Orrorin tugenensis is the name given to a fossil hominin from 6 million years ago. the femur of this species has a long neck characteristic of bipedal species. if an intact skull of this species were located, you would expect to find

There are various morphological differences between bipeds and quadrupeds. There is one obvious difference that can be seen in the skull. The opening in the base of the skull to receive the spinal cord is called the foramen magnum. In quadrupeds, the foramen magnum is situated more towards the back of the skull, whereas in bipeds, the foramen magnum is more or less in the middle of the base of the skull, indicating a more upright position of the head on top of the body.

The rate that would change would be the  searching efficiency/attack rate. there are only two other rates in this model: the  growth rate of prey, and the  predator or consumer mortality rate.the  searching efficiency/attack rate is what indicates how effectively can a predator capture its prey whether in the searching process or actual capturing/attacking process.