sign in sign up
<<
Home , Aldabra, Chelonoidis, Coenobita, Cylindraspis, Giant tortoise, Mascarene Islands

Herpetology Notes, volume 14: 103-116 (2021) (published online on 10 January 2021)

Discovery of the first Mascarene giant nesting site on , Indian (Testudinidae: )

Julian P. Hume1,*, Owen Griffiths2, Aurèle Anquetil Andre3, Arnaud Meunier3, and Roger Bour4,†

† We dedicate this paper to our friend, colleague, and co-author Roger Bour, a world expert on Mascarene and a life-long steam train fanatic, whose passing came much too soon.

Abstract. Five of ( Cylindraspis) once occurred in huge abundance on the Mascarene of , Réunion, and Rodrigues. They disappeared after colonisation of the island by in the 17th and 18th centuries, primarily due to over-hunting and of and young by introduced and . So rapid was their that virtually nothing is known about their life history, especially nesting and -laying behaviour. Here we report the discovery on Rodrigues of the first Mascarene tortoise-nesting site, which contained intact nesting chambers, complete egg clutches and remains of a known native predator of tortoise eggs. We further compare the nesting behaviour with the giant tortoises of in the and the Galapagos in and provide details of the decline and extinction of Mascarene tortoises, most notably those of Rodrigues, for which good historical records exist.

Keywords. Mauritius, Réunion, gigantea, , egg chamber, clutches, extinction

“There are such plenty of land- in this Isle [Rodrigues], that sometimes you see two or three thousand of them in a flock; so that one may go above a hundred paces on their backs; or, to speak more properly on their carapaces, without setting foot to the ground.” [François Leguat 1708: 65]

Introduction due to direct impacts and the introduction of , epitomised by the loss of the iconic The isolated, volcanic of , Raphus cucullatus (Linnaeus, 1758), of Mauritius Mauritius (20.3°S, 57.6°E), Réunion (21.1°S, 55.5°E), (Cheke and Hume, 2008). A diversity of endemic giant and Rodrigues (19.7°S, 63.4°E) are situated in the tortoises once inhabited these islands, with Cylindraspis southwestern , with , the indica (Schneider, 1783) on Réunion featuring highly nearest large landmass, some 665 km to the east of variable shell shapes, the dome-shelled C. inepta Réunion. Rodrigues (Fig. 1A) is the smallest of the Günther, 1873 and the saddleback-shelled C. triserrata Mascarene Islands, only 17.7 km long and 8.5 km wide, Günther, 1873 on Mauritius, and the dome-shelled C. with a surface area of 104 km². The Mascarenes have peltastes (Dumeril & Bibron, 1835) and the saddleback- been subject to extremely high biota extinction rates shelled C. vosmaeri (Suckow, 1798) on Rodrigues (Arnold, 1979; Bour, 1980, 1981; Bour et al., 2014a). Although giant tortoises were abundant on all of the Mascarenes, Rodrigues harboured one of the densest 1 Group, Department of Zoology, Natural History Museum, populations of giant tortoises on Earth, estimated at Akeman Street, Tring, Herts HP23 6AP, . 150,000–200,000 individuals (North-Coombes, 1971). 2 La Vanille Réserve des Mascareignes, Senneville, Rivière des The importance of giant tortoises as fresh meat and Anguilles, Mauritius. 3 Francois Leguat Giant Tortoise and Cave Reserve, Anse to obtain oil for mariners on long sea voyages resulted Quitor, Rodrigues Island, Mauritius. in their over-exploitation, and as soon as settlement 4 Muséum National d’Histoire Naturelle, 57 rue Cuvier, 75005 began on the Mascarenes, thousands were killed Paris, . indiscriminately (Mondini, 1990; Cheke and Bour, * Corresponding author. E-mail: [email protected] 2014). The Mauritius mainland populations disappeared © 2021 by Notes. Open Access by CC BY-NC-ND 4.0. by 1721, with only small numbers of tortoises surviving 104 Julian P. Hume et al.

