Chapter 50-Behavioural Ecology Flashcards
Behavioural Ecology
study of the behavioural adaptations that evolved in response to ecological selection pressures
Proximate (or mechanistic) causation
explains how actions occur
Ultimate (or evolutionary) causation
explains why actions occur
-based on natural selection. Behaviour is a part of phenotype
EX: Do male redback spiders benefit from being eaten by their mates?
- The male actively solicits his own consumption, and females never eat males that do not somersault onto their jaws
- This allows him to insert two sperm packets into female sperm receptacles
How is the process with these spiders done?
Before a male mates, an abdominal constriction forms and protects his heart and other vital organs.
- As a result, he survives the attack long enough to insert his second sperm package, ↑ the number of spiderlings
(can transfer twice as many sperm)
- more successful at plugging the receptacles of their mates, preventing other males from inserting additional sperm
EX: Argentine ant behaviour
In their native range, the ants live in colonies and defend territories by fighting with neighbours
In S California, ants show no aggression, move among adjacent nest, and thus form “supercolonies”
Proximate Cause of argentine ants
ants identify each other via scent - hydrocarbon tags
- This scent is genetically determined, but the ants have almost no genetic variation in this allele, so an ant can’t tell if another is from its colony or not, but see native ants, with unfamiliar scents, as enemies
Ultimate causes of argentine ants
Supercolonies make Argentinian ants superior competitors and therefore the lack of diversity is adaptive in S. California
- low genetic diversity has its dangers: If the supercolony faces a pathogen, the entire colony may collapse
Fixed-action patterns (FAPs)
highly inflexible, stereotypical behaviour patterns
Learning
enduring change in behaviour that results from a specific experience (flexible)
Innate behaviour
requires no learning (fixed)
Fitness trade-offs
compromises balancing costs and benefits
Cost–benefit analysis
behavioural decisions are measured in terms of their impact on fitness
2 things about cost-benefit analysis:
- The choices made by non-human animals are not conscious choices
- Individuals’ behaviour varies within populations
foraging
when animals seek food
-always making choices
EX: Fruit flies
Proximate Causes: Foraging alleles
Fruit fly larvae exhibit one of two behaviours during feeding:
“Rovers” move after feeding in a particular location
“Sitters” stay in one location to feed•
Experiments showed this behaviour inheritable via the foraging (for) gene that produces a protein active in the nervous system
Adult flies express the same foraging alleles as larval flies
EX: Fruit flies
Ultimate Causes: Optimal foraging
The rover allele is favoured at high population density
Rovers are more likely to find unused food patches•
The sitter allele is favoured at low population density Sitters do not waste energy searching for food
Optimal foraging
–individuals make decisions that maximize the amount of food (usable energy they take in)
–weigh costs of finding and ingesting their food and the risk of being eaten while they’re at it
EX: Arctic Seals
have to find shallow water with plenty of food to avoid over-exhausting themselves
EX: Bumblebees
want to fly short distances between flowers to save the most energy and obtain the most honey
EX: Do desert gerbils exhibit optimal foraging?
Control group-without extra seeds
Treatment gorup-with extra seeds
Both exhibit an owl flying over
Results: w/o extra seeds, did not take risk
w extra seeds, took the risk
therefore gerbils weigh the risk of predation and benefits of extra seeds when foraging
Proximate vs Ultimate in Sexual activity
proximate mechanisms responsible for triggering sexual activity
Why animals choose their mates?-ultimate
EX:How is sexual activity triggered in Anolislizards (proximate)?
