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Mean (±s.d.) of (a) δ15N and (b) δ13C values (‰) for modern and historic YNP fauna. Mean differences in isotopic values between time periods (Δ) are included, and levels of significance are shown (*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001). On average, the estimated grazer (winter) population sizes on the northern range of YNP were greater than or equal to 10 times (bison) and greater than or equal to 2 times (elk) smaller during the historic versus modern time periods [3].
