TAXONOMY & NOMENCLATURE
(Auffenberg 1974) (Caccone et al. 1999) (Caccone et al. 2002) (Chiari et al 2009)
(Ernst & Barbour 1989) (Fritz & Havas 2007) (IUCN 2010) (King & Burke 1989) (Le et al. 2006) (Poulakakis et al. 2008) (Pritchard 1996, 1997) (Reptiles Database 2010) (Russello et al 2005) (Russello et al. 2007) (Russello et al. 2010)
(Van Denburgh 1914) (Welch 1994) (Zug 1997)
Describer (Date): Quoy and Gaimard, 1824 (Testudo nigra); Harlan, 1827 (Chelonoidis nigra)
Kingdom: Animalia Phylum: Chordata Class: Reptilia Order:
Testudines Suborder: Cryptodira Family: Testudinidae (Terrestrial turtles with high domed carapace, elephantine feet) Genus:Chelonoidis Species:Chelonoidis nigra Subspecies: (According to Tortoise and Freshwater Turtle Specialist Group 1996)
C. n. abingdoni-Pinta
(Abingdon) Island (extinct in the wild, 1 captive)
C. n. becki -Volcan Wolf
and vicinity, north Isabela (Albemarle) Island
C. n. chathamensis -San Cristobal (Chatham) Island (extinct since 1933)
C. n. darwini-San Salvador
(James or Santiago) Island
C. n. duncanensis - Pinzón (Duncan)
C. n. guntheri -Sierra Negra area of SE Isabela (Albemarle) Is.
C. n. hoodensis -Espanola (Hood) Island
C. n. microphyes -Volcan Darwin and vicinity, N
central Isabela Is.
C. n. nigra-Southwest Isabela
(Albemarle) Island (extinct)
C. n. porteri -Santa Cruz (Indefatigable)
C. n. phantastica -Fernandina (Narborough) Island (probably extinct, see
C. n. vandenburghi -Volcan Alcedo and
vicinity, central Isabela Is.
C. n. vicina -Cerro Azul and vicinity, southern
Notes on genera:
Recent molecular phylogenetic study of testudinids resulted in elevating Chelonoidis (Fitzinger 1835) from subgenus to genus status (Le et al 2006)
The South American tortoises, including the Galapagos Tortoises belong in this genus; this classification is becoming widely accepted. (IUCN 2010, Fritz and Havas 2007, Reptiles Database 2010, CITES 2010)
Notes on species:
Some researchers use elephantopus (rather than nigra) as the species name for
all Galapagos tortoises (Zug 1997).
Other researchers elevate each
subspecies to full species level (Ernst & Barbour 1989).
Some 15 subspecies or species of Galapagos Tortoises have been named; 4 no longer exist; no agreement on taxonomy of remaining. (Caccone et al 2002)
Type Specimens - T. nigra vs. T. elephantopus:
The type specimen upon which was based the original description of Testudo
nigra (a synonym of Chelonoidis) was (a) young, with a carapace of only
10.5" long (b) missing exact locality information (c)
The type specimen upon which T. elephantopus was
described was (a) missing exact locality information (b)
described too generally to be able to determine its
subspecies (c) possibly a young female (d) lost after being
donated to a museum.
Notes on subspecies:
Several researchers prefer to call taxa named from each island (and volcano) by a separate species name (rather than subspecies designation), following Van Denburgh (1914) and Ernst & Barbour (1997). (Poulakakis et al 2008)
International Commission on Zoological Nomenclature will have to help resolve many problems in nomenclature that are still unresolved; a significant revision of Galapagos tortoise taxonomy is needed. (Russello et al 2005) (Le et al 2006) (Fritz & Havas 2007)
Mitochondrial DNA studies of living lineages on Santa Cruzreveal three genetically distinct lineages, each is more closely related to populations on other islands than to each other on Santa Cruz; currently only a single taxon is recognized on Santa Cruz, G. n. porteri. (Russello et al 2005)
Mitochondrial DNA studies reveal little differentiation between
the four subspecies from southern Isabela Island (microphyes,
vandenburghi, guntheri, and vicina); they were probably colonized from neighboring Santa Cruz (Caccone 1999)
Two domed tortoise populations on Santa Cruz are distinct genetically and have distinctly different shell shapes. (Chiari et al 2009)
G.n.phantastica based on
only a single specimen collected in 1906; probably extinct
G.n. abingdoni represented
by a single male from Pinta Island; Lonesome George is held at the Darwin Research Station on Santa Cruz.
