Being Good Moms Couldn't Save the Woolly Mammoth
ScienceDaily (Dec. 21, 2010) — New research from The University of Western Ontario leads investigators to believe that woolly mammoths living north of the Arctic Circle during the Pleistocene Epoch (approx. 150,000 to 40,000 years ago) began weaning infants up to three years later than modern day African elephants due to prolonged hours of darkness.
By studying the chemical composition of adult and infant mammoth teeth, researchers were able to determine that woolly mammoths that once inhabited Old Crow, Yukon didn't begin eating plants and other solid foods before the age of two (and perhaps as late as three). (Credit: Image courtesy of University of Western Ontario)
This adapted nursing pattern could have contributed to the prehistoric elephant's eventual extinction. The findings were published recently in the journal, Palaeogeography, Palaeoclimatology, Palaeoecology.
By studying the chemical composition of adult and infant mammoth teeth, Jessica Metcalfe, an Earth Sciences PhD student working with professor Fred Longstaffe, was able to determine woolly mammoths that once inhabited Old Crow, Yukon didn't begin eating plants and other solid foods before the age of two (and perhaps as late as three) and considers predatory mammals like saber-toothed cats and a lack of sufficient vegetation to be the secondary reasons for delayed weaning.
"In modern Africa, lions can hunt baby elephants but not adults. They can't kill adults. But they can kill babies and by and large, they tend to be successful when they hunt at night because they have adapted night vision," explains Metcalfe, who examined fossil specimens alongside Grant Zazula of the Yukon Paleontology Program. "In Old Crow, where you have long, long hours of darkness, the infants are going to be more vulnerable, so the mothers nursed longer to keep them close."
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Palaeogeography, Palaeoclimatology, Palaeoecology
Volume 298, Issues 3-4, 15 December 2010, Pages 257-270
Nursing, weaning, and tooth development in woolly mammoths from Old Crow, Yukon, Canada: Implications for Pleistocene extinctions
Jessica Z. Metcalfea, , , Fred J. Longstaffea and Grant D. Zazulab
a Department of Earth Sciences, The University of Western Ontario, London, Ontario, Canada N6A 5B7
b Yukon Palaeontology Program, Department of Tourism & Culture, Government of Yukon, P.O. Box 2703, Whitehorse, Yukon, Canada Y1A 2C6
Received 13 May 2010;
revised 27 September 2010;
accepted 29 September 2010.
Available online 7 October 2010.
Abstract
This study investigates differences in the δ13Ccol, δ15N, δ13Csc, δ18Osc, Sr/Ca, and Ba/Ca values of juvenile and adult woolly mammoths (Mammuthus primigenius) from Old Crow, Yukon, Canada. The data indicate that nursing in woolly mammoths lasted at least three years, and was associated with minimal decreases in δ13Ccol (~ 0.2‰), large decreases in δ13Csc (~ 1.5‰), and large increases in δ15N (~ 2‰) and δ18Osc (~ 2‰) values. Sr/Ca and Ba/Ca ratios suggest that woolly mammoth juveniles began consuming plant foods between 2 and 3 “African Elephant Years” of age, much later than the initiation of weaning in modern elephants. We hypothesize that delayed weaning was an adaptation to increased predation risk and decreased food quality/quantity during the extended hours of darkness that occur in winter at high latitudes. Prolonged nursing and delayed weaning may have made mammoths particularly vulnerable to climatic stressors or human hunting.
Keywords: Stable isotopes; Trace elements; Carbon; Nitrogen; Oxygen; Strontium; Barium; Nursing; Weaning; Predation risk; Mammoth; Mammuthus primigenius; Extinction; Old Crow; Yukon
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