Anolis have a breeding season, i.e., their sexual condition changes seasonally
Individuals ready to breed in spring, although male gonads start growing long before female. In both sexes, the gonads shrink afterwards
Testosterone and estradiol
The evidence for the effects of sex hormones is direct
–Injected testosterone induces courtship activity in castrated males with no prior courtship activity; estradiol injections induce sexual activity in females whose ovaries have been removed
Testing the light and social stimuli for lizards
Females vs males
Females: Need to experience spring-like light and temperatures or they do not produce eggs
Males signal females to induce estradiol release:
–During courtship, they bob up and down and extend a brightly coloured patch of skin called a dewlap. The dewlap is the estradiol trigger in females
–Females are slow to produce eggs when exposed to males without dewlaps or males that do not court (castrated)
Ultimate causes: Sexual selection
Synchronizing sexual readiness → more offspring (=higher fitness than those that do not)
Energy and resource savings (long tails and bright colours
Visible features are an honest signal of male quality
Intrasexual selection
when males (or females) compete with each other for mates
Proximate causes: How do animals navigate? (3)
- Piloting: use familiar landmarks
- Compass orientation: movement oriented in a specific direction
- True navigation: ability to locate a specific place on Earth’s surface
Piloting
offspring seem to memorize the route by following their parents south in the fall and north in the spring
(not easy to tell whether an individual uses landmarks (piloting) or a combination of that and mapping)
Compass orientation
Multiple mechanisms for finding a compass direction
- Sun compass
- star compass
- magnetic compass
The Sun is difficult to use as its position changes throughout the day
Circadian clock
maintains a 24-hour rhythm of chemical activity
Use of magnetic field -How?
- Animals’ visual systems may be able to detect it through a chemical reaction that involves electron transfer among molecules
- they may have small particles of magnetic iron (magnetite) in their bodies, allowing them to detect changes in Earth’s magnetic field
EX: Sea turtles navigate using map (True) orientation
Experiment: place soft harnesses over wild turtles and monitor swimming direction in diff artificial magnetic fields
Results: Simulated North location-swam south
Simulated South Location-swan North
Both trying to return to actual location of turtles
Communication
social process in which a signal from one individual can modify the behaviour of another individual
signal
information-containing behaviour
Proximate causes: How do honeybees communicate?
Karl von Frisch observed bees displaying a “round dance” to workers, as well as a “waggle dance
He placed feeders at several distances from the hive and marked the bees that came to the feeders
Observations:
1.Danced when they returned to the hive
2.Returned to the food source with unmarked bees
waggle dance contains information about food location (3)
- The length of the waggle run was proportional to the distance from the feeder
- The direction of the waggle run correlated with the direction to the food source
- The direction of the food source is relative to the current position of the Sun
Ultimate causes: Why do honeybees communicate the way they do
The signal is appropriate to its habitat and type of info needed (helps the whole colony)
Animals use a diversity of signals: sound, scent, or tactile or visual cues, often in combination
Each mode of communication has advantages and disadvantages (think of fitness).
Deceiving Individuals of Another Species
individuals sometimes increase their fitness by providing inaccurate or misleading information to members of a different species
EX: Interspecifc -Fireflies
female fireflies attract males of diff species with flashes to attack male and eat him
EX: Intraspecific -Bluegills
males bluegillds mimic females-look and act like females during courtship with terriotrial males (territorial male thinks he is courting 2 females)
- When the actual female begins to lay eggs, the mimic releases sperm and fertilizes some of the eggs
- In this way the female-mimic male fathers offspring but does not help care for them
Why aren’t all males mimics?
Deceit works only when it is relatively rare
–If deceit becomes common, individuals that can detect and avoid or punish liars would be selected for
– more mimics, more competition → lower reproductive success of the mimic
Altruism
behaviour that has a fitness cost to the actor and a fitness benefit to the recipient
Self-sacrificing
EX: black-tailed prairie dogs
-perform alarm calling when predator is near (brings attention to them, but warns the rest)
Hamilton’s rule states that altruistic behaviour is most likely when three conditions are met:
- The fitness benefits of altruistic behaviour are high for the recipient (B is high)
- The altruist and recipient are close relatives (r is high) 3.The fitness costs to the altruist are low (C is low)
inclusive fitness
combination of direct and indirect fitness components
Kin selection
natural selection that acts through benefits to relatives and results in increased indirect fitness
–decreases direct fitness but increases indirect fitness, resulting in an overall increase in inclusive fitness
Eusociality
altruistic behaviour can be involuntary
ex: bee/wasp/ant workers sacrifice most/all direct reproduction to help queen’s offspring
Reciprocal Altruism
exchange of fitness benefits that are separated in time
Examples of Reciprocal Altruism
ex: vervet monkeys likely to groom unrelated individuals whom groomed/helped them in past
ex: vampire bats likely to share blood meals w non-kin who shared food w them in past
Mutualism
occur when cooperation occurs among individuals of same species
