The Maneaters of Tsavo – Revisited

The events that unfolded in Tsavo (Kenya) in 1898 were unusual to say the least. Laborers were hard at work building a bridge across the Tsavo River and laying track for the Kenya-Uganda Railway. Over a nine-month period two male lions systematically stalked, killed, and ate between 28 and 135 railway workers, before the lions were shot and killed. Lt. Col. Patterson, the railway construction supervisor, estimated that 135 workers had been killed and eaten, but later estimates put the number of victims closer to 35. Regardless, the loss of human lives to lions was unprecedented.


Figure 1. A photo of one of the two maneless male lions that was responsible for the deaths of dozens of railway workers in the Tsavo region in 1898.

Over the years, several books and research papers have attempted to answer such questions as, why did the two male lions turn to a diet of day laborers, and how many workers were actually killed by the pair? Now, using isotopic techniques and environmental data from the time period, Yeakel and colleagues (2009) have shed some light on the behavior of the “maneaters of Tsavo.”

The isotopic data, coupled with estimates of lion food consumption rates, suggest that the pair of Tsavo lions consumed approximately 28-35 humans over the nine-month period; a number far less than that claimed by Lt. Col. Patterson. The isotopic ratios also revealed that the two Tsavo lions switched from a diet of grazing herbivores to a mixture of browsers and humans toward the end of their lives. Finally, one of the two lions (now in the collections of the Field Museum of Natural History) was responsible for the “lions share” of human victims (killing an estimated 24 humans). Interestingly, this lion also suffered an injury to its face that left it missing a lower canine and with maloccluded and abscessed teeth.


Figure 2. Isotopic model of Tsavo lions FMNH 23969 and 23970 and their potential prey. The blue polygon denotes the mixing space for five dietary sources: browsers(purple and blue), grazers (yellow and red), and Taita agropastoralists (green). (B) Source contributions of the diets of the two maneaters from Tsavo (colors are the same as in A above. Note the higher reliance on humans (green) in the diet of lion FMNH 23970 in the bottom panel. (from Yeakel et al., 2009)

Yeakel and colleagues (2009) suggest that a combination of environmental changes and the presence of large numbers of railway workers in the region led to a decline in potential prey in the Tsavo region. With the conventional prey base in decline and with a subsequent injury to one of the lions, this lion was forced to switch to more locally abundant and easier to kill prey (humans). The other member of the lion coalition eventually joined in the killing and the legend was born.

References

Patterson, B. D. 2004.
The Lions of Tsavo : Exploring the Legacy of Africa's Notorious Man-Eaters. McGraw-Hill, New York, 231 pp.

Patterson, B.D., Kays, R.W. Kasik, S.M. and V.M. Sebestyen. 2006. Developmental effects of climate on the mane of the lion (
Panthera leo). Journal of Mammalogy 87(2):193-200.

Yeakel, J.D., Patterson, B.D., Fox-Dobbs, K., Okumura, M.M., Cerling, T.E., Moore, J.W., Koch, P.L., and N.J. Dominy. 2009. Cooperation and individuality among man-eating lions.
Proceedings of the National Academy of Science U S A. 106: 19040–19043. doi:10.1073/pnas.0905309106