The various stages a living thing goes through during its life, these are mainly described in two ways:

  1. In terms of years, for example, Charlie the dog is 6 months old.
  2. In terms of life-stage, for example, Charlie the dog is an adolescent.

Both methods are found throughout the demography database and can be used to describe how proportions of individuals within populations can change through time, most commonly between years.


Lifecycle examples: Species within COMPADRE and COMADRE

Lifecycle of the North American Moose, Alces alces
by Danny Buss, Exeter Node

  • This North American Moose population is stage-structured and displayed here using 3 life stages.
  • The percentage of individuals in each age class varies between populations and within populations between years.
  • 90.7% of Adults Survive over one year
  • On average, each adult produces 1.12 calves per year
  • Approximately 40% of calves survive their first year to become yearlings
  • 100% of yearlings survive to become adults


Lifecycle of the Eurasian Badger, Meles meles
by Anna Sambrook, Exeter Node

  • The Eurasian Badger population commonly follows a Pyramidal Age Structure.
  • Social group size can vary from 1-27 individuals
  • The percentage of individuals in each age class varies with group size.
  • A greater number of Badgers are in the younger age classes as group size increases.
  • This is partly due to more individuals moving up an age class and reproducing.
  • 75% of Adults aged 2 or over Survive over one year
  • Each adult aged 1-2 produces 0.5 cubs per year
  • Each adult aged 2 or over produces 1 cub per year
  • 20% of cubs ages 0-1 survive to become aged 1-2
  • 50% of adolescents aged 1-2 survive to become aged 2-3


Lifecycle of the Spear Thistle, Cirsium vulgare
by Danny Buss, Exeter Node

  • This Spear Thistle population is stage-structured and displayed here using 4 life stages.
  • 31.4% of Large Rosette plants survive over one year
  • 20.7% of Medium Rosette plants survive and remain as Medium Rosettes throughout the year
  • On average, each Large Rosette plant produces 187.47 seeds that do not go onto germinate in that given year
  • On average, each Large Rosette plant produces another 27.69 seeds that germinate and grow to become Small Rosettes
  • 1.1% of ungerminated seeds do not germinate and remain in the seed bank for the following year
  • Can you complete the missing percentages using the lifecycle diagram below (answers at the bottom of the page):
    • _____% of seeds that did not germinate the previous year grow to become Small Rosettes
    • _____% of Small Rosettes survive and grow into Medium Rosettes
    • _____% of Small Rosettes survive and grow into Medium Rosettes
    • _____% of Medium Rosettes survive and grow into Large Rosettes


Lifecycle of the common rhododendron, Rhododendrum ponticum
by Danny Buss, Exeter Node

  • This Rhododendron population is stage-structured and displayed here using 4 life stages.
  • The percentage of individuals in each stage class varies between populations and within populations between years.
  • 90.8% of Adults Survive over one year
  • 68.4% of SubAdults Survive and remain as SubAdults over one year
  • On average, each Adult plant produces 2.445 seedlings that survive to the following year
  • On average, each Adult plant produces another 0.016 seedlings that survive and grow large enough to become juveniles throughout the year
  • 22.5% of Seedlings grow to become Juvenile-sized plants throughout the year
  • Can you complete the missing percentages using the lifecycle diagram below (answers at the bottom of the page):
    • _____% of Juveniles grow to become SubAdult-sized plants throughout the year
    • On average, each SubAdult plant produces _____ seedlings that survive to the following year
    • _____% of SubAdults grow to become Adult plants throughout the year
    • _____% of Juveniles Survive and Remain as Juvenile plants over one year


Answers to exercises

Spear thistle (Cirsium vulgare)
1. 0.2
2. 16
3. 11.5
4. 43.4

Common rhododendron (Rhododendrum ponticum)
1. 44.45
2. 1.4
3. 19.5
4. 53