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What is Dispersal in Ecology?

Christina Keathley, Elizabeth Friedl
  • Author
    Christina Keathley

    Christina graduated with a Master's in biology from the University of Louisiana at Lafayette. She is a current PhD student in biology at Wake Forest University, and has been teaching undergraduate students biology for the last three years.

  • Instructor
    Elizabeth Friedl

    Elizabeth, a Licensed Massage Therapist, has a Master's in Zoology from North Carolina State, one in GIS from Florida State University, and a Bachelor's in Biology from Eastern Michigan University. She has taught college level Physical Science and Biology.

Learn the definition of dispersal in biology. Discover the different types of dispersal, including active and passive dispersal, and review an example of animal dispersal. Updated: 10/25/2021

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Dispersal in Ecology

Dispersal is the necessary action of organisms moving from their point of origin (such as parental plant or original family group) to a new location. Ecology is the study of natural systems, such as organisms and the environments they live in. Dispersal ecology is thus the budding branch of science that has developed to understand the movement of organisms and how it relates to ecosystem health and function. In this lesson, investigate dispersal to understand the following information:

  • How is dispersal defined in biology?
  • What are the different types of dispersal?
  • What are the cost and benefits associated with dispersal?
  • What are some examples of dispersal?

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Dispersal Definition

Dispersal may be casually referred to as movement or spread. However, the dispersal definition in biology specifically refers to the movement of organisms away from an initial population or location to a new area.

Types of Dispersal: Active and Passive Dispersal

Ecological dispersal is either active dispersal or passive dispersal. Active dispersal involves activity (in the form of movement) from the organism engaging in dispersal. This means that it is typically restricted to vagile animals, such as those that can walk, fly, or swim. Because of this, active dispersal is generally considered density-dependent dispersal. This is because as an ecosystem gets crowded, the organisms within that ecosystem can disperse outward to find uninhabited territory with available resources.


Animals that can walk disperse via active dispersal.

A picture of a tiger, which uses active dispersal.


Passive dispersal, on the other hand, is dispersal that cannot occur without assistance from the ecosystem. Plants are typical examples of passive dispersers, as they do not have the ability to get up and walk on their own. Instead, many plants require mechanisms (such as birds or wind) to move their seeds from one place to another. Because these organisms cannot move from an area of high density to an area of low density, passive dispersers engage in density-independent dispersal.

Mechanisms of Dispersal

Animals that can move are fortunate to disperse by their own accord. However, organisms that are not vagile and thus fixed in place must rely on other mechanisms to spread from one location to another. There are five dispersal mechanisms for passive-dispersers:

  • Gravity dispersal
  • Wind dispersal
  • Water dispersal
  • Animal dispersal
  • Ballistic dispersal

Gravity Dispersal

Gravity dispersal occurs when an organism is dispersed thanks to the force provided by gravity. Consider an apple in a tree. As that fruit ripens, it becomes heavy and difficult for the branch to hold. Eventually, the apple may fall from the tree as the branch weakens and lands on the ground. When it hits the ground, the apple can crack and spread its seeds directly at the base, or may roll away, rot, and disperse its seeds in another location.

Gravity dispersal is most effective for species that don't suffer from close proximities between species, such as some grasses and herbs. Because these plants can live relatively close to each other without struggling to find resources, the development of a young plant near the parent plant will not cause major harm to the parent plant.

Wind Dispersal

Many organisms rely on wind to carry them from one place to another. Plants are another common example of organisms that depend on wind, as some species develop seeds with specialized structures that allow them to be carried long distances by wind.


Dandelion seeds are made to disperse through wind, a type of passive dispersal.

A photograph of a dandelion engaging in wind dispersal, a type of passive dispersal.


Interestingly enough, some vagile organisms also rely on wind dispersal. Spiders may not be able to travel long distances by walking alone. To combat this, some spider species create small pieces of web that get swept up in the breeze. By holding onto this web, spiders are able to travel long distances without wasting energy or time by walking. This form of transportation is called ballooning.

Water Dispersal

Water dispersal occurs when organisms rely on the current from water to assist them in dispersal. Again, plants are common water dispersers as spores and seeds that fall into bodies of moving water are carried down stream. There are a variety of animals that depend on water dispersal as well. Some fish larvae are so small and thin that they aren't strong enough to swim through water. In this case, they depend on the movement of the water to move them throughout their environment until they develop into a more mature animal. The man-of-war jellyfish (which isn't really a jellyfish at all) cannot actively swim and thus disperses throughout the ocean based on currents.


The Man-of-War Jellyfish uses passive dispersal via water because it cannot swim.

An illustration of a passive disperser, the Man of War Jellyfish.


Animal Dispersal

Animal dispersal is commonly enlisted by plants and typically occurs when a seed clings to or is ingested by an animal. Seeds that have specialized structures are able to stick to fur as an animal walks past a parent plant. That seed may stick on an animal for a long period of time until it is removed or falls off naturally. Typically, the animal has moved by then, and thus the seed is deposited in a new location.

Plants that have developed tasty fruits and seeds benefit from animal dispersal through ingestion. When the animal eats the fruit, they consume the seed as well. The seed travels through the animal's digestive system and is relocated in a new area when the animal defecates. Some plants rely so heavily on animal dispersal that their seeds cannot properly germinate without traveling through a digestive system. This is a type of scarification, a process that damages an external seed coat to promote germination and growth. Wind, water, ballistic, and gravity are abiotic (non-living) dispersal mechanisms. Animal dispersal is a biotic (living) dispersal mechanism.

Ballistic Dispersal

Ballistic dispersal is a unique and poorly known type of dispersal. Some plant species have developed specialized mechanisms to spread their seeds on their own. These plants typically form a unique pod or pocket for their seeds to form in. As the seeds develop, the pod is moist and full of nutrients. When the seeds finish developing, this pod no longer requires the delivery of fresh water and nutrients for seed formation and becomes unproductive. Through heat and exposure to sunlight it begins to dry out. When the pod becomes too dry it pops open and the seeds are scattered in multiple directions. While this type of dispersal does not result in long distance movement away from the parent plant, it usually provides enough distance for that species to grow and develop.

Dispersal Range

The dispersal range for many organisms is becoming smaller and smaller as human development continues to rise. This is largely due to habitat reduction and fragmentation. When habitats are reduced in size, there are fewer areas for organisms to move to, and thus overcrowding may become an issue. When habitats are fragmented (when a highway bisects them, for instance) organisms may be physically incapable of dispersing from one region to another. This is especially true for organisms that are sensitive to light or sounds and thus avoid roadways altogether.


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Frequently Asked Questions

What are five ways that sessile organisms disperse?

Sessile organisms can disperse by both abiotic (non-living) and biotic (living) methods. The abiotic methods include transportation by wind, water, gravity, and ballistic force. The biotic method is via an animal transporter.

Why is dispersal important in evolution?

Dispersal is an important concept in evolution. Dispersal promotes the flow of genes between subpopulations and thus results in heterogenous gene pools with decreased risk of extinction.

What is an example of active animal dispersal?

Active animal dispersal refers to the movement of animals away from their place of origin. A type of animal dispersal is observed in large predators. When they mature, they are often chased out of their parent's territory and must establish their own territory in a new area.

What is seed dispersal by animals?

Seed dispersal by animals occurs when an animal moves a seed by either accidentally transporting it or ingesting it. It is the only biotic dispersal mechanism for passive dispersers.

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