in
Chicago In 2001, a review of causes for man-eating behaviour among lions revealed that the proposed human toll of 100 or more was most likely an exaggeration and that the more likely death toll was 28–31 victims. This reduced total was based on their review of Colonel Patterson's original journal, courtesy of Alan Patterson. However, the same study also noted that the journal refers only to Indian workers and that Patterson stated that the casualties were much higher in the African worker population but that those numbers were not documented. The two lion specimens in Chicago's Field Museum are known as FMNH 23970, the 'standing' mount, killed on 9 December 1898, and FMNH 23969, the 'crouching' mount, killed on 29 December 1898. Recent studies on the
isotopic signature analysis of
Δ13C and
Nitrogen-15 in their bone
collagen and hair
keratin were published in 2009. Using realistic assumptions on the consumable tissue per victim, lion energetic needs, and their assimilation efficiencies, researchers compared the man-eaters' Δ13C signatures to various reference standards: Tsavo lions with normal (wildlife) diets, grazers, and browsers from Tsavo East and Tsavo West, and the skeletal remains of
Taita people from the early 20th century. Interpolation of their estimates across the nine months of recorded man-eating behavior suggested that FMNH 23969 most likely ate the equivalent of 10.5 humans and that FMNH 23970 most likely ate 24.2 humans. However, the researchers noted that, according to their estimates, a combined death toll as high as 72 was still possible. DNA from compacted hair found in the tooth cavities of the Tsavo man-eaters in 2024 reveals that in addition to humans, the lions fed on
zebras,
oryx,
waterbuck,
wildebeest, and at least two individuals of
Masai giraffe. This suggests the lions would switch between hunting their natural prey and humans, though it remains unclear as to whether the lions began hunting humans as a result of the injuries sustained to the male with the damaged tooth. The DNA analysis also confirmed that the lions were brothers. Each had the other's hair in his tooth cavities, suggesting that they were closely bonded and groomed each other. The scientific analysis does not differentiate between the entire human corpses consumed and the parts of individual prey since the attacks often raise alarms, forcing the lions to slink back into the surrounding area. Many workers over the long construction period went missing, died in accidents, or fled out of fear, so it is likely almost all of the builders who stayed on knew someone missing or supposedly eaten. It appears that Colonel Patterson may have exaggerated his claims, as have subsequent investigators (e.g., "135 armed men", Neiburger and Patterson, 2000), though none of these modern studies have taken into account the people who were killed but not eaten by the animals. Other researchers have also shown that estimates of animal diets derived from isotopic models often deviate considerably from the correct values. == Possible causes of "man-eating" behavior ==