Female Red Kangaroos generally reach sexual maturity between fifteen and twenty months of age. Sexual maturity can be delayed to as much as five years of age if environmental conditions are unfavorable for reproduction. Kangaroos are polyestrous and will be fertile approximately every thirty five days, year round, unless nursing.(Dewey, n.d.; Michaels, 2007; “The Red Kangaroo”, 2007) Once sexual maturity has been reached, the female can give birth, breed again within a few days, become impregnated and have a second fertilized egg in the womb while the first joey is still developing in the pouch. The second egg will develop only to the blastocyte stage and then remain in stasis until the first embryo has reached a point that it is no longer nursing constantly, usually around two hundred and four days. (Dewey, n.d.; Snelling, 1988; “The Red Kangaroo”, 2007) Nursing causes the mother to cease cycling, however pregnancy does not interrupt the fertility cycle. (Dewey, n.d.; Snelling, 2007; “The Red Kangaroo”, 2007) These fertility mechanisms allow the female kangaroo to have three joeys in different developmental stages at once, a blastocyte in stasis, a joey in the pouch and a joey at foot that is still nursing from outside the pouch. (Snelling, 1988)
The gestational period of the kangaroo is approximately thirty three days from conception to parturition however the joey is unviable at this stage. The newborn joey, measuring around 2.5cm and weighing only 0.75grams, has well developed claws, forelimbs and nares but its eyes are not open and its hind limbs are little more than buds at this point. (Dewey, n.d.; Snelling, 1988) It must find its way to the pouch shortly after parturition or it will die; luckily, they seem to b...
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...on growth, the females will resume estrous. (“The Red Kangaroo”, 2007)
Works Cited
Dewey, T. (n.d.). Macropus rufus. In Animal Diversity. Retrieved March 25, 2011, from http://animaldiversity.ummz.umich.edu/site/accounts/information/Macropus_rufus.html#32e0a4ba49bbfb857910bace6b5a179 Dewey, n.d.
Michaels, K. (2007, April 26). Red Kangaroo. Retrieved March 25, 2011, from http://bioweb.uwlax.edu/bio203/s2007/michaels_kell/index.htm Michaels, 2007
Snelling, A. A. (1988, September). Australia’s amazing kangaroos and the birth of their young. In answersingenesis.org. Retrieved March 25, 2011, from http://www.answersingenesis.org/creation/v10/i4/kangaroos.asp Snelling, 1988
The Red Kangaroo. (2007, December 5). In Australian Stamp & Coin . Retrieved March 25, 2011, from http://www.australianstamp.com/Coin-web/feature/nature/redkang.htm “The Red Kangaroo”, 2007