空間分佈 (spatial distribution) ─ 動物行為學 (Ethology) 鄭先祐 (Ayo) 國立...

空間分佈 (spatial distribution)

─ 動物行為學 (Ethology)

鄭先祐 (Ayo)

國立臺南大學環境與生態學院生態科學與技術學系教授

Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/

大學部生態學與保育生物學學程 ( 必選 ) 2010 年秋冬

Ayo 教材 (動物行為學 2010) 2

10 空間分佈 (Spatial distribution)

Remaining at home versus leaving Habitat selection ( 棲地選擇 ) Migration ( 遷徙 )


Introduction to animal movement

Nearly all of the 25 species of sturgeons ( 鱘魚 ) are endangered

Chinese sturgeon can reach 4 or 5 m in length, weigh more than 550 kg (1,000 lbs.), and live for a century It is anadromous, spending most of its life in the sea But returning to freshwater to breed

Anadromous 由海移棲淡水河產卵的


Humans have disrupted sturgeon spawning

Historically, Chinese sturgeon spawned upstream in the Yangtze River Taking 18 months to migrate 3,000 km to their

spawning grounds The Gezhouba Dam blocked Chinese sturgeon from

their migration route They bred below the dam

The number of spawning adults plummeted Disruption by the dam, water pollution, overfishing,

and heavy boat traffic


Dispersal and philopatry

Natal dispersal: movement between the natal area or social group and the area or social group where breeding takes place Animals are born in one place and move to another to

breed They don’t return to their birthplace

Breeding (post-breeding) dispersal: movement between two successive breeding areas or social groups Occurs after reproduction

Natal philopatry: offspring remain at their natal area and share the home range or territory with their parents


Costs of natal philopatry

Inbreeding: mating between relatives Parents and offspring or between siblings Inbreeding reduces variation among offspring

It is hard to determine the fitness costs of inbreeding Because the frequency of inbreeding is usually low

Mexican jays have fitness costs associated with inbreeding Smaller brood sizes, suggesting hatching failure Fewer of the inbred nestlings survived to the next year

Mexican jay


Other costs of natal philopatry

Reproductive suppression: adult breeders suppress reproductive development of young through chemical means (e.g., pheromones) or behavioral methods (e.g., aggression) Suppressed young may not reproduce Their genes are represented by helping rear other young

Young compete with relatives for food, nest sites, or mates


Benefits associated with philopatry

Populations become adapted to local conditions Genes that work well under local conditions are

favored by selection An animal that disperses may not be as well adapted to

its new home Familiarity with the local physical and social setting

Young are efficient at finding and controlling food and escaping from predators

Reduced levels of aggression and stress associated with social interactions


Another benefit of philopatry

Philopatric young may live longer and leave more offspring Because of the low risks and energy use associated with

living in familiar surroundings Offspring may remain at home due to constraints

A shortage of potential mates A lack of suitable territories to settle in


Costs of natal dispersal

Dispersers face high energy costs and increased predation risk Small mammals in underground burrows have a

constant physical environment and safety from predators (hawks and owls)

Long-distance above-ground dispersal exposes them to harsh weather conditions and predators

Other costs: a lack of familiarity with the terrain High levels of aggression from residents in the new

area


Animals in new homes face challenges

Male prairie voles released at unfamiliar locations move greater distances And take longer to find refuge than those released at

familiar locations In woodland voles and Norway rats, nonresidents

face harsh treatment by residents Dispersal-induced mortality can exceed 50% But dispersal costs can be negligible in some species


Benefits of natal dispersal: avoiding competition

Dispersers avoid competition with kin for critical resources

Wolf spider mothers help their offspring disperse Young climb onto their mother’s abdomen Spiderlings face kin competition if they all left their

mother’s abdomen in the same location They do not simultaneously disperse from mom’s

abdomen


Patterns of natal dispersal and maternal movement in wolk spiders ensure that siblings do not compete with one another.


