Average lifespan
The average lifespan of the vast majority of animals is in the range of days, weeks, months and years, with a select few species living into the decades.
Most animals (78%) live in water. Animals that live in water have advantages. There are less extreme fluctuations in temperature. Freezing will occur on the surfaces of the water. They can migrate more easily to other locations in search of food. And there is plentiful amount of food in the form of zooplankton floating around.
In this article, I will highlight the average lifespan of animal groups and point out animals with unusual longevity.
Average lifespan of common animal species
In the table below, I show several species from the 9 phyla that account for the vast majority of the species (1,2). Keep in mind that 84% of the known species of animals belong to the phylum Arthropoda (which includes insects and crustaceans). In terms of sheer numbers, however, roundworms have all the phyla beat: 80% of the animals that exist on the planet are from the phylum Nematoda.
Table of common species, their average lifespan, their representative long-lived members, and members that are capable of regeneration of significant body parts (easier to see on the desktop).
Species (sub-phylum or Class) (Phylum) | Estimated Number on Earth (trillions or # species) | Average lifespan of the group | Creatures in the group that lives longer than 100 years | Which of the group has creatures capable of regeneration significant parts of their body |
---|---|---|---|---|
Amphibians (Amphibia) (Chordata) | Salamanders (3,4) | |||
Mammals (Mammalia) (Chordata) | ||||
birds (Aves) (Chordata) | none | |||
Fish (vertebrata/ (Chordata) | ||||
Annelida (earthworms) | 50 trillion (estimate) | 1-8 years (leeches 10 years)(earthworms 1-8 years) | none | |
Krill (Crustacea) (Arthropoda) | ||||
Insects (Insecta) (Arhtropoda) | 10000000 trillion insects (10 quintillion or 10 billion billion) | termite queens (rare to be 100 year old, but definitely 30-50 years old) | Many insects (limbs) | |
Nematoda (roundworms) | none | |||
Reptiles (Reptilia) (Chordata) | ||||
Mollusca | ||||
Cnideria | ||||
Platyhelminthes (flatworms/ planaria) | 0.2 - 30 years (marine flatworms; tapeworms). | Planaria (theoretically immortal (7) | ||
Porifera | ||||
Echinodermata | sea urchins, red (5) |
Most animals don't live past the age of 30
In looking at the table, you can see the average lifespan of certain species of animals and some notable points:
- In the phyla Annelida (earthworms), Platyhelminthes (flatworms) and Nematoda (round worms), there are none known to live past 30 years
- Most of the creatures in the phyla Mollusca, Arthropoda, and Echinodermata live short lives with a few exceptions (sea urchins, starfish, termite queens, lobsters, quahog clams)
- In the phyla Chordata, there are several long-lived species (for example, parrots/macaws, lungfish, lizards, turtles/tortoise, elephants, and humans). Those live comfortably into the 50 - 100 years.
Given that the phylum Chordata makes up only a fraction of all the animals on the planet (range of trillions in this phylum versus quadrillions of insects and nematodes), it is fair to say that most animals don't live past 30.
The rare animals that beat the average lifespan
Rare are the animals that live more than 100 hundred years.
There are some animals that live amazingly long lives: sea urchins (100 - 200 years), octopuses (100 years), quahog clams (400+years), salamanders (100 years), Greenland sharks (400+ years), and bowhead whales (200+ years). We discussed the important effect of size on lifespan in a previous article.
Animals that can bypass early mortality (from predation, for example) and continue growing in size have a definite advantage. Examples include turtles, lizards, whales, sharks, and elephants.
Beating the average lifespan: Delayed sexual maturity
Interestingly, the age at which the animal attains sexual maturity is closely tied to longevity.
Animals that have delayed reproductive ages live longer (15, 16). This is true even for humans (17). The most impressive animal where delayed sexual maturity correlates with longevity is the Greenland shark. This species of shark delays its sexual maturity till it reaches the age of 150 years. Its average lifespan is more than 400 years (15).
Is it because animals know that they have time on their hands, or does delayed reproduction give the germ cells a chance to breathe?
The issue is complex - as is the literature on aging in humans and animals (15, 18 - 26). It is true that experiments in animals, that delay reproduction enhance longevity (15). However, there are a multitude of other factors that play a role.
For example, several environmental factors tie into each other; those in turn tie into the timing of sexual maturity and longevity.
Many of the animals mentioned with greater average lifespans live in Arctic waters or in deep ocean waters or in caves. How much does te environment play a role in prolonging the average lifespan of animals?
In the next article I will discuss three unusual reasons that help animals live incredibly longer lives.
Picture credits:
- Blatant World. Bowhead Whale: Bowhead Whales swimming in the Arctic Ocean, Taken Dec 1, 2009. From Flickr.com.
- brewbooks. Red sea urchin. Mesocentrotus franciscanus. FromFlickr.com, taken on June 15, 2018.
- Lebendkulturen.de. Hydra vulgaris, dark field. Shutterstock.com, ID: 92793046.
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