Ecology


Site Navigation
Home Page
Origin
Morphology
Australian Marsupials
American Marsupials
Ecology
References and
Acknowledgments

Sexual Reproduction and Development

Introduction.

Male Reproductive System.

Female Reproductive System.

Seasonal Breeding.

Pregnancy, Birth and Diapause.

Lactation

Milk production is one of the defining characteristics of mammals, and is seen in all 3 clades.
Almost all of a females investment of energy into her young comes during this stage of development, and gives the young support and a greater chance of survival by not needing to be able to handle an adult diet, whether herbivorous, omnivorous or carnivorous, at birth.

Most juvenile development occurs during the process of lactation, so it is very important and can last up to 18 months in some groups (such as the macropodids).

There are 3 phases of lactation from gestation until complete weaning of the young.

Phase 1 - occurs during gestation, the mammary glands fully differentiate and develop the ability to secrete milk.
Phase 2 - begins at birth, when the young climbs to the teat and attaches itself to suckle. This phase ends with the beginning of weaning. There are 3 types of milk produced by the mammary glands over this phase. Type 1 starts during late gestation and is a clear fluid rich in proteins including antibodies. Type 2 is secreted soon after the onset of suckling, and is a white colour containing a greater percentage of solids, mostly lipids and proteins, and the type of carbohydrates secreted also changes. Type 3 is secreted near full development, and shows little change from type 2 milk, except for a further increase in lipids.

lactation (4K)
Bush-tailed Marsupial Mouse with many young lactating on teats.
Notice that this species does not have a pouch for its many offspring.


Phase 3 - begins when a juvenile first starts ingesting solid foods similar to the adult diet, and ends when it is fully weaned and does not consume any milk from its' mother.

Due to the process of diapause, it is possible for some marsupials to have two suckling young at different stages of development, and still be able to produce the right milk type for each of their stages simultaneously.