Not all species avoid competition through dispersal

In other species, avoiding competition with kin cannot explain patterns of natal dispersal

If competition for resources leads to dispersal, dispersal would increase with increases in litter size In brown bears and prairie voles natal dispersal is not

associated with litter size Natal dispersal is more common in small groups of

prairie voles Avoidance of competition for resources at home is not an

important function of natal dispersal in this species


Benefits of natal dispersal: avoiding inbreeding

Some young leave home to avoid breeding with close relatives Young disperse in the presence of an opposite-sex

parent All members of one sex may disperse, no matter what

the ecological or social conditions In Belding’s ground squirrels, all males leave home

Regardless of the competition for mates or resources Nearly all male brown bears leave home regardless of

ecological factors (i.e. population density and sex ratio)


Inbreeding may or may not be important

Some scientists argue that it plays a significant role in dispersal Others argue that animals rely on mate choice rather than a

risky behavior like dispersal to avoid inbreeding Young female mammals avoid selecting their brothers as

mates In response, their brothers disperse from the natal site to

find females willing to mate with them So, individuals do not disperse from home to avoid

breeding with relatives Instead, natal dispersal is the result of females not choosing

male relatives as mates


↑Belding’s ground squirrels

← brown bears

spotted hyenas →


Female mate choice can drive natal dispersal

Female spotted hyenas rarely disperse from the natal clan. Most, but not all, males leave their natal clan

Four hypotheses examine natal dispersal by males 1) competition with other males for mates 2) breeding with close female relatives 3) competition for food resources 4) males disperse in response to patterns of mate

choice by females Competition for mates, inbreeding avoidance, and

competition for food do not cause natal dispersal by males


Female avoid mating with close relatives

Female hyenas follow this rule: “Avoid mating with males that were members of your

clan when you were born and select as mates those males that arrived in your clan (through birth or immigration) after your birth”

Reducing the chances that females mate with their father and older brothers


Another aspect of female choice

Young females select males with short residency times in their clan

Males begin their reproductive career in the clan (natal or otherwise) that had the most young females Females choose them as mates Resulting in long-term fitness benefits for the males


Proximate causes of natal dispersal

Ultimate causes of natal dispersal: avoidance of inbreeding and competition with kin for resources or mates

Proximate causes also trigger natal dispersal Sufficient body size or fat reserves, aggression from

other group members, shortage of food, attraction to opposite sex individuals in other groups, and weaken social bonds with members of the natal group

Androgens may organize dispersal behavior through organizational effects of steroid hormones


Natal dispersal is also linked to personality ( 個性 ) Such as “boldness”( 大膽的 ) or exploratory

behavior Female great tit post-fledging movement distances

correlates with exploratory behavior This positive correlation does not characterize all

species In flying squirrels, long distance dispersers explore

less than short distance dispersers


Sex biases in natal dispersal

Males and females differ in whether or not they disperse from their birthplace In most bird species, females are more likely to disperse In mammals, males are more likely to disperse than

females Hypotheses to explain sex-biased dispersal

(1) inbreeding avoidance (2) local resource competition (3) local mate competition (4) cooperative behavior among kin


Sex bias in dispersal is a compromise

It avoids the genetic costs of inbreeding While enjoying the benefits of familiarity with local

physical and social conditions (philopatry) But, which sex leaves home and why is the direction of

the bias different in birds and mammals? Two explanations suggest the direction of sex bias

The sex most involved in territory acquisition and defense stays home because it benefits most from familiarity with the natal territory

The sex that gets first choice of breeding sites remains in the natal area and the other sex disperses


Male birds are philopatric

Most birds are monogamous (they live in male-female pairs)

A resource-defense mating system: males compete for territories that attract females, rather than competing for females directly Familiarity with an area is more important to males than

to females so males should be philopatric Female birds disperse to avoid the genetic costs of

inbreeding And to choose territories with the best resources


Female mammals are philopatric

Many mammals show mate-defense polygyny: a single male mammal defends a group of females Males compete for females rather than territories Young or subordinate males disperse to increase their

chances of mating Female mammals often live in matrilineal social groups

(groups of mothers, daughters, and granddaughters) The benefits of living with kin are high

Females benefit most by staying home Males disperse to avoid the genetic costs of inbreeding


Sex-based dispersal

Female-biased dispersal in birds is linked to resource-defense mating systems

Male-biased dispersal in mammals is linked to mate-defense mating systems Some mammals display resource-defense (rather than

mate defense) polygyny Natal dispersal is female biased, as predicted

i.e. for sac-winged bats But, in European roe deer, dispersal is not female

biased


Sac-winged bat ( 鞘尾蝠科 )