Considered the world's "rarest living creature" according to the Guinness Book of Records.
However, several individuals of mixed abingdoni genotypes have been recognized in tortoises from Volcan Wolf area of Isabella; museum specimens originally collected from the island of Pinta provided valuable genetic data. (Russello 2010)
Closest living relatives are G. n. chathamensis and G.
n. hoodensis from Espanola and San Cristobal Islands, 300 km
Tortoises were gone from islands of Floreana by mid 1800s
(Poulakakis et al 2008)
DNA analysis of tortoises on nearby Isabella revealed some individuals whose genetic profile matches, in part, DNA from museum specimens collected from Floreana in late 1800s and early 1900s.
The genetic line from Floreana could be re-established in the future by selective breeding of these hybrid individuals.
G. n. duncanensis is often referred to as C. n. ephippium.
Galapagos tortoise, giant Galapagos
tortoise, tortuga gigante de los Galapagos
The word "tortoise" is usually used for terrestrial turtles in the family Testudinidae.
Phylogeny and Biogeography (Auffenberg
1974) (Caccone et al. 1999) (Caccone et al. 2002)
(Crawford et al. 2012) (Le et al. 2006)
Major groups of turtles already existed by 210 million years ago (Triassic); their origins assumed to be earlier.
Turtles are the closest relatives of birds and crocodiles (the archosaurs); they are less closely related to snakes, lizards and the tuatara (Crawford et al. 2012)
Testudinidae family of turtles reportedly originated in Asia, according to fossils. (Le et al 2006)
By 34-37 million years ago (Late Eocene), the Testudinidae family had spread from Asia to Europe, North America and Africa.
Surprisingly, Galapagos Tortoises (and all South American tortoises) seem to ultimately have an African origin (not North American as commonly assumed); their genetics indicates a sister relationship with the African hinged turtles (Kinixys sp.) (Le et al 2006)
Westward ocean currents such as the Equatorial Currents could have aided the travel from Africa to South America.
Other groups of other vertebrates also seem to have dispersed from Africa to South America - the caviomorph rodents and the New World platyrrhine monkeys
Closest living relative of Galapagos tortoises, although not a direct ancestor, is the small
Chaco tortoise, Chelonoidis chilensis, from South America. (Caccone et al 1999)
Split of Galapagos tortoises from South American lineages 6 - 12 million years ago (Miocene), before the oldest
Galapagos island was formed; now submerged islands existed around 10 million years ago.
(Caccone et al 1999)
(Christie et al 1992)
around 2 million years ago (Pleistocene) giant tortoises could be found on every continent except for Australia and Antarctica. (Caccone et al 1999)
Tortoises arrived in the Galapagos archipelago at least 3 million years (Pliocene) ago by drifting
from South America; evolved to large size before leaving the mainland.
Moved from island to island within the Galapagos by drifting on currents/swimming, and by relocation by seafaring
people from the 17th - 19th centuries.
Espanola and San Cristobal, the oldest islands, were colonized by tortoises first
Evidence not yet gathered to settle whether domed and saddleback shells have distinct population genetics; saddleback shells seem to have been favored on drier habitat islands, domed shells on larger, more diverse habitat islands.
Galapagos tortoises are only surviving lineage of the giant tortoises in the world that show two different types of shell shapes. (Chiari et al 2009)
Several subspecies inhabit the islands off Ecuador's coast
C. n. abingdoni - Pinta (Abingdon) Island - extinct in the wild
C. n. becki - Volcan Wolf and vicinity, north Isabela (Albemarle) Island
C. n. chathamensis - San Cristobal (Chatham) Island - extinct since 1933
C. n. darwini - San Salvador (James or Santiago) Island
C. n. duncanensis - Pinzón (Duncan) Island
C. n. guntheri - Sierra Negra area of SE Isabela (Albemarle) Island
C. n. hoodensis - Espanola (Hood) Island
C. n. microphyes - Volcan Darwin and vicinity, north-central Isabela Island
C. n. nigra - Southwest Isabela (Albemarle) Island (extinct)
C. n. porteri - Santa Cruz (Indefatigable) Island
C. n. phantastica - Fernandina (Narborough) Island (probably extinct)
C. n. vandenburhi - Volcan Alcedo and vicinity, central Isabela Island
C. n. vicina - Cerro Azul and vicinity, southern Isabela Island
Small, dry lowland (elevation less than 500 m or 1640 ft) islands: Española and Pinzon; Pinta and Volcan Wolf of Isabela Islands
also have arid portions.
