We used analyses of the strontium isotope (Sr-87/Sr-86) ratios of tooth enamel to reconstruct the migration patterns of fossil mammals collected along the Aucilla River in northern Florida. Specimens date to the late-glacial period and before the last glacial maximum (pre-LGM). Deer and tapir displayed low Sr-87/Sr-86 ratios that were similar to the ratios of Florida environments, which suggest that these taxa did not migrate long distance outside of the Florida region. Mastodons, mammoths, and equids all displayed a wide range of Sr-87/Sr-86 ratios. Some individuals in each taxon displayed low Sr-87/Sr-86 ratios that suggest they ranged locally, while other animals had high Sr-87/Sr-86 ratios that suggest they migrated long distances (> 150 km) outside of the Florida region. Mastodons were the only taxa from this region that provided enough well-dated specimens to compare changes in migration patterns over time. Pre-LGM mastodons displayed significantly lower Sr-87/Sr-86 ratios than late-glacial mastodons, which suggests that late-glacial mastodons from Florida migrated longer distances than their earlier counterparts. This change in movement patterns reflects temporal changes in regional vegetation patterns. (c) 2007 University of Washington. All rights reserved.