Table Of ContentTropical Natural History 20(2): 134–143, August 2020
2020 by Chulalongkorn University
Origins of the Extinct, Subfossil Galápagos Giant Tortoises
(Chelonoidis niger) of the Post Office Lava Tube (Inferior) of
Floreana Island: Voluntary or Accidental Occupancy?
DON MOLL1*, LAUREN E. BROWN2 AND ALAN RESETAR3
1Department of Biology, Missouri State University, Springfield, Missouri 65987, USA
2School of Biological Sciences, Illinois State University, Campus Box 4120, Normal, Illinois 61790, USA
3Amphibians and Reptiles, Field Museum of Natural History, 1400 South Lake Shore Drive,
Chicago, Illinois 60605, USA
* Corresponding author. Don Moll ([email protected])
Received: 17 January 2020; Accepted: 5 April 2020
ABSTRACT.– The origins of the remains of giant tortoises that have accumulated in vast quantities on the floors
of caves in some locations where giant tortoises once lived have received only scant attention to date. The
subfossil Galápagos Giant Tortoises (Chelonoidis niger) of Floreana Island’s Post Office lava tube (inferior) are
the main focus of this paper with supporting data obtained from other tortoise populations and locations. These
remains have historically been explained, if at all, as the result of accidental falls (e.g., via pitfall traps). With the
accumulation of greater knowledge of tortoise ecology and paleoecology the likelihood of voluntary cave entry
and exit, sometimes by large numbers of giant tortoises (e.g., the Aldabra Atoll Giant Tortoises), also seems
plausible. If followed by occasional blockages of exits by geological phenomena such as roof collapse the
tortoises could be trapped within as well. An inquiry into the available evidence for the occurrence of both
phenomena is the subject of this paper.
KEY WORDS: giant tortoises, lava tubes, subfossils, Floreana
tube of Floreana Island (= Charles or Santa
INTRODUCTION
Maria) in the Galápagos Archipelago.
Hundreds of their remains are scattered on
The Giant Galápagos Tortoises (Chelo-
the floor of this cave-like lava tube.
noidis niger species complex) of Ecuador’s
Townsend (1928) and Steadman (1986)
Galápagos Islands are among the largest of
suggested the tortoises fell through the
extant land tortoises. They are also long
ceiling “pitfalls” and became trapped,
famous for their role as ships’ fare in the age
resulting in death from injuries sustained in
of sail due to their ability to survive without
their fall or eventual starvation. We herein
sustenance for months in the ships’ holds. A
challenge their explanation of the tortoises’
more detailed knowledge of their biology
means of entry, and suggest an alternative
has gradually accumulated in more recent
explanation for some of the tortoises present
times (e.g., Blake et al., 2012; Blake et al.,
in the lava tube.
2013; Blake et al., 2015; Caccone et al.,
2002; Caccone et al., 1999; Pritchard, 1996,
2007; Rick and Bowman, 1961). However, MATERIALS AND METHODS
relatively little has been published
concerning the extinct subfossil forms Literature Search
including the specimens of Chelonoidis The methodology of Brown et al. (2008)
niger obtained from the Post Office lava was employed to obtain a maximum number
MOLL ET AL. — ORIGINS OF THE EXTINCT, SUBFOSSIL GALÁPAGOS GIANT TORTOISES 135
of relevant references concerning the subject 1980). They are formed by flowing lava and
matter of this paper. Searches employing may be subterranean or formed by crusting-
numerous combinations of search words and over of surface lava channels. They may
the search engines Google, Google Scholar have complex branching and can have a
(Advanced Scholar Search), and JSTOR more or less horizontal or downslope surface
Advanced Search were used along with opening (i.e., window) through which the
traditional library-based searches of paper liquid lava within may escape, leaving a
sources at Illinois State University’s Milner hollow tube. It has also been observed that if
Library, and in LEB’s and DM’s personal a surface window does form, the still-
herpetological and paleontological libraries. flowing lava may rebuild it and not flow
Scientific and common names follow out. At other times, overflow may occur
those designated by the Turtle Taxonomy draining the tube (Greeley, 1971a; Jagger,
Working Group (2017). 1921). Roof collapse may eventually block
Collecting History and Location of the tube when it is void of lava. When this
Specimens occurs near the original surface opening, a
In 1928, Townsend (Director of the New secondary opening may split off creating a
York Aquarium) visited Floreana, one of the steep, vertical, well-like hole.