European roe deer


The sex with the breeding site remains in the natal area

This model assumes that philopatry is more desirable than dispersal

Mating systems affect dispersal patterns of mammals indirectly by influencing whether the father will be present when his daughters are old enough to breed If he is not, females have first choice of the breeding

site, and they choose to stay at home If the father is still around when his daughters reach

sexual maturity, he has first choice of the breeding site, and so females disperse to avoid inbreeding


A male mammal’s parental role is limited

Female mammals nurse their young Males have little involvement in offspring care

So, males can avoid long-term pair bonds They can wander over large areas

With intense competition over mates (i.e. elephant seals, red deer) a male’s opportunity to breed may be limited He leaves before his daughters are old enough to reproduce

So, daughters don’t have to disperse to avoid inbreeding If a male’s reproductive life span is long and he is present

when his daughters are old enough to breed (i.e. chimpanzees) Females usually disperse


Another hypothesis for dispersal: local mate competition

Competition for mates is intense in polygynous male mammals Dispersal should be more common in males

In monogamous species, competition for mates is more equal Males and females should disperse in similar proportions

Reducing competition for mates can’t explain all sex differences in natal dispersal Avoiding inbreeding influences natal dispersal i.e. females disperse in monogamous bird species


Kin cooperation hypothesis

Cooperative behavior contributes to sex biases in dispersal If kin exhibit cooperative behavior, it is beneficial to stay

home If cooperation benefits one sex more than the other

The cooperative sex is philopatric The other sex disperses to avoid inbreeding

The magnitude of sex-biased dispersal increases with increases in social complexity Dramatic sex differences in natal dispersal characterize

highly social polygynous mammals


Sex bias in natal dispersal and social complexity

There is a relationship between sex-biased dispersal and social complexity

In polygynous ground-dwelling sciurids (ground squirrels, marmots, prairie dogs) Social structures range from solitary to large social

groups Male-biased natal dispersal increased with social

complexity Not from expected decreases in female dispersal


ground squirrels

marmots

prairie dogs ( 土撥鼠 )


In polygynous ground-dwelling sciurids (members of the squirrel family), the degree of sex bias in natal dispersal increases with social complexity.


Understanding natal dispersal: implications for conservation

Dispersal affects the genetic structure of populations It promotes gene flow within and between populations And maintains genetic diversity

Habitat destruction fragments populations and hinders dispersal Areas between habitat fragments are inhospitable

To conserve threatened populations Preserve dispersal corridors( 廊道 ) to connect larger

areas and promote gene flow


Stop and think

Natal dispersal and philopatry are measured by mark and recapture methods Genetic methods examine how dispersal translates into

gene flow What are some potential problems in using mark-

recapture methods to study dispersal? How could you know if an animal dispersed or died? How could you design a study to minimize this issue?


Mark-recapture methods are often used to monitor natural populations of small mammals.


Habitat selection

Animals that disperse from their natal site or breeding site must select a new location in which to settle

The process of habitat selection has three phases: (1) search (animal searches for a new habitat) (2) settlement (animal arrives in a new habitat and

begins to establish a home range or territory) (3) residency (animal lives in the new habitat)

The phases of search and settlement are costly The benefits of habitat selection accrue during

residency


Indicators of habitat quality

Animals have clear habitat preferences Forest buffalos of Africa prefers grassy clearings and

open stands of forest with large trees Even though clearings are rare Herd members can maintain visual and physical contact

When selecting a habitat, animals evaluate The presence of resources (e.g., food, nest and rest sites) The presence of conspecifics, and heterospecifics

(members of another species)


Its native habitat is the equatorial forest found in central and western Africa, and its diet consists primarily of grasses, twigs, and young shoots. African Forest Buffalo are sought after by hunters for their meat and horns. In the wild, leopards are its primary predator.

The African Forest Buffalo (Syncerus caffer nanus) is usually weighing 265–565 kilograms (580–1,250 lb), they are reddish brown in color.


How do animals evaluate real estate?

