Which group typically exhibits a mortality rate that remains fairly constant across an individual's life span?

• A. Robin
• B. Turtle
• C. Whale
• D. Caterpillar

Answer: (A)

Mortality that stays roughly the same across age is described by a Type II survivorship pattern. In this pattern, the probability of dying is about constant at any age, so the number of individuals declines at a steady rate over time. Robins, as birds, often show this constant risk of death across life stages due to continuous exposure to predators and environment, leading to a relatively uniform decline in survivors with age.

Turtles and whales tend to have different patterns: many turtles experience high mortality early on with few reaching old age (Type III) or, for some long-lived species, low early mortality and risk increasing with age (Type I). Caterpillars (insects) typically show high juvenile mortality (Type III). So the robin best fits the described pattern.