This paper considers the problem of dynamic task allocation, where tasks are unknowingly distributed over an environment. We aim to address the multi-robot exploration aspect of the problem while solving the task-allocation aspect. To that end, we first propose a novel nature-inspired approach called "hunter and gatherer". We consider each task comprised of two sequential subtasks: detection and completion, where each subtask can only be carried out by a certain type of agent. Thus, this approach employs two complementary teams of agents: one agile in detecting (hunters) and another dexterous in completing (gatherers) the tasks. Then, we propose a multi-robot exploration algorithm for hunters and a multi-robot task allocation algorithm for gatherers, both in a distributed manner and based on innovative notions of "certainty and uncertainty profit margins". Statistical analysis of simulation results confirms the efficacy of the proposed algorithms. Besides, it is statistically proven that the proposed solutions function fairly, i.e. for each type of agent, the overall workload is distributed equally.