Figure 1. (A) Map of Rodrigues Island with place names mentioned in the text. A globe with Rodrigues marked as a point (inset) shows the position of the island in the southwestern Indian Ocean. Based on remains and historical observations, giant tortoises were found in all of these localities, including the islets, but would have formerly occurred all over the island. The white rectangle identifies Petit Butte and the tortoise nesting area. (B) Precise location and excavation pits of the tortoise nesting area at Petit Butte. The white outline designates the approximate maximum extent of the tortoise nesting area. Discovery of the First Cylindraspis Giant Tortoise Nesting Site on Rodrigues Island 105 on surrounding islets until the 1730s, or possibly until Freycinet (1825) reported the discovery of the first as late as the 1870s on Round Island (Cheke and Hume, fossil bones and eggs of Cylindraspis tortoises on 2008; Cheke and Bour, 2014). Réunion tortoises were Mauritius (the present whereabouts of this material extirpated by the 1730s in the lowlands (Bory de Saint- is unknown), which had been buried in volcanic tuff Vincent, 1804; Bour, 1979, 1981; Cheke and Bour, and could be dated to the Middle , since 2014) but, remarkably, a small population survived in the last eruption on the island occurred around 31,000 the remote montane refuge of Cilaos until at least 1840 YBP (Moore et al., 2011; Cheke et al., 2016). The only (Hermann, 1903; Bour et al., 2014a; Cheke and Bour, other discovery of Cylindraspis eggs in the Mascarenes 2014). Tortoises on Rodrigues remained comparatively was made by Bour et al. (2014a), who described four unmolested until the early 18th century, but after the incomplete eggs of C. indica buried in soft sediment and extinction of the populations on Mauritius and Réunion, excavated by Jean-Pierre Esmiol and Roger Bour near attention turned to the more off-the-beaten-path Boucan-Canot, northwestern Réunion. Unusually for Rodrigues (North-Coombes, 1994). extant giant tortoises, the eggs were ellipsoidal and not The Huguenot refugee François Leguat had reported spherical (but see below). the abundance of tortoises during his stay in 1691–93 During an excavation on the right side of their (Leguat, 1708), and in 1725 a reconnaissance party garden to insert a septic tank at Petit Butte, Plaine was sent from Réunion to ascertain the importance Corail, southwestern Rodrigues, in 2017, the Milazar of then uninhabited Rodrigues to French colonial family noticed a continuous layer of broken eggshells strategy, which included ships’ mate Julien Tafforet at approximately 400 mm depth (identified hereafter (North-Coombes, 1971; Dupon, 1974). Tafforet as PB1). Destruction of the site during excavation became marooned on Rodrigues for eight months and prompted Denis Claude Milazar to start a second small subsequently wrote a detailed report on the island and excavation on the left side of the garden (PB2). Careful confirmed the abundance of giant tortoises (Tafforet, removal of sediment revealed almost complete tortoise 1725–26). As a direct result, a tortoise hunting station eggs and a possible nesting chamber, but the discovery was set up on Rodrigues in 1735 to provide meat and oil lacked contextual data. AAA and AM returned to the to the burgeoning colonies on Mauritius and Réunion site for further analysis and examined the eggs and (Herbert and Nichelson, 1780; Cheke and Hume, the locality. Once the importance of the discovery was 2008; Hume, 2019). A holding pound was installed on realised, a scientific team led by JPH and OG excavated Rodrigues to prepare tortoises for shipment, with an the site in 2018 in a community effort that included equivalent facility at Port Louis, the capital of Mauritius, participation of local landowners, staff of the François to receive them (Cheke and Hume, 2008; Cheke and Leguat Cave and Giant Tortoise Reserve (FLR), Bour, 2014). North-Coombes (1994) estimated that Mauritius Wildlife Foundation (MWF), and members of over 280,000 tortoises were butchered on Rodrigues or the Rodrigues Regional Assembly (RRA). This process exported alive between ca. 1732 and 1771, with around proved extremely productive, with fossil remains found 10,000 taken annually for the first two decades. It was over a substantial area adjacent to the coast (Fig. 1B). only due to the collapse of the giant tortoise populations Here we report on the excavation of the first recorded in the 1770s that the slaughter ended, as it was then no nesting site of the endemic Mascarene giant tortoises, longer viable to collect them (North-Coombes, 1971). which includes the description of eggs and egg A single live tortoise was collected in 1786 on the chambers, and the discovery of unhatched young and Plaine Corail, southwestern Rodrigues (Hume et al., an associated natural predator. We further compare 2015), with the last record of two seen around 1795 the nesting behaviour of Rodrigues Cylindraspis giant in inaccessible gorges by the Civil Administrator of tortoises with those of other giant tortoises and discuss Rodrigues, Philibert Marragon (Bour et al., 2014b). the reasons for their decline and extinction, most notably Such was the speed of their extinction that virtually for those on Rodrigues, for which historical data exists. nothing was recorded about the life history of the Mascarene giant tortoises, especially nesting and egg- Materials and Methods laying behaviours. Reports that the tortoises sought out dry coastal areas for laying, with the eggs incubated by Only part of the left side of the Milazar family garden the sun, were the only exceptions (Leguat, 1708; Mundy remained pristine, so excavation of two further sites in Temple, 1914; Lougnon, 2006). (PB3 and PB4) began to the west (PB3) and to the south 106 Julian P. Hume et al.

