Curious Kids is a series for children. If you have a question you’d like an expert to answer, send it to firstname.lastname@example.org. You might also like the podcast Imagine This, a co-production between ABC KIDS Listen and The Conversation, based on Curious Kids.
I would like to know how long garden snails would live if they were not eaten by birds (or other predators). – Alice, age 6, Canberra.
That’s a really good question! There have been reports of at least one snail living as many as 14 years in captivity. His name was George, and he lived in Hawaii in the United States.
Very few people have ever had the patience to study how long garden snails live in the wild. However, it might be longer than we might at first think – studies showed that snails in gardens in California needed to be between two and four years old before they were old enough to have babies. Many of these Californian garden snails, which were studied for almost five years, were, therefore, over six years old at least – more senior than you, Alice! Rats and small mammals were the main predators of these snails.
Counting snail shell rings
There is a snail very similar to the garden snail that is called the Roman or Apple snail – it is the one that some people like to eat.
A study of a population of these snails in England was able to work out how old these snails are. That’s because, as they get older, you can count growth rings at the edge of their shell.
Some of the snails were at least six years old and probably more like eight or nine. The older snails had very thick shells and were often out and about. The scientists thought this might be because as the snails got older and bigger, fewer birds and other predators could crack their thick shells, and so they felt safe enough not to hide away all the time.
So, if you are a snail that can survive long enough to get big, then you might stand a good chance of getting even older – maybe 15 years old. It depends on what type of snail you are.
People ruthlessly remove some trees, but others are sacrificed. The interdependence between trees and humans means that if we wish to have more or less trees in our urban areas, we must know how both people and trees influence each other.
The density of trees in Australia’s cities and suburbs increased dramatically in the past half-century.
In 1961, there were 26 trees for every hectare in the eastern Australian suburb garden. In 2006, this number had risen to 85. The number of street trees has increased from one in every two gardens to four in every five parks. We want trees.
Most city dwellers will tell you that they plant trees for the beauty, wildlife, and “the environment” when asked. Few people mention the fact that trees save cities more money than they cost.
We choose urban trees that will help us to maintain a healthy environment in our cities. Deciduous trees provide shade in the summer and sun during winter in towns that have cold winters and warm summers. In the subtropics and tropics, evergreen trees with dense crowns provide shade in all seasons.