We know tall objects have a higher chance of being struck by lightening than others. Does that mean giraffes, who are by far the tallest animals on Earth, get struck by lightening more than others? Do they have a way to protect from it?
The three separate explanations below answer these questions thoroughly, although they might contradict with each other on a few facts.
This article talks about how four legged animals are more vulnerable to lightning strikes because ground current has high chances to go through vital organs. It also describes how large animals such as giraffes and elephants have higher chances of deadly strikes. There is the obvious thing about the fact that they are tall so even under a tree there is a non-negligible chance that lighting could jump directly to their head. The other less obvious one is that even if they are not directly hit, the large distance their legs span increases the voltage (and potentially the current) going though them (as described in this figure). Sadly the article lacks hard numbers on strike frequency depending on the species.
This blog post seems to suggest that giraffes getting killed by lightning is not that uncommon.
Between 1996 and 1999 the Rhino and Lion Reserve near Krugersdorp, South Africa, had two of its three giraffes killed by lightning – a third animal (a juvenile) was also struck but survived. Betsy the giraffe was killed by lightning at Walt Disney World in Florida in 2003 (in front of lots of witnesses).
A juvenile giraffe at Louisiana’s Global Wildlife Center, named Dusty, was killed after lightning struck a nearby tree.
This is very much a generalized, self-referential answer, but:
The evolution benefit of being as tall as they are (access to food sources unreachable by others, farther vision, etc.) may outweigh the detriment (in this case, being killed by lightening), if giraffe population height isn’t changing due to lightening strikes over time.
We have to keep in mind that “reproductive fitness” does not optimize for a single variable, characteristic, part of anatomy, or behavior, other than overall successful reproduction itself, which is a multi-component thing.
In almost all cases, multiple evolutionary pressures are happening simultaneously, and sometimes these pressures even conflict with each other (higher height = more access to food, but higher height also = possibly more chance of being killed by lightening, more energy expended to grow to that height, etc.).
To see whether the benefit is outweighing the detriment, or whether lightening strike deaths are a limiting factor on giraffe height, or other conclusions, we would need some hard statistical data on the subject, something like: how often giraffes of different heights, at what age and with how many offspring, etc., are dying from it.
Keep in mind that given how uncommon and difficult to observe the event is (a migratory animal that exists in relatively low numbers, interacting with lightening), no one may have collected this type of data yet.
There was a study done at one of the game parks here in South Africa regarding the susceptibility of giraffes to lightning. It was found that a lot of the deaths (wrongly) attributed to lightning were actually caused by snake bites. Black Mamba’s hunt birds in tree tops and the giraffes get fatal bites because they browse in the same area. I live a few kilometers from the lion park mentioned and it has a very high strike rate because of the terrain layout and elevation. Johannesburg has one of the highest lightning strike rates in the world generally.
In a theoretical example where animals are standing in close proximity to where lightning will strike anyways you could expect a Giraffe to get hit a slightly higher percentage of times than a smaller or shorter animal, but I think something like a hippo who has more surface area touching the ground has a higher chance than a Giraffe.
In the end no amount of height or girth is enough to affect the path of lightning as it’s a connection between the upper atmosphere brimming with energy and the earth sinking it: It’s such a massive scale even our most conductive man-made materials have a hard time changing its path more than a short distance.