Population cycle
Encyclopedia
A population cycle in zoology is a phenomenon where population
s rise and fall over a predictable period of time. There are some species where population numbers have reasonably predictable patterns of change although the full reasons for population cycles is one of the major unsolved ecological problems. There are a number of factors which influence population change such as availability of food, predators, diseases and climate.
, the Archbishop of Uppsala
in central Sweden, identified that species of northern rodent
s had periodic peaks in population and published two reports on the subject in the middle of the 16th century.
In North America, the phenomenon was identified in populations of the snowshoe hare
. In 1865, trappers with the Hudson's Bay Company
were catching plenty of animals. By 1870, they were catching very few. It was finally identified that the cycle of high and low catches ran over approximately a ten year period.
The most well known example of creatures which have a population cycle is the lemming
. The biologist Charles Elton
first identified in 1924 that the lemming had regular cycles of population growth and decline. When their population outgrows the resources of their habitat, lemmings migrate, although contrary to popular myth, they do not jump into the sea.
. There are other species which have irregular population explosions such as grasshoppers where overpopulation results in locust
swarms in Africa and Australia.
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
s rise and fall over a predictable period of time. There are some species where population numbers have reasonably predictable patterns of change although the full reasons for population cycles is one of the major unsolved ecological problems. There are a number of factors which influence population change such as availability of food, predators, diseases and climate.
Occurrence in mammal populations
Olaus MagnusOlaus Magnus
Olaus Magnus was a Swedish ecclesiastic and writer, who did pioneering work for the interest of Nordic people. He was reported as born in October 1490 in Östergötland, and died on August 1, 1557. Magnus, Latin for the Swedish Stor “great”, is a Latin family name taken personally, and not a...
, the Archbishop of Uppsala
Uppsala
- Economy :Today Uppsala is well established in medical research and recognized for its leading position in biotechnology.*Abbott Medical Optics *GE Healthcare*Pfizer *Phadia, an offshoot of Pharmacia*Fresenius*Q-Med...
in central Sweden, identified that species of northern rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s had periodic peaks in population and published two reports on the subject in the middle of the 16th century.
In North America, the phenomenon was identified in populations of the snowshoe hare
Snowshoe Hare
The Snowshoe Hare , also called the Varying Hare, or Snowshoe Rabbit, is a species of hare found in North America. It has the name "snowshoe" because of the large size of its hind feet and the marks its tail leaves. The animal's feet prevent it from sinking into the snow when it hops and walks...
. In 1865, trappers with the Hudson's Bay Company
Hudson's Bay Company
The Hudson's Bay Company , abbreviated HBC, or "The Bay" is the oldest commercial corporation in North America and one of the oldest in the world. A fur trading business for much of its existence, today Hudson's Bay Company owns and operates retail stores throughout Canada...
were catching plenty of animals. By 1870, they were catching very few. It was finally identified that the cycle of high and low catches ran over approximately a ten year period.
The most well known example of creatures which have a population cycle is the lemming
Lemming
Lemmings are small rodents, usually found in or near the Arctic, in tundra biomes. They are subniveal animals, and together with voles and muskrats, they make up the subfamily Arvicolinae , which forms part of the largest mammal radiation by far, the superfamily Muroidea, which also includes rats,...
. The biologist Charles Elton
Charles Sutherland Elton
Charles Sutherland Elton FRS was an English zoologist and animal ecologist. His name is associated with the establishment of modern population and community ecology, including studies of invasive organisms.-Personal life:...
first identified in 1924 that the lemming had regular cycles of population growth and decline. When their population outgrows the resources of their habitat, lemmings migrate, although contrary to popular myth, they do not jump into the sea.
Other species
While the phenomenon is often associated with rodents, it does occur in other species such as the ruffed grouseRuffed Grouse
The Ruffed Grouse is a medium-sized grouse occurring in forests from the Appalachian Mountains across Canada to Alaska. It is non-migratory.The Ruffed Grouse is frequently referred to as a "partridge"...
. There are other species which have irregular population explosions such as grasshoppers where overpopulation results in locust
Locust
Locusts are the swarming phase of short-horned grasshoppers of the family Acrididae. These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory...
swarms in Africa and Australia.
Relationships between predators and prey
There is also an interaction between prey with periodic cycles and predators. As the population expands, there is more food available for predators. As it contracts, there is less food available for predators, putting pressure on their population numbers.Online references
- Hutchinson Encyclopaedia article
- University of Minnesota Extension Service article on wildlife populations containing a section on popuation cycles
- National Parks Service Document on population cycles
- Paper by Professor Stenseth, University of Oslo on lemming cycles
- Paper by Baltensweiler, W. & Fischlin, A., 1988. The larch bud moth in the Alps
Software
Creatures! High School interactive simulation program that implements an agent based simulation of grass, rabbits and foxes.Other references
- Encyclopædia Britannica Online 25 August 2005 "Population Ecology" article section on Population Cycles
- Errki Korpimaki and Charles J Krebs "Predation and Population Cycles of Small Mammals" Bioscience November 1996 Volume 46, Number 10
Further reading
- Alan Berryman, Population Cycles, Oxford University Press US, 2002 ISBN 0-19-514098-2