How homing pigeons find their way home?

How homing pigeons find their way home?

Homing pigeons may derive their impeccable navigation skills from their keen sense of low-frequency hearing. This ability to navigate to their nests (or lofts, as their habitats are often known) with astounding accuracy has never really been understood, but a new theory may have just solved the mystery. If a U.S. Geological Survey geologist is correct, homing pigeons use low-frequency sound waves that emanate from just about everything to mentally map their environments and navigate back to their lofts. This ability stems from the fact that birds can hear at far lower frequencies than humans can, down to about 0.1 Hertz. These kinds of waves emanate from the Earth itself--from the oceans really, but also up through the crust and the Earth’s topography and even in the atmosphere. Pigeons use these low-frequency infrasound waves to generate acoustic maps of their surroundings, and that’s how they find home even when they are released miles from where they dwell. This not only explains how pigeons make their way home almost every time, but why they sometimes get lost (high winds, supersonic jets, and various other phenomena can disrupt these infrasound waves, disorienting the birds and setting them on a

false course for home).

Individual behavior

Social behavior

Animal behavior

All observable or otherwise measurable muscular or secretory responses (or lack thereof) to changes in internal or external environment

Some behavior is genetic “innate”

Some behavior can be improved based on experience

Some behavior forms by training

Individual behavior

Innate behavior

Learned behavior

Innate behavior

• Rapid

• Automatic

• No conscious control

Learned behavior

• Habituation• Imprinting• Trial and Error Learning• Conditioning• Insight• Communication

Takes place when behavior changes through practice or experience

Habituation

– A simple form of learning

– When an animal is repeatedly given a stimulus that is not associated with any punishment or reward it finally stops responding to the stimulus

Imprinting

A form of learning in which an animal forms a social attachment to another object.

Occurs at a specific, critical time of its life.

Young geese follow and imprint on their mother

– Occurs through experience, trying one solution and then another.

– The animal receives a reward for making a particular

response.

Trial and error learning

Conditioning

– Is learning by association– An animal begins to respond to a stimulus other

than the one that normally initiates that response.

For example, the pigeon pecks at the brighter and reaches down to pick up the grain of food.

Insight

– The most complex type of learning.– Learning in which an animal uses previous

experience to respond to a new situation.– Involves reasoning, the ability to analyze a

problem and think of possible solutions.– Much human learning is based on insight.

Animal Communication

Transfer of information from one animal to

the other (both must be mutually adapted)

Types of communication signals

– Pheromones– Tactile signals– Visual signals– Acoustical signals

“ 鼠目寸光”

Pheromones

• Chemical signals between members of same species– diffuse through air or water

• Signaling pheromones– Induce immediate response

Tactile Display

• Signaler and receiver communicate by contact

• Honeybee dance language

food close food distant

Visual Displays

• Important in dominance hierarchies• Baring of teeth by baboon communicates

threat• Play bow in wolves solicits

play behavior

Acoustical Signals

• Sounds used in communication

• Lots of examples: -- Dog barking

-- Bird chirping -- Elephants -- Whales

Signal Variation

• Some signals never vary– Zebra ears flat on head always = HOSTILE

• Composite signals combine information encoded in more than one cue– Zebra with ears flat on head and mouth wide

open = VERY HOSTILE

• Signals vary based on context– Lion roar = Threat or trying to contact others

Behavioral ecology

Behavioral ecology emphasizes evolutionary hypothesis: science as a process, based on the expectation that animals behave in ways that will increase their Darwinian fitness (reproductive success).

careful analysis often reveals that any particular behavior is a combination of innate and learned components

Innate behavior can be influenced by experience.

The basis is innate, but the refinement is learning.

For example, in birds that feed their young by fetching food for them and putting it in their beaks. To begin with the chicks just open and close their beaks, but after a few days they learn how to twist their heads in order to grab the parent's beak to get the food more quickly.

Social Behavior

• Members of the same species• Usually live full-time in groups• Can refer to predator-prey interactions

Group Living

• Animal society – stable group of individuals of the same

species that have cooperative relationships outside of mating and raising young.

