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Protein supplements are a common approach to address nutrient deficiencies in rangeland cattle. On-animal sensors have emerged as an alternative for measuring individual cattle behaviour, including supplement intake, in near real-time without human intervention. This study aimed to study the combination of on-animal sensors to monitor behavioural changes in response to varying levels of individual supplement consumption. Fourteen Droughtmaster heifers were fitted with a wireless ear tag (WelfareTag „¢ HerdDogg), GPS collar (i-gotU GT-600), and rumen bolus (SmaXtec® Classic Bolus). They co-grazed a 10-ha paddock from 20/9/22 to 13/12/22. In two consecutive periods, they were offered different supplementary high-protein diets, expected to vary in palatability. During period one (days 1-42), heifers received 300 g/d of a low-intake supplement (26% CP, 5% Urea), and during period two (days 43-85), they received 1000 g/d of a high-intake supplement (30% CP, 4% Urea). Data were analysed using R (version 4.3.1) and RStudio with a linear mixed-effects model ('lmer'), each parameter was considered individually. During period 2, heifers spent 1.7 times more time at the feed trough than in period 1 (p<0.001), suggesting increased supplement consumption. Grazing activity was not significantly higher in period 1 than in period 2 (p<0.1). Resting time in period 1 decreased (p<0.1) but travelling times increased (p<0.01). Rumen temperature and rumination index were lower in period 1 (p<0.05, p>0.1), while oestrus index was higher in period 1 compared to period 2 (p<0.001). Counts of water-drinking events were higher in period 2 (p<0.001). In conclusion, behavioural differences were detected by on-animal sensors associated with greater supplement intake. The adoption of sensors for continuous monitoring enhances nutritional, grazing, and reproductive management in extensive rangelands, supporting better decision-making about target supplement intake and improving grazing behaviour and pasture utilisation.