Topic 8: Dispersal, Migration, Habitat Selection, and TerritorialityDispersal: short-distance, 1-way movementMigration: long-distance, 2-way movements (many times circannual cycle)Dispersal reduces competition and inbreeding, and can improve the ability to find food.1. Identical amounts of food but different animal densities, animals will move from dense areas to less dense areas.2. Identical numbers of animals but different food quantities, more animals will move to areas of greater food availability.Three patterns of dispersal (not restricted to animals – plants also can disperse): random, regular, and clumped.Migration occurs in response to changes in the environment. Technological advances and empirical evidence of global climate change affecting migration have recently increased interest from animal behavior researchers.Zugunruhe is a German term that has been incorporated into the vocabulary of animal behavior to describe the restlessness of migratory animals prevented from migrating.Animals can use almost any environmental stimulus to orient and navigate. Common examples include: Sun, stars (celestial), odors, earth’s magnetic field.Emlen funnels are a common technique to measure Zugunruhe or the ability of an animal to navigate from a point of departure to a point of arrival. Examples of experimentation regarding migration include sea turtles navigating by the earth’s magnetic field, and pigeons using either the sun or magnetic fields depending on whether the pigeon can see the sun or not.One difficulty in establishing earth’s magnetic field as an environmental compass has been a lack of evidence for neural transduction. This hurdle is slowly being overcome by research on Tritonia (mollusks), or more recently at the BaylorCollege of Medicine on pigeons. (http://www.nytimes.com/2012/04/27/science/study-sheds-light-on-how-pigeons-navigate-by-magnetic-field.html?_r=0)Monarch butterflies migrate from sites in North America to sites near Mexico City in the fall. They accurately find their over-wintering area despite the fact that the migrating butterflies are 3-4 generations removed from the animals that moved northward and laid eggs on milkweed. So the southward migrating animals have obviously never been to the over-winter site before. This is still under investigation.Habitat Selection involves complex and multidimensional decisions with many biotic and abiotic variables that must present “trade-offs” or “cost/benefit” aspects.Home ranges are delineated areas of repeated use by animals and are not defended.Territories are delineated and defended so the animal (or mated pairs, or families) have exclusive use of the resources. Home ranges often overlap, but territories rarely if ever overlap.Leks are temporary gatherings of males for the purposes of competitive mating displays. The most dominant males are usually located in the center of the lek. Most leks are ground-dwelling birds, but Uganda Kob and Fruit Bats also show lekking behavior.One of the models to explain and predict where animals are located is the Ideal Free Distribution Model. It basically states that animals will distribute themselves in habitats that reflect the availability of resources in different habitats so that animals will have equal access to the resources and thus equal fitness. This is also called the Resource Matching Rule. However, some animals will invariably out-compete their conspecific rivals for access to the resources and show “despotic” behavior.Territoriality usually has 2 stages: the acquisition of the territory, and the maintenance of a territory.The “Dear Enemy Effect” is important in lowering the necessity for physical combat among territorial species in maintaining territories. In the Dear Enemy Effect, animals learn who their neighbors are and reduce the level of vigilance on the assumption that their neighbor will not invade their territories and can be trusted. An example of testing the Dear Enemy Hypothesis was performed in Hooded Warblers using the vocalizations of territorial males. In most established territorial species, actual combat is reduced to threat displays which can vary widely among animal species, including lateral displays or showing weaponry.Learning can also play a role in acquiring a territory. Judy Stamps showed that juvenile Anole lizards will choose a territory that had been previously occupied rather than an equally well-endowed territory that the juvenile observed had not previously contained a territorial male.Aggressiveness (“hawk” strategy) and passivity (“dove” strategy) can both be found in a population, but the proportion of conspecifics employing each strategy is limited. This can result in an Evolutionary Stable Strategy where 2 different behaviors can be tolerated, but the proportion of the population showing each strategy is limited but stable over many generations.In Summary:Fighting and territorial acquisition can depend on many factors thatsometimes involve a trade-off (cost/benefit analysis).1. Usually only individuals in good body condition can acquire and defend a territory.2. Territory size should be negatively correlated with resource density and competitor density.3. Fighting can escalate from low-cost behaviors to more intense and possibly dangerous behaviors.4. Escalation in a fighting scenario can occur not only for territorialacquisition but for mates as well.Another question about territoriality is whether a non-territorial animal can gain the advantages of a territory without establishing one himself? The answer often is“Yes.”For instance, satellite and sneaker males do not establish their own territories, but will attempt to mate with females that are attracted to the territorial males.• Satellite male - Alternative, parasitic mating tactic in which a male remains near a territorial male to intercept females that are attracted to the territorial male• Sneaker male - Alternative, parasitic mating tactic in which a male attemptsto avoid detection so that he can quickly enter a parental territory to fertilize eggs being deposited in a nestParental (territorial), satellite, and sneaker strategies can all be seen in the Bluegill Sunfish. This is an example of an Evolutionary Stable Strategy. Evidence of this is that 85% of the males in Lake Opinicon are Satellite/Sneakers and 15% are Parentals.In other species such as the Pied Wagtails, satellites can be tolerated on a territory