-"Classical" predators spend a large amount of time and effort searching for, capturing, and handling prey

-Overall, successful kills can be infrequent

(Isle Royale in Lake Superior- wolves have 7% success of killing a moose)

-overall capture success ~10-30%

Implications?

-predators are strongly territorial

-ensures adequate hunting grounds for established individuals

-some animals (wolves) restrict breeding to dominant individuals

THEORY

-predators have more food when prey populations are high, and thus the number of predators increase as their death rate declines

-he increase in predator numbers increases pressure on prey populations, which then decline

-then predator populations decline

-this happens sometimes in nature..... "Snowshoe hare-lynx cycle (around 10 years)

**

-the model oversimplifies nature

-assumes the rate of prey capture increases in direct proportion to density of prey (ie. animals eat no matter how many prey then catch)

-factors such as disease, climate, and other predators exert constant effect

1)Reproductive Output

-hares have 3-4 litters over a sumer (5 young each time)

-reproductive output reaches is peak early in the population increase phase, then falls

2)Changes in Mortality Rates

-adult survival begins to drop slowly as the population increases to a peak, then drops dramatically for 1-2 years

-once low #s are reached, adult survival rates impreve slowly, but takes 4-5 years to reach max densities

-both repreoduction and survival rates begin to decay in the increase phase of the cycle, 2 years before peak densities are reached (max reproduction and survival rates occur early in the increase phase of the cycle)

WHAT CAUSES THE CYCLE?

1)food

-only 3% mortalities due to starvation

-food quality can affect body condition which may lead to reduced ability to escape predation (indirect)

2)predation

-95% of all radio-collared hares died from predation

-indirect: stress, food/body condition

3)social interactions

-everything affect reproductive output

CONCLUSION

-cycle is caused by a time lag in both the indirect and direct effects of predation

-the low phase of the cycle is the combind result of predation mortality and slowly recovering reproductive potential

Density influences both the feeding behaviour (functional response) as well as the number of predators (numerical response)

1)Functional Response

-occurs when the number of prey eaten per predator in a specific time varies directly with prey density

-ie. eat more prey with increasing prey numbers

2)Numerical Response

-occurs when predator populations change directly /w prey populations

3)Total Response

Mortality = Functional*Numerical Response

=(prey consumed/predator)*(predators/area)

ie. (0.5hare/day/lynx)*(25lynx/100km2)

=12.5hares/day/100km2

***
-Functional and Numerical responses have important applications when wildlife managers consider whether predators are responsible for the decline of prey populations

-need to understand the predator-prey system to make informed management decisions

-especially prey populations that have commercial/recreational hunting values (ie. fisheries, ungulates, waterfowl)

Two factors limit the rate of consumption:

Search time- the amount of time spent looking for prey (determines capture rates)

Handling time - time required to capture, eat, digest

Type 1 F. Response

Type 2 F. Response

-most ungulate herbivores (moose, sheep, caribou, deer, elk)

-many mammalian and avian carnivores (lynx-hares, kestrel-voles)

Type 3 F. Response

-Alternative prey and switching behaviour

-ie. coyotes and lynx to snowshoe hare cycle

Other factors that can affect functional response:

-experience of the predator (young vs mature)

-search image (ability of the predator to recognize a prey species as a food item (often related to prey density)

generalist species: tend to show weak numerical response to a particular prey species

specialist species: tend to show strong numerical response to primary prey

-density of prey populatin

-density of predator population

-characteristics of prey including reactions to predators and nutritional condition

-density and quality of alternative foods available to predator

-characteristic of predator such as its means of attack and food preference

Other factors that affect predation rates:

-sonw conditions

-social organization

-vulnerability of prey

-alternative prey sources

-habitat loss (concentrating prey)

-hunting

Definition: Change in prey behaviour due tot he presence of predators are referred to as nonlethal effects or predation risk effect

-Dif areas vary in both forage profitability and risk or predation

-An animal must decide whether to feed and balance its energy gains against the risk of being eaten

PREDATION RISK AND HABITAT SELECTION

-sexual segregation is Dall's Sheep

-females with lambs used poorer quality feeding habitats very close to clifs (less risk)

