We've engineered them that way.
4 seconds sound clip from the Jurassic Park (1993) movie soundboard.
You can hear this line at 00:29:54 in the Blu-ray version of the movie.
Quote context
[...]
- Actually they can't breed in the wild.
- Population control is one of our security precautions.
- There's no unauthorized breeding in Jurassic Park.
- How do you know they can't breed?
- Because all the animals in Jurassic Park are female.
- We've engineered them that way.
- Blood temperature seems like about high 80s, maybe. Wu?
- Homoeothermic? It holds that temperature?
- Yes.
[...]