Cayot, Linda J.

Menoscal, Rafael

English

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Ju1y 1992 NOTICIAS DE GALAPAGOS 11
LAND IGUANAS RETURN TO BALTRA
By: Linda J. Cayot and Rafael Menoscal
After over 40 years of absence, 1and iguanas
(Conolophus subcristatus) were retumed to Isla Ba1-
tra, the first step in an effort to repopulate the Island
with direct descendants of the large iguanas native to
that arid and inhospitable place.
Historically, Baltra had a thriving population of
land iguanas, the largest individuals of the species.
However, the population began to decline near the
beginning of this century, apparent1y due to habitat
destruction by introduced goats (Capra hircus). Then,
following World War 11,the land iguana population
on Baltra disappeared, most likely an unfortunate
result of habitat destruction not only by the intro-
duced goats but also by the construction of a large
U.S. Army Air Base (Woram 1991).
Fortunately, in 1932-33 and prior to their extinc-
tion on Baltra, 70 iguanas had been transferred from
there to North Seymour, a small island a half mile to
the north (Perkins 1932, Banning 1933). Members of
the Hancock Expedition, noting that the land iguanas
on Baltra were skinny and the vegetation was scarce
due to devastation by the goats, decided to make the
transfer as an experiment. Although the two Islands
are similar in terrain and vegetation, land iguanas
were not native to North Seymour, neither were there
introduced goats, and as a result, the vegetation was
much more abundant. Following the transfer, the
iguanas were left on their own for nearly 40 years.
[Editor's Note.-See accompanying article by John
Woram this issue.]
Meanwhile, sometime in the 10 years or so fol-
lowing the end of World War 11,the land iguanas on
Baltra disappeared.
In the mid-1970s, personnel of the Galápagos
National Park Service (GNPS) and the Charles Dar-
win Research Station (CDRS) began occasional
checks of the population on North Seymour (Rey-
nolds 1981a, Snell1984, Werner 1984, Hoyos 1987).
They found only the originallarge adults and no ju-
veniles. It was not until the Niño event of 1982-83
that juveniles were seen on the island.
In 1980, due to the lack of recruitrnent in the pop-
ulation on North Seymour, a pair of adult iguanas was
transferred from there to the GNPS/CDRS Breeding
and Rearing Center in Santa Cruz (Reynolds 1981a,
1981b). By 1985, eight more iguanas were transferred
to the Center. The immediate objective was to repro-
duce the iguanas in captivity in order to save a portion
of the gene pool of the Baltra population. A second,
but equally important, goal was the eventual repop-
ulation of Baltra with descendants of the original
natives.
Reproduction in captivity was a success and, by
1991, approximately 80 young Baltra iguanas were
housed at the Center. Unfortunately, the adults were
very old and, over the years, most of them died; those
remaining were weak and the females had difficulty
recuperating after nesting. The last three adults in the
Center were returned to North Seymour in 1989.
THE REPATRIATION
The repatriation ofland iguanas to Baltra consist-
ed of five phases: 1) the development of an official
agreement regarding the repatriation among the var-
ious institutions, 2) environmental education for the
personnel of the Ecuadorian Armed Forces working
in Baltra, 3) poisoning the cats (Felis catus) in the
area designated for the repatriation, 4) repatriation of
iguanas, and 5) follow-up studies.
Unlike the other Islands of the Galápagos Archi-
pelago, Baltra does not belong to the National Park;
instead it is owned by the Ecuadorian Armed Forces
and houses both an Air Force and a Navy Base (Fig.
1).
Prior to repatriating land iguanas, it was necessary
to reach an agreement with the Ecuadorian Armed
Forces. Negotiations started in 1985, and, on 22 April
1991, an agreement was signed between the Ecua-
dorian Air Force (FAE), the Ministry of Agriculture,
and the Charles Darwin Foundation, permitting the
repatriation of land iguanas to Baltra and allowing
for follow-up studies, future repatriations, and nec-
essary management of the population.
The repatriation site, in the southeastem corner of
the Island, was chosen primarily based on biological
considerations (Fig. 1). In the early 1930s, the igua-
nas in this area were in better condition than elsewhere
12 NOTICIAS DE GALAPAGOS No. 51
on the Island (Perkins 1932, Snell et al. 1986). A
review of the Island in 1986 indicated that the south-
eastern corner had the highest concentration of plant
species important in the diet of land iguanas, such as
Opuntia and Castela (Snell et al. 1986). In addition,
the area has more soil, an important factor for the
construction of burrows.
In the 2 months prior to the repatriation, visits
were made to Baltra by personnel of both the GNPS
and the CDRS to give talks to the Armed Forces per-
sonnel and to con trol cats and dogs (Canis familiaris)
present on the Island. Two control trips were made,
