onto
land to give birth to young. These include seals and sea lions. Whales and dolphins
are entirely aquatic, having modified their appendages in favor of swimming at the
expense of not being able to walk on land. Within the whales and dolphins there
are two major groups, the toothed whales and the baleen whales. Toothed whales
include the dolphins and others like the sperm whale. The baleen whales are large
oceanic whales and include the blue whale, the largest living mammal. The baleen
whales are named because of the large plates of baleen they have in their mouths
that strain food out of the water column and pass it into their digestive system.
What about arms and legs? The arms or forelimbs have been modified
into flippers for swimming. The hindlimbs have become vestigial, or have been
lost. Look at the right whale skeleton at the Paleontological Research Institute to
see the tiny remnants of the pelvis and femur (thighbone). We think that whales
evolved from ancestors of artiodactyls, the group that includes modern camels,
deer and cows.
The earliest whales and dolphins may have been partially aquatic, moving
in and out of the water, but not fully committed to life at sea. The fluke that powers
whale swimming is a modification of the tail region of these mammals and may be
critical to their eventual life as obligate but agile swimmers
Paleontologists have fossils of intermediate forms of whales, with teeth,
forelimbs and hindlimbs designed for walking on land, including hooves on the toes
of the hindlimbs.
Finally, there is good molecular evidence linking dolphins and whales with
modern artiodactyls, like cows and deer. Mammals have been adept at solving the
problems associated with living in the sky, on earth's surface, or in the oceans.
Here's some extra arguments about why dolphins are mammals. The
presence of modified skin glands, or mammary glands, that are used to provide
nourishment to newborn animals is a hallmark of the mammals. Whales or dolphins
have these glands and are able to provide milk to their babies. Unlike reptiles and
birds, mammals are born alive, and do not hatch from a typical egg. A complex set
of teeth comprise yet another characteristic that sets mammals apart from most
other vertebrate animals. Another common characteristic of most mammals is a
coat of hair.
A dolphin is a large, slender, food and game fish widely distributed in warm
seas, especially around Hawaii. Spinner dolphins are most popular, and can be detected
from large distances as they spin high in the air, landing with loud splashes. They are pan
tropical, occurring in all tropical and subtropical waters around the world .
Dolphins do not drink water since the ocean water in which they live in
is too salty for them to drink. Instead of drinking water directly, they obtain their
water from their diet.
Hippopotamuses love water, which is why the Greeks named them the
"river horse." Hippos spend up to 16 hours a day submerged in rivers and lakes to
keep their massive bodies cool under the hot African sun. Hippos are graceful in
water, good swimmers, and can hold their breath underwater for up to five
minutes. However, they are often large enough to simply walk or stand on the lake
floor, or lie in the shallows. Their eyes and nostrils are located high on their heads,
which allows them to see and breathe while mostly submerged.
Hippos also bask on the shoreline and secrete an oily red substance,
which gave rise to the myth that they sweat blood. The liquid is actually a skin
moistener and sunblock that may also provide protection against germs.
At sunset, hippopotamuses leave the water and travel overland to graze.
They may travel 6 miles (10 kilometers) in a night, along single-file pathways, to
consume some 80 pounds (35 kilograms) of grass. Considering their enormous size,
a hippo's food intake is relatively low. If threatened on land hippos may run for the
water—they can match a human's speed for short distances.
Hippo calves weigh nearly 100 pounds (45 kilograms) at birth and can
suckle on land or underwater by closing their ears and nostrils. Each female has
only one calf every two years. Soon after birth, mother and young join schools that
provide some protection against crocodiles, lions, and hyenas.
Hippos once had a broader distribution but now live in eastern central and
southern sub-Saharan Africa, where their populations are in decline.
With a great whoosh and a snort, a seemingly quiet African river suddenly
erupts with the appearance of a great huge beast. Then whoosh, another surfaces,
and another, and another. One by one, about 15 hippopotamuses rise to the
surface of the calm water—some with a great deal of snorting and hissing as they
exhale, others more quietly. At the surface, they each take a breath of fresh air.
The group of hippos is led by one large male. The other members are
females, their young, and a few young adult males. The leader of the group keeps
control of his mating territory by fighting off rivals. When a male hippo in the group
challenges him, the leader opens his enormous mouth, revealing long canines.
Often the display is enough to make the challenging hippopotamus back
off. Sometimes, however, hippos fight aggressively, leading to deep wounds and
sometimes even death. The family group of hippos spends most of the day in the
water. Staying submerged helps a hippo stay cool in the hot, tropical climate where
Hippos are excellent swimmers and can hold their breath for about five
minutes. They can even walk along the bottoms of rivers and lakes.
At dusk, hippos leave their watery daytime spot, lumber onto land, and
walk as far as 5 miles (8 kilometers) from the water to graze on short grasses, their
main food. Grazing until dawn, a hippo may eat up to 150 pounds (68 kilograms) of
grass a night. They avoid the heat of the sun by returning to a river or lake before
The scientific name for the common hippo is Hippopotamus amphibious.
Hippopotamus comes from two Greek words that mean river horse.
Hippos' toes are webbed, which helps them paddle through the water.
Hippopotamuses live in rivers and lakes in central and southern Africa. A hippo's tail
is about 22 inches (56 centimeters) long.
A hippo is 12 to 15 feet (4 to 5 meters) long and weighs from 5,000 to
8,000 pounds (2,300 to 3,600 kilograms).
