Mission 2008:
Solving
Complex Problems
Eric Gilbertson Team Tortugas 3
My
Class Schedule
Galapagos
Ecosystems
Invasive Species Summary
Updated 10/25/04
Background source discovergalapagos.com
Galapagos takes Aim at Foreign Invaders
Science Jul 27 2001; 293,5530 pg 590
2001 - Charles Darwin reasearch Station and Galapagos National Park
Service Develop 6-year project to eradicate alien species
- Given $18 million by UN
and World Bank, $19 million by other sources.
Goal - eradicate most
troubling species all at once.
Implementation - ban
imported goods that could introduce new species.
Early 1600s - first invasives arrive (goats, rats, cats, and dogs) with
sailers, whalers.
Pigs, goats: destroy vegetation, thus removing native food sources
wipe out foliage that shades temporary rain pools and regulates
temperatures of reptile eggs.
Pigs, dogs, rats, cats: eat lizards
eat hatchilings and eggs of native species such as
dark-rumped and Galapagos Petrels, Mangrove finches, tortoises, and
snakes
Frogs: appeared in 1997 after surviving in cargo with help of wet El
Nino weather
95% of all original species remain in Galapagos
1991-2001 Problem Invasives: >60 plants, 15 vertabrates, 6 insects
Eradication Techniques
- Use GPS to track goat herds, eliminate with sharp shooters
- Radio-collar cats to locate those hiding
- Use high-powered air-guns to kill rock-doves (on Santa Cruz) and
smooth-billed anis
- Poisons and bush clearing to eradicate fire ants
- Elevated bait stations to catch black rats but not native rice rats
- Spraying herbicides to eradicate quinine seedlings
- Encourage farmers to grow more produce to reduce imported produce
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An Asssesment
of the Galapagos Rail Population over 13
Years
Journal of
Field Ornithology vol 74 no. 2 pp136-140
Gibbs, Shriver, and Vargar
The largest population of the
Galapagos Rail lives on Santa Cruz Island
From 1986-2000 probability of detecting Rails fell from 36% to 27%
-Rails lilve in coastal mangroves and moist highlands, though
not found in the highlands since Darwin's voyage
- Detected on only 4 islands of the 7 that have highland zones
Results of Study -
moderate 13-year population decline due to invasive cinchona plant
- 30% to 40% of
highlands area now covered with cinchona
-Estimate: entire
zone wil be covered by year 2020
Cinchona - plant is
the source of quinine
replaces sedges and ferns (rail habitat, which offers protection from
predators)
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Non-nativefrogs
hitch to Galapagos Islands
CNN.com July 7 1999
Tree Frog: Scinax
quinquefascila first sighted on islands 1998 in Puerto Ayora (Santa
Cruz Island)
Frogs invaded via cargo ships or airplanes.
For over 20 years, individual frogs have been sighted, but never such a
breeding population.
1997-1998 severe flooding from El
Nino harbored large frog populations on mainland.
Wet conditions aqllowed population establishment on islands
Suitable habitats are
associated with human habitatinos
Impact not known (in 1999)
Speculation: frogs could reduce
native insect populations
could endanger native predators ( if frogs posses skin poison glands)
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Isabella
Project
darwinfoundation.org
Isabella Project - the control and eradication of
invasive species
Jan 31, 2000 - June 2004
Funding - United
Natinos Foundation and UN Fund for International Partnerships
Goals - (1) Provide
proven methods for eradicating invasive species and/or mitigating
effects of them
(2)
Establich quarantine system to prevent new introductino and spread of
existing species.