Young lizards searching for feeding territories spend only hours evaluating a location Do not conduct a detailed assessment of prey availability They assess habitat characteristics (i.e. light intensity

and amount of leaf litter) that correlate with prey availability

A disperser evaluates the presence or absence of conspecifics in the vicinity of a prospective home By settling in an unoccupied site, it avoids intraspecific

competiton


Fitness correlates with numbers of conspecifics

The ideal free distribution: individual fitness declines as the number of conspecifics increases

The Allee effect: individual fitness increases with number of conspecifics at low to moderate densities Having a few neighbors is beneficial Enhanced detection of predators or access to mates

Two explanations for conspecific attraction regarding habitat selection 1) Allee effect 2) conspecifics indicate habitat quality


Conspecifics indicate habitat quality

Juvenile lizards use conspecfic presence as an indirect cue to habitat quality

Individuals evaluate characteristics of resident conspecifics Breeding birds monitor the reproductive success of

conspecifics in their local area And use this information to decide where to nest during future

breeding efforts Public information: information concerning local

conspecifics Personal information: the bird’s own breeding success also

affects whether it remains at that site or leaves


The presence of heterospecifics has costs and benefits

For an animal considering whether to settle in an area Interactions between species that share mutual resources

could be negative due to interspecific competition Interactions between heterospecific individuals can be

beneficial Mixed species flocks of birds experience the benefits of

enhanced food acquisition and antipredator behavior The heterospecific attraction hypothesis: individuals

choose habitat patches based on the presence of established residents of another species


The heterospecific attraction hypothesis

Predicts that individuals searching for a new home display the strongest attraction to heterospecifics When the benefits of social aggregation outweigh the

costs of competition, and When the costs of independent sampling of habitats

(evaluating habitat quality on one’s own rather than using the presence of heterospecifics as a cue) are high


Testing the heterospecific attraction hypothesis

Several possible explanations exist for the attraction of migrant birds of one species to resident birds of other species First, residents indicate high quality habitat Second, migrants may experience food or safety benefits

from grouping with heterospecific residents Third, using presence of heterospecific residents to

indicate habitat quality may be a fast, accurate method of habitat assessment

Residents have all year to assess the quality of habitat patches


Resident titmice influence pied flycatcher presence and fitness

Titmice and pied flycatchers both nest in cavities and forage for arboreal arthropods

Flycatchers are attracted to the vicinity of titmice Flycatchers arrive earlier on forest patches with more

titmice They prefer nest boxes placed near an active titmouse

← Titmice Pied flycatchers →


The fitness effects of habitat selection

Brood sizes of flycatchers were larger in patches with more titmice Flycatchers breeding closer to titmice had larger nestlings

Interspecific competition is not the defining interaction between titmice and flycatchers

← Titmice Pied flycatchers →


Two search tactics for selecting habitat

Comparison (best-of-N strategy): the animal visits several areas, revisits some, and chooses the highest quality area

Sequential search: the animal visits habitats and selects the best one An animal accepts or rejects

a location If rejected, it keeps searching

Both tactics can occur within a single population


Sequential searches

Searchers do not return to areas they have already visited (except by chance) They may travel long distances before establishing residence

Decisions by dispersers are influenced by: The time available for the search, quality of available

habitats, and how often high quality habitats are encountered Dispersers may have an acceptance threshold

Which declines as the search continues (i.e., an animal may be selective at the start of the search and less selective later)


Effects of natal experience

Experience in the natal environment influences habitat selection

Host preferences exhibited by the parasitoid wasp A parasitoid: an organism whose offspring

develop on or within a host, eventually killing the host

The host of a parasitoid is the equivalent of a habitat

Female parasitoids select hosts on (or within) which their offspring will develop


Host preference in parasitoid wasps

Female wasps reared on fruit flies preferred fruit flies as hosts But only when allowed to gain experience attacking them

Cues from the natal host prime females to respond to these cues if encountered again When re-encountered, the cues are learned by females,

establishing host preference The natal environment (here, the natal host) influences

selection of a site for reproduction


The natal habitat preference induction

NHPI: An animal’s experience in its natal habitat induces a preference for a post-dispersal habitat with similar qualities The search phase of habitat selection is costly in time,

energy and predation risk NHPI helps a disperser to more quickly and efficiently

recognize a suitable habitat Minimizing the costs of the search phase

A habitat similar to the one in which the disperser grew up would be of sufficient quality to settle in Because the individual has survived to leave home


