Table 1 Model parameters, their definitions, range of values employed, and notes on their use.

Host

d

Defense level of defended hosts

Held at 1

f

Frequency of defended hosts in the environment

0–1

a

Spatial aggregation level of defended hosts

0–1

a = 0 when defended and undefended hosts are randomly distributed and a→1 when defended and undefended hosts form two distinct patches.

Enemy

P

Probability of encountering a defended host during a random move in the foraging area

0–1

Increases with the frequency f of defended hosts and decreases with their aggregation level a P = f(1-a)

W₀

Maximal potential fitness gain when attacking an host

Held at 1

Corresponds to the fitness gain when attacking a randomly encountered undefended host

H

Fitness loss due to host defense

0–1

Decreases with the level of physiological resistance R of the enemy and increases with the level of defense d of the host H = d(1-R)

S

Fitness loss due to active searching of undefended hosts

0–1

Increases with the difficulty in finding undefended hosts, i.e., with the probability P of encountering a defended host during a random move S = eP

e

Search cost coefficient

0–1

R

Physiological adaptation level

0–1

Physiological adaptation reduces the fitness loss H when attacking a defended victim.

C_R

Physiological adaptation maintenance cost

0–1

Increases with the level of physiological adaptation R C_R = kR^x

B

Behavioral adaptation level

0–1

Behavioral adaptation corresponds to the probability of engaging in the active search of undefended hosts.

C_B

Behavioral adaptation maintenance cost

0–1

Increases with the level of behavioral adaptation B C_B = kB^x

k

Maintenance cost coefficient

0–1

x

Shape coefficient of the maintenance cost functions

Held to 1/2, 1 or 2

Maintenance costs increase with the level of adaptation in an accelerating (x = 2), linear (x = 1) or decelerating (x = 1/2) way