Mobile Ad-Hoc Network (MANET) is a self-configuring network in which mobile devices are connected by wireless links. MANETs face several challenges due to open network architecture, shared wireless medium, highly dynamic network topology and so on. Recently a new class of routing algorithms based on swarm intelligence has emerged for routing problems in MANET. These algorithms are inspired from nature's self-organizing systems such as ant colonies, bird flocks, honey bee, and fish schools. Nature is of course a great and immense source of inspiration for solving hard and complex problems in computer science since it exhibits extremely diverse, dynamic, robust, complex and fascinating phenomenon. It always finds the optimal solution to resolve its problem maintaining seamless balance among its components. This is the thrust behind bio inspired computing mechanisms. Nature inspired algorithms are meta-heuristics that mimics the nature for resolving optimization problems opening a new era in computation. The common features of these biological systems which include their ability of self-organization, robustness, adaptation, self-healing, and local decision making, make them an appropriate source of inspiration for routing in MANETs. For the past eras, numerous research efforts have been focused in this particular area. Still being young and the results being identical amazing, broadens the scope and feasibility of Bio Inspired Algorithms (BIAs) exploring new areas of application and more opportunities in computing. In this paper provide a complete summary of the nature inspired routing algorithms for Mobile Adhoc networks. Then, numerous existing research papers related to bio-inspired models are also discussed and investigated to find the research gaps.