We watched as the Mashaba female leopard ascended a Russet Bushwillow tree and made quick work of devouring what remained of a male impala kill she had recently hoisted. As we looked up at her we noticed vultures beyond, circling high above. As they began to descend I wondered if they would detect her and the kill.
The vultures descended lower and lower until one flew just above the tree canopy where the leopard was feeding, and for the briefest of moments the two species made eye contact.
How had this vulture known from that height that the leopard was there? Had it relied purely on sight or can vultures smell? And, was it going to land and lurk in the vicinity until the leopard left the kill like they do with lion kills?
The vultures we see here at Londolozi are categorized as Old World vultures (found in Africa, across Europe and Asia). These vultures – in this case a white-backed vulture – rely solely on their incredible eyesight as they soar at on average 2600ft/800m to spot carcasses or other predators like lions, Bateleur eagles, Tawny eagles and hyenas that might have seen a carcass before them.
Conversely, the New World vultures found in the Americas such as the Turkey vulture – also commonly referred to as buzzards – have a remarkable sense of smell which is considered unique among birds. These two categories of vultures are however not closely related and have evolved separately to exploit similar food sources, something known as convergent evolution.
The vulture had clearly seen the leopard with the impala kill but as we watched, it started to circle again higher and higher and moved away. If this had been a lion with the kill on the ground the entire flock that was circling, numbering about 25 birds, would have most likely descended and landed on any dead tree in the area, or even on the ground, and waited.
So why did it not stick around for leftovers?
The answer can be found partly in James Tyrrell’s, Why Are Vultures Always in Dead Trees, that tells us that vultures are simply too large and clumsy to land on most foliated trees, especially a relatively small branched tree like the Bushwillow that the leopard was in. Even if this leopard was to leave the kill, which they often do to go and have a drink of water, the vultures would not have been able to get to it, so they don’t bother hanging around.
Leopards will more often than not hoist into densely foliated trees like Weeping Boerbean and Jackalberry trees to avoid attention from above and below; dense canopies, as well as providing shade for the leopard on a hot day, provide cover from the prying eyes of rival leopards and lions, but the vulture threat is one not to be underestimated. Lions will watch where vultures land and go and investigate the area for a potential meal. Although clumsy climbers, lion regularly steal kills from leopards by scrambling up to where the carcass is stashed, and a glaring sign pointing directly to the kill like descending vultures would be, is the last thing a leopard wants.
Vultures, being opportunistic, will most certainly scavenge from a leopard kill if they cam. However, as in most cases in the bush, it is a case of risk vs. reward, allied with energy expenditure. Will the vultures gain enough nutrition from the scraps hanging in a tree to make the effort of getting to it worthwhile? This is of course is dependent on whether they actually see the kill in the first place.
More often than not, the answer is no.