southern Galápagos Islands (Latitude: -1° Post Office lava tube was described in
17' 30.60" S; Longitude: -90° 26' 1.79" W), detail by Townsend (1928) and Steadman
where he observed hundreds of subfossil (1986). There are two elongate branches
fragments of tortoises in a lava tube cave (“inferior” and “superior”) that are now
(Post Office lava tube [inferior]) on the separated from one another by a massive
northwest side of the island, and collected roof collapse. The inferior branch contains
12 nearly complete shells of extinct Giant most of the tortoise remains. Its opening to
Tortoises (Chelonoidis niger). The following the surface was also formed by a roof
year, 1929, K. P. Schmidt (Field Museum of collapse. This opening is ca. 12 ft. (3.7 m) in
Natural History) and S. N. Shurcliff also diameter and was half-concealed by bushes.
explored this same lava tube and found three Ground level beneath the entrance is ca. 20
additional shells in “perfect condition” ft. (6.1 m) deep. One side of the opening has
which had apparently been overlooked a steep slope (Townsend, 1928).
previously (Shurcliff and Schmidt, 1930).
The Field Museum tortoises with nearly
RESULTS AND DISCUSSION
complete shells include FMNH 13522 (now
MCZ Herpetology R-32098) and FMNH
The Tortoise Turnstile Scenario
13523 (2 specimens). A number of carapaces
Townsend (1928), echoed by Steadman
and other subfossil material are held by the
(1986), stated that the tortoises found in the
American Museum of Natural History and
Post Office lava tube (inferior) must have
Harvard University’s Museum of Comparative
entered by falling through the near-vertical
Zoology (D. Dickey, pers. comm.; Poulakakis
opening left by the collapsed roof section
et al., 2008).
described previously. This would presumably
Description of Study Area
have occurred after the major roof rock fall
Lava tubes are cave-like structures
blocked the liquid lava exit pathway that
associated with effusive volcanic eruptions
of low viscosity basalt lavas (Carlquist,
136 TROPICAL NATURAL HISTORY 20(2), AUGUST 2020
previously allowed any tortoises to enter could have been the case for some extinct
and leave the lava tube at will. species also.
Townsend (1928) suggested that, “With Moll and Brown (2017) reviewed and
a steep slope at one side the unluckly [sic] summarized examples of several extant
tortoise that tumbled in did not necessarily tortoise species known to utilize different
strike bottom with a fatal crash but rather forms of rock shelters, from large caves to
rolled down an incline it could not ascend.” crevices. This depended on the size, and
As the shells of most Giant Galápagos sometimes age of the species in question.
Tortoises are thick, hard, and tough (except Protection from predators, heat and
the Pinta Tortoises [Chelonoidis abingdonii]), humidity fluctuation, cold temperatures, and
most individuals falling ~6 m into the lava use as hibernacula are common benefits for
tube in this manner would be unlikely to be these species. Most interesting in the
seriously injured, if at all. Without an context of this discussion was the discovery
accessible exit these tortoises would be of two caves on Grande Terre, Aldabra
doomed to eventually die of starvation or Atoll by D. Hansen and his research team
other stresses in the lava tube. (The collapsed from the University of Zurich that are used
roof section in the Post Office lava tube by many Giant Aldabra Tortoises
[superior] descended at a shallower angle, (Aldabrachelys gigantea) to escape the
resulting in fewer tortoises being trapped potentially lethal afternoon heat on the atoll
than in the inferior tube [Steadman, 1986]). (see photos and text in Bittel [2016], Warne
When Townsend (1928) and even [2016], and photo by Dr. Dennis Hansen in
Steadman (1986) conducted their research Moll and Brown [2017]). Dennis Hansen (in
there was very limited ecological or paleo- Bittel, 2016) believed the use of these caves
ecological information available concerning by tortoises was quite ancient based upon
Giant Galápagos Tortoises, or, indeed, the extent of wear of the rock surfaces in
tortoises in general. As more knowledge has and around the caves. The mid-day heat of
accumulated it has become apparent that Aldabra Atoll is an existential threat to
another explanation for some of the tortoises tortoise survival there and shade is
present in the Post Office lava tube is necessary for coping with the hottest parts
plausible: the tortoises could have of the day. As Bittel (2016) stated, “For
voluntarily entered the lava tube, and were giant tortoises living in the tropics you
subsequently trapped within by some either find a way to get out of the sun or you
geological phenomenon such as a roof die.” Naturalists have observed small
collapse or landslide. juvenile, and larger adult tortoises on
Caves provide favorable environments Aldabra Atoll utilizing shade in rock
for some species of extant tortoises. The crevices and under clumps of Tussock
caves’ other fauna may benefit from their Grass, Sclerodactylon macrostachyum, or
presence also. For example, the large other shade-producing plant clumps (Bittel,
amount of dung produced by Aldabra 2016; Coe and Swingland, 1984; Pritchard,
Tortoises in the caves they visit seems to 2007). The Grande Terre caves, however,
feed resident crabs and insects (Baxter, R.; provide considerably more shade space in
Blake, S. and Hansen, D. in [Bittel, J., addition to those previously known shaded
2016]). It is reasonable to assume that this areas (accommodating up to 85 tortoises in
the larger cave [Bittel, 2016]).
