VETS’
GUIDE
ALL YOU NEED TO KNOW ABOUT ELEPHANTS
Elephants
are large mammals of the family Elephantidae and the order Proboscidea. Three
species are recognised, the African bush elephant (Loxodonta africana),
the African forest elephant (L. cyclotis) the Asian elephant (Elephas
maximus). Elephantidae is the only surviving family of the order
Proboscidea; other, now extinct, members of the order include deinotheres,
gomphotheres, mammoths, and mastodons. Male African elephants are the largest
extant terrestrial animals and can reach a height of 4 m (13 ft) and weigh 7,000
kg (15,000 lb). All elephants have several distinctive features, the most
notable of which is a long trunk or proboscis, used for many purposes,
particularly breathing, lifting water, and grasping objects. Their incisors
grow into tusks, which can serve as weapons and as tools for moving objects and
digging. Elephants' large ear flaps help to control their body temperature.
Their pillar-like legs can carry their great weight. African elephants have
larger ears and concave backs while Asian elephants have smaller ears and
convex or level backs. Elephants are herbivorous and can be found in different
habitats including savannahs, forests, deserts, and marshes. They prefer to
stay near water. Other animals tend to keep their distance from elephants while
predators, such as lions, tigers, hyenas, and wild dogs, usually target only
young elephants (or "calves"). Females ("cows") tend to
live in family groups, which are led by an individual known as the matriarch,
often the oldest cow. Males ("bulls") leave their family groups when
they reach puberty and may live alone or with other males. Adult bulls mostly
interact with family groups when looking for a mate and enter a state of
increased testosterone and aggression known as musth, which helps them gain dominance and reproductive success.
Calves are the centre of attention in their family groups and rely on their
mothers for as long as three years. Elephants can live up to 70 years in the
wild. Elephant’s intelligence has been compared with that of primates and
cetaceans. They appear to have self-awareness and show empathy for dying or
dead individuals of their kind.
Anatomy and morphology
Elephants
are the largest living terrestrial animals. African elephants stand 3–4 m (10–13
ft) and weigh 4,000–7,000 kg (8,800–15,400 lb) while Asian elephants stand
2–3.5 m (7–11 ft) and weigh 3,000–5,000 kg (6,600–11,000 lb). In both cases,
males are larger than females. Among African elephants, the forest form is
smaller than the savannah form.
The
skeleton of the elephant is made up of 326–351 bones. The vertebrae are
connected by tight joints, which limit the backbone's flexibility. African
elephants have 21 pairs of ribs while Asian elephants have 19 or 20 pairs.
An
elephant's skull is resilient enough to withstand the forces generated by the
leverage of the tusks and head to head collisions. The back of the skull is
flattened and spread out, creating arches that protect the brain in every direction.
The skull contains air cavities (sinuses) that reduce the weight of the skull
while maintaining overall strength. These cavities give the inside of the skull
a honeycomb-like appearance. The cranium is particularly large and provides
enough room for the attachment of muscles to support the entire head. The lower
jaw is solid and heavy. Because of the size of the head, the neck is relatively
short to provide better support. Lacking a lacrimal apparatus, the eye relies
on the harderian gland to keep it moist. A durable nictitating membrane protects
the eye globe. The animal's field of vision is compromised by the location and
limited mobility of the eyes.
Elephants
are considered dichromats and they can see well in dim light but not in bright
light. The core body temperature averages 35.9 °C (97 °F), similar to a human.
Like all mammals, an elephant can raise or lower its temperature a few degrees
from the average in response to extreme environmental conditions.
Ears
Elephant
ears have thick bases with thin tips. The ear flaps, or pinnae, contain
numerous blood vessels called capillaries. Warm blood flows into the
capillaries, helping to release excess body heat into the environment. This occurs
when the pinnae are still, and the animal can enhance the effect by flapping
them. Larger ear surfaces contain more capillaries, and more heat can be
released. Of all the elephants, African bush elephants live in the hottest
climates, and have the largest ear flaps. Elephants are capable of hearing at
low frequencies and are most sensitive at 1 kHz.
Trunk
The
trunk, or proboscis, is a fusion of the nose and upper lip, although in early
fetal life, the upper lip and trunk are separated. The trunk is elongated and
specialised to become the elephant's most important and versatile appendage. It
contains up to 150,000 separate muscle fascicles, with no bone and little fat.