In general, saddleback-shaped shell (carapace) populations inhabit places with drier conditions, low elevation, limited
food and other resources
Shape of shell has often been attributed to feeding habits - flatter shell allows tortoises to stretch
neck upwards and reach food higher off the ground
Shape of shell alternately may reflect degree of antagonistic display behavior in competitions for food and mates on lower quality habitats (necks can protrude farther with less of a dome, higher head "wins")
Saddleback males have a higher level of aggressiveness. (Schafer and Krekorian 1983)
Larger islands with humid highlands (elevation greater than 800 m or 2625 ft) and more microenvironments: Santa Cruz, Volcán Alcedo of Isabela
Domed carapace populations live in places with more abundant vegetation
Shell shape restricts extension of neck; food sources available closer to the ground
Domed shell shape also may reflect less aggressive behavior in a more favorable environment (Schafer and Krekorian 1983)
Climatic conditions and flora vary from island to island
Observations of seasonal migrations between drier, low elevations areas
to more moist areas at higher elevations (up to 2,000 ft) are
discussed in Van Denburgh, 1914.
When saddlebacks are frightened and pull into their shell, a large unprotected gap remains at the top of their carapace; predators may exploit this opening
Bile acids in turtles have chemical signatures different from those of all other vertebrates, possibly reflecting their ancient divergence from other reptiles. (McArthur et al 2004)
Sexual Dimorphism (Bonin et al 2006) (Van Denburgh 1914)
Domed carapace individuals: Not much sexual dimorphism.
Intermediates: males - high, angled anterior opening, which makes shell
look flatter; females - domed, with low anterior opening
Saddlebacked carapace males: anterior opening higher than that of intermediates
(sometimes higher than mid-dorsal shell) and narrow medially; females
have same general shape, but less pronounced than in males.
Generally, the plastron in the male is more concave, shorter and has
thickened knobs at the posterior margin.
Males can be up to three times heavier than
females. (Bonin et al 2006)
Feed on cactus, leaves, grass, berries (guayavita), and lichen. Cactus is the preferred food.
Also observed eating fruits of the manzanillo tree which is poisonous to humans, and stinging nettles.
Can survive without food or water for at least a year
Drink through their mouths; drink large quantities of water at a given
time, and store it in their bladders and the "root of the
Water obtained from water holes, springs, rock depressions after a
rain, by licking dew off of rock surfaces, or by eating Opuntia
As in all ectotherms, speed of digestion influenced by outside temperature.
Higher temperature = higher metabolism, quicker
In a study of diets in captive juvenile Galapagos tortoises, efficiency of digestion was found to be similar to that of horses, Asian elephants, and Indian rhinoceroses, all hindgut-fermenting herbivores. (Hatt et al 2005)
An unusual feeding behavior for gaining extra protein noted by Bonin et al (2006):
Tortoise rises up high off the ground (similar to invitation to finches to come pick off ticks)
If a bird goes underneath the tortoise to investigate the ground, the tortoise suddenly drops flat to the ground
Tortoise steps back and eats the dead bird
REPRODUCTION & DEVELOPMENT
(Darwin 1898) (De Vries 1984) (MacFarland et al. 1974) (Rostal et al. 1998) (Russello et al. 2007) (Swingland 1989)
Mating occurs December - August, peaking February - June.
Mating generally coincides with the rainy season
Males and females gather in humid uplands for mating (de Vries 1984)
Male sniffs the air when looking for a female
Male follows the female, who almost always retreats
Male nips at her
heels and rams her causing her to get into a position which allows him
Female lowers her body, retracts her legs
Male's plastron is dished upwards (concave), which allows for easier mounting of the
Incubation:120 - 240 days
Egg laying season is June - December, peaking July - November.
Generally coincides with the dry season.
Females migrate from the higher elevation areas, where resources are
more abundant, to drier coastal areas to lay eggs.
In sandy areas the female digs a hole and urinates to make the sand wet
so it won't collapse on the eggs.
Deposits eggs in a pile and
spreads them out into a single or multiple layers.
Covers eggs with six
inches of sand, which often dries into a hard cover.
MacFarland (1972) observed this to take 5 hours for one Santa Cruz
9 eggs laid in 15 minutes
In rocky areas, the eggs are deposited randomly into cracks.
Eggs are spherical, about 50 mm. across.
Average clutch size during a 1969-1971 study was 9.3/nest for G. n.
porteri and 5.1/nest for G. n. ephippium.
Approximately 78% of the eggs of both sub species hatched
(MacFarland et al. 1974).
