Behavioural Ecology This subdiscipline studies the behaviour of individuals in an ecological context. In general, the behaviours studied are directed toward food, habitat, and mates. In all three areas, dominance and territoriality are common occurrences. Also, in all three genetics and evolution play or have played key roles in determining the behaviours we observe.

What regulates behaviour? There are both genetic and environmental components (i.e. the old ‘nature versus’ nurture controversy). Evidence of the importance of both components is wide-spread. One example: The learning of bird song in white-crowned sparrows… Eggs were gathered in the field and hatched in the lab. Chicks were separated into 3 groups 1. Raised in soundproof chambers unable to hear songs 2. Chicks allowed to hear songs for 5 months (still immature), then deafened 3. Control group

Males normally begin singing what is termed a ‘subsong’ at about 150 days, then the song is refined and practiced, until at about 200 days the ‘full’ song is sung. Here are sonograms of normal song, the subsong, and full song in the control group, then what is seen in experimental groups... Normal adult song -full song in control group The subsong sung at ~ 150 days w/exposure to adult song in isolated birds The full song

You can listen to the song portrayed by the sonograms at:

There is a genetic program which produces the first generalized song, the subsong. If raised in isolation, the song never changes from the subsong, which is viewed as a template. There is a closer match to normal song, even if the normal song is only heard before maturation.

Behaviours that are genetically programmed, and therefore virtually uniform across all members of a species, are called innate or instinctual. The behaviour is termed (by Tinbergen initially) a FIXED ACTION PATTERN or FAP The FAP is elicited by a sign stimulus. Particular, dramatic structures or behaviours may even elicit stronger responses, and are termed superstimuli.

At the opposite end of the spectrum are behaviours that are learned. An example: bees able to communicate the location of food sources to their hives. The behaviour is called a “waggle dance” and communicates both direction and distance to a food source, as well as the quality of that source. Here’s a diagram – you’ll see it again later:

Categories of behaviour 1. Territoriality Under what conditions does territoriality occur? When density increases When there is increased demand (and possibly competition) for resources When competition increases (e.g. for mates) When resources are aggressively defended

Some behaviourists categorize territories according to their purposes… type A - A large defended area for courtship, mating, nesting, and food gathering type B - A large defended area for breeding, but not foraging type C - A small defended area around the nest type D - An area for mating, for courtship activities only type E - An area defended for roosting or shelter

For any of these purposes or types of territory to occur, ANY RESOURCE THAT IS DEFENDED MUST HAVE AN “ECONOMIC GAIN” Defending a resource provides a benefit … the value of the resource. The benefits must exceed the costs of defending the territory. Otherwise the resource is not worth defending.

There is plenty of evidence for the economic model. Territory size should vary with the amount of resource available. In type A territories, there should be a negative correlation between the abundance of food and territory size. Here’s the re-drawn figure showing this in your text... Abundant resources- small territories and a larger number of birds Sparse resources- fewer, but larger territories to protect sufficient resources

It should also be apparent that a larger animal needs to hold a larger territory to defend sufficient food...

What determines the size of an animal’s territory? Simple models provide a rough answer. First, as territory size increases, benefits increase, but only up to a point. As territory size increases, the cost of defense also escalates… there is a larger area to defend there is contact (and potentially aggressive encounters) with a larger number of animals the time spent on defense means other functions may be neglected This suggests a cost-benefit model...

Neither very small nor very large territories are economically defendable. There is an optimum size… where benefits exceed costs to the greatest extent.

How useful is this model in explaining territory size? In a general sense, the model is correct. It correctly predicts that very large and very small territories are too costly. For example, in some birds low food abundance (low benefit) causes them to abandon defending territories. But when food abundance again increases, territories are again defended. However, optimal size is very sensitive to the exact shapes of cost and benefit curves. Therefore, the model is of very limited use in making quantitative predictions.

2. Communication In the context of behavioural ecology, communication means: not just the sending of a signal, but its reception by another, and that the signal is acted upon. Communication has many functions. Here are some… Status - identification of rank Begging - solicitation of parental care by offspring Alarm - warning of the presence of a predator Distress - a call for aid Threat - Show of imminent aggression Appeasement - attempt to dissuade aggression Sexual receptivity - identification of readiness to mate

The signal can be communicated in various ways… Chemical Accoustic Visual Tactile Range long long mediumshort Transmission slow fast fast fast rate Information slow fast fast fast fadeout time Location of difficultfairly easy easy easy sender Energy cost low high low low to moderate

Consider two signal communications… 1) Photinus (firefly) flashes - each species has a specific stereotyped pattern. Males flash, females signal receptivity by flashing back. This is a yes-no signal. 2) The honey bee waggle dance communicates what is called a graded signal, much more than yes-no. The honey bee flies in repeated figure-8s inside the hive. Angle to the vertical communicates the angle between a food source and the sun. The length of the straight, middle run indicates distance. The intensity of the waggle indicates quantity of food.

3) Aggression Aggression has the function of achieving dominance by either physical violence or the threat of it. Aggression can be involved in defense of territory, but dominance is most important in mating and reproduction. Aggression associated with mating has obvious fitness consequences… in wolves, only the  male mates. Aggression preventing other males from mating mean only his genes will be found in offspring. In sea lions, males guard harems of females against both other males & desertion by females

Sometimes, aggression is ritualized rather than injurious. To make evolutionary sense, this must be to the advantage of both animals. The risk of injury to both winner and loser is significant. Thus, rapid recognition of dominance protects both. The loser can try again later, having grown larger and stronger with time. Infanticide is not uncommon… In lions, when a male takes over a pride, cubs are killed and the male mates with females, assuring his genetic contribution to the young he raises. In white-footed mice, males that have not sired pups are infanticidal. Females may also kill pups outside their nests. This may be a response to apparent high density in the population.

4) Social Systems - Mating Systems Mating systems have 3 components: the number of mates an individual takes whether the male and female form a pair bond how long the pair bonding lasts

The evolution of these 3 components (# mates, pair bonding, length of bond) is driven by… Sexual selection and Demography Sexual selection results from the relative investment in reproduction… Males contribute (in most cases) only sperm Females contribute through egg production (more costly than sperm), gestation or incubation, and parental care of neonates. Thus, sexual selection is normally female choice of mate(s).

At one time mating systems were thought to represent cooperation between the sexes. More recently mating systems have been recognized to also represent conflict between the sexes. The conflict arises because… males can maximize reproductive success by mating many times females maximize their reproductive success by producing well-adapted, healthy offspring, (i.e. picking the best mate, not by mating multiple times

Let’s compare the energy expenditure on mating and parental care for (at least) monogamy and polygamy… Mating effort consists of energy spent on courting, mating, and mate defense or guarding Parental effort is that spent on feeding and caring for offspring.

There are a number of different mating systems… Mating systems in vertebrates: ClassParental CareMating System Birdsmale & femalemonogamy Mammalsfemalepolygamy Fish & usually the malepolygamy Amphibians Lizardsabsentvariable

Polygyny - males mate with more than 1 female. Not all males reproduce, there is important variance in male reproductive success. Likely to evolve when there is clumping, either of resources or females, and when there is not high synchrony in the receptive times of females.

When females clump, the polygyny is called: female defense polygyny Example: female gorillas travel in groups to avoid predation by leopards. Males defend these groups from other males. When resources are clumped, the polygyny is called: resource defense polygyny Example: an African bird, the orange-rumped honeyguide feeds on beeswax. Males defend bee colonies from other males. Females come to the bee colony as a food source, and copulate with the male defending it.