Stable Isotopes Reveal The Northern Tropical Highlands as Refugia for Extinct South American Megafauna

South America experienced an extinction event in the late Pleistocene that coincided with environmental and climatic changes as well as anthropogenic influences, resulting in the defaunation of equid and gomphothere megafauna across the continent. This study provides insights into the palaeoecology of these megafauna in the Northern Tropical Andes using stable carbon (δ13C) and oxygen (δ18O) isotope data from the Tibitó (13,805–13,342 cal BP) locality. Reconstruction of the dietary behaviours of Equus (Amerihippus) neogeus and Notiomastodon platenisis, reveal evidence for niche partitioning and seasonal variation in the high-altitude páramo ecotone. Bayesian modelling indicates interregional differences between the Northern Tropical Andean, Pampas, Brazilian Intertropical and Southern Andean regions. Isotopic overlap among equids is largely confined to the northern portion of the Andes across the terminal Pleistocene, supporting the idea of selective habitat use and the Northern Tropical Andes as refugia for relict populations. Isotopic variability amongst gomphothere taxa suggests higher mobility and a proposed ‘corridor’ effect’, whereby high-altitude Andean environments possibly helped buffer megafaunal populations from environmental and anthropogenic effects. Our findings contribute to terminal Pleistocene and Holocene megafauna paleoecology and emphasises the Northern Tropical Andes as a critical local for megafauna extinction dynamics in South America.