Survivorship Curves

Survivorship curves tell us something about how long individuals survive in a population. There are basically three types of survivorship curves:

Type I survivorship curves are for species that have a high survival rate of the young, live out most of their expected life span and die in old age. Humans are a good example of a species with a Type I survivorship curve.

Type II survivorship curves are for species that have a relatively constant death rate throughout their life span. Death could be due to hunting or diseases. Examples of species exhibiting a Type II survivorship curve are coral, squirrels, honey bees and many reptiles.

Type III survivorship curves are found in species that have many young, most of which die very early in their life. Plants, oysters and sea urchins are examples of species that have Type III survivorship curves.

• Which type of survivorship curve does the cheetah have?
• What does parental care have to do with the shape of these curves?
• If you drew separate survivorship curves for female and male cheetahs, what would they look like?

Here is a new challenge for you.

• What do you think the survivorship curve would be for a white-tailed deer population?
• Would you expect the curves to be different for male and female white-tailed deer? (Hints: How long is the life span of a white-tailed deer? At what age do the males begin to grow antlers so they can be identified to sex?)