Muffalos are called "muffalo calf" when babies and juveniles, but they are not renamed "muffalo" when they grow adults.
dogs, on the other end, are called "puppy" when young and are renamed "labrador" when grown up.
(http://i66.tinypic.com/qspqnb.png)
Thank your for the bug report. This a known issue that has been around a while (since animals were introduced most likely). I will close this thread though as it is a duplicate of the following thread.
https://ludeon.com/forums/index.php?topic=25810.0
If anyone finds, or knows of, more naming bugs of this kind then can you please post them in the above linked thread Thank you.