Coyotes Reveal Baseline Nitrogen Decline Across End-Pleistocene Ecosystem Collapse

Abstract

The end Pleistocene was a time of ecological turmoil, coincident with environmental change, extinctions, and anthropogenic impacts on the landscape. As one of the few persisting predators from the Pleistocene, La Brea’s exceptional record of coyotes (Canis latrans) provides a unique opportunity to clarify how a recently documented ecosystem state-shift impacted survivors. Through a multiproxy analysis of Rancho La Brea coyotes from the past 50,000 years to present, we analyzed over 100 individuals for radiocarbon chronologies, stable isotopes, dental microwear, and morphology to assess the consequences of megafaunal extirpation on these predators. Most notably, coyotes demonstrate a significant decline in δ15Nbone collagen values immediately after the extirpation of megafauna. While this decline is suggestive of a change in diet from more to less meat, stable isotopes of amino acids from a subset of samples instead provide evidence of a baseline shift in nitrogen—indicating large scale changes in the availability of nutritional resources. While coyotes do not demonstrate notable changes in diet across the extirpation boundary, as inferred from stable carbon isotopes in tooth enamel and dental microwear texture analysis, significant shifts in stable oxygen isotopes in δ18Oenamel and δ13Cbone collagen indicate more nuanced changes in potential prey-resources. Coyotes also demonstrate a linear decline in body size that begins prior to the local extirpation of megafauna (~20,000 years ago) and may be in response to competition with larger canids, the decline in large prey, and/or concurrent increases in aridity during this interval. A dramatic increase in scavenging of forested prey (e.g., deer) during the past century stands out as significantly distinct from the dietary niches occupied over the past 50,000 years—implying dramatic impacts of human behavior on coyotes, a recent shift in their ecological role, and the highly adaptable nature of these carnivores.