Utheria

Average lifespan

Definition of average lifespan varies greatly in the literature, particularly in the life stage at which lifespan is assessed. Average lifespan of neonates is often referred to in the literature as average life expectancy at birth and the average lifespan of adults is the average age at death of adults. It is often much longer than the average lifespan of neonates, because juvenile mortality is often much higher than adult mortality. A variable sometimes given in the literature is the average life expectancy at maturity: this can be turned into average adult lifespan by adding the age at maturity.

Sample size in estimation of lifespan is the number of individuals that died, not the number of individuals observed, since it is only by dying that individuals contribute to lifespan data. Particular care must be taken to record the lifestage of animals from which lifespan data has been taken. Average Lifespan has its own "Life Stage" drop-down with more options than many of the other measurement types, as follows:

• Embryo
• Neonate
• Weanling
• Juvenile
• After Sexual Maturity
• After First Birth
• Adult
• Unspecified

Generic value types: Data value, Data Range, Measure, Captivity Status, Sex, Life Stage, Weanling Definition and Source Type.