Lions rarely prey on elephants. Botswana's Savuti lions, however, switch to preying on elephants during the late dry season (August-November), and the frequency of this has increased in the last two decades (1985–2005). An opportunity to document this phenomenon was made possible with infrared viewing and filming equipment. A pride of 30 lions killed one elephant every three days. Seven of eight elephants killed were between four and 11 years old, as deduced from molar teeth ageing, and this age group represented over half the kills recorded by Joubert (2006). It is suggested that this weaned, maternally less dependent age class, may be more vulnerable to lion predation. Lions prey on elephants since the density of conventional ungulate prey is reduced as a result of an annual migration, and artificial water provisioning has prompted an increasingly sedentary population of elephants. Notes are presented on the lion's behaviour in hunting elephants and the evolutionary significance of this.