Walruses synchronise their movements with the weather

TIL182 words#walrus#animals#weather

Walruses (Odobenus rosmarus) pile onto land at “haulouts” to rest, amazingly they seem to sync their movements using the weather.

Walruses ashore at Arakamchechen Island plotted above barometric pressure over August–October 1977; the two curves rise and fall together.

Early observers on the Chukotka coast noticed the herds tracked the barometer, walruses leaving land as air pressure fell and returning as it rose.1 A weather system is regional, so the same falling pressure reaches distant haulouts at once, and the walruses move together2 without ever needing to signal each other. I guess this could be because they are safer if they all move the same in large groups.

Footnotes

  1. Kibal’chich (1978, 1988) linked haul-out behaviour to air pressure — departure from land with falling pressure, return with rising pressure — as plotted for Arakamchechen Island in the figure above. Kastelein et al. (2021). ↩

  2. Counts at two Russian haulout sites about 80 km apart changed nearly simultaneously over 21 August–4 September 1987. Kastelein et al., “Ethology and Behavioral Ecology of the Walrus (Odobenus rosmarus)”, Springer (2021), reproduced from Semenov et al. (1988). ↩