  Levy flights are known to be optimal search strategies in the particular case
of revisitable targets. In the relevant situation of non revisitable targets,
we propose an alternative model of bidimensional search processes, which
explicitly relies on the widely observed intermittent behavior of foraging
animals. We show analytically that intermittent strategies can minimize the
search time, and therefore do constitute real optimal strategies. We study two
representative modes of target detection, and determine which features of the
search time are robust and do not depend on the specific characteristics of
detection mechanisms. In particular, both modes lead to a global minimum of the
search time as a function of the typical times spent in each state, for the
same optimal duration of the ballistic phase. This last quantity could be a
universal feature of bidimensional intermittent search strategies.
