Competition in Animals

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By
Mr. Muhammad Irfan
Visiting Lecturer Zoology
University of Narowal, Punjab, Pakistan
January, 2024
ANIMAL COMPETITION

2. What is Competition ?
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Competition is a negative interaction that occurs
among organisms whenever two or more organisms
require the same limited resource.
Competition is an interaction between organisms
or species in which both the species are harmed.
Limited supply of at least one resource (such as
food, water, and territory) used by both can be a
factor(Begon et al., 1996).

3. WHAT DO ORGANISM COMPETE FOR ?
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Organisms compete for the resources they need to
survive
Air
Water
 food, and
space.
Animals and plants that have specific life history
requirements, like cavity-nesting birds, or animals with
obligate feeding behaviors, have a more difficult time
competing.
These resources can be limiting factors for where
organisms are distributed, and competition for them can
be fierce.

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Competition Con’t
Most competition between organisms of the same species surround scarce
resources, like water or food

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 G. F. Gause proposed the competitive exclusion principle
in 1934
“species cannot coexist if they have the same niche”
The Competitive Exclusion Principle
What Is A Niche?
The word "niche" refers to a species' requirements for
survival and reproduction.
These requirements include both resources (like food) and
proper habitat conditions (like temperature, pH ).

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The Competitive Exclusion Principle
1: a smaller (yellow) species of bird forages across whole tree.
2: a larger (red) species competes for resources.
3: red dominates in middle for the more abundant resources. Yellow adapts to
new niche, avoiding competition

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 Gause reasoned that if two species had identical niches
(required identical resources and habitats) they would
attempt to live in the exact same area and would compete
for the exact same resources.
If this happened, the species that was the best
competitor would always exclude its competitors from that
area.
Therefore, species must at least have slightly different
niches in order to coexist.
Competitive Exclusion Principle Con’t

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Forces of Competition
Defensive Behavior
When an animal has found a space that contains all the resources it needs to
survive, it wants to hold on to it. This is why many animals are territorial; they
defend their territory which contains those resources.
Aggressive Behavior
Animals exhibit aggressive behavior when one of their resources is
compromised(Benton, 2012)
Males may compete over an existing territory, available females, nesting sites,
or breeding rights in a social hierarchy.
Defensive behaviors often lead to aggression if problems can’t be sorted out
through threatening displays or intimidation

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By mechanism
Biologists typically recognize two types of competition: interference and
exploitative competition.
1. During interference competition, organisms interact directly by fighting for
scarce resources. This occur directly between individuals via aggression
etc.
 For example, large aphids defend feeding sites on cottonwood leaves by
kicking and shoving smaller aphids from better sites.
An elephant might be able to prevent other animals from using a water hole,
but would be unlikely to be able to chase them away from a river with its long
banks.
Another example of this can be seen between the ant Novomessor
cockerelli and red harvester ants, where the former interferes with the ability
of the latter to forage by plugging the entrances to their colonies with small
rocks.

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Male-male competition in red deer during rut is an example of interference
competition

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Exploitation competition
Exploitation competition Occurs indirectly through a common limiting
resource which acts as an intermediate.
For example, use of resources depletes the amount available to others,
or they compete for space. Also known as exploitative competition.

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BY SPECIES
 Intraspecific competition occurs when members of the same species compete
for the same resources in an ecosystem
 The organism that obtains less resources, will usually perform less well than if
it lives alone
Interspecific competition may occur when individuals of two separate species
share a limiting resource in the same area.
. Interspecific competition has the potential to alter populations, communities
and the evolution of interacting species.
INTRASPECIFIC COMPETITION
INTERSPECIFIC COMPETITION

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An example among animals could be the case of cheetahs
and lions; since both species feed on similar prey, they are
negatively impacted by the presence of the other because
they will have less food (Fedriani et al., 2000)

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How to Avoid Competition
Geographic Isolation
One method of isolation is geographic isolation- not being in the same place at
the same time.
This isolation can occur through animals having different geographic
distributions or by participating in seasonal migrations
For Example Salmon fish ,Wild beasts and horses
Geographic separators might be an expanse of land, a mountain range, a body
of water, or an elevation gradient

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Mechanical Isolation
Behavioral Isolation
This occurs when animals have contradictory behaviors that prevent them from
competing with each other
For example, by day, birds rule the air. By night, however, bats rule the roost.
Come dusk there is a taxonomic tango when the diurnal (active by day) organisms
retire for the evening and the nocturnal (active by night) organisms commence their
daily follies. By the cover of night nocturnal organisms avoid competitive interactions
with their diurnal counterparts.
Today there are many animals that have morphological differences that directly
allow them to avoid competition with other organisms..
Like giraffes who’s browse line is way above that of the other browsers it resides
with, and
Hyenas whose jaw structure and musculature is strong enough to consume the
hides and bones of carcasses left behind by other predators.

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Foraging habits are another way that organisms can avert
competing with each other.
A generalist predator; e.g red-tailed hawk, they eat anything
from rodents to reptiles to other birds.
Specialist predators, however, like the osprey, which eats strictly
fish, are limited in their prey selection as well as their geographic
range because they have to live in areas where their prey resides.
Herbivorous rhinos deal with this conundrum by consuming
different parts of plants.
White rhinos have flat, wide lips for grazing grasses while black
rhinos have pointed, dexterous lips for browsing shrubs.
FORAGING

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The Purple Sea Star (Pisaster ochraeus), below, several of these sea
stars (which range in color from purple to orange) are feeding. Once
again, the mussels are black and the barnacles a lighter color.

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The barnacles, the mussels attach themselves to a rock and filter food
from the water

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The American Alligator (below left) and the American Crocodile (below right) are similar
species but they avoid competition by occupying different habitats

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Begon, M.; Harper, J. L.; Townsend, C. R. (1996) Ecology: Individuals, populations
and communities Blackwell Science.
Sahney, S.; Benton, M.J.; Ferry, P.A. (2010). "Links between global taxonomic
diversity, ecological diversity and the expansion of vertebrates on land" (PDF).
Biology Letters. 6 (4): 544–547.
Jardine, P.E.; Janis, C.M.; Sahney, S.; Benton, M.J. (2012), "Grit not grass:
Concordant patterns of early origin of hypsodonty in Great Plains ungulates Glires",
Palaeogeography, Palaeoclimatology, Palaeoecology, 365-366: 1–10
Holt, Robert D. (1977-10-01). "Predation, apparent competition, and the structure of
prey communities". Theoretical Population Biology. 12 (2): 197–229.
Van Nouhuys, S.; Hanski, I. (2000). "Apparent competition between parasitoids
mediated by a shared hyperparasitoid". Ecology Letters. 3 (2): 82–84.
Fedriani, J. M., T. K. Fuller, R. M. Sauvajot and E. C. York. (2000). Competition and
intraguild predation among three sympatric carnivores. Oecologia, 125:258-270.
Gause, G.F. (1934). The struggle for existence. Baltimore, MD: Williams & Wilkins.
MacArthur, R. and Wilson, E. O. (1967). The Theory of Island Biogeography,
Princeton University Press (2001 reprint)

22. THANK YOU ALL