-whereas males used higher quaity habitats further from cliffs

Yellowstone- Ecology of Fear

-Presence of wolves has resulted in increased predation risk for eld, which have avoided riparian areas and let willows recover

-increased vigilance (alertness)

-migration (wildebeast, Barren Ground Caribou)

-herding/group size (Muskox Group Size)

-spacing out (relies on predators spending time in areas of high prey density.... common in female ungulates ie. Woodland Caribou dispersion into mountains and calving islands to avoid wolves)

-birth synchrony (known as predator swamping)... moose, caribou, wildebeast, lesser snowgoose, colonial seabirds)

Historically, predator control programs and bounties contributed to population declines of many predators including wolves, foxes and coyotes

They were implemented to increase densities of ungulates and waterfowl (hunting) and reduce predation rates on domestic livestock

CONTROVERSY

-Main issue is public acceptability of different methods of control

-agencies need to balance cost-effectiveness of emthod with public acceptability

-Controversies vary according to species, socioeconomic ad urban status of individuals, control technique (lethal vs non-lethal)

QUESTIONS TO ASK

-What are your management objectives? (sustainable yield? increase low denity population?)

-Is predator control necessary (are predators reason for decline? How good is data?)

-Will it work? (significantly?)

-Is it socially and politically acceptable? (lethal? how will it be done?)

Impemented numerous times to increase moose and caribou populations

-Many attempts were unsuccessful due to threatned tourist boycotts and other expressions of public disapproval

-Most recent aerial wolf kill was implemented in 2003-2004

-target was around 200 wolves, monitoring continues today

RESULTS
-increased survival of cow moose and calves

-However, in other areas of Alaska, over half of newborn moose calves are killed by Grizzl bears

-need to consider reducing both populations simultaneously

General Conclusions

-under some conditions, wolf control can increase caribou and moose populations

-it doesn't always work!!

-other factors are important (bad winters, poor habitat conditions, hunting, bears)

-diversionary feeding programs

-enhance habitat for prey species in an effort to improve physical conditions, reproductive success and possibly result in imigration to the area

-enhave habitat for alternative prey species

-predator relocation

-sterility (ie. vasectomy and tubal ligation of dominant male and female in wolf packs)

GROUSE

-pimary predators are raptors, weasels, coyotes

-there is little information regarding effectiveness of predator control to manage North American grouse populations

-Increased pressure on agencies to at least consier predator control because many prairie grouse populations are endangered

SHOREBIRDS

-around 30% of all shorebird nests fail due to predation

-ground-nesting behaviour of shorebirds make them susceptible

-predators include red fox, coyotes, skunks, raccoons, rats, gulls, crows

-densities of predators tend to be higher where humans are (garbage eaters)

-predator control must be implemented to reduce decline of ground nesters

-removal of predators results in increased nest success

-up to 75% higher nest success in areas where predators were removed

-to be successful, need to consider all predators, and continued removal during breeding season.

*Brown tree snakes... innovative predator control

*****Predation can be one of many factors contributing to a decline i prey populations

-predation may not be primary cause of decline, but may accelerate it

-found that coyotes killed 2.5% of adult sheep pop and 8.1% of lamb population

-represents financial loss of 19million dollars annually

-in AB, coyotes cause over 75% of predation losses of livestock

COYOTES

-are territorial

-each territory controlled by alpha male and femals with beta and individual pups

-Monestrous producing one litter per territory each spring

-live 3-10 years and produce 4-8young/litter

***Food abundance regulates coyote density (influences reproduction, survival, dispersal, space use patterns, pack size)

METHODS TO CONTROL COYOTES
-poisoning (asphyxiation using CO)

-Shooting

-trapping (steel leg-hold, snares)

EFFECTIVENESS OF CONTROL

-Animal Damage Control (ADC) in US killes 70-85K per year over 12 states (18-29% coyote population)

-overall, effects of removal are temporary and short-term

***estimate is that it would take a removal of 75% coyote population over a continuous 50 year period to reduce coyote population growth

selective removal- of coyotes with territories that overlapped lamb/ewe operations

sterilization- has produced varied results

**some studies have shown no significant difference in total sheep losses b/w areas with and whithout coyote control

OTHER METHODS:

1)Flock and herd management

-confining livestock at night

-minimize use of high-risk pastures

-dispose of carcasses

-late fall lambing

2)Electric Fencing

3)Livestock Guardians (dogs, llamas, donkeys)

4)Fladry

-Flagging hung on fence line

-frightens predator

-temporary solution due to habituation

-studies showed that it caused wolves to kill instead on neighboring ranches

Types of predators and prey

The Theory behind Lotka-Volterra Model

The response of predators to prey density (Functional response curves, numerical response, total response)

Summary of Factors (5) that should be considered when studying predator-prey interactions

Predator-prey systems are coplex. Predation can be one of many factors contributing to a decline in prey populations

Response of Prey to Predators (predation risk)

Predator Control (effectiveness - lethal and non-lethal methods... public debate)

Population Size

Pop Density

Death Rate

-# of deaths per number of individuals per year

Birth Rate

-number of individuals born per number of individuals in the population per unit time

Recruitment

-the number of new indiiduals that reach breeding age

Sex Ratio

Age Structure

Birth/Death rates are key components of pop dynamics

-birth rates measured using Fecundity Rate (number of female live births per female per unit time)

mortality rate- the # of animals that die dring a unit of time divided by the number alive at the beginning of the time unit

change in N/change in t = rN

-growth rate (r) expresses populaion increase (or decrease) on a "per individual basis"

-rate of increase varies in direct proportion to population size

-It flucturates, so to estimate long term population growht rate, need to count individuals at the same time of the year to account for the cycle of births and deaths

-an increase or decrease over discrete intervals

-most commonly expressed as a ratio of population size in one year to that in the preceding year

-denoed by lambda

lambda = N(t+1)/N(t)

Projecting population size through a single time interval is given by...

N(t+1) = N(t)lambda

To calculate growth over many time periods...

N(t+1)=N(t)lambda^t

***Geometric and Exponential Growth Equations are related

exponential growth rate = r = births (b) - deaths (d)

geometric growht rate = lambda = Births (B) - Deaths (D)

**** If per capita growth rate per year is 30%, then lambda is 1.3

POPULATION SIZE TRENDS

-stable

-erratic (large fluctutations at varying intervals)

-cyclic (large repeated flucuations at approximately constant levels)

The proportion of the total population that are in each age class

-age classes can be absolute of relative

**How fast a population grows depends on age structure because birth rates vary by age class

Cohort Life Tables

-cohort is group of individuals born at the same time

-keep records on them from birth to death

-however, this is very difficult to do!

-Time consuming, especially for long lived species or species difficult t o ifnd and count

x=age class

nx= # individuals in age class x

dx= # deaths in age class (=nx - nx+1)

qx= mortality rate in age class (=dx/nx)

sx= survival rate in age class (=1-qx)

lx= cumulative survival rate from birth until age x (=nx/n0)

Static Life Tables

-record the age at death of a large number of individuals or observe age structure at a specific time

-this is a snapshop

**inferring mortality rates from age structure requires assumptions....

-# newbords is constant

-no migration

-age-specific ortality rate is constant b/w cohorts

r= births rate -deaths rate

b=birth rate

d=death rate

**lambda = population size in current year/population size in previous year

OPEN POPULATION

r=b-d + i-e

-birth and death rates differ with age structure and sex ratios

-high # adult females means pop will grow

AGE SPECIFIC BIRTH RATES

1)age of sexual maturation of males/females

2)length of gestation period

3)sex ratios

4)whether the species is monogamous or poly

5)number of females that breed at each age

6)# of young per female of various ages

7)influence of nutritional conditions on reproduction

More realistic to consider on a continuum

additive= when mortality factors act independent of each other

-EX. a pop of 100 loses 20 to food shortage and disease

-predators get 10

-if these were additive, then a total of 30 animals would die from these combined forces (independent)

compensatory= when mortality factos have a dependent relationship with each other (ie. an increase of disease in one form of mortality results in an increase or decrese in another form of mortality)

-EX.

