L7: Extinction Flashcards
What types of extinction are there?
-Local extinction
-Extinct in the wild
-Ecological / Functional extinction
-Extinction debt
-Numerical extinction
What is local extinction?
-When an organism is no longer found in a specific area it once inhabited, but found in the rest of the world
eg. grey wolf in Ireland
What does extinct in the wild mean?
-Only exists in ex-situ institutes
eg. Spix’s Macaw Cyanopistta spixii
What is ecological extinction?
-When very small numbers remain
-Effects on other species in community are negligible
-Probability of survival of species is low
What is an example of species being ecologically extinct?
-Hawksbill turtle
-Prey for sharks, crocodiles, octopuses and human
-Shells are hunting trophies
-Entanglement in fishing gear occurs
-Specialise in eating sponge species on reefs which allows for other species to grow
-Sponges are now overtaking coral reefs, decrease in reef biodiversity, can suffocate corals
Describe extinct debt.
-Time lag between environmental disturbance affecting a species and its final disappearance
-Reflects future ecological cost
-The living dead / zombie species
-Small remnant populations
-Species with long generation times, near extinction threshold
-Can cause underestimation of currently endangered species.
What is numerical extinction?
-When the last existing member of a species dies / there are no individuals left to reproduce
What is an example of a numerically extinct species?
-Western Black Rhinoceros
-Extinct in 2011
-Increased demand for illegal rhino horn decimated the species
Describe the extinction vortex.
Small fragmented isolated populations ->
Inbreeding, loss of genetic diversity ->
Reduced adaptability survival and reproduction ->
Reduced population size ->
What is one biggest drivers of extinction?
-Habitat degradation
What are the main drivers of extinction?
-Habitat degradation
-Predation / invasive species
-Overexploitation
-Pollution
-Climate change
What are examples of species affected by habitat loss?
Javan / Silvery Gibbon (Hylobates moloch)
98% of original habitat has been destroyed
Less than 5000 individuals remain
Freshwater pearl mussel (margaritifera margaritifera) susceptible to sedimentation of river channels
Describe habitat degradation.
-Both natural and anthropogenic origins
-Eg. Amazon rainforest fires 2019 >9000 km 2
Can cause direct mortality
Can lead to increased competition for limited resources
Describe predation and invasive species impacts.
-Contributing factor to 33% of known animal extinctions
-Cats, rats and snakes
-Direct mortality
-Competition for resources
-Introduce diseases
-Habitat modification
How does invasive species affect New Zealand?
-Kill around 25 million native birds per year, including Kiwis
-Natives did not evolve with predators, very vulnerable to invasive species
-Plan to eradicate rats, stoats and possums by 2050 with trapping programme.
What is an example of an invasive species going out of control?
70% of Polynesian Tree snail driven to brink of extinction.
-Cause due to invasive carnivorous snail Euglandina rosea which was introduced to control another invasive species, African land snail
-Native snail was smaller and slower and easy prey
Describe an example of overexploitation.
-Passenger pigeon
-3-5 billion in North America before Europeans
-1850s large scale commercials hunting of pigeons
-1900s extinct in wild, last known individual Martha died in captivity 1914
Describe an example of pollution.
Yangtze river dolphin, used to be 5000 - 6000 dolphins in 1950s
-1998 only 13 left
-Driven to extinction by pollution, electrofishing, engineering explosions, inbreeding, fishing gear
-Last individual in captivity dead in 2002
Declared functionally extinct in December 2006
Describe a case of extinction due to climate change.
-Bramble cay melomys
-First mammal driven to extinction by climate change in 2015
-Habitat destroyed by rising sea levels
-Found on Bramble Cay island in Great Barrier Reef
Why is it important to identify vulnerable species?
-Some species are more at risk than others
-Population viability analyses an option
-Conservation biology often requires rapid assessment and decision making
-Reliable and easily measured indicators of extinction risk is important
What does intrinsic mean?
