Ad hoc networks are dynamic networks formed "on the fly" by a set of nodes. Achieving secure routing in such networks is a big challenge. Asymmetric signature schemes provide mechanisms for authentication, but may result in inefficient implementations, specially when a large number of nodes is expected. Some of these efficiency problems can be mitigated with the use of aggregate signatures, which reduce the space and computations required for managing many different signatures. In this work we formalize a new concept, aggregate designated verifier signature schemes, which is suitable for authentication of routes in reactive protocols. We propose a specific and efficient scheme with provable security in the random oracle model.