(PB4) of PB2 (Fig. 1B). PB3 and PB4 measured 3 x 2.5 a 1-m, twice-daily sea level rise and fall. Examination of m and were divided into 1-m quadrants with string lines. the surface area, some of which was under cultivation, A datum was set at 600 mm above surface between PB2 revealed disturbed eggshell fragments extending to all and PB4. Removal of the surface vegetation and humic sides of the soil boundary. Covering much of the surface layer exposed the underlying sandy soil layer. Excavation area is Sand Couch, Sporobolus virginicus (L.) Kunth, of 30 mm layers, each prefixed with PB (= Petit Butte), a grass species introduced in the 19th century (Hubbard were taken to a maximum depth of 600 mm, which and Vaughan, 1940), with roots and a disturbed humic was about 200 mm below the visible horizon of fossil- layer descending to a soil depth of 80–100 mm. Directly bearing sediments. Careful excavation revealed potential underneath the humic layer, undisturbed sediments egg chambers, and where these were still intact, removal were dry and loose with good drainage, comprising of sediment occurred around and below the chamber undifferentiated < 1 mm sub-angular to rounded coral in order to preserve as much detail as possible. As the sand and light brown silt, which remained uniform to sediment was dry, sieving of each excavated 30 mm level at least 600 mm depth. The sediments contained large occurred on site. Sieving was undertaken using three terrestrial snails, predominantly Tropidophora articulata sieve sizes, 15 mm, 10 mm, and 2 mm, with all finds (Gray, 1834), T. fimbriata rodriguesensis (Crosse, deposited away from the nesting site. Precise locations 1873), and the small Omphalotropis littorinula Crosse, of all fossil material were recorded with pencil on graph 1873 (see Griffiths and Florens, 2006), and local marine paper, including the egg chambers and their relationship molluscs, with variably sized fragments of calcarenite. to each other. All fossil material was photographed in- The base of the nesting area comprised a layer of around situ, with particular emphasis placed on intact tortoise 30 mm containing broken, compacted eggshell, naturally incubation chambers that still contained eggs and egg hardened by tortoise urine that appeared translucent clutches. Intact eggs and a unique clutch of eggs (PB47) white depending on the angle of light (Fig. 2). were hardened with Paraloid B72 before removal. All Three intact egg chambers, one each in PB2, PB3, fossil material was bulk labelled, individually packed and PB4, ranged from 360–700 mm in length and 150– and sent for analysis at the research facilities at FLR. 300 mm in depth (Table 1), with the base consistently Once excavation was complete, the entire fossil locality reaching a depth of ~400 mm (300 mm below the upper was back-filled, with the excavated boundaries lined with 100-mm humic layer (Fig. 3). PB2 sat 2 m east of PB3, sheet plastic to allow continued research in the future. All with PB4 2.5 m further inland and to the west. One fossil material is stored at FLR for curation. chamber (PB2) was ‘sock-shaped’, with a plug of soil Plaine Corail is a vast calcarenite outcrop, which extending from the surface to its ‘heel’ (Fig. 4). Two of contains pockets of soil, intermixed with large expanses the chambers contained outlines of eggs, with clutches of of exposed limestone without sediment. Using a 50-m eight (PB21) and nine (PB314), which proved impossible tape, perimeter measurements were done to record the to remove intact (Fig. 2). However, a complete clutch entire soft-sediment area at Petit Butte, with the surface in PB4, removed intact from the chamber, contained examined for eggshell deposits. 13 eggs (PB47) (Fig. 5). The excavation revealed five incomplete hatchling tortoise bones (three humeri and two scapula-coroacoids; PB22), with the most complete Results humerus measuring 15 mm in total length; a complete The maximum size of the nesting area, defined as the phalanx of the Rodrigues Rail Erythromachus leguati area that included a suitable depth of soil (> 300 mm), Milne-Edwards, 1874 was also recovered (PB23). A was 90 x 133 m. It is bordered on all sides by exposed Cylindraspis carapace fragment (PB35), fibula fragment calcarenite with no sediment (Fig. 1B). No other soil (PB38), and scapula- (PB41) were the only other deposits occur near Petit Butte, the next nearest at Anse bones found. Two eggs were extremely small, at only 11 Quitor to the west (Fig. 1A). The to the south x 12.5 mm these were measuring approximately one- created a natural border, with the closest nesting site (PB3) fifth the size of the larger-sized specimens (Table 1; Fig. situated 8 m to the north, and the furthest soil deposit 55 6C) but were collected at the same depth and in the same m inland, both measurements taken from the shoreline. nesting cavity of PB3. Most of the eggs recovered from Separating the nesting area from the lagoon edge is a PB2, PB3, and PB4 were spherical (n = 10), averaging garden wall and access track (Fig. 1B). The nesting area 51 mm in diameter (Fig. 6B), but one (PB32) was oval- is 3.5 m above present sea level (PSL) in the lagoon, with shaped, measuring 40 x 55 mm (Table 1; Fig. 6A). Discovery of the First Cylindraspis Giant Tortoise Nesting Site on Rodrigues Island 107

