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Type II survivorship curve
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Graph showing three survivorship curves: Type I (red, with human figures) has high survival early and drops steeply at old age; Type II (blue, with a bird) declines steadily; Type III (green, with a plant) drops sharply early, then levels off. X-axis is age, y-axis is number of survivors on a log scale.
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survivorship curve
survivorship curve Type I, II, and III survivorship curves. A survivorship curve is the graphic representation of the number of individuals in a population that can be expected to survive to any specific age.

Type II survivorship curve

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Type II survivorship curve, in ecology, a curve displayed on a semilogarithmic scale that tracks organisms whose mortality (or survivorship) remains relatively constant regardless of age. Survivorship curves can be created by plotting the number of those members of a cohort that are still alive at each age. The Type II survivorship curve is presented as a straight line, with a constant slope, that decreases over time toward zero.

Certain lizards, perching birds, and rodents exhibit this type of survivorship curve. In some species that produce many offspring but provide little care for them (that is, r-selected species), mortality is greatest among the youngest individuals.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by John P. Rafferty.