It had been a long day in the field and we were all exhausted. I crawled into bed amid a thunderstorm and listened to the loud claps of thunder and the rushing sound of rain falling on the ground outside. I started to doze as the thunder gradually softened and the rain turned to light drizzle. Abruptly, I was jarred awake by the harsh and unmistakable vibrations of an earthquake. We ran outside and waited another 30 seconds or so until it passed. Everything seemed fine. No major damage, but people yelled loudly from the nearby village as monkeys gave loud alarm calls.
This earthquake was the second in as many days. The first measured magnitude 5.2. This one felt quite a bit stronger,measuring magnitude 5.7. We had a restless night, with aftershocks as strong as magnitude 5.4 occurring frequently throughout the night. Seismic activity is not uncommon in this area. Western Uganda lies along the Albertine Rift, an active area of tectonic shifts that are slowly separating the Somali Plate in East Africa from the rest of the continent. The earthquakes we've experienced in the past week have had their epicenter along the rift in Lake Albert to the west.
On our way to the field the next morning, we were all a bit bleary-eyed, but the earthquake was an animated topic of conversation among all. Amid our discussions of how our Ugandan friends responded to the event, I wondered how the chimpanzees in the region fared as well. Ethologists and others have written numerous articles regarding how animal behavior changes preceding and during seismic activity (e.g., Buskirk et al. 1981; Shaw 1977). Most of these accounts have come from captive animals. For example, in 2011 the National Zoo described the responses of various animals to an earthquake of magnitude 5.8 in the Washington, DC area. Orangutans and western lowland gorillas were among the zoo inhabitants to respond to the quake, with members of both species climbing higher in their enclosures and vocalizing.
What about free-living primates? Snarr (2005) similarly reported that wild mantled howler monkeys (Alouatta palliata) responded to an earthquake by vocalizing and climbing higher in the trees. Fujimoto and Hanamura (2008) provided a rare account of wild chimpanzee responses during a strong earthquake and its aftershocks in the Mahale Mountains, Tanzania. The chimpanzees vocalized loudly (but were not visually observed) during the main quake. During aftershocks, they typically responded by climbing higher or by interrupting their activities. Interestingly, one female was observed to climb down and touch the ground with her hand, as though to explore the vibrations she was feeling from the ground. Few other accounts exist regarding the behavior of wild non-human primates in response to earthquakes, however. ...more