Blue Whale Songs Have Been Getting Lower in Pitch Since the 1960s

Since the late 1990s, researchers monitoring blue whale (Balaenoptera musculus) calls have noticed something consistent and strange: the calls are getting lower. Not by a lot, and not all at once, but measurably — roughly 0.35 to 0.4 Hz per decade — across populations in the North Pacific, South Pacific, Indian Ocean, and Southern Ocean. The trend appears in recordings that go back to the 1960s, and it has continued steadily across every population that's been studied.

Mark McDonald and John Hildebrand at the Scripps Institution of Oceanography published the first systematic analysis in 2009, compiling data from multiple ocean basins and confirming that the frequency drop was not noise or equipment drift. Every population was doing it.

Several explanations have been proposed. One is body size: blue whale populations, devastated by industrial whaling in the 20th century, have been recovering since the 1986 International Whaling Commission moratorium. Larger whales produce lower calls. If recovering populations skew toward larger average body size, the average call pitch would drop. A second hypothesis concerns the noise floor: as ocean shipping traffic has increased since the 1960s, low-frequency noise has increased, and whales may be compensating by calling at different amplitudes or frequencies. A third is more speculative — that the shift reflects social learning, with whales slowly adopting a different cultural norm for call pitch, the way human music pitch standards have drifted over centuries.

None of these explanations fully accounts for the pattern's uniformity across isolated ocean populations. The calls are still dropping.