sloth

树獭

即不讲究卫生，

以至于它粗糙的毛发上生出绿苔，

成群的寄生蛾生长在它的皮毛深处，

< br>变成

毛毛虫，并以它的脏毛为食。

85.

The

sloth

pays

such

little

attention

to

its

personal

hygiene

that

green

algae grow on its coarse hair and communities of a parasitic moth live

in

the

depths

of

its

coat

producing

caterpillars

which

graze

on

its

mouldy

hair.

Sloth

Rainforest Animals

Sloths are extremely slow-moving

mammals found in the rainforest

canopies of Central and South

America. There are two species of

sloths:two-toed and three-toed.

Most sloths are about the size of a

small dog and they have short,

flat flat heads. Their hair is

grayish brown but, at times they

look grey-green in color because

they move so slowly that tiny

camouflaging algae grow all over

their coats.

Some sloths stay in the same tree

for years. Their huge hooked claws

and long arms allow them to spend

most of their time hanging

upside-down from trees. Since they

have a slow metabolism, they need

very little food. They feed on fruit,

leaves, buds, and young twigs.

Sloths also sleep upside-down for

up to 18 hours at a time. Mothers

also give birth to babies

upside-down. Babies cling to their

mothers until they are able to take

care of themselves.

Sloths are nocturnal and sleep

curled up with their head placed

between the arms and the feet

drawn close together. This

disguises them as part of a tree so

that its enemies like the jaguar do

not see them. Sloths rarely climb

down from the trees and can live

for up to 30 years.

Sloths

are the six

species

of medium-sized

mammals

belonging to the

families

Megalonychidae

and

Bradypodidae

,

part

of

the

order

Pilosa

.

They

are

arboreal

residents of the

rainforests

of

Central

and

South America

.

The

sloth's

taxonomic

suborder

is

Folivora

,

while

some

call

it

Phyllophaga

.

Both

names

mean

derived

from

Latin

and

Greek

respectively.

Names for the animals used by tribes in

Ecuador

include

Ritto

,

Rit

and

Ridette

,

mostly

forms

of

the

word

and

from

Tagaeri

tribe

of

Huaorani

.

In

Brazil,

sloths

are

commonly

called

pregui?a

(

metabolism.

Contents

[

hide

]

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1 Ecology

2 Physiology

3 Classification

4 Extinction

5 Media

6 References

7 External links

[

edit

] Ecology

Feeding

Brown-throated Three-toed Sloth

(

Bradypus variegatus

),

Cahuita

National Park

,

Costa Rica

Sloths are classified as

folivores

as the bulk of their diet consists

mostly

of

buds,

tender

shoots,

and

leaves,

mainly

of

Cecropia

trees.

Some

two-toed sloths have been documented as eating

insects

, small reptiles

and

birds

as

a

small supplement

to

their

diet.

Linnaeus's

Two-toed

Sloth

has recently been documented eating human faeces from open latrines.

[2]

They have made extraordinary adaptations to an

arboreal

browsing

lifestyle.

Leaves,

their

main

food

source,

provide

very

little

energy

or

nutrition and do not digest easily. Sloths therefore have very large,

specialized, slow-acting

stomachs

with multiple compartments in which

symbiotic

bacteria

break

down

the

tough

leaves.

As

much

as

two-thirds

of

a well-fed sloth's body-weight consists of the contents of its stomach,

and the digestive process can take a month or more to complete.

Even

so,

leaves

provide

little

energy,

and

sloths

deal

with

this

by

a

range

of economy measures: they have very low

metabolic

rates (less than half

of that expected for a mammal of their size), and maintain low body

temperatures

when

active

(30

°C

(86

°F)

to

34

°C

(

93

°F)),

and

still

lower temperatures when resting.

Although

unable

to

survive

outside

the

tropical

rainforests

of

South

and

Central America, within that environment sloths are outstandingly

successful

creatures:

they

can

account

for

as

much

as

half

the

total

energy

consumption

and

two-thirds

of

the

total

terrestrial

mammalian

biomass

in

some areas.

[

citation needed

]

Of the six living

species

, only one, the

Maned

Three-toed Sloth

(

Bradypus torquatus

), has a classification of

forests, however, may soon prove a threat to other sloth species.

[

edit

] Physiology

Sloth furs exhibit specialized functions: the outer hairs grow in a

direction

opposite

from

that

of

other

mammals.

In

most

mammals,

hairs

grow

toward

the

extremities,

but

because

sloths

spend

so

much

time

with

their

legs above their bodies, their hairs grow away from the extremities in

order

to

provide

protection

from

the

elements

while

the

sloth

hangs

upside

down. In most conditions, the fur hosts two species of

symbiotic

cyanobacteria

,

which

provide

camouflage.

[3][4]

Because

of

the

cyanobacteria

,

sloth fur is a small ecosystem of its own, hosting many species of

non- parasitic insects. Sloths have short, flat heads; big eyes; a short

snout; long legs; and tiny ears. They also have stubby tails, usually

6

–

7 cm

long.

Altogether,

sloths'

bodies

usually

are

anywhere

between

50

and 60 cm long.

Sloths' claws serve as their only natural defense. A cornered sloth may

swipe at its attackers in an effort to scare them away or wound them.

Despite sloths' apparent defenselessness, predators do not pose special

problems: sloths

blend in

with

the trees and, moving

only slowly, do

not

attract attention. Only during their infrequent visits to ground level

do they become vulnerable. The main predators of sloths are the

jaguar

,

the

harpy eagle

, and humans. The majority of sloth deaths in Costa Rica

are due to contact with

electrical lines

and

poachers

. Despite their

adaptation

to

living

in

trees,

sloths

make

competent

swimmers.

Their

claws

also

provide

a

further

unexpected

deterrent

to

human

hunters:

when

hanging

upside-down in a tree they are held in place by the claws themselves and

often do not fall down even if shot from below.

Pale-throated Three-toed Sloth

(

Bradypus tridactylus

) in a Costa Rican

rehabilitation center

Sloths

move

only

when

necessary

and

even

then

very

slowly:

they

have

about

a

quarter as much muscle

tissue as other

animals of

similar weight. They

can

move

at

a

marginally

higher

speed

if

they

are

in

immediate

danger

from

a

predator

(4 m

or

13

feet

per

minute

for

the

three- toed

sloth),

but

they

burn large amounts of energy doing so. Their specialized hands and feet

have long, curved claws to allow them to hang upside-down from branches

without

effort.

[5]

While

they

sometimes

sit

on

top

of

branches,

they

usually

eat,

sleep,

and

even

give

birth

hanging

from

limbs.

They

sometimes

remain

hanging

from

branches

after

death.

On

the

ground

the

maximum

speed

of

the

three-toed sloth is 2 m or 6.5 feet per minute.

[6]

Three-toed Sloth

in the Dallas World Aquarium

It had been thought that sloths were among the most

somnolent

animals,

sleeping from 15 to 18 hours each day. Recently, however, Dr. Neil

Rattenborg and his colleagues from the Max Planck Institute for

Ornithology in Starnberg, Germany, published a study testing sloth

sleep-patterns

in

the

wild;

this

is

the

first

study

of

its

kind.

The

study

indicated that sloths sleep just under 10 hours a day.

[7]