Study

Severe drought and calf survival in elephants

Foley, Charles; Pettorelli, Nathalie; Foley, Lara

Biology Letters, 2008

Peer-reviewedlongitudinal studywild

What they did

Calf mortality across elephant family groups during a severe drought in Tarangire, Tanzania was compared against the age of each group’s matriarch and the group’s movement decisions.

Studied in: Loxodonta africana
Sample size: family groups monitored through the 1993 Tarangire drought

Groups led by older matriarchs suffered substantially lower calf mortality, and were more likely to leave the park for areas holding water — a pattern consistent with a drought of comparable severity having occurred within those matriarchs’ lifetimes decades earlier.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

Older matriarchs carry ecological knowledge that materially improves group survival in rare severe conditions.

How NatureHQ reads it

This is the study that gives the matriarch literature its stakes. Earlier work showed older females respond better to unfamiliar calls; this shows the consequence in dead and living calves. It also carries a hard conservation implication that NatureHQ states rather than softens: ivory poaching removes the oldest animals preferentially, so it destroys the knowledge a family needs to survive the next rare event, long after the population count recovers.

Limitations

A single drought event; matriarch age correlates with other group properties such as size and range familiarity.
The memory explanation is inferred from age, not demonstrated directly.
Observational; no comparable manipulation is possible or ethical.