“Why did you risk your life for me?” Diego the Saber-Toothed Tiger (voice of Denis Leary) asks Manfred the Mammoth (voice of Ray Romano) as the two Ice Age adventurers lay exhausted from escaping certain death in the sea of boiling lava below. “That’s what you do in a herd,” Manfred says matter of factly, shrugging his huge woolly shoulders. Such noble sentiment, when combined with the stunning computer-generated animation (from Oscar-winner Chris Wedge, in his full-length feature debut), puts Ice Age squarely at the top of the family-entertainment pack (with a beastly wallop). The story is comfortably predictable: Three unlikely Ice Age mammals become the Odd Trio as they conquer glaciers, volcanoes, enemy beasts and themselves in their attempt to return a human infant to its tribe. It’s embarrassing to let a cartoon melt your heart, but when the gooey little baby is carried to his father’s arms on the end of the mammoth proboscis — and David Newman’s lush music is going full blast through the stereo speakers — you can’t help let loose with a crocodile drop or two. Don’t worry, though, hilarity is Ice Age’s main trajectory’ the kids will laugh themselves silly through the entire film. Scratch is an acorn-obsessed saber-toothed squirrel who triggers an avalanche that snowballs into the grandest animated disaster in film history. It’s a riotous introduction to the vast frozen tundra of 20,000 years ago. Everybody’s heading south in search of warmer weather — all except the moody mammoth Manfred, that is, who’s going off alone in the opposite direction. Goofy Sid the Sloth, who has been left behind by his family, desperately attaches himself to Manfred. Meanwhile, the humans have overhunted the saber-toothed tigers and the tigers hatch a devious revenge plot to capture and kill the tribe’s littlest member. (The tigers are pretty scary, thus the movie’s PG rating for “mild peril.”) The baby’s mother flees the attacking tigers and just before she dies, she manages to place him on the bank of the river-right in front of the tusks of the astonished mammoth. Soon Uncle Manfred and Uncle Sid are joined by Diego, the Saber-Toothed Tiger who has been sent by the head tiger to lead the baby-carrying mammoth into an ambush. Along the journey — despite their innate animosity — the three animals engage in interspecies communication, and like a regular bunch of guys from dozens of other buddy movies, they create a new herd among themselves. As they learn together how to change a baby’s diaper (seemingly the most hilarious sequence for the under-5 crowd), they form a heroic one-for-all/all-for-one Musketeer stand against all obstacles. I hope it’s obvious by now that Ice Age is about guys. In fact, it’s such a guy movie, that even little kids can easily figure out why all those animals became extinct: There are no girls! The only memorable female presence in the whole movie (I’m not counting the too-silly Do-Do birds) is the mother of the baby, who doesn’t even talk. Concerned parents can address the gender-invisibility issue with their kids and let them enjoy Ice Age for its technical wizardry. For older kids, check out the movie’s excellent Web site, iceagemovie.com, for fascinating behind the scenes looks at the complicated steps of computerized animation.