Do all mammals have hair?

Question

So I'm sitting in my English class right now and there's been a claim made that all mammals have hair. I argued against this. All mammals breastfeed their babies, that's the criterion. Am I right about the hair - not all of them have it, right? Dolphins and whales are mammals, and I do not think they have hair (well, maybe nose hair).

Answer 1

All extant mammals have hair, at least at some time of their lives. Indeed, hair is one of the synapomorphies (shared derived characters) that define mammals.

These hairs may occur only during early life (in embryos, newborns or juveniles), and then disappear, or be maintained throughout life and present many different types (including the guard hairs, wool, underfur, etc that we know well).
In fact, mammal embryos are often covered with special hair called lanugo that is lost before birth.

Whales do have hair: at least the young of some species have some vibrissae-like hairs on their snout (and even when these hairs are lost, the sensory terminals associated with them remain).
http://animaldiversity.ummz.umich.edu/site/accounts/information/Cetacea.html

And naked mole rats have tactile vibrissae too :-)

So at least sensory hairs are present in all mammals, associated with sensory nerve cells and those little muscles, the arrector pili, responsible for hair erection and our goosebumps.

More about mammalian hair:
http://animaldiversity.ummz.umich.edu/site/topics/mammal_anatomy/hair.html

BTW you're right about the breastfeeding part: the presence of mammary glands that produce milk for the young is another of the synapomorphies of mammals. However, only marsupials and placental mammals have nipples (monotremes don't).

More about the definition of mammals:
http://answers.yahoo.com/question/index;_ylt=AtCVw_TRjltISPXKUQvh8ojsy6IX?qid=20060908193154AAbbjml

Answer 2

Do All Mammals Have Hair

Answer 3

This Site Might Help You.

RE:
Do all mammals have hair?
So I'm sitting in my English class right now and there's been a claim made that all mammals have hair. I argued against this. All mammals breastfeed their babies, that's the criterion. Am I right about the hair - not all of them have it, right? Dolphins and whales are mammals, and I do...

Answer 4

Does A Dolphin Have Hair

Answer 5

There are people with alopecia areata and they don't have any hair. I think the dolphins have hairy skin near their blow hole and whales have some hair on their chins or noses and some on their backs. Whales have more hair when they are little.

So, I guess all mammals have hair and even if they have 1 hair on their chinny chin chinny there! They have a label - Mammal!

Answer 6

YES as far as I know all mammals have hair, though some only have it in early life stages (I think that some only have hair as a fetus... not sure though). Even dolphins have small amounts of hair when babies, but lose it in adulthood, though they still retain the hair follicles.

Answer 7

Technically mammals are the only animals with keratinous fibers that make up hair, hooves, horns, nails, and claws. Naked mole rats have whiskers that are made out of the same thing that hair is made of. Whales are the exception, in place of the hair to help maintain there body temperature, like most mammals, they have really thick blubber. Mammals all also have: three inner ear bones, mammary glands and a diaphragm.

Answer 8

Yes even whales have hair, I've seen it on whales, and have to take it on credit that dolphins do to.

Answer 9

Nop. Acuatic mammals don't have hair (like dolphins or whales)

Answer 10

yes there are some species that don't have hair