This study was carried out with five rubber clones planted in Côte d'Ivoire from the first tapping up to the 18th month of tree tapping (1 tapping / 4 days). Changes in the natural rubber native mesostructure (macromolecular structure, macrogel, and microgel) of films prepared from fresh field latex were monitored. At the same time, the evolution of the thermo-oxidation sensitivity of raw rubber samples [grade 10 technically specified rubber (TSR10)] was also monitored with the plasticity retention index (PRI). The substantial initial macrogel rate (70-86%, depending on the clone) fell during the first 18 months of tree tapping to reach a few percent. However, during the same period, the initially low microgel rate (5-15%) increased and then remain stabilized around 55% rubber. The macromolecular structure [weight-average molecular weight (Mw) and molar mass distribution (MMD)] also changed after tree opening. Mw increased and stabilized after 7.5 months of tapping. The bimodal MMD primarily involved short chains (molar mass < 400 kg/mol) at the opening of the trees. The TSR10 samples, prepared with latex from virgin trees, showed high PRIs and, therefore, low sensitivity to thermo-oxidation.