Survivorship

Definition

In population ecology and life-history studies, the proportion or absolute number of individuals from a given cohort that remain alive at successive ages or stages; often represented as lₓ in life tables. Survivorship curves (Types I, II, and III) graphically depict how mortality risk is distributed across the lifespan, revealing trade-offs between parental investment and offspring survival.

Etymology

From survive + -ship, denoting condition or state; ecological usage formalized in life-table analysis during early 20th century demography.

Example

A Type III survivorship curve characterizes many insects such as periodical cicadas (Magicicada), where overwhelming early mortality due to predation and environmental hazards is offset by extremely low adult mortality once individuals emerge and reproduce.

Synonyms

• survival
• lₓ (life-table notation)

Related Terms

• Life table
• cohort
• mortality
• Fecundity
• life-history strategy
• Semelparity
• iteroparity
• age structure
• lxmx table

Usage Notes

Distinguish from individual 'survival' (staying alive) and 'survivability' (engineering resilience). In entomology, survivorship is frequently stage-specific (egg, larval, pupal, adult) rather than strictly age-based due to discrete metamorphosis. Type I curves (low early mortality, high late mortality) typify social insects with extended parental care; Type II (constant mortality) appears in some adult beetles and arachnids with steady predation risk.