We are beginning to piece together a more sophisticated understanding of ecosystems
and their inhabitants. Let’s now discuss behavioral ecology, or the ramifications
of organismal behavior on an ecosystem. First let’s talk about foraging. You may
have heard this term before - from your parents, asking what you are foraging for
from the refrigerator at such a late hour. In the wild, this simply refers to searching for food
resources. It’s a lot tougher to maintain stable food stores without a refrigerator, and unlike us,
animals have to physically find their food. An animal’s foraging efficiency directly impacts its
fitness because it plays a role in how well that animal will be able to survive and reproduce. The
ecological “payoff” of this efficiency is a higher ratio of energetic gain to the cost of foraging.
In other words, animals experience pressure associated with figuring out how to best maximize
energy per unit time. Learning quickly is key to successful foraging behavior. Since environments
are constantly changing, the ability to adjust foraging behavior is of ultimate importance for
an animal’s survival. In primates, the young learn from their elders - simply by watching
others forage and then copying that behavior. This trains the young on what is safe to eat as
well as how to eat it. Foraging “innovation” is when an animal eats a new food or uses a
new foraging technique in response to a dynamic living environment. This is considered learning
because it involves behavioral “plasticity” on the animal’s part. An example of this type
of foraging is birds following tractors and eating frogs or insects killed by the tractor.
Now let’s discuss parasitism. Parasitism is a form of symbiosis. It is considered a long-term
relationship - but not a healthy one! One organism - the parasite - causes harm to another, the host,
for its own survival. The parasite utilizes the host as a habitat and depends on it for acquiring
resources. Some common examples of parasites include those which live on the skin and suck
on the blood of their animal hosts, like ticks, lice, leeches, and fleas. The three main classes
of parasites that can cause disease in humans include protozoa, helminths, and ectoparasites.
Protozoa are microscopic single-celled organisms. These can live in a human’s
intestine, as well as in the blood and tissues, when transmitted via an arthropod vector,
like a mosquito or tick. They’re tiny but they pack a nasty punch in the gut, quite literally.
Helminths are large, multicellular organisms that are generally visible to the naked eye
when in adult phase. Common examples of these include flatworms like tapeworms, and roundworms.
Finally, ectoparasites are the blood-sucking arthropods, like mosquitos, ticks, and fleas. They
can cause disease in their own right, but they are even more important as vectors or transmitters
of different pathogens. More on all of these species can be found in the zoology series.
Somewhat related to parasitism there is exploitation. Exploitation is the interaction
between populations that enhances the fitness of one individual while reducing the fitness of the
exploited individual. For example, predators kill and consume other organisms, instead of relying
on them for a prolonged period of time, which is different from parasitism. Continuing from there,
we have mutualism. A mutualistic relationship is when two organisms of different species
work together, each benefiting from the relationship. Humans require oxygen for
life and plants use the exhaled carbon dioxide from humans for photosynthesis. Both humans
and plants are mutually benefited. Certain insects like ants and termites rely on each
other to work as a team to build mounds where the group will live. In the ocean,
clownfish and sea anemones have a mutualistic relationship where both species benefit:
the anemone provides the clownfish with shelter and protection from predators, while the clownfish
provides the anemone with nutrients in the form of waste, while also scaring off predator fish.
Now let’s examine competition and its influence on natural selection. Intraspecific competition
is the type of competition that occurs between members of the same species. For example,
consider males of the same species competing for mates in the same geographical area. This
type of competition is a basic driver of natural selection because it leads to the evolution of
better adaptations within a species. Competition, more broadly, can be described as an interaction
between organisms or species in which both require the same resource. Besides a mate,
this could include things like food, water, or territory, that is in limited supply. When
two species compete for the same limiting resource, reduction of the niche overlap may
lead to evolutionary changes in both species. Here, niche overlap describes the situation in
which co-occurring species share part of their space with each other. High overlap may lead
to conflict. The dominant species might not change and can even expand its niche,
reducing space for other species, leading to even more competition. Other than the classic examples
of animals fighting over territory, food, or water, plants also compete with each other but for
light exposure, growing space, and pollinators, while microbes compete for chemical substrates.
Mate choice can be defined as the process that occurs whenever the effects of traits expressed
in one sex leads to non-random mating with members of the opposite sex. Why is it important? Because
it contributes to selection of a vast array of traits, some of which are very beneficial
from an evolutionary standpoint. Bright colors, exhibitions of strength, and rhythmic sounds all
play a role in trying to attract mates. Usually the males take the lead on this,
although in humans, females may show off as much as males. For many birds and mammals,
sexual selection appears to favor females who choose mates that provide them with some direct
benefit to increase their own chances of survival and the survival of their offspring. This can
include food, a safe home, or fewer parasites. Lastly let’s examine social groups. Social
behavior and groupings correspond to a set of interactions among individuals of the same
species, leading to some benefit. The most highly social animals form tightly knit colonies. A good
example of this is ants. Many social behaviors of animals are adaptive - meaning that being social
increases an animal’s fitness, and therefore its lifetime reproductive success. What are
the reasons that animals might group together? One reason would be to fend off predatory aggression.
A pack is stronger - and looks more intimidating - than a solitary animal. Then of course there
are the intricate behaviors of ants and bees in collecting resources according to specific tasks.
Social costs are a problem - for example, herd animals may overgraze an area,
leading to not enough food for the individual animals. But oftentimes, the costs are much
smaller than the overall benefits of defense against predation. With aspects of behavioral
ecology understood, it’s now time to zoom out and examine entire populations next.