Lycanthropes are humans with the ability to assume animal form.
During the hours of darkness, they most commonly shape change to their animal form.
In periods of a full moon lycanthropes are 90% likely to be compelled to assume their alter-shape.
They usually move about as humans for whatever purposes they may have.
Each type has its own language which is spoken in addition to common.

<LYCANTHROPY (Overview)>
Any humanoid creature bitten by a lycanthrope for damage equal to or
greater than 50% of its total potential, but not actually killed (and eaten),
is infected by the disease of lycanthropy.

If the person is carrying
belladonna there is a 25% chance that this will cure the affliction if eaten
within one hour. Note that this infusion will incapacitate the person for 1-4
days and there is a 1% chance of the poison in it killing the creature.

Otherwise, a cure disease spell from a 12th or higher level patriarch must
be placed upon the creature within 3 days or it will become a lycanthrope
in 7-14 days. There are some other forms of lycanthropes, but these are
very rare in the extreme.

<
(Lycanthropy, In Detail)

SPECIAL DEFENSES: All are hit only by silver or +1 or better magic weapons
MAGIC RESISTANCE: All lycanthropes have standard resistance
PSIONIC ABILITY: No lycanthrope possesss psionic abilities
>

Q. Should a player be told that his
character is fighting a skinwalker?
For example, are the adventurers told
that they have met a werewolf |or| just
a wolf.
A. Unless the characters see a lycanthrope
changing form, how will they
know that they are fighting such a
beast? The DM may choose to drop
hints that they have met with a wolf,
or whatever, that seems more intelligent
than normal, but that is all. It is
up to the characters to discover
exactly what they have encountered. <Animal Lore & Druids: both should be able to recognize that the animal is not what it seems to be>
    The 1st knowledge that the characters
may have that they fought a
lycanthrope is when one (or more) of
their number has restless nights
during the period of the full moon
-- and the local villagers start looking
for the were-creature.  Assuming
that none of the characters connect
the 2 pieces of information, an
imaginative DM could even have the
infected PC(s) join in
the hunt for the creature, without
ever knowing that the thing they are
hunting is closer than they imagine!
(Imagine #23)

Q: Can a character get lycanthropy
from a lycanthrope's claws?
A: No, only from the bite. When characters
fight lycanthropes, it's best to keep separate
track of the claw and bite damage
each character suffers.
(138.13)
 

ADQ: Do lycanthropes have the same HP
in human form as in animal form,
regardless of whether they were 0-level
humans or character types before contracting
lycanthropy?  If so, will the creature's
HP be the same as it had as a
human, or do you roll new HP
according to the HD given in the
MM for the particular weretype?
What about other shapechangers,
such as bronze dragons?
ADA: Any creature, regardless of shape-changing
or polymorphing abilities, retains
the same HP and saves in all
forms. The stats given in the Monster
Manuals are nice and convenient, but are
not binding; nearly anything can be found
in a form larger, smaller, dumber, smarter,
(et al.) than those described.
(Polyhedron #22)

<>
1. The DMG notes "humans are the only beings able to contract lycanthropy".
2. The MM notes "any humanoid creature".
3. To keep it simple, I recommend "humans only" : this is backed up by the MM & MM2 definition of lycanthropes as "humans with the ability to assume animal form". (italics added)