Solving the woolly mammoth conundrum: amino acid 15N-enrichment suggests a distinct forage or habitat

Abstract

Understanding woolly mammoth ecology is key to understanding Pleistocene community dynamics and evaluating the roles of human hunting and climate change in late Quaternary megafaunal extinctions. Previous isotopic studies of mammoths’ diet and physiology have been hampered by the ‘mammoth conundrum’: woolly mammoths have anomalously high collagen δ15N values, which are more similar to coeval carnivores than herbivores, and which could imply a distinct diet and (or) habitat, or a physiological adaptation. We analyzed individual amino acids from collagen of adult woolly mammoths and coeval species, and discovered greater 15N enrichment in source amino acids of woolly mammoths than in most other herbivores or carnivores. Woolly mammoths consumed an isotopically distinct food source, reflective of extreme aridity, dung fertilization, and (or) plant selection. This dietary signal suggests that woolly mammoths occupied a distinct habitat or forage niche relative to other Pleistocene herbivores.

Evidence for herbivorous cave bears (Ursus spelaeus) in Goyet Cave, Belgium: implications for palaeodietary reconstruction of fossil bears using amino acid δ15N approaches

“…These results caution against hasty interpretation of δ 15 N results for collagen in the examination of feeding habits of fossil animals. Indeed, a brown bear from Yukon with collagen δ 15 N of +8.4‰ that is lower than that of the herbivorous brown bear from Goyet (+9.0‰) exhibited a TP of 2.7, suggesting a more carnivorous feeding habit, while the other individual with collagen δ 15 N of +11.5‰ from same region exhibited a TP of 2.4 (Schwartz‐Narbonne et al ., ). Similarly, modern grizzly bears from Alberta had TP estimates that are not consistent with the prediction based on collagen δ 15 N values; specimen 30345 with a collagen δ 15 N value of +7.2‰ showed a TP of 2.4 while specimen 30333 with a collagen δ 15 N value of +8.1‰ had a TP of 2.1 (Tables and ).…”

“…). In contrast, fossil brown bears ( U. arctos ) from Europe and Yukon, Canada, showed more omnivorous feeding habits as suggested by higher TPs of 2.0–2.7 relative to the cave bears (Schwartz‐Narbonne et al ., ). One short‐faced bear ( Arctodus spp.…”

The dietary protein paradox and threonine 15N‐depletion: Pyridoxal‐5'‐phosphate enzyme activity as a mechanism for the δ15N trophic level effect

“…Thus, diet, species and tissue‐specific TDFs Glx or the use of multiple AA TDFs will be necessary in some cases for accurate trophic level reconstructions . This appears to be especially relevant for studies focused on carnivorous species higher up in the food chain, and may significantly affect the interpretations derived from archaeological or paleontological studies of δ 15 N AA results …”

Non‐traditional isotope perspectives in vertebrate palaeobiology

“…Previous studies based on nitrogen isotopes have underlined the discrepancy between mammoth δ 15 N values and those of other herbivores, suggesting that mammoths fed on highly 15 N‐enriched plants (Schwartz‐Narbonne et al . ) or practiced coprophagy (Clementz et al . ; van Geel et al .…”