ATOLL RESEARCH BULLETIN NO. 337
CONTROL OF FERAL GOATS ON ALDABRA ATOLL BY
BRUCE E. COBLENTZ, DIRK
VAN
VUREN AND MARTIN B. MAINISSUED BY
NATIONAL MUSEUM OF NATURAL HISTORY SMITHSONIAN INSTITUTION
WASHINGTON, D.C., U.S.A.
January 1990
CONTROL OF FERAL GOATS ON ALDABRA ATOLL
AND MARTIN B.
MAIN^
Abstract:
Recent increases in the numbers o f feral goats (Caoora hircus) on Aldabra Atoll, Republic of the Seychelles, raised concerns for the future o f sensitive endemic biota because herbivory by goats was
damaging some habitats and preventing seedling regeneration of preferred woody plants. A control program was initiated January-March 1987 in which most (n=56) o f the goats on Ile Malabar were killed over 5 weeks.
In addition, 292 goats were killed in the Cinq Cases region of Grande Terre over a 6-day period. A maximum kill rate o f 5.15 goats/hunter- hour was achieved on Grande Terre. A second control program was
conducted on Aldabra January-March 1988 and 525 goats were shot in 385 hunter-hours (1.36 goats/hunter-hour). We recommend continued efforts to eradicate the remaining goats on Aldabra.
A major threat to the biota of many insular systems is the feral goat ( C a ~ r a hircus). Effects of an exotic, generalist mammalian herbivore, such as the goat, are so pervasive that Vitousek (1988) acknowledged the impossibility of preserving island ecosystems without eliminating such animals. There have been attempts to eradicate feral goats from at least 39 islands in the past 140 years (Daly and Goriup 1987); they have been eradicated from only a few (Parkes 1984, Rudge 1976, Will iams and Rudge 1969). Many more islands are in need of
immediate act ion. Information concerning the efficiency of goat control operations and their results on endemic insular biota need to be
available to assist in the planning process.
Feral goats are an ecological liability on islands (Coblentz 1978, Daly and Goriup 1987, Vitousek 1988). Most reports concerning their
influence on insular biota describe negative effects (reviewed by Daly and Goriup 1987, Coblentz 1978), including competition for food, removal o f forest understory, severe erosion, and extinct ion of endemic species.
Bates (1956) label led the feral goat an "ecological dominant", and our experiences support that view. We define an ecological dominant as a species that has the ability to negatively influence structure o f the physical habitat and depress production and species composition of the biota, and set back biotic succession to earlier sera1 stages,
ultimately reducing biodiversity.
Feral goats ( C a ~ r a hircus) have been present on Aldabra Atoll, Republic o f the Seychelles (46'20' E. Long., 9'24' S. Lat., Fig. 1) in
' 1 3
Department of Fisheries and Wi 1 dl
ife, Oregon State University, Corvall i s, Oregon 97331, USA
Department o f Systematics and Ecology, University of Kansas,
Lawrence, Kansas 66045, USA
t h e western I n d i a n Ocean, since b e f o r e 1878 (Stoddart 1981); however, o n l y r e c e n t l y has t h e i r presence been viewed w i t h alarm. Goats on Aldabra (up t o 17/km2, Gould and Swingland 1980)have n o t achieved t h e h i g h d e n s i t i e s recorded on other, morf p r o d u c t i v e oceanic i s l ands (up t o 490/km2, Rudge and C l a r k 1978, 983/km
,
W i l l iams and Rudge 1969)a1 though Dupont (1929, c i t e d by Stoddart 1981) r e p o r t e d "several thousands" i n 1929.
Goat numbers on Aldabra were r e l a t i v e l y low i n r e c e n t decades ( S t o d d a r t 1971, Gould and Swingland 1980), b u t were b e l i e v e d t o have increased r a p i d l y s i n c e 1968 a t which t i m e few goats were seen o r heard d u r i n g a 2-month b o t a n i c a l e x p e d i t i o n (F.R. Fosberg, Smithsonian
I n s t i t u t i o n , pers. commun.). By 1976-77 goats were estimated a t 500-600 on t h e a t o l l (Gould and Swingland 1980), and had increased t o 1300 i n 1985 (Burke 1988). T h i s r a p i d increase prompted concern f o r t h e f u t u r e o f t h e Aldabran b i o t a i n general, and s u r v i v a l o f t h e endangered
Aldabran brush w a r b l e r ( N e s i l l a s aldabranus) i n p a r t i c u l a r .
