After waiting patiently for some calm offshore weather, we finally had a good start to the 2026 Atlantic BRS field season this week. We were able to spend two full days at our field site 40 nautical miles off Cape Hatteras and encountered a large number of goose-beaked whales, our focal species. On Friday we deployed four satellite-linked dive recorders, which puts us in a good position for a Controlled Experimental Exposure (CEE) trial with a Navy destroyer later this month.
On Thursday, we encountered several groups of goose-beaked whales and observed some very interesting and unusual behavior. We came across a lone neonate (newborn) whale at the surface – we have long wondered how newborn beaked whales manage to stay with their mothers when they are feeding a mile beneath the surface. We do not see baby sitting in this species, as we do with deep-diving social toothed whales, such as sperm and pilot whales. So we were surprised to find this little whale alone at the surface. Shortly after it submerged, we came across a group of three adult males and a female – it seems that a pair of males were trying to displace another male, who was with the female. Shortly thereafter, we found the male, female, and baby together. The sociality of beaked whales is very poorly understood because of the challenges in studying these deep-diving pelagic whales, so we were fascinated to gain a glimpse into their complicated social behavior, which resembles that of much better-studied coastal bottlenose dolphins.
On Friday, we had even better weather – the southeast swell that made tagging challenging on Thursday had laid down a little – and we were able to deploy four tags. The tags are attached to the whales’ dorsal fins and record depth every five minutes. When the whale surfaces, the tags transmit the stored depth data to orbiting satellites, allowing us to reconstruct their diving behavior. In addition, Service ARGOS estimates the position of the tagged whale at the surface, allowing us to put together a continuous record of their movements. Thus we can determine whether exposure to mid-frequency active sonar affects either the diving behavior or movements of the tagged whales during a CEE. Our previous experiments have shown that whales typically alter their diving behavior and move away from the source of the sonar. In addition, using a different type of tag, we have shown that exposed whales stop vocalizing when exposed to sonar signals. Taken together, these responses suggest that goose-beaked whales perceive the sonar signals as a potential threat – likely a generalized response to the sound of a potential predator, as the sonar signals resemble the calls of killer whales, the primary predator of beaked whales.
We are hoping for some more good offshore weather this coming week, so that we can deploy additional tags and relocate some of our tagged whales. And we’d like to find the female and her new calf to see who she is associating with. We are starting to build a long-term dataset of social associations of our whales and it is our hope that we will soon be able to incorporate potential changes in social associations as another metric to understand their response to mid-frequency active sonar signals.
Many thanks to our exceptional field team – Zach Swaim, Meghan Bradley, and Daniel Webster, for their hard work this week.