Another explanation for NHPI

Dispersers have greater fitness if they settle in a habitat similar to their natal habitat Because their particular phenotype has been shaped by

this type of habitat While living at home, individuals develop specific

methods for finding and capturing prey These methods might work best in post-dispersal habitats

similar to their natal habitat NHPI has been documented in diverse taxa

Insects, fishes, amphibians, birds, and mammals


Habitat selection and conservation biology: translocation and captive-release programs

Conservation efforts using translocation (moving animals from one part of their natural range to another) and captive-release programs (breeding animals in captivity and then releasing them to the wild) often fail Animals travel long distances away from the release site Survivors may exhibit decreased condition and

reproduction Movement away from the release site make provisioning

and monitoring extremely difficult


Many translocated animals travel long distances from the site of release. In cougars ( 美洲獅 ) , this is especially true for adult males.


Making captive-release programs and translocations work

Movement from a release site suggests that the animal rejects the habitat and is searching for suitable habitat

Understanding habitat selection and natal habitat preference induction may inspire modifications to programs And help animals find the release site more acceptable Providing captive animals with stimuli and cues similar to

those at the release site May make them more inclined to stay at the release site

Placing stimuli and cues from the original habitat at the release site might reduce the disparity between the two habitats


Habitat selection and conservation biology: ecological traps

Ecological trap ( 生態陷阱 ): a low quality habitat that animals prefer over a high quality habitat

Cooper’s hawks in Arizona select Tucson because of its plentiful nest sites and prey (pigeons and doves) Urban hawks nest earlier and have larger clutches But nestling mortality is higher in Tucson than rural areas Prey carry trichomoniasis ( 滴蟲病 ) , which kills nestling

hawks The hawks selected an inferior habitat – an ecological trap

Populations in an ecological trap move toward extinction


Cooper's Hawk

Cooper's Hawk (Accipiter cooperii) is a medium-sized hawk native to the North American continent and found from Canada to Mexico.

As in many birds of prey, the male is smaller than the female. The birds found east of the Mississippi River tend to be larger on average than the birds found to the west.


Migration

Migration: movement away from the home range that does not stop upon encountering the first suitable location Animals move until they respond to the presence of

resources (nest sites and food), and then they stop Migratory movements occur over greater distances than

dispersal


Migrating caribou marching through Alaska in July. During the spring, many caribou breed in the tundra. Beginning in July, they migrate south, where food will be available through winter.


Migration: one-way or round trip

In some species, migration involves movement away from an area and the subsequent return to that area Migration between breeding areas and over wintering,

or feeding, areas Associated with long-lived species (e.g., vertebrates)

In other species, migration is a one-way affair Migratory insects permanently abandon their site of

origin Associated with short-lived species (e.g., insects)


Animals vary in the distance they migrate

A salamander travels less than a kilometer from its woodland home to its breeding pond

Northern elephant seals migrate twice a year from beaches in southern California to northern feeding grounds in the Aleutian Islands - 8000 kilometers each year

The arctic tern migrates 20,000 kilometers one-way, between its southern wintering area and northern breeding area

Long distance migrants insects: desert locusts and monarch butterflies have one-way migration distances of 5,000 km and 3,600 km, respectively


desert locusts monarch salamander

elephant seals arctic tern


Migration can take several forms

Migration can be obligate: an individual always migrates Facultative migrants migrate only if local conditions

deteriorate Differential migration: migration of individuals differs

by age or gender Small passerines (perching birds) may migrate in their first

year but remain on breeding grounds in subsequent years Female and juvenile blue tits migrate because they are less

able to compete for food on the breeding grounds when it becomes scarce during the nonbreeding period


Costs of migration

Animals migrate because they produce more offspring this way then if they stayed put

But, migration takes a tremendous toll Less than half of the waterfowl in North America that

migrate south each fall return to their breeding grounds The mortality rate of black-throated blue warblers is

15 times higher during spring and autumn migration than during periods when individuals are not migrating


Costs of migration: energy

Traveling long distances requires a great deal of energy Bird use 6-8 times more energy when flying than resting

