| MadSci Network: Zoology |
Hi Michael - Squirrels are eutherian mammals, meaning they bear live young which are nourished in utero through a placenta.
The umbilical cord transports the fetal blood to the placenta, where it is nourished with oxygen and nutrients from the mother's circulation. After birth, the remnant of the umbilical cord connection is the belly button, or umbilicus. Squirrels thus have a belly button.
Mammals also nurse their young through mammary glands which produce the milk. The milk in eutherian mammals is exuded through the nipples. Squirrels, being eutherian mammals, thus have nipples.
Try the links in the MadSci Library for more information on Zoology.