Inherent factors directly relating to the species, biological and ecological
What does extrinsic mean?
Environmental factors, usually human activities
What intrinsic traits drive species extinction?
-Population size / number of populations
-Narrow geographical ranges
-Habitat specialists
-Rare species
-Body size
What extrinsic factors are correlated with extinction?
-Commercial value of species
-Commercial value of habitat
-Whether population or habitat is protected
-Whether there is laws protecting the species
How does population size affect a species?
-Some species have naturally small populations like large populations with large territories
-Greater vulnerability to stochastic factors
-Best predictor of extinction rate of isolated populations
-Species with several populations less vulnerable
How does a narrow geographical range affect a species?
-Linked to population size
-May be endemic
-Many rare species occupy islands or isolated habitats, eg. snow leopard
How many snow leopards are left in the wild?
2000 -3000 left
What is the home ranges of snow leopards?
30 - 62 km2 where prey is abundant
>1,000 km2 where prey is rare
How does being a habitat specialist affect a species?
-May need specialist habit
-Alternation of ecosystem can result in an unsuitable habitat
-Parasites (co-extinction)
What is some examples of habitat specialists?
-Wetland plants require very specific and regular changes in water levels
-These may be rapidly changed by human activity changing the hydrology of the system
-Salt marsh cord grass Spartina patens, is only found in salt marshes and no where else
What is the name of the tongue eating parasite?
Cymothoa exigua
-Parasitizes eight species of fish
What makes a species rare?
1- Only found in small populations
2- Lives in a narrow geographical range
3- Occupies only one or a few specialised habitats
What is specialisation?
“Use of a relatively restricted subset of resources or habitats compared with other species”
-Koalas- limited diet of eucalyptus leaves
-Palm-nut vulture- eats fruit from the oil palm
-Life-history specialization, like migration
How does body size affect a species?
Large animals have
-Large ranges
-Low reproductive rates
-Require more food
-Are hunted by humans
-Most extinctions were of the largest animals such as woolly mammoths and the Tasmanian tiger
What intrinsic factors affect orangutans?
-Long lived species
-Late reproduction (10-15 years)
-Long interbirth periods
-Low birth rate (1 or 2 offspring)
What are the two species of orangutans?
-Pongo abelii (Sumatra)
-Pongo pygmaeus (Borneo)
How long do orangutans live for?
Up to 50 years
How long is the interbirth period for orangutans?
Once every 5 years
What species are most at risk of extinction?
-Large specialised species that live in narrow geographic ranges most at risk of extinction
How does commercial value of species affect them?
-They be overexploited
-Elephants value of ivory tusks
How does commercial value of habitats affect species?
-Large scale of forest turned into oil palm plantations
-Industry worth US$67 bn
-Estimated 25million hectares destroyed in Borneo and Sumatra
-Orangutan is flagship species
How does the existence of protective legislation affect species?
Endangered species act played a role in return of grey wolves to Yellowstone, rollback of this law is now a new threat for this species
How many marine mammals are threatened with extinction?
25%
What are drivers of threats against marine mammals?
-Fishing
-Invasive species
-Development
-Hunting
-Climate change
Almost half are threatened by 2 or more human impacts
What marine mammal species are at high risk?
-Species with low reproductive rates
-Slow life histories
-River dolphins with narrow ranges
-Family Phocidae (seals) and famliy diphiidae (beaked whales)
What marine mammals are at lower risk?
-Toothed whales- low reproduction but large range and social groups
-Baleen whales, like Humpbacks and Greys
-Fast life histories, strong recoveries after bans on whaling
What are the conclusions of this lecture?
-Most important predictor- speed of life history as potential to rebound from human impacts
-Intrinsic traits are more important predictors of risk
-Measure the inherent susceptibility to human impacts and ability to recover from them
-Emphasizes the importance of understanding the basic biology and ecology of marine mammals
What is the summary of this lecture?
-Rare and specialised species are more prone to extinction
-Species with slow life histories are more prone to extinction