Natural selection favors behaviors that reduce the risk of starvation during migration

Storing fat before the journey begins Fat provides more energy than carbohydrates or proteins Insects, fish, birds, and mammals put on fat reserves The body mass of long-distance migratory birds can double

Increasing body mass to avoid starvation must be balanced against the negative effects of a heavy fuel load while flying


Saving energy during migration: stopovers

Some animals do not have sufficient fat stores to migrate without stopping

Small birds reduce their risk of starvation by refueling along the way They alternate flight and stopovers Spending more time in stopover than in flight

How do they know where to stop for food? They use landscape features (i.e. amount of hardwood

forests) which are positively correlated with arthropod abundance


Fly-and-forage migration

Ospreys combine foraging and migration Individuals forage for fish in nearby bodies of water They move on in less than 12 hours

Other birds (i.e. falcons and seabirds) that fly extensively also use this strategy Birds that feed on the ground or in vegetation have longer

stopovers


← 鶚（學名： Pandion haliaetus ）或稱作魚鷹，是一種善於捕魚的猛禽。

鶚在隼形目中屬於鶚科，這個科只有一屬一種。

隼屬（學名 Falco ）在生物分類學上是隼形目隼科中的一個屬，屬於小型猛禽，現存共有三十多種。→


Costs of migration: risk of predation

Migrants experience heavy predation Predation risk has shaped timing and routing of migration

The predator landscape for migrants has two components Non-migratory predators along the route and the endpoints Migratory predators

Lions, cheetahs ( 獵豹 ) , and hyenas ( 鬣狗 ) track African ungulates( 有蹄類 ) Wolves follow North American caribou Water pythons( 蟒蛇 ) migrate seasonally to follow dusky

rats Songbirds flying south face five million raptors ( 猛禽

類 ) that are also making the trip


Costs of migration: inclement weather ( 險惡的天氣 )

Migration occurs during the spring and fall Unstable weather drastically raises the cost of migration Severe rainstorms and snowstorms kill millions of migrating

monarch butterflies In birds, the most devastating mortality occurs when land

species encounter storms over water A sudden snowstorm in Minnesota killed 1.5 million

Lapland longspurs ( 鐵爪鵐 ) Unseasonably cold temperatures after arriving at breeding

areas or before departing from such areas kills migrants


Costs of migration: obstacles

Birds crash into lighthouses, skyscrapers, and TV towers In a single night, seven towers in Illinois felled 3,200

birds Wind-powered turbines that generate electricity have

been erected in many locations Both on a small scale and large-scale wind farms


Wind turbines kill migrants

Particularly for nocturnally active birds and bats Direct problems: animals collide with wind turbines Indirect problems result from changes to the landscape

(e.g., construction of roads, buildings, and electrical transmission lines)

Monitoring fatalities at wind facilities is hard Issues of searcher efficiency Removal of carcasses by scavengers before they can be

counted


Benefits of migration: energy profit

Animals trade a less hospitable habitat for a more hospitable one Each fall, millions of monarch

butterflies migrate southward from Canada and the United States to fir forests in central Mexico


Monarch butterflies settle in forests

The forest is cool but not freezing Freezing temperatures kill

monarchs Warmer temperatures elevate

metabolic rates and waste energy reserves

Tall trees provide branches on which the butterflies can roost Their thick, protective canopy

shields them from rain, snow, or hail


Forests protect migrating monarchs

A dry monarch withstands colder temperatures better than one with water on its body

The forest canopy also serves as a blanket that keeps the butterflies warm


Climate changes affect food supply

Migration permits exploitation of temporary or moving resources

Larvae of monarch butterflies feed only on milkweed ( 乳草 ) In the eastern United States, the plants grow during

spring and summer Despite the energy required for migration, energy is

saved By avoiding temperature stresses of northern winters,

species compensate for the energy spent on migration


Benefits of migration: reproductive benefits

If there is so much food in the warmer winter habitats, why do species migrate?

