Examples of Behavior Patterns

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This page offers brief examples of patterns in behavior and intelligence. Proposed explanations are offered here.


According to Wikipedia, altruism “ is a well-documented animal behavior, which appears most obviously in kin relationships but may also be evident amongst wider social groups, in which an animal sacrifices its own well-being for the benefit of another animal.

Vampire bats regularly regurgitate blood and donate it to other members of their group who have failed to feed that night. In numerous bird species, a breeding pair receives help in raising its young from other ‘helper’ birds, who protect the nest from predators and help to feed the fledglings. Vervet monkeys give alarm calls to warn fellow monkeys of the presence of predators, even though in doing so they attract attention to themselves, increasing their own chance of being attacked. In social insect colonies (ants, wasps, bees and termites), sterile workers devote their whole lives to caring for the queen, constructing and protecting the nest, foraging for food, and tending the larvae.

Foraging and Task Allocation in Ant Colonies

Melanie Mitchell, in her paper Complex Systems:Network Thinking , provides two examples of large-scale intelligent and adaptive behaviors in ant colonies. First, the ability of ants to optimally and adaptively allocate labor in foraging for food and, second, the ability to adaptively allocate ants to different tasks as needed by the colony. Both types of behavior are accomplished with no central control. Her description (in italics) is paraphrased below.

In many ant species, foraging ants in a colony set out moving randomly in different directions. When an ant encounters a food source, it returns to the nest, leaving a pheromone trail. When other ants encounter a pheromone trail, they are likely to follow it. The greater the concentration of pheromone, the more likely an ant will be to follow the trail. If an ant encounters the food source, it returns to the nest, reinforcing the trail. In the absence of reinforcement, a pheromone trail will dissipate. In this way,ants collectively build up and communicate information about the locations and quality of different food sources, and this information adapts to changes in these environmental conditions. At any given time, the existing trails and their strengths form a good model of the food environment discovered collectively by the foragers.

Task allocation is another way in which an ant colony regulates its own behavior in a decentralizedway. D.M. Gordon has studied task allocation in colonies of Red Harvester ants. Workers in these colonies divide themselves among four types of tasks: foraging, nest maintenance, patrolling, and midden (refuse sorting) work. The numbers of workers pursuing each type of task adapts to changes in the environment. Gordon found, for example, that if the nest is disturbed in some small way, the number of nest maintenance workers will increase. Likewise, if the food supply in the neighborhood is large and high quality, the number of foragers will increase. How does an individual ant decide which task to adopt in response to nest-wide environmental conditions, even though no ant directs the decision of any other ant and each ant only interacts with a small number of other ants? The answer seems to be that ants decide to switch tasks both as a function of what they encounter in the environment and as a function of their rate of interaction with ants performing different tasks. For example, an inactive ant (one not currently performing a task) who encounters a foreign object near the nest has increased probability of doing nest-maintenance work. In addition, an inactive ant that encounters many nest-maintenance workers entering and leaving the nest will also have an increased probability of adopting the nest-maintenance task; the increased activity in some way signals that there are important nest maintenance tasks to be done. Similarly, a nest-maintenance worker who encounters many foragers returning to the nest carrying seeds will have an increased probability of switching to foraging; the increased seed delivery signals in some way that a quality food source has been found and needs to be exploited. Ants are apparently able to sense, through direct contact of their antennae with other ants, what task the other ants have been engaged in, by perceiving specific chemical residues associated with each task. Gordon points out that the proposed mechanism of task switching based on interaction rate can explain an initially puzzling finding of her experiments. She found that perturbing a nest by placing toothpicks around it increased the number of nest maintenance workers, who proceeded to assist in removing the toothpicks. However, this increase was more reliably seen in older colonies (ones that have produced more generations of ants) than in younger colonies. The individual ants in each type of colony were the same age, and ants presumablydo not have the ability to pass on complex information about tasks and task switching to their offspring. But it does turn out that older colonies are larger than younger colonies, and in larger colonies ants relying on individual interactions for information would be ableto obtain better statistics about the proportion of ants currently doing each task. Thus onewould expect a stronger effect in larger colonies, which is what Gordon observed.

Bird flocking, fish schooling, animal herding, epidemics

Flocking, schooling, herding, and epidemics are all names for a phenomena called emergent behavior, or self-organization. The “emergent behavior” refers to the overall behavior of the group. The macro-level behaviors associated with bird flocks, fish schools, animal herds, and contagious diseases are generally understood. In all cases, group behavior results from the independent actions of individuals within the group who, without a leader, all following the same set of rules (usually rules of engagement with nearest neighbors). These rules are acted upon by each individual from limited knowledge of local information only. Group behavior is a systematic behavior that an individual alone could never accomplish. Group behavior cannot be predicted from these individual actions.
While the origin of group behavior is generally understood and can be easily simulated on a computer, the underlying reasons for the individual behavior that results in group self-organization are not understood. Typically, explanations of individual behavior are relegated to the “black box” that we call “instinct”. Nonetheless, there have been some studies on interrelationships between individuals in a group.

A well studied example of group behavior resulting from self organization is fish schools. In the early 1980s, Brian Partridge and others performed studies on fish visual abilities and their pressure sensing lateral lines. They showed that fish can sense and keep a distance from their nearest neighbors. In 1986, Craig Reynolds developed computer simulations of bird flocks and fish schools that mimicked the behavior of real self-organizing biological systems. Later, David Hooper developed Cool School, a realistic simulation of fish schools and their interactions with predators.

Both the live experiments and the simulations showed that group behavior at a system level can result from individual behaviors. Reynolds describes the three necessary rule sets for each individual with respect only to its nearest neighbors to be keeping a defined separation, aligning in the same direction, and maintaining a cohesion. The connectivity within the school, or a flock, or a herd comes from behavioral interactions between individuals and not physical relationships. Scott Camazine notes that the distinguishing features of all self organizing systems are large numbers of individuals within the system, large numbers of individual interactions, simple individual rules of interaction, decentralized control, and emergent properties. The work described above still leaves the question of how and why individuals behave the way they do.

Gray whale migration

One of the longest of animals migrations known to man is the annual 12,000 mile round trip gray whale migration between the Bering Sea and the lagoons of Baja California in Mexico. Each summer, these 40-50 foot creatures feed in the Bering Sea. In October, they begin a three month journey south, arriving in Baja California around December. In three shallow lagoons along the Pacific coast of the Baja Peninsula, the whales give birth and breed. In February, males and pregnant females start heading north. In March and April, females and their calves likewise head north.

There are many animal, bird, and insect species that migrate. Reasons given for these migrations are generally speculative and anthropomorphic. And in most cases, an organism’s mechanism for navigation during a migration is unknown.

Humpback Whale Bubble Nets

According to Wikipedia, humpback whales sometimes work together to catch prey by creating “bubble nets” to trap small fish. A group of whales swims in a shrinking circle blowing bubbles below a school of prey. The shrinking ring of bubbles encircles the school. The small fish believe they are trapped inside the ring and confine themselves it in an ever-smaller cylinder. The whales then suddenly swim upward through the 'net', mouths agape, swallowing thousands of fish in one gulp. The plated grooves in the whales mouth allow the creature to easily drain all the water that was initially taken in. Many times, there is a division of labor amongst the animals. The bubble ring can be up to 30 meters in diameter through  the cooperation of a dozen animals. Some whales blow the bubbles, some dive deeper to drive fish toward the surface, and others herd prey into the net by vocalizing. Humpbacks have been observed bubble net feeding alone as well.

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