focusing primarily on the repatriation site, but also
on the two military bases.
On 19 June 1991,35 5-year-old iguanas were tak-
en from the Breeding and Rearing Center on Santa
Cruz and transferred to Baltra. There, they were car-
ried in cloth sacks to the repatriation site, a series of
small rock hills to the south of the airstrip (Fig. 1).
N
1
Kilometers
t.:.:.:.:.:.:.:.:.}:.:-:-:-:.:-:-:.:¡
o 1 2
Figure 1. Map oI Isla Baltra showing the repatriation site, the
airport and active airstrip, and the two miIitary bases.
Figure 2. Repatriation of land iguanas to Baltra, 19 June 1991,
showing Linda Cayot, Head ofHerpetoIogy, CDRS, handing an
iguana to Fernando Rodríguez G., Port Captain ofBaItra; Edgar
Sierra R., Chief of Baltra Airport (FAE), reIeasing an iguana;
and Daniel Evans, Director, CDRS, and OswaIdo Sarango,
Acting Head oI the GNPS, looking on.
Given the historical importance of the repatria-
tion, more than 40 people participated, including
personnel ofthe GNPS, the CDRS, the FAE, and the
Ecuadorian Navy. The officials of each institution
spoke in a short ceremony. Personnel of the four in-
stitutions assisted in the liberation of the young
iguanas, which soon dispersed throughout the nearby
rock outcrops (Fig. 2).
During the first year following the repatriation,
several moni toring trips were made to the Island, four
for 3-6 days each (June and September 1991, and
January and April 1992), as well as four l-day trips
(June, July, and August 1991).
Results of the monitoring trips since September
1991 indicate a survivorship of at least400/0. In April,
the remains of an iguana, apparently consumed by a
cat, was found. However, iguanas and iguana sign
indicate dispersal from the repatriation site. The re-
patriates are still relatively small and not easy to locate.
Therefore, it is likely that several of the surviving
iguanas were missed. A census of the population has
not yet been done.
In ApriI1992, 12 more iguanas, aged 8-10 years,
were repatriated to Baltra (Fig. 3). These were the
first Baltra iguanas hatched in the Breeding and Rear-
ing Center and several of them had already reproduced
in captivity.
An additional 32 Baltra iguanas (4-5 years old)
f'"
July 1992 NOTICIAS DE GALAPAGOS 13
Figure 3. AlbertoJaramillo,iguanacaretakerat the Brecding
and Rearing Center, releasing a land iguana on Baltra, 10Apnl
1992.
are still at the Center. In 1992, three pairs of adults
wilI be brought to the Center from North Seymour in
order to continue the Breeding and Rearing Program
for this population and thus provide more individuals
for repatriation to Baltra. A study of the iguanas in
North Seymour in 1989-90 (Izurieta 1991) provides
the knowledge needed to select the most fit individ-
uals.
The reestablishment of a population will ultimate-
ly be judged on documentation of successful
recruitment into the population. The importance of
introduced mammal control cannot be forgotten. A
management plan for continual control and monitor-
ing of these species (particularly cats and goats), or
better yet their complete eradication, must be devel-
oped.
We hope to repatriate iguanas to Baltra until the
population is well established. The existence, after so
many years, of land iguanas on Baltra, descendants
of the native population, and the valuable collabora-
tion among the different institutions, have achieved
a historical step forward in the conservation of the
Galápagos Islands, giving us more hope for the fu-
ture of the Archipelago.
LITERATURE CITED
Banning, G.H. 1933. Hancock expedition to the
Galagagos, 1933, general report. Bulletin of the
Zoological Society of San Diego 10: 1-15.
Hoyos, M. 1987. Reporte de viaje a Seymour Norte.
Intemal report, CDRS.
Izurieta v., A.I. 1991. Historia natural de las iguanas
terrestres (Conolophus subcristatus) de la Isla
Seymour Norte, Ga1ápagos. Unpublished thesis,
Pontificia Universidad Católica del Ecuador,
Quito.
Perkins, c.B. 1932. Galapágos Island trip, Decem-
ber 4, 1931 to February 27, 1932. Unpublished
manuscript. Zoological Society of San Diego
Library, San Oiego.
Reyno1ds, R. 1981a. Land iguanas (Conolophus sub-
cristatus) on North Seymour Island. Noticias de
Galápagos 34: 17-18.
Reynolds, R. 1981 b. Programa de Herpetología.
Informe Anual 1981, CORSo
Snell, H. 1984. Evolutionary ecology of Ga1apagos
land iguanas (Iguanidae: Conolophus). Unpub-
1ishedPh.O. dissertation, ColoradoState University,
Fort Collins.
Snell, H., M. Wilson, and C. Márquez. 1986. Informe
sobre viaje a Baltra (22 enero 1986). Interna1 re-
port, CORSo
Werner, O. 1984. The Galapagos land iguana (Conol-
ophus) natural history and conservation survey.
National Geographic Society Report 17:81-94.
Woram, J.M. 1991. Whokilled the iguanas? Noticias
de Ga1apagos 50: 12-17.
Linda J. Cayot and Rafael Menoscal, Charles
Darwin Research Station, Isla Santa Cruz, Galápa-
gos, Ecuador.


Land iguanas return to Baltra

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Land iguanas return to Baltra

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