MOLL ET AL. — ORIGINS OF THE EXTINCT, SUBFOSSIL GALÁPAGOS GIANT TORTOISES 137
As the Galápagos, Seychelles, and 1870 in Bour et al., 2014). Large deposits of
Mascarene archipelagos are within the their fossil and (mainly) subfossil remains
tropical latitudes, the resident giant tortoises litter the cave floors of all three main islands
must have coped with periods (if not daily and some of their smaller satellites,
exposure) of extreme heat. The use of caves including caves of limestone karst and
would have been a natural, simple, volcanic (including lava tube) origin. The
behavioral mechanism to cope with heat condition of the remains vary greatly due to
stress where accessible caves are available. the environments of the caves, the age of the
Other reasons for tortoise aggregations in remains, and the degree of disruption of the
caves, related to possible social interactions cave floors by animal and/or human traffic.
among tortoises, and not just benefits In Cylindraspis, the generally more fragile
provided by the cave itself are also possible, morphology of the thin carapaces and
but have not yet been identified in tortoises lighter skeletal structure are quite different
(e.g., group mating behavior, kleptothermy, from most other tortoises (Bour et al., 2014;
etc., have been observed in other reptiles Hume, 2014). Moll and Brown (2017) found
congregating in caves and cave-like C. vosmaeri and C. peltastes of Rodrigues
structures [S. Blake, in Bittel, 2016]). particularly interesting in regard to their
There are few other recent observations possible voluntary use of caves as shelters
of extant giant tortoises in caves. Pritchard since their remains are often extremely well
(2007) recorded one very large, seemingly preserved and articulated, with numerous
“deranged” Galápagos Tortoise (presumably complete or nearly complete sets of remains
Chelonoidis becki) encountered by a BBC on cave floors despite their aforementioned
film crew in a lava tube on Volcan Wolf, fragility. Signs of damage which would
Isabela Island (=Albemarle Island). It was probably result from falls are often not
presumed to have fallen in from an opening present, suggesting the possibility of
above, but was unable to ascend the steep voluntary entry into the caves.
slope leading back to the surface. Despite the long history of association
Giant extinct tortoises which may have between humans and Cylindraspis on the
used caves for shelter (or were victimized Mascarenes, and the existence of numerous
by them) are known from Madagascar (two published and unpublished accounts of
species of Aldabrachelys). One species, A. observations of their natural history (e.g.,
grandidieri, may have been associated with Cheke and Bour, 2014), we are aware of
the caves of Andranoboka (north of only one historical observation related to
Mahanjanga) according to Cheke and Bour voluntary cave use. Bellanger de Lespinay
(2014). (1671) wrote (on La Réunion) “through an
The Mascarene Islands (La Réunion, instinctual sense, two or three days before
Mauritius, and Rodrigues) were inhabited bad weather (referring to a cyclone), the
by five species of giant tortoises of the birds, tortoises and other animals, withdraw
genus Cylindraspis (one, two, and two into rocks or caves from which they do not
species, respectively – Gerlach [2014]). All leave until the bad weather has passed” (in
are now extinct, but one live female (species Bour et al., 2014). Perhaps this should not
unknown) was captured in a cave on Round be too surprising since scores of naturalists
Island (22.4 km off the north coast of and trained researchers who have observed
Mauritius) sometime after 1844 (Barkly, the Giant Tortoises of Aldabra Atoll over a
138 TROPICAL NATURAL HISTORY 20(2), AUGUST 2020
period of many years failed to detect their alone is staggering, however, and begs
impressive daily migrations to and from the further inquiry.
caves of Grande Terre. Early observations by Gilbert White in
Shell fragments of the Giant North Carr (1952) suggested that a pet tortoise was
American Tortoise, Hesperotestudo sp., “… much too wise to walk into a well” and
have been found in Crevice Cave and Tom was perceptive enough to retreat from the
Moore Cave in Perry County, south-eastern rim of a precipice it had encountered.
