It's fall/early winter. The alphas are coming into the camps from their isolation to ready and willing omegas and betas. Beta males will also participate. Alpha and beta makes will do different martial competitions to gain the females favor.

(There's no really manogamous traits here. An alpha can mate with several omegas and vice versa. Though like other animals like elk the omega/beta females will choose one male who they deem the best for fathering children. And not all females get pregnant each year. Some may, some may not. They could get pregnant the next year. Or they could not if they got pregnant before)