We generally think of gestation as the length of time needed for an embryo to grow from a fertilized egg to the stage where it's ready for birth. Usually, this is true, but for many kinds of mammals, gestation includes a long period of time in which virtually nothing happens.
In the form known as delayed implantation, the embryo begins
development but then quickly ceases to grow and merely floats around in the uterus (the
womb) for some period of time before resuming activity. One of the common animals of
the Chihuahuan Desert, the Western Spotted Skunk, illustrates this process. Mating
takes place in September or October, but after a brief period of development, the
embryo merely lazes around, floating in the uterus, for about 6 1/2 months. Finally
becoming implanted into the mother's womb, it starts growing again and is born
about a month later, between April and June. Of the total gestation period of between
210 and 260 days, perhaps only a little over 30 days actually are devoted to becoming
an adorable, baby spotted skunk.
Contributor: Arthur H. Harris, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. 1999. Mammalogy. McGraw Hill, Boston. 563 pp.
Delayed Implantation—Semi-technical