Lion depredations on livestock are largely responsible for their conflicts with humans and for the historic collapse of their geographic range. Understanding of patterns associated with such predation can be used to mitigate its effects and promote more stable coexistence of lions and humans. We analyzed attacks on livestock over a four-years period on two neighboring arid-land ranches adjoining Tsavo East National Park, Kenya. A total of 312 attacks claiming 433 head of stock were examined. Lions were responsible for 85.9\% of the attacks; hyenas and cheetahs were the other predators responsible. Lions and hyenas attacked mainly cattle and did so at night, whereas cheetahs almost exclusively took smaller sheep and goats. There was no temporal autocorrelation of daily losses, suggesting that the attacks are independent events. Both number of attacks and number of stock killed showed significant seasonal differences, and their monthly totals correlated positively with precipitation. Intensified predation in the wet season differs from patterns of lion predation elsewhere but reinforces the pattern that large carnivores take more livestock when native prey are most difficult to find and kill. On average, wildlife attacks claimed 2.4\% of range stock annually, and livestock represented ca. 5.8\% of the diet of ranch lions. This predation represented 2.6\% of the herd’s estimated economic value, and cost the ranch 8749 per annum. Each lion cost ranchers approximately 290 per year in depredations.