Clutch size range for species: 8-17; varies among individuals,
subspecies, and annually.
Interclutch interval: 1-2 weeks
Incubation takes 3-8 months and is influenced by ambient temperature.
Hatching and emergence late December to early April.
Digging out of nest may take hours or days.
Young weigh around 50 g (.1 lb) at hatching
Shells striated when young; loss of this character as adults differs
Subspecies are indistinguishable at this time; all young have domed
carapaces, with the front not sharply angled
Shorter extremities than adults
Young grow at a more rapid rate than adults
Young remain in lowland areas, perhaps to avoid cooler highland temperatures. (DeVries 1984)
Sexual maturity reached at 20-25 years in captivity; possibly up to 40
years in the wild.
Carapace grows by increasing diameter of each plate along its margins.
It is difficult or impossible to age tortoises; rings on scutes (bony
plates on carapace) vary with climatic conditions.
Estimated to live up to 150 years (MacFarland, 1972).
Mortality rate in hatchlings and young animals varies depending on
Some hatchlings trapped underground in nest if soil is too dry and baked.
Other hatchlings drown if nest area is flooded.
Young tortoises may die by falling into cracks, being crushed by
falling rock, or being exposed to excessive heat stress.
Mortality of older tortoises often due to a long fall
In present times major wildfires and settlers and fishermen thwarted by land use restrictions have led to tortoise deaths (Bonin et al. 2005)
Hybrids occur at low rates in the wild and in captivity (Russello et al. 2007)
Results from reproduction studies of captive tortoises at Gladys
Porter Zoo, Brownsville, TX (Rostal et al. 1998) show:
Males and females showed seasonal, rather than year round,
Corresponding changes in physiology included:
Males: prior to mating- rise in testosterone level,
maturation of gonads, and spermatogenesis. No changes in
serum calcium levels were observed.
Females: Pre-mating rise in estradiol, increased serum
calcium levels, ovarian follicular maturation, and
vitellogenesis (ovarian development). Mating period, prior
to ovulation- rise in testosterone level, maturation of
ovaries, increased receptivity of female. Mating/nesting
period- sharp rise in progesterone coinciding with
(CDFG 2003) (Shaw 1967) (Zoonooz 1928, 1978, 1997)
1928: San Diego Zoo received its first Galapagos tortoises,
collected by Charles Townsend on Isabela island. San Diego Zoo and several
others began breeding programs as an
attempt to stave off extinction.
1930's: A second group (G. n. hoodensis) was received
from Espanola (Hood) Island.
1920s - 1950s:: Most attempts to incubate eggs were
1959: First successful hatching at San Diego Zoo.
1977: San Diego Zoo returns its only G. n. hoodensis to
the Galapagos rearing station. It is one of only 13 surviving
Present: Some of the original 1928 tortoises are still alive and
well. Based on age estimates upon their arrival, these individuals
could be over 100 years old.
CONSERVATION AND POPULATION STATUS
(Caccone 1999) (Caccone et al. 2002) (CDFG
(Ciofi 2002) (GCT website
2003) (MacFarland et al. 1974b) (Milinkovitch et al. 2004) (Parham 2008) (Russello et al. 2005) (Russello et al. 2007) (Swingland 1989) (Van Denburgh 1914)
(Watkins & Cruz 2007)
Current population estimates, from GCT website, 2003:
Santiago Island: 800 (G. n. darwini)
Pinzon: 300 (G. n. ephippium)
Santa Cruz: 3000 (G. n. porteri)
San Cristobal: 700 (G. n. chathamensis)
Española:120 (G. n. hoodensis)
Volcan Cerro Azul: 700 (C. n. vicina)
Sierra Negra: 500 (G. n. guntheri)
Volcan Alcedo: 5000 (G. n. vandenburghi)
Volcan Darwin: 1000 (G. n. microphyes)
Volcan Wolf: 2000 (G. n. becki)
Pinta Island: extinct in the wild. One individual in captivity. (G.
1936: Ecuadorian government lists the giant tortoise as a
1959: Galapagos National Park and the Charles Darwin Foundation
1965: Tortoise Rearing Program established on the Galapagos
Islands to breed and restore populations to the wild, and to control
harmful exotic species (goats, rats, etc.). First project was to save
Pinzon Island populations from the black rat. Most of the funding came
from San Diego Zoological Society.
G. n. abingdoni (1, 1972) and G. n. hoodensis (only 14 in
late 1960's) were so rare that they were removed from the wild
for their protection.
