Isabela eps:Layout 1 - Advanced Conservation Strategies

MANAGEMENT
& STRATEGY
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Eradication methods
“On large islands a range of methods used sequentially
and simultaneously are required to put all animals at risk”
Strategic use of methods
Throughout all our eradication work we followed some simple rules. Where possible as close to 100 % of the animals were
removed on their first encounter, reducing the possibility that survivors learn from their exposure to a certain hunting
method. We studied the vegetation type, topography and goat densities; and hunters’ efforts revolved heavily around
techniques to minimize escapes. For example, on Santiago mustering was used in the highlands in the first months as this
was the only practical method by which herds of thousands of animals could be removed with near zero escapes. In
eradication, efficacy (being efficient and effective) is a combination of minimizing cost per kill and maximizing the ratio of
goats killed to escapes. Each method is suited to different terrain, vegetation type and goat densities. This creates a hierarchy
of methods that can be used sequentially. The development of wary animals to any one method requires a change in
methods to place those animals at risk. In various situations it is also highly
advantageous to use different methods simultaneously.
Aerial hunting
Landscape or vegetation type offer refuge for goats from one or more
methods; however no vegetation or terrain type provides refuge for goats from
all methods. On Santiago goats found refuge from ground hunters with dogs
in lava fields, a place where aerial hunting excels. Conversely, goats found
refuge from helicopters by remaining motionless under vegetation and by
hiding under thick vegetation and in caves; these areas and tactics then made
goats vulnerable to ground hunters with dogs. On a large scale and on
complex islands, a refuge will likely exist for most methods. As such, on large
islands a range of methods used sequentially and simultaneously is required
to put all animals at risk.
Ground based mustering and corrals
In order to channel goats into corrals, we used netting strung out in large
“wings” up to several kilometers in length. This method was developed to
facilitate the removal of vast herds of goats that could not effectively be
removed by other means without significant numbers of escapes. Prior to the
arrival of helicopters this method was fundamental as an initial knock-down
tool, and was very cost-effective.
In the 1970s New Zealanders began using helicopters intensively as aerial shooting
platforms and for recovering deer carcasses for a demanding European market. Aerial
shooting is now practiced extensively in Australia and New Zealand to control feral
animals cost-effectively and on a large scale. Contrary to common belief this method is
actually endorsed by animal welfare organizations as the most humane method of
removing feral goats in rough terrain. It is highly effective in sparsely vegetated areas or
areas with trees with open canopy; the majority of Isabela and large tracts of Santiago
fit this description. Aerial shooting is cost-effective at high and low animal densities and
allows for the rapid coverage of large areas.
Ground hunting
Traditional hunting, or, as we’ve dubbed it, free hunting, involves individual or pairs of
hunters with or without their dogs hunting freely within a zone. This allows hunters to
concentrate their efforts and use various hunting tactics in areas where goats are frequent,
such as hill-tops, rocky ridges, cliffs, craters and lines of caves. This method
is most efficient when goats are at high, medium and low densities. Skilled and motivated
hunters are required. Large areas can be effectively covered with multiple camps of 2-3
hunters spaced throughout.
Mata Haris is a line-hunting technique adopted and improved from our local hunters and
conservation practitioners in New Zealand. The technique involves a team of hunters
working at fixed spacing (100-150m) and systematically moving through an area, typically
proceeding into or perpendicular to the prevailing wind. Hunters maintain their place in
the line by radio communications and hand-held GPSs with pre-determined points from
the GIS. In this way, we produced a coordinated wall of hunters and dogs optimally spaced
and covering swaths typically 3 km wide. This method is ideal for detecting animals at very low densities and covering areas
systematically; it ensures that all areas are covered, and even the most wary animals are at risk. Deployment/retrieval of
hunters and dogs by helicopter allows them to work remote areas and still remain ‘fresh’ for when goats are detected.
Dogs
Eradication methods
“On large islands a range of methods used sequentially
and simultaneously are required to put all animals at risk”
New Zealand is the only country in the world where specialist goat dogs are
employed by many hunters, providing breeds that facilitate training of pups due
to natural instincts. A core breeding and training stock of five dogs was imported
from New Zealand in 2000 and specialist dog trainers from there were employed
to train hunters and develop trainers and a team of specialist goat dogs. Other
hunting dogs from the Galapagos were selected for skills missing in the imported
team and a team of over 70 skilled dogs was developed within 2.5 years.
Certification at basic and advanced levels maintained dogs at high standards,
and aversion training was conducted to ensure dogs were species specific and showed no interest in native wildlife. Hunters
would work with one or two dogs each. Dogs were finder-bailers (dogs that track, find and contain the goats while waiting for
the hunter to arrive), and could typically work with ground and air scents to detect and find goats. Dogs are highly effective with
small groups of goats at low densities. They perform well in dense vegetation where other methods are ineffective, making them
a key element when confronted with vast areas of that vegetation.
Judas goats
Goats are highly social and gregarious animals; they have an aversion to
isolation, and will seek out others when isolated. The Judas goat method
exploits these elements of goat biology to increase the cost efficiency of
control and eradication operations when animals are at low densities. Judas
goats are selected, captured, fitted with radio telemetry collars and released.
They can then be tracked down and any associated feral goats will be
removed. The Judas goat method is used as an accessory to other hunting
methods, being most commonly used in conjunction with aerial hunting by
helicopter and ground hunting with and without dogs.
Judas goats increase the efficiency of removing animals at low density by reducing search time for hunters locating remnant
herds or individuals. However, we discovered on Pinta that current Judas goat methodology fell short of its potential efficacy.
The ideal Judas goat would search strongly for goats, be searched for by other goats, be sterile and not become wary. Reasons
that goats may search for conspecifics include isolation and sexual cues. To maintain Judas goats in a state of isolation,
managers in addition to shooting feral goats, shoot or capture any additional Judas goats associated with a particular Judas
goat. Sexual cues involve both sexes searching strongly for mates, particularly when females are in estrus. Females in estrus
actively search for males and likely attract them using pheromones. We developed protocols to sterilize, terminate pregnancy
and induce female goats into a prolonged estrus with hormone implants. We then compared the efficiency of three types of
Judas goats; sterile male, sterile female and sterile females in a prolonged estrus which we have dubbed Mata Haris (after the
seductive and lethal World War I double agent).
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