untitled

The searching efficiency or attack rate of the predator, a, depends on the area searched

per unit time, a′, and the probability of successful attack, pc, so that:

a =a′pc (10.3)

The number of prey eaten per predator per unit time (Na) increases with search time,

search efficiency, and prey density, so that:

166 Chapter 10

Prey density

(b)

% of prey population eaten

Number of prey eaten per predator

(a)

Type I

Type II

Type III

Type I

Type II

Type III

Fig. 10.2(a) Types of
functional response
shown as the number of
prey eaten per predator
per unit time relative to
prey density. (b) As for
(a) but plotted as the
percentage of the prey
population eaten.

20

15

10

5

(^00100200300400)
Lichen biomass (g / m^2 )
Food intake (g dry matter / min)
Fig. 10.3The linear
(Type I) functional
response of reindeer
feeding (dry matter
intake) on lichen. (After
White et al. 1981.)