The bottom of the ladder: insects
Many insects have very short lives as grown-ups. A grown-up firefly lights up the summer evenings for a short while, long enough to flash, to find another firefly and to lay eggs. Many insects spend longer as a caterpillar or a grub than they do as a grown-up.
Even within one kind, lifespans can differ. Honey bees that work all summer wear out quickly, but the bees born in fall stay inside the hive and live right through the winter. A monarch butterfly born in summer lives a short life, while the monarchs that fly south for the winter live far longer.
The middle of the ladder: foxes and deer
Foxes, deer, squirrels and many small birds live for years, not just a season. They grow up fast and have young of their own, but in the wild most do not reach old age. Cold winters, hungry spells, sickness and other animals that eat them all make life hard. Bigger animals in this group tend to live longer than smaller ones.
The top of the ladder: elephants, whales and tortoises
Big, slow animals often live the longest. An elephant can live about as long as a person, and some whales live longer than any person. Giant tortoises are famous for long lives too: some Aldabra tortoises outlive the people who look after them.
It is not only about size. Slow, steady lives in cool water or on a quiet island tend to be long ones, and a few small surprises live a long time for their size. A little brown bat can fly around for many years.
In the wild or in a zoo?
The same kind of animal can live a different length of time in different places. In a zoo or a sanctuary an animal has food and water every day, a safe place to sleep, and a vet when it is sick. In the wild it has to find all of these itself, and cope with storms, dry spells and sickness. Many animals live longer with that kind of care.
Not every animal does better in a zoo, though, and some record ages come from the wild. When a page gives a lifespan, the note beside it says what the number is for. Read that note before you compare two numbers.
Pets and a long, healthy life
Pets often live longer than their wild cousins, too. A dog or a cat that gets good food, clean water, check-ups with a vet, shots to stop sickness and a safe home often lives longer than its wild cousins usually do. That long life is part of the promise you make when you care for a pet.
Every kind of pet has different needs, so learn what yours needs before you bring it home. Peabody's pets pages are a good place to start.
For Big readers: lifespan and life expectancy
Scientists use two different ideas. The maximum lifespan is the longest any single animal of its kind has been known to live. Life expectancy is how long a typical newborn can expect to live, and it is usually much shorter, because so many babies do not live to be grown up. A sea turtle lays many eggs, and only a few of the babies grow up. So the record is not the same as the usual.
How do scientists know an animal's age? For some, they read growth rings, the way you can count the rings in a tree: clam shells have them, and so do the layered earplugs of some whales. For others, they put a tag on an animal and follow it for years. Each method has limits, which is why a lifespan on a page is often an estimate and comes with its note.
Pick Big at the top to see the part for older readers.