raptor easily keeps pace with sprinting soldier

Something moved in the corner of his vision.
He kept running, picking up the pace but bringing up his rifle and snicking off the safety catch. In his head there ran childish prayers he hadn't uttered since school, when the Christian Brothers had beaten them into him.
On both his right and left, the shadows moved up. They were loping smoothly, keeping pace perhaps a hundred meters out on either side.
McCann began to spint. The breath tore in and out of his lungs. The bright gleam of the anomaly was above him now, at the top of the slope.
One of the things broke trail in front of him, tearing at incredible speed through the ferns, uttering a series of high-pitched squawks which sounded almost birdlike. He felt a rush of relief. They were small, these things, not more than five- or six-feet tall. It wasn't so bad after all. They weren't real dinosaurs.
Another streaked across his path, and there were more behind him. He could hear movement all about in the ferns; the starlit slope seemed to have come alive. He turned, still running, and fired a burst behind him at the shadows, the muzzle flash momentarily blinding him.

Chapter 19, Page 197-198