In this article, the single term Walsh series (STWS) method is presented to solve the system of nonlinear delay Volterra integro-differential equations, which arises in biology. The STWS method reduces the model problem into recursive system of nonlinear algebraic equations. The solutions of the algebraic equations lead to the solution of the problem. Illustrative examples related to the biological species living together are experimented with the STWS method. The numerical results are compared with an existing method. That shows the effectiveness and applicability of the method. The STWS method is working well for the modeled problem. It will give more accuracy when the choice of m increases.