Missouri (Hawksley, 1986). The latter Yerkes (1904) conducted research that
specimen was collected from the clay and suggested terrestrial turtles hesitated to walk
gravel of a stream in the cave. off platforms a foot (.305 m) in height and
The remains of Meiolania mackayi, an became even more apprehensive at greater
Australasian Horned Turtle, have been heights, while aquatic turtles showed little
discovered in the Pindaï Caves of New concern about leaving the platform at
Caledonia (Bauer and Sadlier, 2000). similar heights. Case (1969), Patterson
Finally, a bone of the Radiated Tortoise (1971) and Routtenberg and Glickman
(Astrochelys radiata) with a tool cut on it (1964) demonstrated experimentally that a
was found in a cave on La Réunion. As this variety of terrestrial turtles and tortoises
cave is beyond the range of this tortoise, and were able to perceive and avoid deep visual
the cave had been disturbed previously by cliffs. This degree of visual acuity, depth
cave explorers (Bour, 1981), its transport to perception and judgement should make the
the site by humans is considered likely. likelihood of accidentally tumbling into a
Before the Fall pitfall extremely unlikely, yet evidence in
A related issue when considering the the caves suggests otherwise.
origin of tortoise remains in caves is, why Golubović et al. (2013) conducted
are there so many tortoises that have experimental studies of willingness to “step”
presumably fallen in? An obvious, partial off a 50 cm high step by Hermann’s
answer is that animals have steadily fallen in Tortoises (Testudo hermanni) from a rocky,
through the pitfalls described above by rugged, island habitat compared to those
Townsend (1928), Steadman (1986) and from a lowland plain habitat in Macedonia.
others in the Galápagos Islands, and in Bour They found that significantly more tortoises
et al. (2014) and Hume (2014) in the from the rugged habitat were willing to take
Mascarene Islands over the millennia that the plunge compared to those from the
tortoises and caves have been present. plain. Golubović et al. (2013) believed that
Additional contributions could have been the more rugged habitat required greater
made through water transport of already boldness in its resident tortoises in order to
dead animals into the caves (Hume, 2014), accomplish essential tortoise requirements
human transport for butchering, cooking, (compared to lowland plain tortoises) even
etc. (Bour, 1981; Cheke and Bour, 2014), or though risks were involved. Indeed, they
in the case of small tortoises, perhaps observed tortoises in the field losing their
transfer as prey by cave-dwelling owls balance and falling from steep cliffs they
(Steadman, 1986). The sheer quantity of the were attempting to ascend (non-fatally).
remains which have been discovered in They also found dead tortoises at the foot of
caves in the Galápagos and Mascarenes 15-30 m high cliffs atop which they
previously observed living, active tortoises
MOLL ET AL. — ORIGINS OF THE EXTINCT, SUBFOSSIL GALÁPAGOS GIANT TORTOISES 139
had been present. Griffiths (2014) also population extending from the southern
recorded a fatal fall of an introduced lowlands into the uplands. The lowland
Radiated Tortoise (A. radiata) a month after dwellers were the first to be decimated by
its release on Round Island in the collectors because of the greater ease in
Mascarenes. It had tumbled about 71 m acquiring them there. The upland tortoises
down a rock slab and she considered such were able to survive a bit longer because the
falls “… not uncommon for tortoises.” rugged uplands made collecting more
Many tortoise populations live in rocky, difficult. The explanation for the demise of
uneven environments and individuals must the last upland Pinta Tortoises may never be
often travel extensively to meet their needs fully known.
in spite of the possible dangers along the Although the ravines in question did not
way (Calzolai and Chelazzi, 1991; lead into subterranean caverns, the
Golubović et al., 2013; Longepierre et al., likelihood of similar behaviors which could
2001). Individuals from populations in lead to cave entrapment seem plausible.
lowland plains and other less rugged Other factors could influence tortoise falls
habitats may be at a disadvantage if also. Male tortoises are often more active
confronted with the opposite as Golubović (Lagarde et al., 2002; Lagarde et al., 1999)
et al. (2013) have demonstrated. Therefore, and more agile than females (Bonnet et al.,
it is interesting that Miguel Castro and 2001), although Golubović et al. (2013)
David Cavagnaro (in Pritchard, 2007), noted observed no significant difference in
high mortality in (now extinct) Pinta Island jumping ability between males and females
Galápagos Giant Tortoises (mainly males) from the populations tested in their study.
