BZ3740 – Wildlife Ecology and Management – Flashcards

Interaction between organisms and their environment, i.e how an animal interacts with other animals and the abiotic (Physical) environment

managing wild populations, includes conservation, harvesting valuable spp, controlling pest spp, dealing with human-wildlife conflicts

1. maintain many populations at 'natural' densities (biodiversity) 2. increase populations of threatened species 3. sustainably harvest populations of valuable species 4. reduce populations of unwanted species (typically invasive spp.) 5. manage populations of 'problem species'

some species considered important, people want to utilize wildlife, people want to interact and live amongst wildlife

people want to live amongst wildlife but they want risks removed, big predators (elephants etc) are popular but they can be a threat to life, livestock and property, people want to live in the bush but then burning changes landscape as is needed.

humans are fundamentally selfish, corruption (eg, wildlife trade, development, development approvals), actions of a few (eg arsons) impact greatly, governments follow popular opinions and quick gain

what used to be sustainable is not now.

1. exploiting a population while holding abundance constant- sustained yield harvest. 2. reducing abundance of population that is too dense- pest control. 3. increasing abundance of a population that is too small- threatened species management. 4. managing populations of all species in an area at 'natural levels' (biodiversity management). 5. dealing with humans

prehuman- millions of years to about 50,000 years ago. aboriginal- 50,000 years ago to approx, 200 years ago current- 220 years ago to present 5000 years ago to present - introduction of dingo (now considered native). This impacts most decisions:burning, hunting, threatened species etc etc

in some parts of the world, just in 'wilderness' areas, in other parts of the world almost everywhere. Cant just expect to only protect wildlife in wilderness and national parks as much biodiversity and threatened species now occur amongst humans in impacted areas

becoming rare, often impacted in various ways (ferals, fragmentation, fire etc)

many species have drawn a lucky card by adapting to living within mountainous ranges, many protected areas are mountainous ranges as humans didn't/don't generally inhabit them

1. Sustainable harvest of animals for human uses 2. Overexploitation of animals for human uses 3. Reduction of pest or problem animals 4. Increase in declining/threatened animals 5. Maintaining 'natural systems' & biodiversity

food, clothing & materials, pets/collections, medicines, traditional beliefs. for any of these to be acceptable the harvest must be sustainable

a harvest that can continue indefinitely forever, that is if we harvest at a rate H now, the population will replenish itself at the rate r=H, so we can go on harvesting at that rate

harvest program should not chnage the population of the harvested species in unwanted ways, for example by driving evolution of undesirable characteristics

-effects can be demographic (short-term) or evolutionary (long-term). A population growing at a rate r can be harvested at a rate H = r, to hold size constant. H gives a sustained yield. But, most wild populations aren't growing - they're 'stable' (with stochastic fluctuations) at 'K' = carrying capacity

Carrying capacity (K) is simply the number of individuals that the environment can support (e.g., due to food/competition, habitat limitation, predation)

we have to make it start increasing

1. provide extra resources for the population. 2. remove predation, or some other constraint, on population growth. 3. reduce the population below K, to provoke a compensatory increase in the population growth. we can then harvest at the rate at which the population would otherwise grow towards K...this is how sustainable harvesting is usually done.

pushes numbers down, population can then be harvested sustainably at any rate where H is equal to the density-specific growth rate. Note: the initial yield from the population at K is high, the equilibrium yield will be lower.

this method only works if reducing the size of a population provokes compensatory population growth, this means the sustaibable harvest depends on density dependence of population growth rates.

some populations (eg humans) are growing exponentially and are not density dependent, but this is rare-most wildlife populations show density dependent population and logistic (restricted) growth.density dependent population growth

initially growth is limited by births, then population goes though a rapid growth phase, then survival/fecundity is reduced due to competition as you approach carrying capacity for that environment. population growth rate is hard to determine because it requires a population growing from scratch (population recovery, introduced species and lab studies are from scratch populations). growth rate plots can also focus on recruitment rate, with a maximum recruitment rate at intermediate population size (often about half of K).

Assuming density dependent population growth (i.e., logistic population growth), the MSY is about K/2. harvesting below or above this point results in lower yields due to lower recruitment rates. hill shape graph is considered a production curve

best strategy for variable environments is fixed proportion at a harvest level below MSY.

MSY and 1 are too risky given uncertainty in MSY, N and K. A SY at point 2 (approx. halfway between MSY and K) is the safest. Offers high yield but big buffer for population. see notes image

estimate buffered SY (i.e approx 0.75 of K), this gives you a fixed yield that is hopefully sustainable, accounts for issues in estimating population size (N), carrying capacity (K), variation across seasons & years, estimating the shape of recruitment.

fixed quota at the MSY, but it is very risky, it is safer to go for a lower SY (ie. harvest at a high recruitment rate between MSY and K). however this doesn't really account for changes in population size through time

fixed proportion, better than fixed quota. does not rely on knowing what the production curve looks like and allows constant assessment.adjustment of quota, more ecologically robust but still need to harvest above MSY (because K and population size can change a lot year to year), but logistically tricky because the size of the population has to be estimated before each harvest season, so that the number to be taken in that season can be set, if the population drops, the size of the harvest drops and harvesters don't like that.

possible to assess harvest statistics (catch vs effort) to determine quotas based on catch-effort, requires less information on population size and demography within catch effort curve: cat (or yield): the size of the harvest taken (numbers, biomass), effort: the amount of harvesting activity (number of hunting licences issues, number of boat-days etc). Idea is that catch per unit effort (CPUE) can be used to assess population size, but: requires good data, to produce an informative catch-effort curve, need to have harvested at extremes (High CUPE-low CUPE) which is inefficient at one end and high impact on the population at the other, each level o effort should have been applied long enough to allow the population to equilibrate with it-often not true.

1. fixed quota:least knowledge required, most acceptable to harvesters, most likely yo lead to exploitation. 2. fixed proportion: safest, most common knowledge required, least common method. 3. catch-effort: requires tricky data to be successful.

1. aiming for the MSY, especially in variable systems, many examples of failures in fisheries. 2. over-capitilization, initial yield from a harvested population may be higher than the equilibrium yield, harvest may need to be lowered through some periods (eg fixed proportion), bu harvesters want to keep taking high yields. 3. valuing short-term gains over long term sustainability, sustainable harvest requires deferring part of a harvest to allow ongoing replenishment, for populations that replenish slowly, a strict economic argument would advocate rapid over-harvest too extinction. 4. greed, lack of regulation/enforcement, particularly doomed to fail if there is: open access to resource, species cross political boundaries (no single control), harvest is illegal. tradedgy of the commons will prevail in these cases (no use limiting harvest because if i don't take it, someone else will). 5. harvesting different species together, severely compromises the ability to sustainably harvest any one of them, the rarer species can be driven to extinction because effort remains high even when it becomes very rare (due to more common spp). 6. the basic biology was not suitable - eg some species dont have symmetrical density dependent growth rates