Our o b j e c t i v e was t o e r a d i c a t e a l l goats from one o f t h e major i s l a n d s , I l e Malabar; and t o assess t h e p o s s i b i l i t y o f e r a d i c a t i n g goats from t h e e n t i r e a t o l l .
STUDY AREA AND METHODS
Aldabra A t o l l c o n s i s t s o f 4 major i s l a n d s o f which 3 c u r r e n t l y have goats (Picard, Malabar, Grande T e r r e ) . T h i s area i s a l a r g e up1 i f t e d c o r a l at01 1 o f 155 km i n c l u d i n g mangrove areas (Gould and Swingland 1980). The c l i m a t e i s s e m i - a r i d (mean annual r a i n f a l l 94.1 cm, S t o d d a r t and Mole ,1977) and t r o p i c a l , w i t h a May-October d r y season and a November-Apri 1 wet season (Gould and Swing1 and 1980).
We hunted goats from 30 January t o 8 March 1987 and 20 January t o 15 March 1988 w i t h c e n t e r f i r e ( p r i m a r i l y .223 Rem.) b o l t - a c t i o n r i f l e s equipped w i t h t e l e s c o p i c (4X) s i g h t s . I n 1987 a l l a c c e s s i b l e areas on I l e Malabar were searched f o r goats and goat s i g n (feces, browsing, v o c a l i z a t i o n s ) . Goats were shot when seen, and areas having s i g n were hunted r e p e a t e d l y u n t i l i t appeared a l l i n d i v i d u a l s had been l o c a t e d and k i l l e d .
I n 1987, goats were hunted f o r 6 days on Grande T e r r e . Goats k i l l e d d u r i n g t h e f i r s t 4-day v i s i t were weighed and examined; those k i l l e d d u r i n g a subsequent 2-day v i s i t were n o t . Weighing was t i m e - consuming and was e l im i n a t e d d u r i n g t h e second hunt so t h a t a maximum r a t e o f k i l l c o u l d be determined. Our 1987 e f f o r t on Grande T e r r e was focused i n an area about 1 km wide between t h e boat l a n d i n g a t Bras Cinq Cases and t h e c o a s t a l zone t o t h e South o f Cinq Cases.
D u r i n g t h e 1988 program, most h u n t i n g e f f o r t was on Grande Terre.
A 3-day v i s i t was made t o I l e Malabar t o assess t h e success o f t h e 1987 e f f o r t ; a1 1 goats observed on Ma1 abar i n 1988 were k i l l e d .
A d d i t i o n a l l y , t h e small p o p u l a t i o n o f goats on I l e P i c a r d was hunted whenever t i m e and weather p e r m i t t e d .
I n b o t h years, t h e number o f hunter-hours o f e f f o r t and t h e number o f b u l l e t s used were recorded. Hunting i n 1987 was done by a 2-person team; a 3-person team was employed i n 1988.
RESULTS Goats Killed on Ile Malabar
Fifty-six goats were killed in 1987 (Table I), representing all goats that were observed except 2 males (that might have been killed in
subsequent encounters). In 1988, the entire area hunted during 1987 was examined carefully for goats and goat sign. A single group of 5 goats was observed and kill ed in the Middle Camp area. There may have been other surviving goats on Ile Malabar, but we could not find them.
Of 61 goats removed from Ile Malabar during two hunts, 3 4 were killed in the vicinity of Middle Camp at the east end of the island, and 27 from the area adjacent to and east of Anse Halabar. In 1987 we
located no sign of goats farther west than Anse Grand Grabeau, and no evidence o f regular use by goats more than about 1 km west o f Anse Malabar. In 1988 we encountered no goat sign west of Middle Camp.
