Many pleistocene fossil sights contain the remains of many Mammoths, some of the sights represent the mass death of entire herds. These assumelages are evidence of intense predation by Humans and used to reconstruct Mammoth population dynamics. Anyhow, these interpretations continue controversial due to the taphonomic context of many sites are still debated.To reconstruct the taphonomic setting of each site and the movement patterns of mammoths among sites, you have to analyse carbon, oxygen, and strontium isotope ratios in mammoth tooth enamel. The carbon isotopes of fossils vary with diet and local vegetation, oxygen isotopes vary with local climate, and strontium isotopes vary with local soil chemistry. If Pleistocene mammoths traveled together in small family groups, then mammoths from sites that represent family groups should have lower isotopic variability than mammoths from sites containing unrelated individuals. Low levels of carbon isotope variability were found to be the most diagnostic signal of herd/family group association. Although the variability of oxygen and strontium isotope ratios proved less useful for identifying family group assemblages, these signals did provide information about the movement patterns of individuals among different sites. High levels of variability in each of the isotope systems at Clovis sites suggest that all of the sites examined represent time-averaged accumulations of unrelated individuals, rather than the mass deaths of family groups. In addition, analyses of the mean isotope values of Clovis mammoths show that although most mammoths from Blackwater and Miami (2 of the fossil sites) had similar values, the values of Dent mammoths were significantly different. This demonstrates that the Dent mammoths exist to a separate population and suggests that Clovis mammoths did not routinely commence long distance (600 km) migrations.
Despite their vulnerable canines, prominent muscle attachment scars on sabertooth limb bones suggest the cat was powerfully built. Saber-toothed cats may have used their muscular arms to immobilize prey and protect their teeth from fracture, she explained.
To estimate how strong sabertooth forelimbs were relative to other cats, the researchers used x-rays to measure the cross-sectional dimensions of the upper arm and leg bones of fossils recovered from the La Brea Tar Pits in Los Angeles. They also measured the limb bones of 28 cat species living today -- ranging in size from the 6-pound margay to the 600-pound tiger -- as well as the extinct American lion, the largest conical-toothed cat that ever lived.
The researchers used their cross-sectional measurements to estimate bone strength and rigidity for each species. When they plotted rigidity against length for the 30 species in their study, species with longer limbs generally had stronger bones. But the data for the saber-toothed cat fell well outside the normal range --while their leg bones scaled to size, their arm bones were exceptionally thick for their length.
"When I looked at the arm bones, Smilodon fatalis was way out in left field," said Meachen-Samuels.
Sabertooth arm bones were not only larger in diameter than other cats, they also had thicker cortical bone, the dense outer layer that makes bones strong and stiff. Thicker cortical bone is consistent with the idea that sabertooth forelimbs were under greater stress than would be expected for cats their size, Meachen-Samuels explained. Just like weight-bearing exercise remodels our bones and improves bone density over time, the repeated strain of grappling with prey may have resulted in thicker and stronger arm bones in saber-toothed cats.
"As muscles pull on bones, bones respond by getting stronger," said Meachen-Samuels. "Because saber-toothed cats had thicker arm bones we think they must have used their forelimbs more than other cats did."
"The findings give us new information about how strong their forelimbs were and how they were built," she added. "This is the first study to look inside sabertooth arm bones to see exactly how much stress and strain they could handle."
These X-Ray images show cross-sectional dimensions of the upper arm bone of a Jaguar (A and B) compared to a Saber-Toothed Cat (C and D)
This is a chunk of a Pleistocene Brown Bear cranial fragment.
Here are where Pleistocene Brown Bears fossils have been found. One was found in Ontario which was a skull which was dated 11 700 Bp, another Brown Bear fossil was found in Woodbridge which was a Brown Bear Humerus, the 3rd one was found in Trou Otis which was a Brown Bear skull. The last one was Gosselin San-pit (Saint Nicolas)
Here is the third metatarsal bone of 3 Bears, far left is a Black Bear, middle is a Pleistocene Brown Bear, and far right is a modern Brown Bear. Notice there is rough patches of arthritic bone on the Pleistocene Brown Bear and that its smaller than the modern Brown Bears
Tooth eruption and wear is usually used to predict the age of an Elephant and this system can also be used to predict the age of a Mammoth. Unfortunately it has not been used on a Mammoth tooth due to there being differences in wear rates for Mammoths when compared to African Elephants. Unfortunately the initiation of tooth mineralization hasn't been studied well in African Elephant foetuses. The average length of an African Elephant foetus is roughly 21cm and using evidence you could estimate the metal age to be 192 days. A mandible from a 9.5cm African Elephant foetus that corresponded to a metal age of around 140 days, but the amount of mineralization sadly wasn't mentioned. Mineralised-tissue occurs in the deciduous tusk. The crown formation in the deciduous tusk is finished after 16 months.
The dentin grows by accretion and periodic growth appear at distinct temporal scales. In Mammoths however, first oder growth increments occur each year in periodicity. Second-order increments have a period of roughly 7 days, and third-order increments happen daily. Applying these growth increments you could then predict the period of time over which a tooth would be formed.
Teeth do not begin to mineralize at conception, so the period of prenatal dentin accretion in a Mammoth tooth does not directly give us the gestation period of mammoths. By itself, the period of prenatal dentin accretion gives an underestimate of gestation length. In combination with comparative data from elephants, it permits estimation of relative gestation length. For example, African elephants have a prenatal mineralization period of about 15 months 17 months (for initiation between 140 and 192 days of gestation). If we observe a similar prenatal mineralization period in Mammoths, we could infer that their gestation lengths were probably similar.
Finding the gestation period of Mammoth requires looking at the gestation period of Elephants. African Elephants tend to have a gestation period of 650 days (21 months) and it isn't any different in captive African Elephants, its does not differ much in Asian Elephants as their gestation period is roughly 660 days. Giving the gestation periods of modern-day Elephants you could imagine Mammoths gestation periods shouldn't be any different, but for now there is no evidence to suggest its similar.
The season of birth will depend on the gestation length and season of conception, conception tends to occur year-round in African Elephants but there can be seasonal peaks (like the rainy season) when productivity is much higher. Majority of conceptions carried to term happened following seasonal peaks in prime productivity and given the 650 day gestation, births happen closer to the onset of seasonal increases in primary production. Mammoths would of been likely similar but potentially more extreme seasonal abnormality in nutrients availability and could of restrained the birth of calves to correspond with the start of the growing season. If we consider that Mammoths alike Elephants had condition dependent estrus, the greatest time for breeding could of been from August to October like that of Muskoxen and Caribou other Tundra animals. If you then assume the gestation period was similar to that of extant Elephants and that births would of been timed just before the growing season, you could predict that the gestation period would of been roughly 20 months.