The whales sing lower than they used to.
Blue whale calls run between roughly 10 and 40 Hz — well below human hearing. McDonald and colleagues compared half a century of North Pacific recordings (1963 vs 2008) and found that the typical song frequency had dropped by about a third. Miller et al. confirmed the same trend for Antarctic blue whales. We pitch the signal up by five octaves so you can hear what changed.
What happened in the ocean.
1960s — the ocean fills with engines.
Post-war shipping triples by tonnage between 1950 and 1970. Andrew, Howe and Mercer (2002) compared ambient ocean noise off California in 1965 and 1995 and found the low-frequency band had risen by about 10 dB — a tenfold increase in acoustic energy.
1972 — Save the Whales.
Roger Payne's whale-song recordings reach mass audiences and shift public opinion. The first concerted moratorium debates begin at the IWC. Whale populations are at historical lows: blue whales are estimated at 1-3% of pre-whaling numbers.
1986 — moratorium, populations recover.
The IWC enacts a global moratorium on commercial whaling. Blue whales begin a slow recovery. By the 2010s, populations are climbing back to perhaps 10-15% of pre-whaling levels in some basins. More whales now share the same acoustic channels.
Today — two hypotheses compete.
Why are the songs lower? McDonald proposed that as populations recover, males don't need to broadcast as loudly to be heard by other whales — they can sing lower-pitched, lower-energy songs. Others argue the shift dodges rising ship noise, which still dominates the same frequencies. Likely both, with shipping noise still the bigger force.
- McDonald, M. A. et al. (2009) — A 50-year comparison of blue whale song frequency in the North Pacific. Endangered Species Research 9.
- Miller, B. S. et al. (2014) — Long-term shifts in vocalisation frequency of Antarctic blue whales. JASA 135 (3).
- Andrew, R. K., Howe, B. M. & Mercer, J. A. (2002) — Ocean ambient sound: comparing the 1960s with the 1990s for a receiver off the California coast. ARLO 3 (2).
- Frisk, G. V. (2012) — Noiseonomics: The relationship between ambient noise levels in the sea and global economic trends. Scientific Reports 2.