LOS ANGELES (AP) — Shrek Forever After roared its way to the top of the box office, making $71.3 million in its opening weekend.

But the fourth film in the monster franchise from DreamWorks Animation had the weakest debut of all Shrek sequels, according to studio estimates Sunday. Shrek 2, from 2004, opened with $108 million. Shrek the Third, from 2007, made $121.6 million in its first weekend.

And the latest installment was available for the first time in 3-D and IMAX 3-D, where ticket prices are higher — up to $19 in Manhattan. Shrek made just under $5 million on IMAX screens, or seven per cent of the film’s weekend gross.

This time, Shrek — voiced as always by Mike Myers — is experiencing a mid-life crisis, so he makes a deal with Rumpelstiltskin to live as a fearsome ogre again for one day. Cameron Diaz, Eddie Murphy and Antonio Banderas return to the voice cast.

“We’re obviously happy to be the No 1 movie, which we anticipated,” said Anne Globe, head of worldwide marketing for DreamWorks Animation.

“It’s a little lower than we anticipated but it’s still No 4 among all animated openings of all time, behind the first two Shrek sequels and The Simpsons (Movie),” which opened with $74 million in 2007.

Paul Dergarabedian, box office analyst for Hollywood.com, said the cost of tickets may have been too high for some families.

“I think it’s a very pragmatic situation. Families want to see Shrek, it’s the summer, and right now for kids there’s not a whole lot out there so it’s kind of a no-brainer,” he said. “Then people look in their pocketbooks and go, ‘Whoa’.”

Having said that, Dergarabedian said he expects Shrek Forever After will have legs throughout the summer, similar to another recent 3-D movie from DreamWorks Animation, How to Train Your Dragon. It opened in March with $43.7 million and has gone on to make nearly $211 million.

Last week’s No 1 movie, Iron Man 2, dropped to second place with $26.6 million. The superhero sequel from Paramount Pictures has now made over $251 million in three weeks.

The other new wide release, MacGruber, opened in sixth place with a disappointing $4.1 million. Based on the Saturday Night Live television sketch, the Universal Pictures comedy stars Will Forte as a bumbling version of the mulleted ’80s television character MacGyver, who was famous for his makeshift method of defusing threats.

But MacGruber was a relatively low-risk production because it cost under $10 million to make, which was offset by tax credits and foreign sales, said Geoffrey Ammer, head of worldwide marketing for Relativity Media, which produced the film.

Estimated ticket sales for Friday through Sunday at US and Canadian theaters, according to Hollywood.com; final figures will be released Monday:

1. Shrek Forever After, $71.3 million.

2. Iron Man 2, $26.6 million.

3. Robin Hood, $18.7 million.

4. Letters to Juliet, $9.1 million.

5. Just Wright, $4.2 million.

6. MacGruber, $4.1 million.

7. Date Night, $2.8 million.

8. A Nightmare on Elm Street, $2.3 million.

9. How to Train Your Dragon, $1.9 million.

10. Kites, $1 million.