Although we caution against excessive optimism, there are several lines of evidence that support our belief that we have nearly eradicated goats from Ile Malabar. Indeed, goats initially seen but not killed usually were observed repeatedly unt
i1 ki 1 1 ed. Nearly a1 1 goats
visually identified (56 or 58) in 1987 were eventually killed. In a few areas dense vegetation made visual contact with goats difficult,
although goats were often heard calling. Three groups recognizable by both adult and juvenile vocalizations were killed eventually in the general area (<1 km) where initially heard. Number and age of goats we killed invariably agreed with our expectation of group composition based on vocalizations.
Lastly, by the time we had killed what we believed to be the last goats in each area, we never again found fresh sign in that locality.
For example, in the Middle Camp area where a1 1 goats ki 1 led in 1987 were shot in 5 days (Fig. ZA), no goats or fresh sign were seen in 3
subsequent days o f intensive searching. In 1988 only a single group was seen in 3 days; after they were killed no other goats were evident.
Goats Killed on Grande Terre
In 1987, the first 4-day hunting effort resulted in 127 goats killed (Table 1). Because much hunting time was spent measuring and examining goats, a subsequent visit of 2 days was made to Cinq Cases to determine potential rate of kill; during this visit (1987, Cinq Cases
2,Table 1) the kill rate increased dramatically.
In 1988, we shot
525goats (Table
1).An additional 10 goats were captured on Grande Terre and killed without shooting, for a total o f 535 goats killed in 1988.
Most goats killed in 1988 (390) came from the Cinq Cases region in three hunting periods, totaling 11 hunting days, from approximately the same area that was hunted in 1987, except that hunting in 1988 extended further north past Pt. Hodoul . Only 24 of 390 goats (6%) killed at Cinq Cases were encountered and killed near the lagoon; most goats were
encountered in the coastal zone.
An average of 1.36 goats ki 1 1 ed/hunter- hour was achieved during
1988; however, this measure of efficiency varied considerably among
areas hunted depending upon our level of effort and availability of
goats. Efficiency in the Cinq Cases region was consistent, with 2 goats
killed/hunter-hour (Table 1) during all three hunting periods. Only
0.18 and 0.31 goats were killed per hunter-hour on Ile Malabar and Ile
Picard, respectively, probably because both areas had very few goats at low density and relatively thick vegetation. Number o f shots fired per goat killed varied from 1 shot/goat on Ile Ma1 abar to 2.36 and 2.38 shots/goat at Dune D'Messe and Anse Cedres, respectively (Tab1 e 1) ,
where goats (6 groups) were surprised at close range in thick cover.
P r o ~ o r t i o n o f qoats ki 1 1 ed
Populations o f feral goats tend to 1 i ve in discrete ranges (Coblentz 1974). On Aldabra we were able to quickly establish the geographic 1 imi ts and approximate number of individuals in relatively small populations when such populations inhabited fairly open terrain, most individuals were killed in a few days (Fig. 2).
Population sizes for Middle Camp in 1987 (1
=32) and Dune Jean- Louis in 1988 (N
=49) were estimated by the method of Leslie and Davis
(1939) in which catch per unit effort (Y) is regressed against
cumulaf ive catch (x) , and population size determined by the x-intercept (N
=- /b). Our results indicate that we killed 91% and 90%,
respectively, of the goats estimated to be present in these populations when the project began.
Large numbers of goats that inhabited the region from Pt. Hodoul to several kilometers west of Cinq Cases were a series of discrete
populations. Because of time limitations we chose to work the entire area simultaneously, and as a result our kill rate remained somewhat stable throughout the entire project (Fig. 3). In this area, the
estimated population (1352) was greatly in error, and if the project had continued the kill rate would have declined as goats became increasingly scarce.
In two short field seasons total ing 11 weeks on Aldabra we eliminated 883 goats. Assuming Burke's (1988) estimate (1300) was representative of the total population, we eliminated nearly 70% of the popul at i on.