• Invertebrates and vertebrates

Bumblebees are social insects, there is a certain level of interrelation between individuals of the same colony. The latter is divided into a number of groups, each with a specific task. At the top of the hierarchy stands the queen, that does not differ physically from the workers except for its size which is much bigger than the size of the largest worker.

Dominance Hierarchy

Dominance Hierarchy

• Some individuals accept subordinate status

• Higher ranked members have higher reproductive success than subordinates

• So why stay if some individual are ranked low?

Benefits of Social Living

• Improve foraging efficiency

• Share care for their young and increase feeding efficiency

• Protection from enemies• Easy access to potential

mates

Costs of Social Living

• Increased competition for food, mates, and other limiting resources

• Attractive to predators • Increased vulnerability to disease

and parasitism• Risk of exploitation by other group

members

Animal Social Behavior

Costs and disadvantages• competition…• diseases, parasites• degradation of

environments• increased

conspicuousness…

Benefits and advantages• efficiency of foraging,

predation…• avoidance of predation• opportunity to modify

environment• interaction with genetic

relatives• recall that “family” is one of

the levels of biological organization

Questions about lions and tigers

• What are their living pattern? Individual or social living?

• Please try to explain their difference… … …

the Foraging Behavior of Animals and Plants

Foraging Behavior

• Energy costs and benefits– Optimal foraging predicts animals must balance

energy expenditure and food benefit– Maximize benefits, minimize costs

• Risk of predation– Must avoid becoming prey for an optimal forager– Amount of time foraging is balanced with amount

of time scanning for predators

Foraging Strategies

Foraging predictions in terms of SEARCH time and PURSUIT time

Search > Pursuit then predict generalist strategy (some birds)

Pursuit > Search then predict specialist strategy (lions)

Life costs and energy is the currency

Foraging Strategies:Foraging in Patches

Let us assume that in any moment it can choose between two kinds of activities: either to consume food in the actual site (exploitation) or to move on (exploration)

The question is “What is the optimal rule for switching between exploitation and exploration in order to maximize the total amount of food taken up in a habitat with multiple patches?”

Optimality Theory

1. Decisions - selecting a behavioral option2. Currency - what is being maximized?3. Constraints - behavior, morphology, physiology

Optimality models attempt to predict the combination of costs and benefits that will ultimately maximize an individual’s inclusive fitness

Animals are not perfectly adapted to their environment (mutation, rapid environmental change, evol. lag). Also, they don’t “work” on the assumptions presented in models. Natural selection is the mechanism which works as a maximizing process.

Optimality Theory

Optimality models attempt to predict the combination of costs and benefits that will ultimately maximize an individual’s inclusive fitness

costs

benefits

Net gaincosts

benefits

Net loss

Foraging Strategies:Foraging in Patches

How hard to work to most efficiently exploit a patch

1. Movement rules in a patch2. How long to stay in patch (marginal value theorem)3. Where to next?

A foraging animal (an unitary organism) vs. a plant (a modular organism)

Spacer

Feeding sites

As the plant is growing and branching, its parts can meet various environmental conditions

Plant modular growth and foraging for resources

In order to relate a growth pattern to a resource pattern, a functional subdivision of the plant body:

“Feeding sites” are typically specialized for the uptake of resources (e.g. roots for nutrients, leaves for photosynthesis)

“Spacers” are specialized for placing the feeding sites preferably into resource-rich sites

The plant develops by the repeated production of discrete subunits

Spacer

Feeding sites

“Feeding sites” are typically specialized for the uptake of resources (e.g. roots for nutrients, leaves for photosynthesis)

“Spacers” are specialized for placing the feeding sites preferably into resource-rich sites

Plant modular growth and foraging for resources

On one hand, plant foraging is simpler than animal foraging, because plants do not have any cognitive capacity for processing individual experience; the developmental decision is based on an inherited set of rules. The rules can be plastic, i.e. dependent on the environment.