Figure 2. Dorsal view of the Cylindraspis vosmaeri egg chamber in quadrant PB3 on Rodrigues Island. The egg outlines sit in a mixture of tortoise mucus and urine, which is still visible as translucent white patches on the surface. Scale bar = 100 mm.

Comparison of giant tortoise nesting behaviour. On Réunion, Sieur Luillier (in Lougnon, 2006) stated The nesting behaviour of Aldabra and Galapagos giant in 1703 that “There is a season when they lay their tortoises is comparatively well known, but it is in complete eggs, but it is the sun that incubates them…,” and that contrast to what our study reveals about Mascarene “for months each they neither eat or drink, while tortoises. Only a few observers mention any details, but during the remaining eight months they lay their eggs all agree that coastal sandy areas were essential for laying and take what sustenance they need for the four others.” and the sun necessary for incubating the eggs. Melet (in Cheke and Bour, 2014) reported in 1671 Mascarenes.—In 1673, Hubert Hugo, commander of that herds of hundreds of tortoises descended from the Mauritius from 1673–77 (Moree, 1998), described the mountains every day, and that a single tortoise may carnage that introduced pigs caused among and contain three or four hundred eggs. The daily migration tortoise eggs by devouring them on the shore as they may be in reference to the tortoises travelling to the were laid, and that they also took eggs laid in hollow coast to breed, as the heavily forested mountain slopes exposed to the sun (Pitot, 1905; Cheke, 1987). This were much cooler and presumably lacked suitable suggests that not all tortoises buried their eggs, which nesting localities. Melet’s description of a dissected appears to be in direct contrast with those on Rodrigues. tortoise containing hundreds of eggs is almost certainly However, it is more likely that this egg-laying behaviour in reference to a mature ovary in which hundreds of was atypical, perhaps a result of high competition for a egg follicles are stored until optimum conditions induce suitable sandy-soil medium. The explorer Peter Mundy ovulation, which would also include atrophied follicles (in Temple, 1914) reported that “They lay their eggs in and remains of mature follicles after the expulsion the sand, which are hatched by the sunne,” as do the of the ripe ovum (Bourn, 1977; Swingland and Coe, tortoises on Aldabra and Galapagos. 1978). 108 Julian P. Hume et al.

