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din fe S ienc phenomena. One hypothesis states that they are secondary destruction [7,8], has been recently discussed in a broader Opinionoutcomes of resource exploitation by the parasite and have no adaptive value for the parasite or the host. A second hypothesis states that they could be host adaptations that aim to reduce or compensate for the detrimental fitness consequences of infection. Finally, the ‘manipulation hy-pothesis ’ states that host behavioural changes that follow infection constitute parasitic adaptations that facilitate transmission. The evolutionary capacity of parasites is often greater than that of the host. For this reason, natural selection often favours parasite transmission traits. There are many examples of host behavioural changes that indeed increase the chances of infective stages reaching their next host or being released in a suitable habitat. With few exceptions, parasitic manipulation dramatic-ally reduces host fitness. Therefore, the ‘manipulation hypothesis ’ sensu stricto is commonly seen as a ‘zero-sum game ’ (i.e. the gain or loss of one antagonist is exactly parasitological context [9]. Although conceptually appeal-ing, the ‘mafia-like ’ hypothesis faces criticism regarding how the strategy originates and is maintained in natural populations [9]. Apart from two studies on avian brood parasites [7,8], no experimental evidence currently sup-ports this hypothesis, even after specific tests in other systems [10]. Here, a novel scenario of interactive manip-ulation, which has the potential to resolve issues that are specific to the evolution of behavioural alterations induced by parasites, is presented. Compensatory responses in the living world The genotype of an individual determines its developmen-tal limits, but the resulting phenotype is also shaped by numerous environmental influences [11]. In response to adverse environmental conditions, many species have evolved phenotypically plastic life-history traits that are altered in a state-dependent manner to alleviate fitnes