Late Pleistocene climate and proboscidean paleoecology in North America: Insights from stable isotope compositions of skeletal remains

• Main Author: Metcalfe, Jessica Z
• Format: Text
• Language: English
• Published: Scholarship@Western 2011
• Subjects: stable isotopes; mammoth; mastodon; Pleistocene; enamel; bone; dentin; cementum; environmental niche; seasonality; paleoclimate; paleoecology; Arizona; San Pedro Valley; Great Lakes; Ontario; New York; Alberta; Yukon; British Columbia; Mammuthus; Mammut; proboscidean; Biogeochemistry; Canada; Old Crow
• Online Access: https://ir.lib.uwo.ca/etd/194; https://ir.lib.uwo.ca/context/etd/article/1295/viewcontent/Metcalfe_PhD_Thesis_Final_Version_1.pdf

This thesis uses the carbon, nitrogen, and oxygen isotope compositions of mammoth (Mammuthus) and mastodon (Mammut) skeletal remains to reconstruct paleoclimate and paleoecology in Late Pleistocene North America. Analytical methods, sampling strategies, environmental adaptations and seasonal behaviors of proboscideans were investigated. Reliable and reproducible results are crucial for a study of this nature. A persistent methodological problem in the isotope analysis of structural carbonate in bioapatite was solved by reacting bioapatite under “sealed vessel” conditions. Growth rate determinations are critical for designing sampling strategies and interpreting results. Histological and isotopic measurements demonstrated variations in enamel growth rates within and among teeth. Sequentially sampling through the enamel thickness can resolve shorter-term (weekly) isotopic variations, and sampling along the tooth height (especially on the inner enamel surface) can resolve longer-term (monthly or yearly) variations. Proboscideans adapted to the conditions of their local environments. Clovis-age mammoths in Arizona sought out C4 grasslands that “greened up” as a result of summer rainfall. In C3-dominated environments (Great Lakes and Western Canada), seasonal variations were larger in mastodons than mammoths, possibly because the latter exploited a greater number of microhabitats, averaging plant and drinking water isotopic compositions. Mammoths and mastodons occupied different environmental niches, but both consumed a wide range of resources and regional differences were evident. Woolly mammoths in Old Crow delayed the initiation of weaning relative to modern elephants, perhaps as a defensive adaptation to the increased predation risk and decreased food quality/quantity during long hours of winter darkness at this high latitude location. Potential consequences of delayed weaning, such as longer inter-birth intervals and greater maternal energy investments, may have increased the population’s vulnerability to ...