Species to be eradicated(on
Santa Cruz and Santiago)
Smooth billed
anis
Rock doves
Feral cats
Black rats
Little red
fire ants
Impact Mitigation
Black rats on
Dark rumped petrels, Mangrove finches, and Galapagos tortoises
Feral pigs on
sea turtles and Galapagos tortoises
Black fly on
native fauna
Experimental control of quinine
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Galapagos:
A Natural History
Michael H. Jackson 2002
Introduced Species:
guava - easily distributed
by feral cattle
quinine - dispersed by
wind
dogs - prey on yung
tortoises, tortoise eggs, land/marine iguanas, and penguins
(Santa Cruz late
1970s) wild dogs attacked and killed > 500 land iguanas, leaving
bodies to rot
experiments now to
sterilize dogs in inhabited areas
goats - 38,000 goats
on Pinta island were decendants of 3 goats only 14 years earlier
Santiago - >80,000 goats
pigs - destroy
vegetation
dig up and destroy tortoise/turtle eggs
prey on young tortoises/ground-nesting
birds
have taken eggs of sea turtles as they
were being laid
Sea turtle hatching rates have fallen
from 80% to 3% because of pigs
(Santiago) - 2,000 to 3,000 pigs
(estimated by Bruce Coblentz 1987)
black rats - led to
extinctino of endemic rice rats
kill and eat tortoise hatchllings and nesting dark-rumed petrels
feral cats - eat black
rats (most important food), native birds, insecvts, crabs, lizards
little fire ant -
nuisance to people
detrimental to other arthropods
Over 300 species of exotic plants exist in the Galapagos (100
introduced in past 10 years)
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Galapagos
John Krichner 2002
War of 1812 - Captain David Portre on
shi "Essex" released 4 goats on Santiago to graze
Goats escaped, leading to large feral population
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Galapagos
Roger
Perry
Pergamon Press 1984
Islands very vulnerable to most introduced species,
because of absense of ground predators
11 introduced mammal species
First introduced: rodents on whaling ships, which became feral
(Feral - wild,
self-sustaining descendants of domestic ancestors)
Island
|
Species
|
|
Cattle
|
Goats
|
Guinea Pig
|
Donkey
|
Horse
|
Sheep
|
Black Rat
|
Mouse
|
Pig
|
Dog
|
Cat
|
Santa Cruz
|
i d 1923
|
i d f 1925
|
i d
|
i d f
|
i d
|
i d
|
i before 1934
|
present
|
i d f 1920s
|
i d f 1868
|
i d f
|
Santiago
|
-----
|
i f 1813
|
-----
|
i f
|
-----
|
-----
|
i 1835
|
present
|
f 1930
|
-----
|
-----
|
Note: (i) = introduced, f = feral, d = domestic, year = year of
introduction, " - " = not present,
Cattle - introduced in
1832
eradicated
from Santa Curz in late 1970s by National Park authorities
Goats - (17th
century)Viceroy of Peru ordered dogs released on Santiago to kill
goats, which provided food for British pirates
1906 - Rollo
Beck transferred 4 goats from Baltra
goats =
primary cause of destructino of vegetation on subtropical islands
Santiago -
highland forests turned into pampalike grasslands
- trees prevented
from propogating
Goats have been observed drinking sea water when fresh water is scarce
(Dunson 1974)
New Zealand
Study: goats breed year-round
females can breed at age 6 months
52% of
conceptions are twins
population can double in 2 years
Donkeys/Horses -
compete with tortoises and iguanas for food
trample/wallow in nesting sites
man is
their only predator
Pigs - caused
extinctino of dodo in 1681
prey on bird/turtle/iguana
eggs
eradication is difficult
since pigs are nocturnal
Santiago beaches:
pigs dig up every sea turtle nest
prey on insect larvae and uproot
plants
New Zealand Study: pigs are dmore likely to be vectors of contagious
diseases than other mammals
Dogs - introduced
after settlements and convist colonies were abandoned
Santa Cruz
population: 25-70 feral (1984)
1. Highland Dogs - pack size
7.7
feed on feral cattle
2. Coastal Dogs - pack size 2.6
feed on marine iguanas,
fur seals, blue-footed boobies, and penguins
consume over 15% of
marine iguana population
prefer males
(larger, easier to catch, sleep in open where easy targets)
Southern
Santa Cruz: marine iguanas eradicated by dogs (captive breeding program
instituted at Charles Darwin Station)
Only coastal dogs are found on Santa Cruz (domestic dogs
in highlands)
Cats - damage insects,
small birds
widespread on Santa Cruz
Food: (in order of
importance) black rats, small birds, insects, crustaceans, lizards
Black Rats - replaced
endemic rats on Santa Cruz
Diet: 83% plant material (adults), 70% (young rats)
found in all vegetation zones
predators: Galapagos hawk, short-eared owls, cat
1976 - Bartolome island near Santiago - rats were
eliminated via concentrated trapping and poison.
Invertabrates - Flies,
cockroashes, moths, spiders carried in by cargo ships
Fire Ant - on Santa Cruz,
density increases with altitude
not present in driest or wettest
locations
Density: 190/m^2
(lowlands)
1150/m^2 (humid zone)
Diet: native ants, snails,
insect larvae, grasshoppers, beetles, spiders.
Solutions - long-term
breeding programs of native species until alien species are eradicated
Problem - limited
genetic diversity would impair chances of long-term survival of these
species.
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