Table 1. Egg and clutch characteristics of the Giant Rodrigues Saddleback Tortoise Cylindraspis vosmaeri (n = 10). Parameters are provided with means ± standard deviations and ranges. Measurements are given in millimeters.

Egg Diameter Clutch Size Chamber Length Chamber Depth Species (n = 10) (n = 4) (n = 3) (n = 3)

50–53 8–13 360–700 150–300 Cylindraspis vosmaeri 51.1 ± 1.5 10 ± 2.50 546.6 ± 172.4 210 ± 79.3

Leguat (1708), who was marooned on Rodrigues Aldabra.—Around 100,000–150,000 tortoises occur from 1691–93, provided the most detailed account of on Aldabra (Bourn, 1977; Gerlach, 2014). The nesting the Mascarene tortoises and remarked that “The land- season takes place in June–September, with a peak in turtles lay theirs in the sand, and cover them, that they July and coinciding with the dry season (Swingland and may be hatch’d.” Leguat stayed in the north, where Coe, 1978). Females locate the nesting site by detecting the capital is now (Fig. 1A), so he the odour of urine from previous nesting attempts, and presumably witnessed tortoises breeding on the north the same female returns to the same site in subsequent coast. However, sandy soil deposits predominate in the (Swingland and Coe, 1978); this also helps prevent north, west, and east of the island, and especially on the females excavating other nests. At least 300 mm depth Plaine Corail, where caverns have produced hundreds of soil is essential, and with some shade, which provides of hatchling/juvenile tortoise bones (Hume, 2014a). nest exposure to direct sun for at least 5 h of the day Accurate estimations can be made of the Rodrigues (Swingland and Coe, 1978; Gerlach, 2004). The 300- tortoise population density, because of detailed shipment records taken during the peak of tortoise exploitation (North-Coombes, 1994). Based on Aldabra tortoise density, woodland areas on Aldabra support 20 per hectare (= 2000 per km2; Aldabra has an area of 155.4 km²) (Bourn and Coe, 1979; Cheke and Bour, 2014), which is also a reasonable estimate for Rodrigues (Cheke and Hume, 2008). Rodrigues is larger, covering 109 km2, and has a higher average rainfall (1200 mm per year) compared with Aldabra (946 mm per year) (Coe et al., 1979). Vast numbers of Rodrigues tortoise fossil remains have been found in caverns on the Plaine Corail, primarily due to the excellent depositional preservation environment limestone caves provide (Hume, 2005), but individual bones have been found elsewhere (Fig. 1A), confirming that tortoises occurred all over the island. The reports of Leguat (1708), Tafforet (1725–26), and Pingré (1763) show that the tortoises were numerous on the lagoonal islets, particularly Ȋle Frégate and Ȋle Gombrani (Fig. 1A). Based on distribution, a total population of 218,000 was possible, but this would have been fluctuating drastically, with the limit set by Figure 3. A profile of the Cylindraspis vosmaeri nesting area drought years rather than an average (Cheke and Bour, in quadrant PB1 at Petit Butte, Rodrigues Island. The solid 2014). Rodrigues may also have had a higher carrying line represents the original surface, with the dotted line around capacity due to increased rainfall and that the population 300 mm below the surface line marking the top of the nesting included two ecologically separated species (see Cheke chamber. The 100 mm scale bar is directly above the tortoise and Hume, 2008). eggshell layer. Note the sandy composition of the soil. Discovery of the First Cylindraspis Giant Tortoise Nesting Site on Rodrigues Island 109

Figure 4. Lateral view of a Cylindraspis vosmaeri tortoise egg chamber in PB2 on Rodrigues Island. Note the ‘sock-shaped’ chamber with a ‘heel’ to the right and a connection to the surface. The original plug that sealed the chamber has fallen away.