1977: San Diego Zoo returned a male G.n. hoodensis to the
captive colony, which was composed of 2 males and 12 females.
1971: Very successful captive breeding program at breeding center of the Charles Darwin Research Station and Galapagos National Park on Santa Cruz with 12 females and 3 males from Española (Milankovitch et al. 2004)
Begun for restoration of a tortoise population on Española
Some 1200 offspring hatched in captivity were repatriated over next 33 years
In 1994 offspring in wild documented from individuals hatched in captivity
1999: mtDNA studies showing G. n. abingdoni's close
relationship to populations from Espanola and San Cristobal island;
May make breeding attempts more successful in the future if these tortoises are matched
breeding used Isabela Island populations (Caccone et al.
2005: DNA analysis designates two genetically distinct significant populations on Santa Cruz and a third much smaller population, also distinct; at least the two most numerous should be considered a separate conservation units.
(Russello et al 2005)
Currently the taxonomy only recognizes a single taxon, G. n. porteri.
Problems facing especially the Cerro Fatal population include poaching, agriculture encroaching on habitat, and lack of genetic variation.
Attempts to breed Lonesome George (G. n. abingdoni)
have been unsuccessful, but there is still hope.
Approx. 200 G. n. ephippium have been reintroduced to
Pinzon Island (Ciofi et al. 2002).
By 2001, some 2500 individuals have been reintroduced to the
islands (CDFG 2001)
Galapagos Conservancy project to restore tortoise population to Pinta Island:
(Galapagos Conservancy 2010)
Goats eliminated in 1999 from Pinta
39 sterilized hybrids tortoises to be released May 2010 to help bring ecological balance to the islands that these large herbivores provide
By 2030 genetically appropriate individuals will have been released; this is facilitated by the recognition of hybrid individuals on nearby islands and in captive populations in zoos
Descendants of tortoises from islands of Floreana, thought to be extinct, survive as hybrids on Isabella; the genetics of the hybrids match the DNA from museum specimens collected in late 1800s and early 1900s from Floreana.(Poulakakis et al 2008)
Descendants of tortoises from island of Pinta include Lonesome George and newly recognized hybrid individuals from nearby Isabela Island; six museum specimens from Pinta Island aided in this genetic study. (Russello et al 2007)
With selective breeding, these hybrids could in time, help restore "the genetic constitution" of the original population. (Poulakakis et al. 2008)
IUCN Status: Species vulnerable.(Version 2.3) IUCN says this assessment needs updating since it was based in 1996. Individual subspecies are
listed as vulnerable, endangered, critically endangered, or extinct.
CITES Status: Appendix I
All conservation efforts on the Galapagos Islands depend on curbing the growth of tourism that decreases the isolation of the islands and increases the arrival of invasive species which are the "greatest threat to native biodiversity". (Watkins & Cruz 2007)
Threats to survival
Prior to the 20th century, up to an estimated 200,000 were
collected by whalers and other seafarers as a source of
Based on ships' logs, 13,013 tortoises were collected
during 189 visits between 1831 and 1838. (This number only
includes ships whose logs were available.)
collecting had occurred since the 17th century, this
represents only a small fraction of actual captures.
Settlers began moving to the islands in the 1800's; they
killed tortoises for meat and oil and destroyed their
habitat when clearing for pasture and fences.
In 1897, one observer found 150 skeletons by a water hole,
and 100 more half a mile away.
Also observed at a nearby
settlement: 1200 gallons of tortoise oil, representing 400
to 1200 large tortoises (1-3 gallons per tortoise) (Van
Non-endemic mammals introduced, which preyed on eggs and
young, and competed for resources (goats, rats, dogs,
donkeys, pigs, cats).
Scientific collecting expeditions took 661 tortoises between
1888 and 1930
Since 1990 up to 120 tortoises thought to have been killed by poachers.
Introduced mammals are still a threat
The only endemic predator is the Galapagos Hawk, which preys
on eggs and hatchlings
Poaching and habitat destruction by humans continues.
Characteristics making them vulnerable to extinction:
(Chiari et al. 2009)
Galapagos Conservancy: Website for Project Pinta that will documents the return in May 2010 of tortoises to Pinta Island, the birthplace of "Lonesome George"; video clips, blogs and will have links to tracking maps for tagged tortoises.
California Turtle and Tortoise Club (CTTC): Website for "turtle and tortoise preservation, conservation and education"; club organized in 1964. Has archives of all articles published by the CTTC, general turtle information, a photo gallery, and a detailed account of efforts to conserve tortoises on Pinzon in the Galapagos islands.