Cost of eradication
Accurate calculation of the cost Der qoat killed durinq this project is tenuous. Excluding salaries, the cost per goat killed on Aldabra in 1988 was approximately $12 U.S., and about
65%of that was travel costs from Port1 and, Oregon, to Mahe, Republ ic of Seychelles. We purchased reloaded ,223 cal
iber (soft-point) ammunition for $180
U.S./1000 rounds, therefore the bullets used to shoot goats (n
=1004, Table 1) cost $180.72 U.S., or $0.34/goat.
DISCUSSION
Consequences of goat popul ati ons on
isl and vegetation are negative and well documented (Coblentz 1978, Daly and Goriup 1987). Taylor's (1968:62) caution that precipitous removal o f goats may lead to
"unexpected and even undesireable results" pales in comparison to the certain ecol ogi cal catastrophe of a1 1 owing goats to remain unchecked in insular ecosystems.
Although no figure is available, there may be more than 100 islands
worldwide supporting feral goat populations. Length of time goats are
present on an island before being removed partly determines the recovery
rate o f affected plant species (Hamann 1979). For example, Hamann
r e p o r t e d t h a t v e g e t a t i o n recovery on I s 1 a P i n t a (Gal apagos)
,
where goats e x i s t e d i n h i g h nmumbers f o r l e s s t h a n 3 decades, has been c o n s i d e r a b l y more r a p i d t h a n on I s l a Santa Fe where goats were p r e s e n t f o r a t l e a s t t w i c e as l o n g . It can be i n f e r r e d from Hamann (1979) t h a t t h e sooner f e r a l g o a t s a r e e l i m i n a t e d from an i s l a n d , t h e more r a p i d l y p l a n t species w i l l r e c o v e r because t h e number o f v i a b l e seeds o f s e n s i t i v e p l a n t species, and t h e number o f seed producing i n d i v i d u a l s , i s i n v e r s e l y r e l a t e d t o t h e l e n g t h o f t i m e t h a t goats have been present.Goats were s e v e r e l y damaging some p o r t i o n s o f Grande T e r r e
(Coblentz and Van Vuren 1987). We n o t i c e d e x t e n s i v e browsing w e l l i n t o t h e mangrove zone, and a n e a r l y continuous browse l i n e o f r o u g h l y 2-m h e i g h t on a l l p a l a t a b l e species. Regeneration o f p a l a t a b l e woody species was n o n e x i s t e n t , even i n areas where t h e endemic t o r t o i s e s (Geochel one a i a a n t e a ) were e x c l uded by dense brush o r jagged champignon limestone. Although t o r t o i s e s a r e a major i n f l u e n c e on t h e v e g e t a t i o n o f Aldabra (Hnatiuk e t a l . 1976, Merton e t a l . 1976, Swingland and Coe 1979, Gould and Swingland 1980), goats a r e an a d d i t i v e i n f l u e n c e t h a t a l s o can e l i m i n a t e p l a n t s i n r e f u g i a s a f e from t o r t o i s e s , t h u s
i n c r e a s i n g t h e chance o f e x t i n c t i o n o f s e n s i t i v e species.
R e s u l t s o f t h e 1987 program on I l e Malabar were d r a m a t i c a l l y v i s i b l e i n 1988. Although n o t measured q u a n t i t a t i v e l y , v e g e t a t i o n i n t h e M i d d l e Camp area was v i s i b l y more dense w i t h i n 2 m o f t h e ground and we considered t h i s t o be s t r o n g c i r c u m s t a n t i a l evidence t h a t e l i m i n a t i o n o f g o a t s allowed p l a n t s t o regrow i n t h i s l a y e r .
I n former s l e e p i n g areas o f goats t o t h e e a s t o f M i d d l e Camp, and e x t e n d i n g t o t h e e a s t o f Anse Malabar, areas t h a t f o r m e r l y had been browsed h e a v i l y were growing back r a p i d l y . I n these areas, P e m ~ h i s shrubs had f o r m e r l y been browsed h e a v i l y as h i g h as g o a t s c o u l d reach.
When we examined Pemphis i n these areas i n 1988, a l u x u r i a n t growth o f basal s p r o u t s o f up t o 0.5 m i n l e n g t h was apparent a t t h e base o f each shrub. Presumably these basal s p r o u t s a r e evidence o f lowered browsing pressure by goats.
