This March, conservationists working at the Rockwood wildlife reserve in South Africa noticed two giraffes missing from the local herd. The day after a heavy thunderstorm, the park staff found the two females, aged four and five years old, lying about 23 feet apart. The giraffes smelled like ammonia, a sign they’d been killed by lightning, Mindy Weisberger reports for Live Science.
A case study of the giraffes’ deaths was published this month in the African Journal of Ecology. The lightning strike apparently hit one giraffe on the top of its head, judging by a fracture in the skull near the base of its antler-like ossicone, George Dvorsky reports for Gizmodo. The other giraffe may have been killed by the strike indirectly, by the lightning’s dispersal through the air or ground.
Adult giraffes stand at between 15 and 19 feet tall, and they live in the savannahs of 12 African countries. Common wisdom tells us that lightning strikes the tallest thing in an open area—so are giraffes at a greater risk of lightning strikes than other animals?
“When the giraffes died, I tried to look for scientific papers on giraffe kills by lightning, but surprisingly I could only find a few cases, which were only described in non-scientific journals,” Ciska P. J. Scheijen, a conservationist at the Rockwood Conservation Fund and the sole author of the new study, tells Gizmodo in an email. “At the same time, few circumstantial details are given, especially regarding their movement patterns and habitat.”
Giraffes in captivity are occasionally killed by lightning strikes and make the news. In 2019 and 2003, lightning killed giraffes in Florida; according to the National Oceanic and Atmospheric Administration, the land between Tampa and Orlando sees the most cloud-to-ground lightning in the United States. In 2010, a giraffe on a South African game reserve was struck.
"If you're in the wrong place at the wrong time you're susceptible - it's not that giraffes stand out like lightning rods," Namibia-based conservationist Julian Fennessy told BBC News in 2010. "I can think of a number of cases where a giraffe has been killed by lightning, both from a direct hit and by being struck by a tree that it was standing beneath. But it is still quite rare."
In some ways, lightning strikes are just another risk of being outdoors during a thunderstorm. To the BBC, Fennessey pointed to an incident when a pack of wild dogs were killed when lightning struck the tree they were sheltering under. And in 2016, a lightning bolt and the shock it sent through the ground killed over 300 reindeer in Norway, Meilan Solly wrote for Smithsonian magazine in 2018.
Direct strikes are also not the only way that lightning can kill. There are three others: a side flash, where the lightning arcs sideways into an animal after hitting something nearby; a touch potential, where the electrical current zaps the animal if it’s touching whatever was hit; and a step potential, where the electrical current disperses through the ground and hits anything standing nearby.
There’s a lot left to learn about lightning itself, too. As Carl Engelking reported for Discover magazine in 2016, scientists are still studying how lightning is initiated in a thunderstorm’s clouds. And height may not be the leading factor in where lightning strikes.
“Twenty-seven percent of the time, depending on conditions, the shorter object is hit by lightning rather than the tall object,” Florida Institute of Technology physicist Hamid Rassoul told Discover magazine.
It’s the positive charge that extends above a lightning rod, tree or animal that attracts the storm’s negatively-charged lightning.
“Sometimes objects change electrical potential so much, they project their positive charge higher than a tower,” Rassoul told Discover magazine. “But why am I sending such a long streamer up there? Again, none of these questions have been answered.”
The new study does not provide data to suggest whether giraffes’ height contributes to their risk of lightning strikes. Instead, it examines the deaths of the giraffes in the Rockwood reserve and presents questions that giraffe experts may want to research further. Like, if giraffes are more at risk from lightning strikes, have they learned any strategies to reduce that risk?
On the other hand, if the chances of being hit by lightning are very low, then the benefits of being tall might win out.
“If the chances of reproduction increase when you are tall and strong, but the chance that you get hit by lightning stays relatively low even though you’re the tallest, then the trait of the length will ‘win,’” Scheijen tells Gizmodo, adding that her main goal by publishing the study was to “inform colleagues and make them curious and trigger a discussion.”