presumably resulting from falls into upland Male Galápagos Giant Tortoises are known
ravines. They suggested that grazing to chase females (Pritchard, 2007) and these
competition from introduced goats at lower higher male activity levels, and perhaps the
altitudes had forced the tortoises to forage at distractions inherent in intersexual premating
higher altitudes in more rugged habitats behavior (e.g., perhaps with females running
where fatal falls into ravines would be more into pitfalls to escape males, pursuing males
likely due to their lack of experience in entering the pitfalls, etc.) and intraspecific
coping with such obstacles in their male combat, might increase their likelihood
movements. Despite their possible reticence of stumbling into a pitfall trap. The
in negotiating uneven, fractured terrain, the overwhelming male bias in mortality in the
requirements for finding food, mates, etc., Pinta ravines examined by Pritchard (2007)
may have forced displaced lowland forms to suggests greater male activity levels may be
take risks they would have declined in more a factor, but the male-biased sex ratio
normal times and habitats. Pritchard (2007) observed in this dwindling population
discounted their hypothesis, but Golubović before its total demise (Pritchard, 2007)
et al. (2013) might have predicted such masks the significance of this factor. Many
results if lowland populations shifted into “surviving intact caves are well concealed
higher altitudes, and more rugged habitats to with small, often precarious entrances”
which they were poorly adapted (Hume, 2014). These may increase their
behaviorally. Pritchard (2007) argued that likelihood of remaining undetected by
the upland tortoises were just the last wandering tortoises, especially if partially
remaining individuals of a once continuous concealed by bushes (e.g., Hume, 2014;
140 TROPICAL NATURAL HISTORY 20(2), AUGUST 2020
Steadman, 1986; Townsend, 1928). Individuals Even the presence of the intact or nearly
could also potentially seek an interior cave intact remains of the La Réunion Island
water supply, seek out potential mates caves are attributed to falls or water
inside, or seek shelter from the conditions transport (Hume, 2014). Uncertainty will
experienced outside the cave. John B. always be an issue when attempting to
Iverson (pers. obs.) has observed Red- reconstruct the past, but it can never be
Footed Tortoises (Chelonoidis carbonarius) completely avoided in paleoecological
using “borrowed” armadillo burrows for research. Decisions must be based upon the
shelter and Branch (2012) has recorded the best available evidence, and in this case the
use of animal burrows as shelters by Cape data suggest that some of the remains in
tortoises (Homopus areolatus and H. these caves could have resulted from
femoralis). A tortoise which misjudged the voluntary ingress and subsequent entrapment,
depth of a “presumed” burrow and tumbled in addition to, or instead of, accidental falls.
into a cave below could be interred
permanently as a result. Giant Galápagos
CONCLUSIONS
tortoise remains have been observed in deep
crevasses formed by collapsed lava tubes
Water-, predator-, and human-mediated
(Hennessy, 2019). It is also possible that
transport, accidental falls, and voluntary
some tortoises could have been trapped in
entry and subsequent entrapment are
lava tubes by simply walking across their
possible mechanisms resulting in the
roofs, causing them to collapse. Some parts
accumulation of tortoise remains in caves.
of their roofs are very thin and unstable
Voluntary entry followed by entrapment
because the rocks which form them are only
appears to best explain the presence of some
held together by pressure exerted against
of the subfossil tortoise fauna of the Post
each other. A giant tortoise could be heavy
Office lava tube (inferior). In order to
enough to initiate such a collapse (T. Banik,
determine which is the most likely
pers. com.).
explanation for the majority of the remains
Despite the accumulated direct evidence
discovered in a particular location, the
from living tortoises, and indirect evidence
following suggestions are offered: 1) The
suggested by the subfossil remains from
condition and abundance of the shells
caves discussed in the Mascarene Islands
should be scrutinized. The presence of many
(mainly), there are evidently researchers that
intact or nearly intact carapaces, plastrons,
have not considered voluntary cave ingress
and delicate skeletal elements in a cave,
and use as a mechanism to explain the
especially those characterized by particularly
presence of fossil, subfossil, and/or recent
thin shells and less sturdy skeletal elements
remains in caves such as the Post Office
(e.g., the Mascarene Rodrigues Cylindraspis
lava tube (inferior) of Floreana Island. It is
[Hume, 2014] and the Pinta Island
interesting that Bour et al. (2014) and Hume
Galápagos Tortoises [Pritchard, 2007]) may
(2014), in the chapters in Gerlach (2014)
suggest voluntary entry. 2) The geological
that mainly deal with Mascarene Islands
and chronological history of the caves
Tortoise cave remains, never mention the
themselves should be considered in as much
possibility of voluntary entry with the
detail as possible to determine when and
exception of the historical account by
where travel in and out of the caves might
Bellanger de Lespinay (1671) quoted earlier.
