Did adapted Nursing Pattern Contribute to the Prehistoric Elephant's Extinction?

Mammoths lived all over the world for thousands of years. It could be even millions of years. They became extinct about 10,000 years ago, which was around the time the climate started warming the last time. The extinction is still shrouded in mystery.

A path breaking research by University of Western Ontario researchers on the extinction of prehistoric elephants, lead them to postulate that adapted nursing pattern could have contributed to the prehistoric elephant's eventual extinction. The investigators believe that woolly mammoths north of the Arctic Circle during the Pleistocene Epoch (approx. 150,000 to 40,000 years ago) began weaning up to three years later than modern day African elephants due to prolonged hours of darkness. This adapted nursing pattern could have contributed to the prehistoric elephant's eventual extinction.

Jessica Metcalfe, an Earth Sciences PhD student working with Professor Fred Longstaffe, analyzed the chemical composition of adult and infant mammoth teeth. The scientists say the young ones didn't begin eating plants and other solid foods before the age of two to three. They add that predatory mammals like saber-toothed cats and a lack of sufficient vegetation could be the secondary reasons for delayed weaning.

Metcalfe, who examined fossil specimens alongside Grant Zazula of the Yukon Paleontology Program say that 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. "In Old Crow mammoths 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.

Metcalf says “Today, a leading cause of infant elephant deaths in Myanmar is insufficient maternal milk production,". "Woolly mammoths may have been more vulnerable to the effects of climate change and human hunting than modern elephants not only because of their harsher environment, but also because of the metabolic demands of lactation and prolonged nursing, especially during the longer winter months."

Most of the convoluted part of the paper went over my head. Here is a sample from the abstract.

This study investigates differences in the δ¹³C_col, δ¹⁵N, δ¹³C_sc, δ¹⁸O_sc, 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 δ¹³C_col (~ 0.2‰), large decreases in δ¹³C_sc (~ 1.5‰), and large increases in δ¹⁵N (~ 2‰) and δ¹⁸O_sc (~ 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.

Nursing, weaning, and tooth development in woolly mammoths from Old Crow, Yukon, Canada: Implications for Pleistocene extinctions

 Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 298, Issues 3-4, 15 December 2010, Pages 257-270
Jessica Z. Metcalfe, Fred J. Longstaffe and Grant D. Zazula