V e g e t a t i o n recovery on Grande T e r r e f o l l owing t h e 1987 c o n t r o l program was n o t e v i d e n t i n 1988. We d i d n o t see r e g r o w t h o f v e g e t a t i o n i n t h e 2-meter-high zone browsed by goats. With t h e k i l l o f an
a d d i t i o n a l 390 goats i n t h i s area i n 1988 we p r e d i c t t h a t growth o f v e g e t a t i o n w i l l proceed more r a p i d l y .
There a r e two a l t e r n a t i v e l e v e l s o f c o n t r o l f o r f e r a l goats:
p a r t i a1 r e d u c t i o n ( c o n t r o l ) ; and complete e r a d i c a t i o n . C o n t r o l e n t a i 1 s p e r i o d i c e f f o r t s and prolonged expense, e s s e n t i a l l y
ad
i n f i n i t u m .I n a d d i t i o n , goats respond t o r e d u c t io n s i n a densi ty-dependent manner by i n c r e a s i n g n a t a l i t y (Cob1 e n t z 1982, Parkes 1984). On Raoul I s 1 and, Parkes (1984) documented an increase i n p r o d u c t i v i t y o f g o a t s a f t e r popul a t i on r e d u c t ion, whereas Rudge and Smi t (1970) determined t h a t a g o a t popul a t i o n reduced by 80% c o u l d rebound t o 90% o f t h e former l e v e l
i n 4 years. Conseauentlv, c o n t r o l e f f o r t s must be conducted r e g u l a r l y i c t i n g t o r a p i d recovery. o f goat popul a t ions.
Methods o t h e r t h a n s h o o t i n g have been suggested f o r erad goats, i n c l u d i n g poisoning, i n t r o d u c i n g p r e d a t o r s o r disease, s t e r i l i z i n g males, and t r a p p i n g . Poisoning w i t h sodium
monofluoroacetate (Compound 1080) was e f f e c t i v e , k i l l i n g >90%
i n t r e a t m e n t b l o c k s i n New Zealand (Parkes 1983) ; however, po unacceptable f o r use i n a World H e r i t a g e S i t e such as Aldabra
o f goats i s o n i n g i s
because o f
t h e p o s s i b i l i t y o f p r i m a r y and secondary e f f e c t s on endemic species.
D i e t a r y over1 ap between g o a t s and t o r t o i s e s , and our o b s e r v a t i o n s o f t o r t o i s e s scavenging on dead g o a t s on Grande T e r r e i n d i c a t e t h e p o t e n t i a l f o r n o n t a r g e t poisoning, although t h e median l e t h a l dose (LD,,) f o r t h e p o i k i l o t h e r m i c t o r t o i s e s i s p r o b a b l y h i g h i n comparison t o g o a t s ( A t z e r t 1971).
I n t r o d u c t i o n o f p r e d a t o r s i s u n s u i t a b l e on Aldabra because o f p o t e n t i a l e f f e c t s on endemic species. I n t r o d u c t i o n o f a disease, i f a s u i t a b l e one c o u l d be found, m i g h t t e m p o r a r i l y c o n t r o l a p o p u l a t i o n , b u t n o t e r a d i c a t e i t . S t e r i l i z a t i o n o f males i s unworkable because every male would f i r s t have t o be trapped o r t r a n q u i l i z e d , a p r o h i b i t i v e l y expensive and p r o b a b l y i m p o s s i b l e o p e r a t i o n . Also, k i l l i n g t r a p p e d goats would be more e f f e c t i v e t h a n r e l e a s i n g them t o c o n t i n u e damaging t h e environment.
I f p o i s o n i n g i s judged unacceptable, t h e n s h o o t i n g i s p r o b a b l y t h e most e f f e c t i v e and c o s t e f f i c i e n t method o f e l i m i n a t i n g f e r a l goats i n t h e i n i t i a l phase o f an e r a d i c a t i o n program. C a r e f u l l y done, l a r g e numbers o f g o a t s can be k i l l e d q u i c k l y (up t o 5 goats/hunter-hour, t h i s study), i n e x p e n s i v e l y , and humanely.