MOLL ET AL. — ORIGINS OF THE EXTINCT, SUBFOSSIL GALÁPAGOS GIANT TORTOISES 141
have been feasible or not. The lava tube Few or no caves would be expected to
caves like Floreana’s Post Office lava tubes provide all of the necessary criteria to
would often have been likely to allow establish a completely certain explanation
tortoise entry soon (geologically speaking) for the origins of its fossil or subfossil
after their lava drained out through tortoise fauna. The more criteria evaluated,
relatively horizontal or downslope openings as described above, that suggest the
described and portrayed by Carlquist (1980) likelihood of one explanation over another
and Greeley (1971a, b). Subsequent would be extremely valuable in contributing
blockage by roof collapse and/or landslides to a consensus viewpoint concerning the
would have obstructed such movement and cave faunas’ origins. This approach would
entrapped tortoises within, while pitfall surely be better than automatically assuming
openings in the ceiling would allow only that all the tortoises within result solely
one-way entry from above in the future. from accidental entrapment by pitfall or
Sophisticated dating techniques should be other involuntary means. Voluntary cave
employed to pinpoint the timing of those use by extant tortoises is too prevalent and
phenomena and to evaluate the resulting widespread to be excluded from consideration
tortoise mortality patterns. For example, the in paleoecological research designed to
presence of large numbers of subfossil elucidate use patterns of the past.
tortoises of the same geological age within a
cave might suggest voluntary entries, and
ACKNOWLEDGEMENTS
subsequent entrapment within (or perhaps a
mass mortality event followed by
We thank Tenley Banik, Evan Brown,
interment). Accidental entry by falls and
Jill Brown, Angelo Capparella, Janice Moll
other types of misjudgment may be
and Ben Sadd for critically reading the
suggested by the presence of subfossil
manuscript, and Janice Moll for typing the
tortoises of various age periods, perhaps in
manuscript. David Kizirian and David
different strata on the cave floor. 3)
Dickey of the American Museum of Natural
Preferably, the cave floor remains should be
History provided holdings details on
undisturbed by animal and/or human
Townsend’s tortoises from Floreana in the
intrusion and excavation until investigations
AMNH collection.
of the above phenomena are initiated.
Analysis of the tortoises’ stratification
patterns on and within the cave floor, and LITERATURE CITED
the opportunity to apply appropriate dating
Bauer, A.M. and Sadlier, R.A. 2000. The
techniques upon the remains for comparison
Herpetofauna of New Caledonia. Ithaca, New
with the timing of critical geological
York: Society for the Study of Amphibians and
phenomena would be particularly informative. Reptiles. 310 pp.
Finally, 4) The exploration of new, untouched, Bellanger de Lespinay, L.A. 1671. Mémoirs de L. A.
cave systems to accumulate more relevant Bellanger de Lespinay, Vendômois, sur son Voyage
aux Indes Orientales (1670-1675). Vendôme. 219
data (as suggested by Hume [2014] on
pp.
Rodrigues) would provide more data for
Bittel, J. 2016. Cave-dwelling giant tortoises are a big
comparison with previously available surprise. http://news.nationalgeographic.com/
material. 2016/02/160212-caves-giant-tortoises-animals-
science-seychelles/ (accessed 2016).
142 TROPICAL NATURAL HISTORY 20(2), AUGUST 2020
Blake, S., Wikelski, M., Cabrera, F., Guezou, A., Gmelin (Reptilia Testudinidae). Ethology Ecology
Silva, M., Sadeghayobi, E., Yackulic, C.B. and and Evolution, 3: 153-166.
Jaramillo, P. 2012. Seed dispersal by Galápagos Carlquist, S. 1980. Hawaii A Natural History:
tortoises. Journal of Biogeography, 39: 1961- Geology, Climate, Native Flora and Fauna Above
1972. the Shoreline. Lawai, Kauai, Hawaii USA: Pacific
Blake, S., Yackulic, C.B., Cabrera, F., Tapia, W., Tropical Botanical Garden. 468 pp.
Gibbs, J.P., Kümmeth, F. and Wikelski, M. 2013. Carr, A.F., Jr. 1952. Handbook of Turtles: The Turtles
Vegetation dynamics drive segregation by body of the United States, Canada, and Baja California.
size in Galapagos tortoises migrating across Ithaca and London: Cornell University Press. 542
altitudinal gradients. Journal of Animal Ecology, pp.
