Tracing Deuterium through the food web and into Birds and Mammals along an elevational gradient in the Southern Rocky Mountains

Animals incorporate local δ 2 H values from available water and dietary sources during tissue synthesis, which can provide evidence of elevational movements if multiple tissues with different turnover times are examined. Here we test the applicability of using δ 2 H as an indicator of altitudinal movements by examining multiple tissues (δ 2 Hbw (body water), δ 2 Hfeather, δ 2 Hfur, and δ 2 Hclaw) in birds and mammals in the Sangre de Cristo Mountains. Additionally, we measured δ 2 Hsw (stem water) and insect δ 2 Hbw and δ 2 Hwb (whole body) values to assess changes with elevation. We sampled 15 species of birds and two small mammal species along with potential food sources (three plant families and four insect groups) over an ~1200 m elevational gradient. δ 2 Hsw and δ 2 Hbw of plants, birds, and mammals decreased with increasing elevation. δ 2 Hfur, δ 2 Hfeather, δ 2 Hclaw, and δ 2 Hbw of insects did not show any discernable pattern with increasing elevation. Only one animal species, the least chipmunk (Tamias minimus), showed significant decreases in δ 2 H values with increasing elevation. Additionally, δ 2 H feather differed based on foraging guild. Other contributing factors such as diet, physiology, ecology, and within site variation may all contribute wide variation in values observed at a specific elevation. Given the amount of variability in each tissue type sampled in this study, we conclude that the use