Wildlife Conservation Flashcards
(100 cards)
Examples of ecological catastrophes
- Dramatic reduction in number of insects
- Permafrost melting
- Wildfires becoming extensive beyond historical range
- Great pacific garbage patch
Bio-magnification
toxin is magnified the further up the food chain you go
Why do we need to estimate population sizes?
- Evaluation of status
- Changes in status
- Effectiveness of management strategies
- Almost all decisions in population management require information on population size and density
Things to consider when estimating population
- Is an absolute number needed, or is an index okay?
- Do I need a rough or accurate estimate?
- Is a measure of density important?
- What method is appropriate?
- Cost?
- Opportunity cost?
- Ethical consideration?
Direct counts of population estimate
- Observations
- Counts of quadrats, driving transects, spotlighting, camera traps, etc.
- Checking nest boxes
- Trapping
indirect counts of population size
- sand pads
- diggings
- scats
- hair tubes
- calls
- nest box use
- genetic ID of individuals
Schnabel formula
N = total (Ct/Mt) / total (Rt)
Mt = total number of previously marked animals at time t
Ct = number of caught animals at time t
Rt = number of marked animals caught at time t
Assumptions of Schnabel method
- closed population (dispersal barriers, slow reproductive rate, slow mortality rate)
- Equal trap-ability
- marks do not influence mortality or trap-ability
- independent sampling
- no marks are lost
Methods of marking animals for survey
- paint
- ear tags
- ear notching system
- passive implant transponders (PIT)
- leg bands (birds)
- tow clipping
- tattoos
- use of natural variation
Transects
- Covers large areas
- Suitable for species with large home range
- Relative estimates of abundance
- Detect movement between habitats
- Random or systematic placement is important
- Sampling lines must be parallel to gradient
Quadrats
- Cover smaller area
- Can target particular habitat type
- Provides estimate of abundance or density
- Systematic or random spacing may result in some habitats/areas being missed entirely
- Measure of density (D = n/a)
Considering spacing of survey technique
- Distance apart is important (far enough to sample home ranges of numerous animals, close enough so each home range can be sampled)
- Wide spacing may underestimate density
- Ideal sample spacing depends on population density and size of home range
Types of traps
- Cage
- Elliot
- Pitfall
- Funnel
- Leg-hold
Trapping considerations
- Trap spacing
- Number of traps
- Duration of trapping
- Local placement
- Bait
- Odor (re-use of unwashed traps)
- Local placement - stability of trap
Invertebrate population decline
45% decrease over the past 40 years
Causes of invertebrate decline
- Habitat clearing
- Pesticide use
- climate change
Why is invertebrate conservation so important?
- Pollination services
- Population control (controls invasive insects)
- nutrient recycling
- critical link in the food chain
Thermal fertility limit
in invertebrates it is 1.15 degrees lower than critical thermal limit (where they die) - invertebrates will become infertile in heatwaves
What is population viability analysis (pva)
- essentially a quantitative ‘risk assessment’ for the future that is species-specific
- estimates the likelihood of species extinction
- estimates the minimum viable population size (for population to be self-sustaining)
What is PVA based on
models that relate a dependent variable (population size) to the independent variables that influence it (e.g. weather, mortality, disease)
Stochastic events that affect population parameters in PVA
- Extrinsic – environmental uncertainty; natural catastrophe
- Intrinsic – demographic influences (e.g. fecundity, mortality); genetic influences (e.g. inbreeding, variability)
What is quasi-extinction
the number of individuals below which the population is likely to be critically imperiled (known as the MVP size for PVA)
What is an invasive species
introduced species (non-native) that have a tendency to spread in the new area to a degree that causes damage to the environment, economy, and/or health
What is an introduced species
species that are not native to an area and reached that area by accidental or deliberate human activity