82: 310-321. Case, D. 1969. Depth and perception. International
Blake, S., Yackulic, C.B., Wikelski, M., Tapia, W., Turtle and Tortoise Society Journal, 3: 12-14 and
Gibbs, J.P., Deem, S., Villamar, F. and Cabrera, F. 36.
2015. Migration by Galapagos giant tortoises Cheke, A.S. and Bour, R. 2014. Unequal struggle -
requires landscape-scale conservation efforts. In: how humans displaced the dominance of tortoises
Biodiversity and Ecosystem Restoration, in island ecosystems. In Western Indian Ocean
Galapagos Report, 144-150. Tortoises, Ecology, Diversity, Evolution,
Bonnet, X., Lagarde, F., Henen, B., Corbin, J., Nagy, Conservation, Paleontology. Gerlach, J. (Eds)
K., Naulleau, G., Balhoul, K., Chastel, O., Legrand, Manchester, UK: Siri Scientific Press. pp. 31-120.
A. and Cambag, R. 2001. Sexual dimorphism in Coe, M.J. and Swingland, I.R. 1984. Giant tortoises of
steppe tortoises (Testudo horsfieldii): influence of the Seychelles. In Biogeography and Ecology of
the environment and sexual selection on body the Seyschelles Islands. Stoddart, D. R. (Eds) The
shape and mobility. Biological Journal of the Hague, Boston, and Lancaster: Dr. W. Junk
Linnean Society, 72: 357-372. Publishers. pp. 309-330.
Bour, R. 1981. Histoire de la tortue terrestre de Gerlach, J. 2014. Western Indian Ocean Tortoises:
Bourbon. In: Bulletin de I’lle de La Réunion, 358 Ecology, Diversity, Evolution, Conservation,
pp. Palaeontology. Manchester, UK: Siri Scientific
Bour, R., Mourer-Chauvire, C. and Ribes, S. 2014. Press. 352 pp.
Morphology and palaeontological exploration Greeley, R. 1971a. Observations of actively forming
(until 2000) of the extinct tortoises of the lava tubes and associated structures, Hawaii.
Mascarene islands (sic.). In Western Indian Ocean NASA Technical Memorandum. NASA TM X-
Tortoises, Ecology, Diversity, Evolution, 62,014. Ames Research Center, Moffett Field,
Conservation, Palaeontology. Gerlach, J. (Eds) California, USA.
Manchester, UK: Siri Scientific Press. pp. 121- Greeley, R. 1971b. Observations of actively forming
202. lava tubes and associated structures, Hawaii. Part
Branch W.R. 2012. Tortoises, terrapins and turtles of II. NASA Technical Memorandum. NASA TM X-
Africa: Penguin Random House South Africa. 128 62,096. Ames Research Center, Moffett Field,
pp. California, USA.
Brown, L.E., Dubois, A. and Shepard, D.B. 2008. Golubović, A., Arsovski, D., Ajtić, R., Tomović, L.
Inefficiency and bias of search engines in and Bonnet, X. 2013. Moving in the real world:
retrieving references containing scientific names tortoises take the plunge to cross steep steps.
of fossil amphibians. Bulletin of Science, Biological Journal of the Linnean Society, 108:
Technology and Society, 28: 279-288. 719-726.
Caccone, A., Gibbs, J.P., Ketmaier, V., Suatoni, E. Griffiths, C. 2014. Rewilding in the western Indian
and Powell, J.R. 1999. Origin and evolutionary Ocean. In Western Indian Ocean Tortoises:
relationships of giant Galápagos tortoises. Ecology, Diversity, Evolution, Conservation,
Proceedings of the National Academy of Sciences Palaeontology. Gerlach, J. (Eds) Manchester, UK:
USA, 96: 13223-13228. Siri Scientific Press. pp. 325-349.
Caccone, A., Gentile, G., Gibbs, J.P., Fritts, T.H., Hawksley, O. 1986. Remains of Quaternary vertebrates
Snell, H.L., Betts, J. and Powell, J.R. 2002. from Ozark caves and other miscellaneous sites.