-if predators ge 20, only 5 may die of disease

-one cause kills animals that ould otherwise die of other causes

-mortality from predation is usually additive when predators kill individuals that would have likely lived to reproduce

-compensatory occurs when predators kill individuals that likely would have died from other causes

PREDATION AND MOOSE
-age and nutritional status of predator-killed moose indicated predation on adults was largely additive. They considered predation to be...

additive when moose were not severely malnourished or old

compensatory when moose were old and malnourished

-testing this involves substantially reducing predation and subsequently determinging whether moose survival and pop size increases

-a result of increased calf survival would suggest additive.

What si a population?

Population growth patterns (logistic growth and K, trends)

Population characteristics (birth rate, fecundity, death rate, etc)

How to construct and read a Life Table

Interpretation of Survivorship Curves

How to calculate population growth rates (r or lambda)

Know the difference b/w additive and compensatory mortality

In the past, unregulated harvest has caused wildlife extinctions (passenger pigeon) and near extinctions (bison)

-era of exploiation, market hunting

Sport hunting is populatr and economically important in both Can and US

-13 million hunters in US spend over 10 billion dollars in hunting related exenditures per year

-16.1 million ducks and 4.2 million geese were harvested in the US and Can during 2001-2002 hunting season

-plus unknown amount from subsistence hunters

-in some cases, recreational hunting can represent up to 25% of the post-breeding populations size

Harvesting animals is based onthe premise that without hunting, growth and recruitment of the population are balanced by natural mortality (ie. r=0)

-hunting reduces a population, which increases its growth rate (due to higher birth rates and lower death rates from less competition for food)

-consequently, the accelerated growth rate provides a surplus of animals beyond the number required to replace the losses (surplus)

-theoretically, in good habitat, wildlife populations can produce a sustained yield

IT IS SIMPLE!

-harvest a population at r (if r = 0.2, harvest 20% of population per year)

***Managers need to know whether hunting/trappnig is acting in an additive or compensatory manner to determine how many animals can be harvested

total mortality= sum of natural mortality and hunting mortality

additive mortality= occurs when harvest mortality results in total mortality exceeding what would have occurred from natural causes alone

compensatory hunting mortality simply replaces about the same proportion of natural mortality

***this is hotly debated.... varies among species

HARVEST MORTALITY EFFECTS

-hunting mortality tends to be compensatory at high population densities (pop near K)

-tends to be additive at low densities

To meet various biological objectives

-control the # of animals to reduce habitat deterioration

-reduce competition for selected species

-alter sex ratios to maximize production

-predator control

WHY HARVEST ANIMALS?

Social and Economic Objectives

-provide commercial opportunitie (guide outfitting, trapping)

-max recreational opportunities

-maintain public safety

-promote landowner-hunter relationships

-provide for subsistence harvest

70% natural mortality rate

-35% harvested, 35% non-harvest mortality

-equals 70%...

COMPENSATORY

If total mortality exceeded 70%, then harvest mortality would be considered additive

THEORY AND REALITY

-although additive mortality due to harvest, may be posible, that level or mortality may not occur because..... human interest declines and densities decline, wary animals may result in increased hunter effort, harvest regulations limit additive mortality by limiting the number of permits.

Factors Affecting Harvest Levels

-higher if it is compensatory mortality

-lower if additive

HUNTING REGULATION OPTIONS

Manage Effort And Yield

-limit # permits

-daily/possession limits

-season length

-opening and closing dates and times

-sex/age specific harvest

-weapon restrictions (archery)

-control hunter access (road closures)

-stop harvest when predetermined # of animals have been killed

-establish refuges

1. Set Management objectives

2.assess willife population size census/count

3.Set Harvest Goals

4.Set Harvest Regulations

5.Implement Hunting Season

6.Monitor Harvest.. compare /w goals

**Harvest Systm Results will VARY

-a combination of antler restrictions and limiting hunter numbers is ususally required to allow escapement of bulls into older age classes

-therefore, there are inherent trade-offs managing for enhanced mature bull elk

-need to have specific managment goals and good information to be successful