Relationship with other Wildlife and People
Last Review/Updated: May 31, 2002
Directly or indirectly, invertebrates play important roles in the lives of other kinds of wildlife and people.
Parasites and Disease
In
Alberta, mosquitoes are considered generally to be a nuisance because
they bite and suck blood. But in some situations they can transmit
diseases, such as sleeping sickness. This disease usually infects horses,
but it can infect people. Sleeping sickness is caused by an invertebrate
(a single-celled parasite) that spends part of its life in horses (or
people) and part in mosquitoes. In other parts of the world, mosquitoes
can transmit malaria and yellow fever.
In Alberta, ticks have been known to carry Rocky Mountain Spotted Fever, a disease that can be fatal to people. Fortunately, this disease has not been reported in Alberta for many years. An infected tick can transmit the disease after penetrating the skin of a victim. Since ticks take several hours to find a suitable site to penetrate the skin, they usually can be found and removed before they attach. When traveling in the mountains and foothills, it is wise to check yourself for ticks at least once a day. The ticks commonly found on moose in Alberta do not carry diseases that infect people.
Parasites
are invertebrates that live on or inside other animals and feed on
tissues and fluids of their hosts. People, livestock, and wildlife
can be infected by many parasites. Parasites are common in wildlife
populations, and normally do not seriously affect them. However, when
parasites infect domestic animals or people, they can cause serious
harm. One species of tapeworm, normally found in coyotes and wolves,
may be transmitted to domestic dogs and in turn, to humans, causing
serious disease. Other parasites may cause only temporary discomfort.
For example, people often get "swimmers' itch" when they swim in Alberta's
lakes in early summer. Swimmers' itch is caused by a parasite called
a fluke. The fluke normally lives inside ducks, or other water birds.
Eggs of the fluke pass out of the duck into water, where they hatch
into tiny larvae. These burrow into snails and multiply. Eventually,
they leave the snail and go looking for a duck. These larvae may attempt
to burrow into the skin of people who swim in contaminated lakes. However,
human skin is too thick, and the larvae cannot penetrate through it.
But while trying to do so, they die and cause an itch. Although swimmers'
itch is a nuisance, it is not serious, and the symptoms soon go away.
Food for Other Wildlife
Many other animals depend upon invertebrates for food. Fish eat aquatic insects. Young grouse and ptarmigan feed on insects during the first few weeks of their lives. Ducks and other water birds feed on aquatic invertebrates. Hawks and owls eat grasshoppers, beetles and moths. Many other birds are insectivorous (insect eating), and help control mosquitoes and other pests. Bats in Alberta are also insectivorous, feeding mainly on flying insects. In forests and fields, certain mammals, such as shrews and mice, regularly feed on insects and other invertebrates. Larger mammals, such as bears, coyotes and foxes, also eat invertebrates as part of their diets. Bears can be a problem for beekeepers because they frequently destroy domestic bee hives to eat the bees and honey found in the combs.
Crop and Garden Pests
Invertebrates
cause millions of dollars worth of damage to crops each year. Every
few years, populations of some species of grasshoppers increase dramatically
and decimate local grain crops. Some caterpillars, beetles and slugs
eat garden vegetables and reduce the harvest. Tent caterpillars prefer
the leaves of poplar trees, but often attack ornamentals around houses
and parks.
Recreation
Invertebrates provide a variety of recreational activities. Some people
enjoy collecting various insects and arranging them for display.
Butterfly and beetle collections are perhaps the most common.
Dedicated trout anglers spend many hours creating artificial lures to imitate mayflies, stoneflies, or other vertebrates. These lures are used in fly fishing. Other anglers use live bait such as worms, grasshoppers, and stonefly nymphs.
Much enjoyment can be had from watching invertebrates such as snails, clams, shrimps or crayfish in aquariums, and beetles or spiders in terrariums. Ant colonies are kept in plastic or glass "ant farms." These farms are easy to make, and can provide an opportunity to see how insects build nests, feed young and communicate with each other.
Science and Technology
Scientists use invertebrates to study genetics and environmental pollution. Much of our knowledge about heredity and how it is affected by radiation and chemicals comes from the study of fruit flies (Drosophila). These insects are much more sensitive to radiation and chemicals than other animals, including man. Their brief life cycle makes it easy to study the effects of chemicals and radiation over several generations.
Other invertebrates are sensitive to slight changes in their environments. The presence of poisonous chemicals, the result of improper waste disposal or pesticide application, may affect and reduce the numbers of these animals long before people realize that harmful chemicals are present. On land, beetles and spiders can be used as "biological indicators" of pollution. In water environments, changes in the numbers of mayfly, stonefly and caddisfly larvae indicate the degree of pollution present. Such biological indicators are much more sensitive to changes in their environment than any physical instrument made by humans.
Food Production
Many kinds of invertebrates are used by man as food. Lobsters, crabs,
oysters and shrimp are some examples. In Alberta, invertebrates are
essential to the production of many foods used by people. Many insects
are important plant pollinators. Without insect pollination, we would
not have apples, cherries, berries, and many vegetables.
In addition to their role as pollinators, honeybees produce honey from the nectar of flowers. For example, the Peace River district is one of North America's most productive honey regions.
The tunnels of earthworms help aerate soil and allow water to penetrate. This develops good soils in croplands and gardens. Earthworms, beetles, flies and centipedes are some of the invertebrates that help break down once-living (organic) material into foods that can be used by plants.