Two tusks, or canine teeth, in the hippo's lower jaw can grow more than a
foot (30 centimeters) long.
Hippos eat only vegetation—grasses and water plants.
Nutrients from the hippos' dung provide food for microorganisms, which in turn are
food for fish.
Female hippos are able to have babies at about seven years old.
Baby hippos are born underwater. They can swim almost from the moment they're
Baby hippos are called calves. They often nurse underwater.
Hippos can live to be more than 40 years old in the wild.
Male hippos fighting
Hippopotamuses are by nature very aggressive animals. Hippos involved
in attacks on other animals are often either mature bulls, which tend to be very
territorial and indiscriminately ill-tempered, or females, which are quite protective
of their young calves. Living on the African continent, hippopotamus coexist with a
variety of formidable predators. Nile crocodilies, lions and spotted hyenas are
known to prey on young hippos. However, due to their ill temperament and great
size, adult hippopotamus are not usually subject to predation by other animals,
except humans. Cases where very large lion prides or cooperating groups of Nile
crocodiles have successfully preyed on adult hippopotamus have been reported,
but this is typically believed to be exceptionally rare.Crocodilies are particularly
frequent targets of hippo aggression, likely because they often inhabit the same
riparian habitats as hippos. Crocodiles may be either aggressively displaced or killed
by hippopotamuses. Hippos are also very aggressive towards humans, whom they
commonly attack whether in boats or on land with no apparent provocation. They
are widely considered to be one of the most dangerous large animals in Africa.
To mark territory, hippos spin their tails while defecating to distribute
their excrement over a greater area. "Yawning" serves as a threat display. When in
combat, male hippos use their incisors to block each other's attacks, and their
canines to inflict damage. Hippos rarely kill each other, even in territorial
challenges. Usually, a territorial bull and a challenging bachelor stop fighting when
it is clear that one hippo is stronger.
When hippos become overpopulated, or when a habitat starts to shrink,
bulls sometimes attempt to kill infants, but this behavior is not common under
normal conditions.Some incidents of hippo cannibalism have been documented,
but it is believed to be the behavior of distressed or sick hippos, and not healthy
With the exception of eating, most of hippopotamuses' lives – from
childbirth, fighting with other hippos, to reproduction – occurs in the water. Hippos
leave the water at dusk and travel inland, sometimes up to 10 km (6 mi), to graze
on short grasses, their main source of food. They spend four to five hours grazing
and can consume 68 kg (150 lb) of grass each night. Like almost any herbivore, they
consume other plants if presented with them, but their diets in nature consists
almost entirely of grass, with only minimal consumption of aquatic plants. Hippos
have (rarely) been filmed eating carrion, usually close to the water. There are other
reports of meat-eating, and even cannibalism and predation. The stomach anatomy
of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant
behavior or nutritional stress.
Hippo defecation creates allochthonous deposits of organic matter along
the river beds. These deposits have an unclear ecological function.Because of their
size and their habit of taking the same paths to feed, hippos can have a significant
impact on the land across which they walk, both by keeping the land clear of
vegetation and depressing the ground. Over prolonged periods, hippos can divert
the paths of swamps and channels.
Adult hippos move at speeds up to 8 km/h (5 mph) in water; typically
resurfacing to breathe every three to five minutes. The young have to breathe every
two to three minutes.The process of surfacing and breathing is automatic. A hippo
sleeping underwater rises and breathes without waking. A hippo closes its nostrils
when it submerges into the water.As with fish and turtles on a coral reef, hippos
occasionally visit cleaning stations and signal, by opening their mouths wide, their
readiness for being cleaned of parasites by certain species of fishes. This is an
example of mutualism in which the hippo benefits from the cleaning, while the fish
Water lilies grow completely within water, with their blossoms flourishing
on top of or above the water’s surface. They typically grow to suit the size of the
area in which they are placed, spreading their leaves across the surface of the water
and filling it with color.
Water lilies require a lot of sun to grow properly. In frost-free regions,
they bloom all year. In cooler regions, they bloom during the summer and often
into the fall. Throughout their growing season, they constantly generate leaf
growth. These leaves live up to three or four weeks at the peak of the season.
The most striking feature of water lilies is the incredible amount of
variation found among the different plants. From their shape and size, their color
and fragrance, or their blooming patterns and growing periods, there is a water lily
for every preference and every pond.
Water lilies range notably in size --– from miniature flowers with small
leaves to giant plants that spread over 25 square feet. They come in a variety of
shapes – star shaped, cup shaped, pointed or fluffy, though that’s certainly not all.
The leaves can be smooth or jagged, rounded or pointed.
The colors are just as varied, ranging from yellow, pink, red, white, purple,
blue and orange. Several types of lilies are incredibly fragrant, as well.
There are two kinds of tropical water lilies: night bloomers and day
bloomers. Lilies in the white, pink or red color range tend to be night bloomers, and
these types are typically more fragrant. These flowers can take an entire hour to
fully open, and tend to open in the late afternoon or early evening and close the
Day bloomers, however, are the most common kind of tropical water
lilies. They are fragrant, as well, but their scents are usually lighter and sweeter
than the heavy-scented tropicals. Day bloomers have pointed petals and come in
various shades, from magenta, red or pink, to white or yellow, or to blue or violet.
They open midmorning and close again during the late afternoon hours.
The blooms of both day and night bloomers open and close for periods of
three to four days, holding their flowers above the water on strong, stiff stems.