MAMMALS

Characteristics of mammals:

• they have mammary gland that produce milk
• a body covered by hair
• they are warm blooded (Endothermic)
• external ear structure
• 3 bone structures in the inner ear (ossicles)
• 4 chambered heart

Mammals are divided into 3 groups depending of the way that they reproduce:

1. Montremes
2. Marsupials
3. Placentals

MONOTREMES

(Order Monotremata)

• eggs laying (oviparous)
• most primitive mammals
• no gestation
• rear their youngs on milk
• eggs carried in a pouch on the abdomen or kept warm in a nest
• no Monotremes found in South Africa but in Australia (Duck-billed platypus; Spiny anteater)

MARSUPIALS

(Order Marsupialia)

• pouched mammal with a prolonged lactation period
• abdominal pouch: marsupium in which they rear their young
• primitive placenta: yolk-sac placenta
• short gestation
• no Marsupials in South Africa but in Australia and New Zealand

Lactation: period during which milk is produced by the mammary glands.

Embryo: animal or human before it is born, when it is beginning to develop and grow.

PLACENTALS

• viviparous mammals with a prolonged gestation period
• have developped and advanced placenta
• Impalas, Leopards, Elephants...

Eutherian: mammal whose young develops within a womb that is surrounded by a placenta.

Viviparous: animal that bear live young and does not carry or lay eggs.

Placenta: vascular organ that develops inside the uterus of most pregnant mammals to supply food and oxygen to the foetus through the umbilical cord. It is expelled after birth.

The mammal FOOT STRUCTURE:

• Plantigrade
• Digitigrade
• Unguligrade

PLANTIGRADES

- standing or/and walking on the whole lenght of the foot

- Man, Apes, Monkeys, Bears, Insectivores

DIGITIGRADES

- heel and instep are raised in order that only the digits touch the ground

- predatory animals (Dogs, Cats) enabling to move silently

UNGULIGRADES

- adaptation to running

- allow to stand right on the tips of their toes that have enlarged nails or hooves

Number of DIGITS:

Plantigrade and Digitigrade mammals have 4 or 5 digits.

A pentadactyl has 5 digits on each foot (Elephant)

2 groups of Ungulates: 

1. ODD-TOED
2. EVEN-TOED

A ungulate is an animal that has hooves.

TRUE UNGULATES

- hoofed mammals that walk on tiptoe:

• odd-toed ungulates
• even-toed ungulates
• near ungulates

ODD-TOED HOOFED UNGULATES (order Perissodactyla)

- 1 single toe (zebra)

- or 3 toes together with a large middle toe (rhino)

EVEN-TOED HOOFED UNGULATES

- 2 or 4 toes on each foot

Order Ruminantia

- 2 toes on each foot

- antelope, buffalo, giraffe

Order Surriformes

- 2 toes on each foot

- warthogs, bushpigs

Order Whippomorpha

- 4 toes on each foot

- Hippo

NEAR UNGULATES

- toenails rather than proper hooves

- Elephant, Dassie

- walk on whole foot (plantigrade)

- teats between forelegs

- same type of placenta and womb

- upper incisors reduced in number and modified as tusks

- molar have transverse ridges

The mammal DIGESTIVE SYSTEM

The Ungulates and Near-Ungulates can be classified according to their digestive systems.

Most ungulates eat large amounts of indeigestible cellulose. The cellulose can be digested through a process of bacterial fermentation.

Herbivores have developped 2 different digestive systems:

1. Hindgout fermentation
2. Rumination

Cellulose: substance that forms the outer layer of plant cells and plant fibers.

Fermentation: breakdown of carbohydrates by microorganisms.

Rumination: to regurgitate partiaally digested food and chew it again.

HINDGUT FERMENTERS

Vegetable matter is completely digested in the stomach from where it moves to the large intestine and cecum where microorganisms ferment the cellulose.

RUMINANTS

Animals that ruminate pass the vegetable matter directly to the 1st chamber (Rumen) where fermentation takes place and is then later regurgatited to be chewed and mixed with saliva. The cud ball then passes back to the 2nd stomach chamber (Reticulum) bypassing the rumen. The digestive process then continues in the 3rd chamber (Omassum) and is completed in the 4th chamber (Abomassum).

example of a cow

DIET

• Ruminants: animals with 4 chambered stomach to extract the maximum of nutrients from vegetation (selective grazers or mixed feeders).
• Hindgut fermenters: animals that can cope with eating larger quantities of less nutrious vegetation (bulk grazers).

• Bulk grazers: animals that are not selective about which grass to eat.
• Selective grazers: animals that only eat specific kind of grass or vegetation.
• Mixed feeders: Animals that may graze or browse or eat fruit, bulbs, forbs,...

• Bowsers: animals that eat mostly leaves.
• Fructivores: eat fruits.
• Omnivores: eat a mixed diet.
• Piscivores: eat fish.
• Carnivores: eat meat.