What is a werewolf cub?

Question

In Harry Potter, werewolves are people that turn into wolves at full moon, and go around biting people, turning them into werewolves. Examples include Remus Lupin and Fenrir Greyback, both of which are humans until the moon changes.

Tom Riddle claims that Hagrid kept werewolf cubs under his bed:

big, blundering Hagrid, in trouble every other week, trying to raise werewolf cubs under his bed, sneaking off to the Forbidden Forest to wrestle trolls...

_{Chamber of Secrets, Chapter 16}

Surely a werewolf cub is a baby that turns into a werewolf cub at full moon.

Am I correct in this? Are werewolf cubs actually human infants with a weird reaction to full moons, or something else? Or is Tom Riddle simply trying to frame another 'bad' thing on him? (which seems unlikely, why would he continue the lie to Harry, when it means nothing?) If they are human, how did he get away with it, and what was the motivation? (knowing his affiliation with more exotic beasts)

Answer 1

First, according to J.K. Rowling in a Barnes and Noble chat, Riddle was lying:

blaise_42 asks: In Chamber of Secrets, Hagrid is supposed to have raised werewolf cubs under his bed. Are these the same kind of werewolves as Professor Lupin?

jkrowling_bn: no... Riddle was telling lies about Hagrid, just slandering him

So, initially, one may consider her answer as either saying that there is no such thing as werewolf cubs or that werewolf cubs simply aren't the same type of werewolf as Lupin.

But, the Pottermore article on Werewolves (written by J.K.) has this to say about werewolf cubs:

One curious feature of the condition is that if two werewolves meet and mate at the full moon (a highly unlikely contingency which is known to have occurred only twice) the result of the mating will be wolf cubs which resemble true wolves in everything except their abnormally high intelligence.

So, in light of all that, werewolf cubs are a thing and Hagrid didn't try to hide any under his bed.

Answer 2

In the 2001 version of Fantastic Beasts and Where to Find Them (currently not officially available), the entry for "Werewolf" reads:

The werewolf is found worldwide, though it is believed to have originated in northern Europe. Humans turn into werewolves only when bitten. There is no known cure, though recent developments in potion-making have to a great extent alleviated the worst symptoms. Once a month, at the full moon, the otherwise sane and normal wizard or Muggle afflicted transforms into a murderous beast. Almost uniquely among fantastic creatures, the werewolf actively seeks humans in preference to any other kind of prey.

(Emphasis added)

Since werewolf cubs don't appear to be a thing, Riddle was likely slandering Hagrid with some misinformation.