Figure 5. A complete clutch of Cylindraspis vosmaeri eggs removed intact from PB4 on Rodrigues Island. The clutch contains 13 eggs. Scale bar = 100 mm. 110 Julian P. Hume et al. mm depth of soil is essential to maintaining a steady nest temperature (Swingland and Coe, 1978). The nest chamber is dug with each hind foot operating alternately, and large quantities of urine (1–6 litres) and mucus are released when the hole is around 200 mm deep to prevent collapse (Swingland and Coe, 1978). The nesting cavity is ‘sock-shaped’, with the clutch glued together with mucus in the ‘heel’ of the sock to prevent eggs rolling into the ‘toe,’ a cavity left open for the hatchling tortoises to crawl into (Swingland and Coe, 1978). One hind foot gently spreads the eggs, which can form multiple egg layers (Swingland and Coe, 1978; Gerlach, 2004). The chamber is then back-filled with sediment (nest plug) (Swingland and Coe, 1978). The high mucus content of the urine soaks the area around the nesting chamber and forms a concrete-hard encasement protecting the eggs from predators and also as a control over humidity and temperature, which remains between 27–30°C (Swingland and Coe, 1978); any increase in temperature would potentially produce all female clutches (Swingland, 1991). Most nesting chambers (82%) are at a depth of 300–400 mm, as deep as the full hind leg length (Swingland and Coe, 1978; Gerlach, 2004). The parents play no further part in the process. Hatchlings remain underground for 10–20 days or up to four weeks after hatching, relying on the yolk sac for nutrition for 5–7 days before it is absorbed, and Figure 6. Three variations of egg shapes and sizes of break through to the surface at night by digging (Bourn, Cylindraspis vosmaeri found at Petit Butte on Rodrigues 1977; Swingland and Coe, 1978). Hatching occurs just Island. A single egg (FB32) is ellipsoid (A), with almost all prior to the first rains, which prevents drowning of other eggs spherical in shape (B). Two extremely small eggs nests and fungal attack due to increased humidity and (C) are abnormalities. Scale bar = 10 mm. provides new plant growth for the emergent hatchlings (Swingland and Coe, 1978; Gerlach, 2004, 2014). Depending on environmental conditions, females may hind legs excavate a deep cylindrical chamber, and the lay more than one clutch per season (Gerlach, 2004), but tortoise lays up to 17 eggs within (Swingland, 1989a; recruitment can cease if the population density reaches Rostal et al., 1998). The digging process is facilitated capacity (Swingland, 1989b). by wetting the soil with urine and, after laying, the Galapagos.—Divided into 15 species or , cavity is plugged with urine-saturated soil and sealed with four now extinct, Galapagos tortoises have a by pressing down with the plastron (Macfarland et al., combined present day population of ~19,000 animals, 1974). Galapagos tortoise nest in beach sand and in a reduced to just over 3000 by 1974, compared with small area, concentrating eggs and hatchlings, which an estimated population of around 250,000 upon makes them more vulnerable to predation (Macfarland discovery in the early 17th century (Swingland, 1989a; et al., 1974). Caccone et al., 1999, 2002; Ciofi et al., 2006). The Egg and clutch size. Rodrigues tortoise eggs are nesting behaviour of Galapagos tortoises is similar to spherical and almost all uniform in size (Table 1), but that of Aldabra tortoises. The egg-laying season occurs with a few exceptions. As seen in C. indica eggs (Bour in July–November, when females may travel several et al., 2014a), one of the Rodrigues eggs is ellipsoidal, kilometres to reach a suitable nesting area on a dry, while another two are anomalies, being extremely sandy coast, which must have at least 300 mm depth small (Fig. 6C). However, a number of tortoise species of sandy soil (de Vries, 1984; Swingland, 1989a). The produce these abnormal eggs (Cooper, 1983). As two Discovery of the First Cylindraspis Giant Tortoise Nesting Site on Rodrigues Island 111

