Transcript Addressing Limiting Factors-John

Are We Treating the Symptom or the
Cause of the Problem?
• Often rush into captive propagation without
addressing limiting factor
– “Headstarting” Sea Turtles (Tate 1990)
• rear until old enough to avoid predation on nesting grounds
• Better to protect nesting ground
– Hatcheries and barges for Salmon
• damns, habitat loss, fishing, etc are cause
– May be justified to learn about propagation and
control
• Mariana Crow
Removing the Cause of Decline
• This is really the crux of endangered species
conservation
• Requires detailed observation and likely
experimentation to fully understand reason for
decline
– Brown tree snake was not immediately recognized
– Condor limiting factors required telemetry to ID
• not 1080, not disturbance at nest, not shooting, likely
lead poison because Condors need open habitat to find
food and hunters/ranchers common there
Facing the Evil Quartet
• Typically we are up against
– habitat destruction/degradation
– exotics
– trophic cascades
– overharvest
– contaminants
• Contaminants and overharvest are easiest to
remove or reduce
Recovery after Agent of Decline
Removed
• Stop Over harvest
– whales, alligator
• Remove Pesticides
– Peregrine, Bald Eagle, Brown Pelican
• Remove Pesticides and Modify Habitat Needs
– Mauritius Kestrel (Jones et al. 1991)
• 1974-----4 birds
• 1991-----127-145 birds
A Complex Example of Addressing
Limiting Factors
• Rhinos in Africa
http://gurukul.ucc.american.edu/Ted/RHINOBLK.HTM
• Destruction of habitat, hunting, illegal trade in
products (folk medicine, dagger handles)
– reduction in numbers from 65,000-100,000 in 1960s to
~3,000 today
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regulations (CITES)
scientific study of medicinal effects
Leader of Yehman using agate handle dagger
shoot to kill poacher policy
De-horning
Ranching to flood market
Little Progress with Rhinos
• Can’t change old beliefs quickly
– medicinal effects of horn
• Value of horn in poor countries makes risk of
death worth it
• De-horning not very effective (Berger 1998, Rachlow and
Berger 1997)
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grow back (possible sustainable harvest?)
killed out of spite
even small portion of horn near skull valuable
dehorned mothers less able to defend calfs from hyenas
• Need to work at both ends of trade routes
Hope with One-horned Rhinos (Dinerstein 2003)
• Rhinos in India-Nepal are increasing with creation
of Royal Chitwan National Park
– Community pride, ecotourism, natural resource
benefits to residents, Royal family of Nepal leadership
• General approach
– Design landscapes with large, protected cores
– Introduce powerful economic incentives, legislation,
awareness
– Identify bold leadership to rally political will
• Translocation
• Redistribution of park revenue to locals
• Resettlement or land transfer
Exotics are Very Difficult to Control
• Disease, Snakes
– Technology not adequate to control
– Buy time by “marooning” (Williams 1977)
• release small numbers of species with poor dispersal
ability in isolated habitat (typically islands)
• 700 islands off New Zealand
– Saddleback, Kakapo (flightless parrot), Takahe (Rail)
• Buys time until feral introduced mammals can be
removed
• Guam Rail released on Rota
Conservation in New Zealand
Marooning on Islands
Tiritiri Matangi
Predator Removal
Improve Nesting Success
Translocation
Supplements
Revegetation and Recolonization
Little Barrier Island in Distance
Mainland Strategies
Revegetation
Native Parrot Habitat
It will be more difficult
7.4 billion (2016)
References
• Dinerstein, E. 2003. The return of the
unicorns. Columbia University Press, NY.
• Williams, GR. 1977. Marooning--a technique
for saving threatened species from extinction.
International Zoo Yearbook 17:102-106.