Plant foraging vs animal foraging

Plant foraging vs animal foraging

On the other hand, plant foraging has some specificities which make it more complex than animal foraging is.

First, the foraging pathway can branch (in animals, this happens only in the case of group foraging, e.g. in ant trails) Secondly, plants do not necessarily abandon those places that have been visited

Plants have “multiple mouths”, i.e. they can feed from many sites simultaneously. Moreover, the feeding sites can exchange resources and/or information

The spatial expansion of clonal plants

Clonal plants depend on asexual reproduction to produce offspring ramets and expand the population

Among plants, clonal species are particularly suitable for studying foraging, because their branching structure is primarily two-dimensional, and feeding sites vs. spacers can usually be distinguished clearly.

The spatial expansion of clonal plants

Key points about spatial expansion:

driving force of expansion

directionality of expansion

speed or distance of expansion

Experimental station

A3A2A1

Parent ramet

Direction of stolons or rhizomes

Experimental design

Experimental design

B2

B3

B1

B4

A2

A3

A1

A4

stolon or rhizome parent ramet

A1 － A4 、 B1 － B4 ： different level of abiotic factor (A or B)

Multi-patch environmental heterogeneity

Results and discussion

Results and discussion

Species-specific patterns of foraging responses

Results and discussion

Results and discussion

Experiment 2: Potentilla anserina

Experimental design

CK Cluster

Random Uniform

Results and discussion

Results and discussion

When the pattern of resources was cluster distribution, ramet number and leaf biomass in rich-nutrient patches were highest

Results and discussion

Spacer length of P. anserina in homogeneous environments was higher than that under heterogeneous habitats

Spacer length of P. anserina in high-nutrient patches was higher that that in low-nutrient patches

Distributionpattern

扩散系数 (DI)

平均拥挤指数 (m*)

泊阿松分布的 X2拟合检验

负二项分布的 X2拟合检验

格局类型

Cluster 13.1205* * 14.5994 P<0.01 P>0.05 聚集Cluster 16.7698* * 19.8475 P<0.01 P>0.05 聚集Cluster 11.8530* * 12.8385 P<0.01 P>0.05 聚集Cluster 13.9109* * 16.6646 P<0.01 P>0.05 聚集

Cluster 16.3156* * 18.0644 P<0.01 P>0.05 聚集Random 16.3073* * 17.6991 P<0.01 P>0.05 聚集Random 16.2493* * 18.8999 P<0.01 P>0.05 聚集Random 11.4725* * 10.9931 P<0.01 P>0.05 聚集Random 17.6367* * 18.7228 P<0.01 P>0.05 聚集Random 9.9925* * 10.6921 P<0.01 P>0.05 聚集

* * P<0.01

格局类型与格局强度分析

Pattern intensity

编号 分布系数 （ DI）

平均拥挤指数 (m*)

泊阿松分布的 X2拟合检验

负二项分布的 X2拟合检验

格局类型

Uniform 9.4657* * 9.8603 P<0.01 P>0.05 聚集Uniform 10.1467* * 10.9670 P<0.01 P>0.05 聚集Uniform 11.9372* * 11.9781 P<0.01 P>0.05 聚集Uniform 10.3828* * 10.1852 P<0.01 P>0.05 聚集Uniform 16.9384* * 19.1241 P<0.01 P>0.05 聚集CK 14.3112* * 17.1773 P<0.01 P>0.05 聚集CK 20.1000* * 21.9628 P<0.01 P>0.05 聚集CK 16.8547* * 20.1677 P<0.01 P>0.05 聚集CK 21.3846* * 23.8475 P<0.01 P>0.05 聚集CK 13.1441* * 13.9896 P<0.01 P>0.05 聚集

Pattern intensity* *P<0.01

Carnivorous plants

Carnivorous plants and autocatalysis

a) Sketch of a typical ‘leaf’ of Utricularia floridana, with detail of the interior of a utricle containing a captured invertebrate

b) Schematic of the autocatalytic loop in this system

Carnivorous plants and autocatalysis

A hypothetical three-component autocatalytic cycle

C B

A

Thanks