What mammoths ate and where they lived: Clues from ancient California fossils

Jenn Hoskins
8th January, 2026

What mammoths ate and where they lived: Clues from ancient California fossils

To reconstruct the diets and environments of mammoths over different timescales, enamel powder was collected from teeth using either serial drilling to capture seasonal variations (a) or bulk drilling for a long-term average (b).

Image adapted from: Hannold et al. / CC BY (Source)

Key Findings

  • This study analyzed teeth from mammoths on California’s Channel Islands and mainland to understand their diets and environment around 13,000 years ago
  • Both pygmy and Columbian mammoths primarily ate C3 plants, but some individuals consumed C4 plants, CAM plants, or plants stressed by drought
  • Mainland mammoths likely lived in drier conditions than island mammoths, as indicated by their diets, suggesting environmental flexibility but potential vulnerability to climate shifts
The extinction of large mammals, known as megafauna, at the end of the Pleistocene epoch (roughly 11,700 years ago) remains a significant mystery in paleontology. Numerous factors have been proposed, ranging from climate change and human hunting to disease and extraterrestrial impacts. Understanding the diets and environments of these extinct creatures is crucial to unraveling the causes of their disappearance. Recent research from[1] Florida State University & National High Magnetic Field Laboratory, alongside collaborators from the University of Southern California, Natural History Museum of Los Angeles County, La Brea Tar Pits and Museum, and Santa Barbara Museum of Natural History, has shed new light on the lives of pygmy mammoths (Mammuthus exilis) and Columbian mammoths (Mammuthus columbi) that once inhabited the Northern Channel Islands of California and the mainland. The study focused on reconstructing the diets of these mammoths by analyzing the stable isotopes found within their tooth enamel. Stable isotopes are different forms of an element with varying atomic masses. The ratio of these isotopes in an animal’s tissues reflects the types of plants they consumed, providing a window into their paleoecology. Specifically, the researchers examined carbon-13 (δ13C) and oxygen-18 (δ18O) isotopes. C3 plants are the most common type of plant, while C4 plants are more adapted to warmer, drier climates. CAM plants are also adapted to arid conditions and use a different photosynthetic pathway. By measuring the δ13C values, the team could estimate the proportion of C3, C4, and CAM plants in the mammoths’ diets. The analysis revealed that both pygmy and Columbian mammoths primarily ate C3 vegetation. However, a noteworthy finding was the presence of individuals from both populations that consumed significant amounts of C4 plants, CAM plants, or water-stressed woody C3 plants. This suggests a more complex dietary flexibility than previously assumed. Interestingly, the mainland mammoths exhibited higher mean diet-δ13C values compared to their island counterparts. This difference indicates that mainland mammoths likely consumed either water-stressed C3 vegetation or a combination of C4 and CAM plants, pointing to drier conditions on the mainland during the Late Pleistocene. To further contextualize the dietary findings, the researchers also reconstructed the paleo-water’s δ18O values. Oxygen isotopes in water are influenced by temperature and evaporation rates, allowing for estimations of past precipitation and climate conditions. The results showed that paleo-water on the mainland had lower δ18O values than modern precipitation in Southern California, suggesting that the region was wetter and/or cooler than it is today. In contrast, the islands’ paleo-water δ18O values were more similar to modern levels. These findings align with previous research indicating significant climate fluctuations during the Late Pleistocene[2]. The study’s δ13C-based estimates of mean annual precipitation ranged from 159 to 1407 millimeters per year on the islands and from 28 to 387 millimeters per year on the mainland. However, the researchers acknowledge that the consumption of even small amounts of C4 and CAM plants could underestimate precipitation levels, particularly for the mainland population. This is because C4 and CAM plants exhibit different isotopic signatures compared to C3 plants, potentially skewing the overall δ13C values. The timing of these dietary and environmental shifts is particularly relevant when considered alongside other evidence for the megafaunal extinctions. A layer of carbon-rich material dating to approximately 12,900 years ago, found at numerous Clovis-age sites across North America, coincides with the abrupt onset of the Younger Dryas cooling period[3]. This layer contains evidence of widespread biomass burning and is associated with the disappearance of many megafauna species, including mammoths. Recent research even proposes an extraterrestrial impact event at this time as a potential catalyst for these changes[4]. The findings of build upon earlier work at Rancho La Brea, which established that several megafauna species disappeared by 12.9 ka, coinciding with an ecological shift following aridification and vegetation changes[3]. The current study’s data supports the idea that these changes were driven by large-scale fires and mounting human impacts in a drying ecosystem. The observed differences in mammoth diets between the islands and mainland suggest that these animals were adapting to varying environmental conditions. The fact that mainland mammoths consumed more C4 and CAM plants, possibly due to drier conditions, could have made them more vulnerable to environmental changes and ultimately contributed to their extinction. Furthermore, a broad compilation of modern carbon isotope data[5] reveals a consistent relationship between δ13C values and mean annual precipitation, providing a valuable tool for interpreting paleoecological data. This study’s refinement of this relationship, correcting for factors like altitude and latitude, enhances the accuracy of precipitation estimates based on isotopic analysis. Additional radiometric dating of fossils from both the islands and mainland will be crucial to further refine the timeline of climate change and mammoth evolution and extinction in the region. This research highlights the importance of multi-proxy approaches, combining isotopic analysis with other paleoclimatic data, to gain a more comprehensive understanding of the complex factors that shaped the fate of these iconic megafauna.

EcologyEvolution

References

Main Study

1) Diets and environments of late pleistocene pygmy and Columbian mammoths: Isotopic evidence from Southern California

Published 7th January, 2026

https://doi.org/10.1371/journal.pone.0338674

Related Studies

2) Sea-level and deep-sea-temperature variability over the past 5.3 million years.

https://doi.org/10.1038/nature13230

3) Pre-Younger Dryas megafaunal extirpation at Rancho La Brea linked to fire-driven state shift.

https://doi.org/10.1126/science.abo3594

4) Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling.

Journal: Proceedings of the National Academy of Sciences of the United States of America, Issue: Vol 104, Issue 41, Oct 2007

5) Carbon isotope compositions of terrestrial C3 plants as indicators of (paleo)ecology and (paleo)climate.

https://doi.org/10.1073/pnas.1004933107


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