Phylogeography and history of giant Galápagos Missouri Speleology, 26: 1-67.
tortoises. Evolution, 56: 2052-2066. Hennessy E. 2019. On the Backs of Tortoises:
Calzolai, R. and Chelazzi, G. 1991. Habitat use in a Darwin, the Galápagos, and the Fate of an
central Italy population of Testudo hermanni
MOLL ET AL. — ORIGINS OF THE EXTINCT, SUBFOSSIL GALÁPAGOS GIANT TORTOISES 143
Evolutionary Eden. New Haven and London: Yale Massachusetts, USA: Chelonian Research
University Press. 310 pp. Foundation. 85 pp.
Hume, J.P. 2014. Fossil discoveries on Mauritius and Pritchard, P.C.H. 2007. Tales from the Thébaide,
Rodrigues. In Western Indian Ocean Tortoises, Reflections of a Turtleman. Malabar, Florida,
Ecology, Diversity, Evolution, Conservation, USA: Krieger Publishing Company. 330 pp.
Palacontology. Gerlach, J. (Eds) Manchester, UK: Rick, C.M. and Bowman, R.I. 1961. Galapagos
Siri Scientific Press. pp. 203-228. tomatoes and tortoises. Evolution, 407-417.
Jagger, T.A. 1921. Volcanic conditions in February, Routtenberg, A. and Glickman, S.E. 1964. Visual cliff
activity of Halemaumau: Monthly Bulletin. behavior in undomesticated rodents, land and
Hawaii Volcano Observer. 9: 91-37. aquatic turtles, and cats (Panthera). Journal of
Lagarde, F., Bonnet, X., Nagy, K., Henen, B., Corbin, Comparative and Physiological Psychology, 58:
J. and Naulleau, G. 2002. A short spring before a 143.
long jump: the ecological challenge to the steppe Shurcliff, S.N. and Schmidt, K.P. 1930. Jungle
tortoise (Testudo horsfieldi). Canadian Journal of Islands: The "Illyria" in the South Seas. London
Zoology, 80: 493-502. GP Putnam's Sons. 298 pp.
Lagarde, F., Bonnet, X., Naulleau, G., Corbin, J., Steadman, D.W. 1986. Holocene vertebrate fossils
Bahloul, K., Laurent, J. and Cambag, R. 1999. from Isla Floreana, Galápagos. Smithsonian
Short annual activity period in Testudo horsfieldi: Contributions to Zoology, (413): 1-103.
consequences on daily displacements. In Current Townsend, C.H. 1928. The Galápagos Islands
studies in herpetology. Miaud, C. and Guyetant, revisited. Bulletin: New York Zoological Society,
R. Eds. France: Le Bourget du Lac, Societas 31: 148-169.
Europaea Herpetologica. pp. 249-253. Turtle Taxonomy Working Group [Rhodin, A.G.J.,
Longepierre, S., Hailey, A. and Grenot, C. 2001. Iverson, J.B., Bour, R., Fritz, U., Georges, A.,
Home range area in the tortoise Testudo hermanni Schaffer, H.B. and van dijk, P.P.]. 2017. Turtles of
in relation to habitat complexity: implications for the World: Annotated Checklist and Atlas of
conservation of biodiversity. Biodiversity and Taxonomy, Synonymy, Distribution, and
Conservation, 10: 1131-1140. Conservation Status (8th Ed.). In: Rhodin, A. G. J.,
Moll, D. and Brown, L.E. 2017. Reinterpretation of Iverson, J. B., Van Dijk, P. P., Saumure, R. A.,
the climatic adaptation of giant fossil tortoises in Buhlmann, K. A., Pritchard, P. C. H. and
North America. Herpetological Journal, 27: 276- Mittermeier, R. A. (Eds) Conservation Biology of
286. Freshwater Turtles and Tortoises: A Compilation
Patterson, R. 1971. Visual cliff perception in tortoises. Project of the IUCN/SSC Tortoise and Freshwater
Herpetologica 27: 339-341. Turtle Specialist Group. Chelonian Research
Poulakakis, N., Glaberman, S., Russello, M., Monographs, 7: 1-292. 10.3854/crm.7.checklist.atlas.
Beheregaray, L.B., Ciofi, C., Powell, J.R. and v8.2017.
Caccone, A. 2008. Historical DNA analysis Warne, K. 2016. Return of the Seychelles. National
reveals living descendants of an extinct species of Geographic 229: 82-87.
Galápagos tortoise. Proceedings of the National Yerkes, R.M. 1904. Space perception of tortoises.
Academy of Sciences 105: 15,464-15,469. Journal of Comparative Neurology and Psychology,
Pritchard, P.C.H. 1996. The Galápagos tortoises: 14: 17-26.
nomenclatural and survival status. Lunenburg,
