A theoretical investigation into the direct and indirect effects of state on the risk of predation

Welton, NJ Houston, AI

Nj. Welton et Ai. Houston, A theoretical investigation into the direct and indirect effects of state on the risk of predation, J THEOR BIO, 213(2), 2001, pp. 275-297

54

INGLESE

Article

Multidisciplinary

JOURNAL OF THEORETICAL BIOLOGY

0022-5193 → ACNP

213

2

2001

275 - 297

ISI

0022-5193(20011121)213:2<275:ATIITD>2.0.ZU;2-#

As well as there being a direct physical effect of the state (for example f at reserves, or size) of an animal on the risk of being caught by a predato r, state also has an effect on predation risk indirectly through changes in behaviour. We present a mathematical model which looks at these two compon ents of the effect of state on predation risk. We focus on two different mo dels, (i) where the animal must achieve a fixed state and its fitness depen ds on the time at which this state is reached and (ii) where the animal mus t survive until a fixed time and its fitness depends on its final state. We investigate conditions under which the indirect effect of increased state is to increase or decrease predation risk, and give some numerical illustra tions. Under certain conditions in the fixed-state model, the indirect effe ct of state is to increase predation risk, whereas under certain conditions in the fixed-time model the indirect effect of state is to decrease predat ion risk. We discuss the implications of our results for empirical investig ations into the effect of state on predation risk. (C) 2001 Academic Press.