Phils stuff Flashcards
Caughly 1994- what did he do
Came up with 2 paradigms because he noticed a lack of integration between practitioners of conservation and scientists
- Small pop paradigm
- Declining pop paradigm
Still major challenge to unite these paradigms
Small population paradigm
Theoretical work dealing with the problems of small populations. Dominated conservation biology up to this point.
Environmental stochasticity- randomness in the environment eg inter annual variation in food available. Cant predict but have big impact on small pop
MVP- minimum viable pop
PVA- Population Viability Analysis. How we might manage a population to get them viable. The conditions under which they are viable.
Metapopulation management- how we manage sub populations. Can we move individuals between them to alleviate interbreeding etc?
Captive breeding- take away from wild threat and put them back when threat removed
Protected area- one big one or multiple small?
Declining pop paradigm
Empirical work identifying and attempting to prevent processes causing the decline of populations. Practitioners use this.
Identify cause of decline and treat it. More practical value than various other approaches- essential to determine causal threats
- correlation isnt causation
- management must be run as an experiment or nothing learned
- consequences of actions must be evaluated according to standard experimentation rules
Issue is often situations are so specific it can be difficult to generalise the results - so not of interest to high profile publications
Example of declining pop paradigm working
Lord Howe Woodhen
- series of ecological disturbances. Pigs introduced, cats, rats. Human settlement in 1834
- Woodhen is a flightless rail endemic to the island that suffered a steady decline.
- By 1853 restricted to mountainous regions,
- by 1920 only on 2 summits of least accessible mountains.
- By 1969 conservation started. Numbers stabilised at 8-10 pairs.
- Intensive field work to assess diet and habitat ruled out food shortages and habitat loss as a possible cause of decline
- Surveyed rat population = rat most abundant where woodhen were= not that
- Mapped pig distribution- fine in 2D but in 3D realised pig couldn’t access the remote mountain peaks and so …
- Pigs eradicated between 1971-1989.
- 1980-83 CB programme
- ‘87 population stable at 180 birds, habitat saturated.
- No inbreeding depression —> shouldn’t just write off populations because they are small
- $200,000
Single threat identified in closed island system
Example of declining pop paradigm failing
Californian condor
- north ameiricas largest bird. Rapid decline
- 60 individuals in 50s, 20 in 83
- 1987 last 7 birds taken into captivity
- 1960s thought food shortages may have caused the decline. So put feeding stations up in 71-73.
- Also learnt about organochlorides causing shell thinning. They were banned in 1972. Circumstantial link to OC accepted as cause of decline.
- Then thought lead was the cause and identified as cause of death in 3/5 birds. Lead likely from deer carcasses because hunts use lead bullets. Condors have very strong digestion so can break down and assimilate lead. Tried to get hunted to use copper bullets but they were reluctant
- 91 reintroductions started
- 06- 44 individuals in the wild >6 years old (maturity age)
$35,000,000!!
Multiple interacting threats and condor are large and slowly multiplying and maturing birds. Mortality from electrical power lines and egg collectors too –> little follow up, nothing rigorously tested
Tiger causes of decline
Poorly studied
Poaching, fragmentation (loss of genetic variability), habitat loss to agriculture, loss of food sources,
Karanth and Smith 99 believed it was because of loss of food sources. This was a new cause at this point, after 20/30 years of trying to stop the tiger decline. Used a simple population model for this
Chapman et al 2008- used data on life history parameters. Tiger have slower life history so vulnerability to poaching i higher than for other solitary big cats. Even good juvenile survival must be accompanied by high adult survival for population stability. So they conclude poaching bigger threat than food shortages.
Other cats mature quicker, have bigger litters, short birth intervals so can withstand larger demographic insult than tigers
Cougar adult survival can be 0.5 and juvenile 0.7 and still be stable
Tigers adult can be 0.75 if all juvenile survive (1)- only need low levels of poaching to cause adult survival to go down resulting in a population decline
Pic on phone
Both studies model based- not that reliable. Need stats
Why is population modelling important?
Data we observe is very noisy with many interacting factors so it can be difficult to find out what is causing a particular response.
Scale of problems we are facing are huge. Make models to replicate environment and study there.
Manipulation of the environment could be too risky. If endangered species often have to make rapid decisions cant wait for generations to see potential impact of what we’ve done
What can population modelling be used for?
Predict how a population can change with interventions, what has the best impact
Can assess risk eg temperature changing, how this will influence the population. Can figure out the scale and urgency of the problem from this without having to collect many years of data
Understand trophic interactions. Manipulation of 1 may influence other. Can see which has the most influence and target.
Understand link between where a species occur and what climate is like there. Can then predict changes. This is species distribution modelling. Can understand how large the threats of CC are.
An expected demographic response can be modelled for each potential cause and decline and compared with independently collected data –> more exploratory than explanatory because doesn’t incorporate explicit info on the cause of decline eg marbled murrelet Peery et al 2014
Write out a simple population model for
- single number
- pop size at time intervals
- continuous time pop growth model
pic on phone
continuous time pop growth model = how much time elapsed up to the point you want to get next estimate
Draw a discrete time model
phone
Draw a continuous time model
phone
How can we model pops with greater realism
Add carrying capacities, density dependence, info about pop structure too eg spatial structure, meta populations, age stages and matrices, individuals
Types of density dependence
Negative (competition)- can be direct or indirect eg scramble competition depletes resources available but not in contact with each other. Contest- competition over indivisible resource- only 1 gets it
Positive (allee effects)
Example of positive density dependence
Wild dogs- need big groups to hunt and care for pups and protect kill from kleptoparasites
Small pops may struggle to find mates. Plus reasonable chance there is a skew in the sex ratio- retard pop growth.
When in company individual more likely to escape predator- dilution effect eg nesting birds
Co-operative vigilance eg meerkats more likely to see predator
Why is it difficult to collect data about allee effects
Populations often decline so rapidly hard to collect data, also the focus should be on helping the pop not modelling their decline
Would also need lots of data