Figure 7. A reconstruction of Rodrigues giant tortoises on the Plaine Corail, based on a unique stuffed Saddleback Tortoise Cylindraspis vosmaeri male (MNHN 1883.558; centre left) and a complete carapace of Domed Tortoise C. peltastes (MNHN 7831; front) (see Bour et al. 2014a). The Rodrigues rail Erythromachus leguati, a predator of tortoise eggs and young, forages amongst the tortoises. Illustration by JPH. sympatric Cylindraspis tortoise species inhabited (Gerlach, 2004; Bour et al., 2014a). Aldabra tortoises Rodrigues, a comparison of physical remains of the are similar in straight carapace length (450–1230 mm) animals themselves is necessary to identify the eggs. (Gerlach, 2004) to C. vosmaeri, as is the size range The Rodrigues Saddleback, C. vosmaeri, is known from of eggs: Cylindraspis 51 mm, Aldabrachelys 48–55 a stuffed male (MNHN 1883.558), the only known skin mm (Table 1; Terahara and Moriyama, 1998). We specimen of an adult Cylindraspis tortoise, and there therefore consider the eggs found at Petit Butte most are a number of carapaces and plastrons referable to likely referable to C. vosmaeri. Clutch size in Aldabra both species that originate from slaughtered specimens tortoises ranges from 5–15 in the wild (Swingland or those that died in captivity (Gerlach, 2004; Bour, and Coe, 1978), with Galapagos species laying from 2005; Bour et al., 2014a). Two hatchlings (species 5–17 eggs (Swingland, 1989a). The clutch size of C. indeterminate) are also preserved in spirit (Bour et vosmaeri ranged from 8–13 in the three nest cavities al. 2014a). Subfossil specimens comprise complete discovered. Aldabra tortoises lay eggs on top of each carapaces, including some with scutes, as well as other, and there is evidence to suggest that the top huge quantities of bones, almost all from caverns on layer hatches first (Swingland and Coe, 1978), which the Plaine Corail (Hume, 2005, 2014a). Cylindraspis may have also been the case for the multi-layered egg vosmaeri reached 1100 mm in straight carapace length clutches of C. vosmaeri. (a linear measurement taken from the proximal nuchal Tortoise egg and hatchling predators. A phalanx scute and distal supracaudal scute) in the male, whereas (III-I) of the flightless Rodrigues Rail Erythromachus the female was much smaller at 560–680 mm (Gerlach, leguati Milne-Edwards, 1874, a known predator of 2004; Bour et al., 2014a), a common sexually dimorphic tortoise eggs (Hume, 2019), was found in tortoise character in giant tortoises (Fritts, 1984; Gerlach, 2004; eggshell layer PB3 (25–30 cm), confirming its Bonin et al., 2006; Stanford, 2010). Cylindraspis association with them (Fig. 7). Tafforet (1625–26) gave peltastes was around half the size of C. vosmaeri, the only description of the rail’s diet and stated: ranging from 390–410 mm in straight carapace length 112 Julian P. Hume et al.

