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The Great Migration

When these happened

8 dated records from 1960 to 2024. Each is drawn as wide as its date is certain — a band is a band because nobody knows the year, not because the drawing is imprecise.

1960196519701975198019851990199520002005201020152020Rinderpest disappears from the Serengeti–Mara ecosystem — c. 1960–1964The wildebeest population irrupts from roughly 250,000 to over a million — 1963–1977The Mara–Loita migration collapses by about 81% — 1977–2016Edge degradation squeezes wildlife into the ecosystem core — c. 1977–2018 (40-year record)Serengeti National Park inscribed on the UNESCO World Heritage List — 1981Drought kills roughly a quarter of the wildebeest population — 1993–1994AI satellite survey returns fewer than 600,000, and is contested — 2022–2023 imagery; published 2025TAWIRI Aerial Point Survey estimates 1,366,109 wildebeest — 2023
8 shown · 8 dated · 4 cannot be placed on an axis · Approximate or contested. Draw a band and do not sharpen its edges.
In order8
  1. c. 1960–1964Rinderpest disappears from the Serengeti–Mara ecosystem

    It happened, and the record is settled.

  2. 1963–1977The wildebeest population irrupts from roughly 250,000 to over a million

    It happened, and the record is settled.

  3. 1977–2016The Mara–Loita migration collapses by about 81%

    It happened, and the record is settled.

  4. c. 1977–2018 (40-year record)Edge degradation squeezes wildlife into the ecosystem core

    It was measured or witnessed, with the observation cited.

  5. 1981Serengeti National Park inscribed on the UNESCO World Heritage List

    It happened, and the record is settled.

  6. 1993–1994Drought kills roughly a quarter of the wildebeest population

    It happened, and the record is settled.

  7. 2022–2023 imagery; published 2025AI satellite survey returns fewer than 600,000, and is contested

    It was measured or witnessed, with the observation cited.

  8. 2023TAWIRI Aerial Point Survey estimates 1,366,109 wildebeest

    It was measured or witnessed, with the observation cited.

Not on the axis4
  • May–June (annual) — This recurs every year, so no single year on the axis is the answer.
  • late January – mid March (annual) — This recurs every year, so no single year on the axis is the answer.
  • May–July (annual) — This recurs every year, so no single year on the axis is the answer.
  • July–October (annual) — This recurs every year, so no single year on the axis is the answer.