Elephant trunks have multiple functions, including breathing, olfaction, touching,
grasping, and sound production. The animal's sense of smell may be four times
as sensitive as that of a bloodhound. The trunk's ability to make powerful
twisting and coiling movements allows it to collect food, wrestle with
conspecifics, and lift up to 350 kg (770 lb). It can be used for delicate
tasks, such as wiping an eye and checking an orifice, and is capable of
cracking a peanut shell without breaking the seed. With its trunk, an elephant
can reach items at heights of up to 7 m (23 ft) and dig for water under mud or
sand. Elephants can suck up water both to drink and to spray on their bodies.
When underwater, the elephant uses its trunk as a snorkel.
The
African elephant has two fingerlike extensions at the tip of the trunk that
allow it to grasp and bring food to its mouth. The Asian elephant has only one,
and relies more on wrapping around a food item and squeezing it into its mouth.
Asian elephants have more muscle coordination and can perform more complex
tasks.
Teeth
Elephants
usually have 26 teeth: the incisors, known as the tusks, 12 deciduous premolars,
and 12 molars. Unlike most mammals, which grow baby teeth and then replace them
with a single permanent set of adult teeth, elephants are polyphyodonts that
have cycles of tooth rotation throughout their lives.
Internal and sexual organs
The
brain of an elephant weighs 4.5–5.5 kg (10–12 lb) compared to 1.6 kg (4 lb) for
a human brain. While the elephant brain is larger overall, it is proportionally
smaller. At birth, an elephant's brain already weighs 30–40% of its adult
weight. The cerebrum and cerebellum are well developed, and the temporal lobes
are so large that they bulge out laterally. The throat of an elephant appears
to contain a pouch where it can store water for later use. The heart of an
elephant weighs 12–21 kg (26–46 lb). When standing, the elephant's heart beats
approximately 30 times per minute. Unlike many other animals, the heart rate
speeds up by 8 to 10 beats per minute when the elephant is lying down. The
lungs are attached to the diaphragm, and breathing relies mainly on the
diaphragm rather than the expansion of the ribcage. Connective tissue exists in
place of the pleural cavity.
Mating
Elephants
are polygynous breeders, and copulations are most frequent during the peak of
the wet season. A cow in oestrus releases chemical signals (pheromones) in
her urine and vaginal secretions to signal her readiness to mate. A bull will
follow a potential mate and assess her condition with the flehmen response,
which requires the male to collect a chemical sample with his trunk and bring
it to the vomeronasal organ. The oestrous cycle of a cow lasts 14–16 weeks with
a 4–6week follicular phase and an 8–10week luteal phase. While most mammals
have one surge of luteinizing hormone during the follicular phase, elephants
have two. The first (or anovulatory) surge, could signal to males that the
female is in oestrus by changing her scent, but ovulation does not occur until
the second (or ovulatory) surge. Fertility rates in cows decline around 45–50
years of age.
Bulls
engage in a behaviour known as mate-guarding, where they follow oestrous
females and defend them from other males. Most mate-guarding is done by musth
males, and females actively seek to be guarded by them, particularly older
ones. Thus these bulls have more reproductive success. Musth appears to signal
to females the condition of the male, as weak or injured males do not have normal
musths.
Birthing and calves
Gestation
in elephants typically lasts around two years with interbirth intervals usually
lasting four to five years. Births tend to take place during the wet season.
Calves are born 85 cm (33 in) tall and weigh around 120 kg (260 lb). Typically,
only a single young is born, but twins sometimes occur.
When
a predator is near, the family group gathers together with the calves in the
centre. For the first few days, the newborn is unsteady on its feet, and needs
the support of its mother. It relies on touch, smell, and hearing, as its
eyesight is poor. It has little precise control over its trunk, which wiggles
around and may cause it to trip. By its second week of life, the calf can walk
more firmly and has more control over its trunk.
After
its first month, a calf can pick up, hold, and put objects in its mouth, but
cannot suck water through the trunk and must drink directly through the mouth.
It is still dependent on its mother and keeps close to her.
For
its first three months, a calf relies entirely on milk from its mother for
nutrition after which it begins to forage for vegetation and can use its trunk
to collect water. At the same time, improvements in lip and leg coordination occur.
Calves continue to suckle at the same rate as before until their sixth month,
after which they become more independent when feeding.
References:
Elephant facts, Wikipedia. Compiled and Edited by Martial.
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