Any s h o o t i n g program should minimize t h e number o f g o a t s t h a t
s u r v i v e encounters w i t h hunters. During t h e 1981-83 e r a d i c a t i o n program on Raoul I s 1 and, New Zeal and, an average o f 19% o f goats seen escaped
(Parkes 1984). D u r i n g o u r 1987 program on I l e Malabar, 20% (14 o f 70) o f goats i n groups t h a t were f i r e d upon escaped ( a l l b u t 2 males
subsequently k i l l e d ) , and on Grande T e r r e d u r i n g t h e i n i t i a l 4-day s h o o t i n g p e r i o d 11% (16 o f 142) escaped (number subsequently k i l l e d unknown). D u r i n g t h e 1988 program 14% (83 o f 581) o f g o a t s i n groups t h a t were f i r e d upon escaped, b u t we know t h a t a number o f these escapees were k i l l e d i n subsequent encounters. Goats t h a t escape an encounter w i t h shooters may become more wary and d i f f i c u l t t o k i l l ; t h e 1 a s t 5 g o a t s removed from Raoul I s l a n d r e q u i r e d a t o t a l o f 2 man-years and c o s t $12,500 NZ each (J.P. Parkes, New Zealand F o r e s t Service, 1985 personal communication t o D.W. Baber)
.
We b e l i e v e t h a t t h e 3-person s h o o t i n g team employed i n 1988 was a t r a d e - o f f between increased f i r e p o w e r and increased r i s k o f a l a r m i n g goats. Escape by g o a t s t h a t were f i r e d upon was n o t s u b s t a n i t a l l y a f f e c t e d by t h e a d d i t i o n a l f i r e p o w e r , n o r was t h e number o f b u l l e t s f i r e d p e r g o a t k i l l e d . We d i d n o t i c e i n s e v e r a l i n s t a n c e s t h a t t h e r e was i n s u f f i c i e n t cover t o conceal 3 s t a l k i n g hunters, and i n such i n s t a n c e s g o a t s became alarmed sooner t h a n i f t h e r e had been two h u n t e r s . The h i g h e s t k i l l r a t e s ( 5 goats/hunter-hour) and l o w e s t e x p e n d i t u r e o f ammunition p e r goat k i l l e d (1.4 b u l l e t s / g o a t , I l e Malabar, 1987) were accomplished by t h e 2-person team.
D i f f e r e n c e s i n r a t e o f k i l l and accuracy among areas hunted (Table 1) r e s u l t e d f r o m several f a c t o r s i n c l u d i n g group s i z e o f goats, amount o f cover a v a i l a b l e f o r s t a l k i n g , d i s t a n c e t o goats when f i r s t observed, and l e v e l o f e x c i t a b i l i t y o f goats t h a t were encountered. I n c o n t r a s t , t h e s t a b l e r a t e o f k i l l achieved d u r i n g t h r e e h u n t i n g p e r i o d s a t Cinq Cases i n 1988 (Table 1) was due t o t h e combination o f a l a r g e p o p u l a t i o n i n a 1 arge area, 1 i m i t a t i o n s on how much area c o u l d be covered i n a day, and t o o u r improving a b i l i t y t o a n t i c i p a t e , f i n d , and shoot g o a t s even as popul a t i ons d e c l i ned.
We expected that difficult terrain (champignon limestone), dense vegetation and extreme heat would combine to make the eradication of goats on Aldabra difficult, but control was easier than anticipated. We attribute this to our experience from similar projects, and the
re1 atively narrow 1 andmass forming the ring of the at01 1 . We be1 i eve that goats can successfully eradicated from Aldabra. We have
demonstrated that large numbers can initially be killed; after the majority have been killed, as they were by our efforts, the remainder can be efficiently located and killed through the use of radiocollared
"Judas goats" (Taylor and Katahira 1988). In this technique the
gregarious sociality of the goat is exploited by repeatedly relocating radiocollared goats and shooting the other members of their groups.
Judas goats repeatedly (Taylor and Katahira 1988) and quickly (BEC, pers. obs., San Clemente Island, California) locate other goats.