There are advantages in rearing broods in the summer habitats Long days in the far north Birds can bring more food to

their offspring Species that breed farther north

have larger broods


Areas provide conditions for breeding

Species migrate to areas that provide the necessary conditions for breeding or that offer protection from predators

Gray and humpback whales breed in warm coastal bays and lagoons which help protect the calves from predation

Seals( 海狗 ), sea lions( 海獅 ), and walrus( 海象 ) migrate to protected rookery sites

Sea turtles migrate thousands of kilometers between feeding grounds and breeding areas Isolated beaches have fewer predators


座頭鯨

座頭鯨（學名： Megaptera novaeangliae ），又名大翅鯨、駝背鯨、巨臂鯨，屬於鬚鯨亞目的海洋哺乳動物。該物種為大型鯨魚：成年鯨身長可達 12 至 16 米之間（ 40 至 50 英尺），目前最大記錄的雌性可達 18 米。體重 25 至 35 噸（ 36 噸合 79,000 磅）。座頭鯨以其躍出水面姿勢、超長的前翅與複雜的叫聲而聞名。全世界各大海洋都有座頭鯨的蹤跡，是賞鯨者的最愛之一。已列入《瀕危野生動植物種國際貿易公約》目錄。


灰鯨

灰鯨（ Eschrichtius robustus ），現又稱東太平洋灰鯨，是一種每年來往攝食區和繁殖區的鯨。

在中國，分布於黃海、東海等海域，多棲息於熱帶及暖溫帶海域。

該物種的模式產地在瑞典。牠們約有 16 米長， 36 公頓重，一般可活到 50–60 歲。

灰鯨曾一度被稱為「魔鬼魚」，因為當牠們被追獵時會奮力搏鬥。

灰鯨是灰鯨屬中唯一的物種，亦是灰鯨科中唯一的物種。這種動物是最古老的物種之一，在地球上已有約 3000 萬年的歷史。在很久之前牠們一度是巨牙鯊的捕食對象（巨牙鯊現已滅絕）。


海龜

Some green turtles migrate from their feeding ground off the coast of Brazil to Ascension island to breed on sheltered beaches, where it is safe from predators.


Benefits of migration: reduced competition and predation

Animals returning to the temperate zone escape the intense competition found in warmer, more densely populated areas Without competition from nonmigrants in the tropics

Returning to temperate zones to breed reduces predation In the far north, breeding periods are very short

Birds nest simultaneously, reducing the likelihood of any single individual being taken by a predator

With decreased food, predator numbers are kept low Migratory species deprive parasites and microorganisms

of permanent hosts


Migration and conservation biology

Long distance migrations, one of the most spectacular of biological phenomena, are becoming increasingly rare events

The Greater Yellowstone Ecosystem is a 19 million acre temperate ecosystem in Idaho, Wyoming, and Montana All 14 bison(北美野牛 ) migration routes have been lost And 78% of the pronghorn(叉角羚 ) and 58% of elk ( 駝鹿 )

routes are gone Causes include: increased human population and habitat loss

Fences, highways, and housing subdivisions block routes One solution: create a protected network of wildlife

migration corridors ( 遷徙廊道 )


Summary

Natal dispersal: permanent movement away from the natal area or social group

In natal philopatry, offspring remain at their birth place Breeding dispersal: movement between two breeding areas or

social groups Costs of philopatry: inbreeding, reproductive suppression, and

competition with relatives for mates or resources Advantages of philopatry: genes are suited to local

conditions, familiarity with the local physical and social setting Dispersers face high energy costs and risks of predation,

increased movement and lack of familiarity with the environment


Summary

Patterns of dispersal are due to: inbreeding avoidance, resource competition, mate competition, and cooperative behavior

Habitat selection involves search, settlement, and residency Habitat selection uses comparison (best of N) strategies and

sequential search strategies Migration occurs over greater distances than dispersal Costs of migration: energy expenditure, risks of predation,

unfamiliar and inhospitable terrain, and severe weather Advantages of migration: favorable energy balance, escaping

harsh temperatures, avoiding competition from reduced food, and reduced predation and parasitism


問題與討論

[email protected]

Ayo 台南 NUTN 站 http://myweb.nutn.edu.tw/~hycheng/

空間分佈 (spatial distribution) ─ 動物行為學 (Ethology) 鄭先祐 (Ayo) 國立...

Documents

Transcript of 空間分佈 (spatial distribution) ─ 動物行為學 (Ethology) 鄭先祐 (Ayo) 國立...