Katy Payne is bioacoustics researcher also known for her work on whalesongs, vocalizations that will travel thousands of miles. I met her around 2010 when she gave a guest lecture on whale communication and Merleau-Ponty's idea of "the Flesh of the World." I got this book at the event and finally got around to reading it.

Silent Thunder is Payne's memoirs on her work with African elephants, which also communicate over long distances. This was unknown until the 80s, when it was discovered they communicate and coordinate their movents at frequencies below the threshold of human hearing. This infrasonic communication, however, is a bit less impressive when you realize it's about 4km on average, with an upper range of 10km. Despite the title, its a small part of the focus of the book, which also describes elephant group structures, courtship, and delving for water in dry areas.

The elephant groups are usually segregated by gender and they'll use the infrasonic communication to locate one another. Sometimes, as the case with female groups, they can use this to keep distance from one another. However, it also allows male elephants to locate them. Male elephants enter a state called musth, where they get supercharged with testosterone and excrete temporin from glands between their eyes and ears, fervently seeking out mates. It makes me wonder why enterprising quacks haven't latched onto this as some sort of cure for impotence. No longer would they need to kill the elephant, abscond with ivory, and grind it up for dick-pills. They'd just need to dart the elephant, massage its unconscious, waxy jowls, and sop up those sweet secretions. A perfectly renewable resource!

In dry areas they'll dig wells for water, creating watering holes used by other species. It's not exactly known how they know where to dig, but I'd wager a guess that they can probably hear subterranean water.

The latter half of the book details issues with conservation, and Payne's frustration with Zimbabwe's practice of culling. Even though she's against it, the culler's rationale comes through in the narrative: the elephants can destroy crops and farmland, so they're pushed out of habitats and into national parks. However, overpopulation in the parks becomes a problem when there are too many elephants. If they eat all the acacia trees there will be no acacia trees to feed the elephants. So at some point, the national parks have to do some culls.