SUMMARY
Recent increases in the numbers of feral goats on Aldabra Atoll, Republic of the Seychelles, raised concerns for the future of sensitive endemic biota because grazing by goats was damaging some habitats and preventing seed1 i ng regeneration of preferred woody pl ants. We
initiated a control program, by shooting, in January-March 1987 and continued January-March 1988. In 11 weeks on Aldabra, 883 goats were eliminated, including most (N
=61) inhabiting Ile Malabar. In small populations 1 iving on re1 atively open habitats, most individuals (91%
Middle Camp, 90% Dune Jean-Louis) were killed in only 5 days of hunting.
Our total kill may have been as high as 70% of the goat population on A1 dabra.
Goats shot/hunter-hour ranged from a low of 0.18 (Ile Malabar, 1988) to 5.15 (Cinq Cases 2, 1987). The mean efficiency was 1.36 goats shot/hunter-hour in 1987 and 1.61 in 1988. The cost per goat killed in 1988 was approximately $12 U.S.; ammunition costs were only $0.34 U.S.
Most of the costs were for transportation.
We demonstrated that large numbers of goats can be killed quickly and cheaply on Aldabra, and probably many other islands as well.
Because of numerous direct and indirect effects of goats on insular biota, we strongly advocate removal of the remaining goats from Aldabra in particular, and from sensitive oceanic is1 ands in general. We
recommend that goats be killed by shooting them with small caliber centerfire rifles by trained 2-person teams of marksman.
Acknowl edqments
We are indebted to
L.U. Mole, M. Sitni k, and Dr. D. R. Stoddart for assistance and encouragement in obtaining funding for this project, and physically getting us to Mahe.
L.Chong Seng and W. Andre provided invaluable assistance arranging for transportation from Mahe to Aldabra and back to Mahe. We thank D. W. Baber, 0. S. decalesta, and P. H.
O'Brien for critically reviewing the manuscript. Financial support was provided by emergency assistance funds from the World Heritage Program of UNESCO (Contract SC 293.018.8), and by the Oregon Agricultural
Experiment Station (Project ORE 00925). This is Oregon State University
Agricultural Experiment Station Technical Paper No. 8340.
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Table 1. Numbers o f goats k i l l e d , hunter-hours, number o f shots f i r e d , and e f f i c i e n c y o f hunting by l o c a t i o n f o r goats ki1,led on Aldabra A t o l l , Republic o f t h e Seychelles, January
-
March 1987 and January-March 1988.Goats Hunter- Shots Goats Shot/ Shots Fired/
Locat i on Shot Hours F i re d Hunter-Hour Goat K i 1 1 ed
I l e Malabar Cinq Cases
-
1 Cinq Cases-
2 T o t a l 1987- -
Cinq Cases
-
1 Cinq Cases-
2 Cinq Cases-
3 Dune Jean-Louis Dune D'Messe Dune Blanc-Gros I l o t Anse Cedres
I 1 e Ma1 abar I l e Picard T o t a l 1988
a data n o t gathered d u r i n g t h i s hunt
ANSE GRAND GRABEAU
I C A R D POL. .,
MIDDLE C A M P
ANSE CEDRES
JEAN- LOUIS
T
DUNE D'MESSE
I
DUNE BLANC
Figure
1.
Aldabra Atoll, Republic of the Seychelles, showing pl acenames in areas where goats were hunted.A
Middle Camp 1987*O
1
1 2 3 4 5 6 7 8
Days Hunted
B
Dune Jean-Louis 1988*O
1
1 2 3 4 5
Days Hunted
F i g u r e 2. Number o f goats k i l l e d on successive days o f h u n t i n g a t M i d d l e Camp (A), and Dune Jean-Loui s (B)
,
Aldabra At01 1,
February, 1987 and January, 1988, r e s p e c t i v e l y .
Cinq Cases I988
1 2 3 4 5 6 7 8 9 1 0 1 1
Days Hunted
F i g u r e 3 . Number o f goats k i l l e d on successive days o f hunting i n t h e Cinq Cases
-
P t . Hodoul r e g i o n , Aldabra A t o l l , January- March, 1988.