“There is another kind of bird, the size of a young hen, which on tortoise eggs and young (Pitot, 1905; Lougnon, 2006; has the and legs red. […] They generally feed on the eggs Cheke and Hume, 2008), as they do in the Galapagos of the land tortoises, which they take from the ground, and it (Hoeck, 1984; Cruz et al., 2005), but this was not the case makes them so fat that they often have difficulty running.” on Rodrigues. Pigs were first introduced to the island [translation from Hume, 2019] around 1795, when the tortoises were all but extinct The rail was likely an opportunistic predator, feeding (Cheke and Hume, 2008; Bour et al., 2014a). Black on tortoise eggs and young during the tortoise-breeding , Rattus rattus (Linnaeus, 1758), are particularly season and on and sea bird colonies devastating to Galapagos tortoises, preying on hatchlings at other times of the year (Hume, 2019). The rail and juveniles 1–2 years old (Swingland, 1989a), but they disappeared from Rodrigues between 1750 and 1760, are less of a threat on Aldabra, although they will take around a decade after the introduction of cats, which tortoise hatchlings (Swingland, 1989b). On Rodrigues, are lethal predators of , especially flightless island were abundant in 1691 (Leguat, 1708), so they were species (Hume, 2017, 2019). introduced much earlier (Hume, 2019), but they do not Other possible terrestrial predators of tortoise eggs and appear to have overly affected the tortoise population. young were the extinct Rodrigues , Necropsar Atkinson (1985, 2000) showed that on islands where rodericanus Günther & Newton, 1879, which certainly land crabs are abundant, ground-nesting birds commonly scavenged tortoise carcasses (Tafforet, 1625–26; Hume, withstand rats, as they are pre-adapted to this functionally 2014b), and the Rodrigues Night , Nycticorax similar predator; Rodrigues rail survived alongside rats megacephalus Milne-Edwards, 1874, a predator of the for decades (Hume, 2019). Therefore, tortoise hatchlings large, 23-cm long Newton’s Day Gecko, may have been similarly adapted. On Aldabra, female edwardnewtoni J. Vinson & J.-M. Vinson, 1969, and tortoises take around 17–23 years to reach maturity clearly capable of taking hatchling tortoises. Two (Swingland and Coe, 1979), so a reproductive crash and species of frigatebird, Greater Frigatebird Fregata minor noticeable decline in numbers of Mascarene tortoises (Gmelin, 1789) and F. ariel (G.R. would take five or ten years (Cheke and Hume, 2008). Gray, 1845) were once resident on Rodrigues (Cheke The vast numbers of tortoises reported by Tafforet in & Hume, 2008). Both species prey on marine turtle 1725–26 and later collectors up to the 1760s (Pingré, hatchlings (Safford and Hawkins, 2013), and have been 1763; North-Coombes, 1994; Cheke and Hume, 2008) reported to do so on Rodrigues (Leguat, 1708: 66–67). confirm that the majority of young grew to maturity. Tortoise hatchlings exposed on the coast may have been Although it was primarily over-collecting for meat equally vulnerable. that decimated the tortoises on Rodrigues (North- Terrestrial crabs that predominantly or temporarily Coombes, 1994), recruitment may still have continued inhabit dry on Mauritius and Rodrigues are throughout this period and replenished the population, now almost extirpated on the mainland, but prior to with juveniles taking advantage of space made available human settlement there was a great density and diversity after removal of adults (Cheke and Hume, 2008). of species (Hume, 2005). On Rodrigues, the large, As on Aldabra (Swingland, 1989b), recruitment may carnivorous and scavenging species Geograpsus grayi have ceased once the carrying capacity of tortoises (Milne-Edwards, 1853), Ocypode cordimanus Latreille, was reached. However, after the establishment of cats 1818, and the Coenobita rugosa Milne- around 1750 or earlier, survival of hatchling tortoises Edwards, 1837 once occurred in woods and at some drastically diminished (Cheke and Hume, 2008). Both distance from the shore (Miers, 1879). Their diet consists Pingré (1763) and Marragon (in Bour et al., 2014b) of other crabs, tortoise and turtle young, and they also blamed cats entirely for the demise of the Rodrigues scavenge carcasses (Alexander, 1979; Bourn and Coe, tortoises. Furthermore, Cylindraspis tortoises had 1979), so they would likely have been predators of extremely thin shells (Arnold, 1979), which would hatchling Rodrigues tortoises. have made them more vulnerable to predation. Once Decline and extinction. The wasteful extermination recruitment stopped, and with the large scale, continual of tortoises in the Mascarenes is testament to human harvesting of surviving adult tortoises, the population greed and short-sightedness, but over-hunting itself crashed. After the settlement began in 1735, tortoise may not have been the coup de grace for the tortoises, collecting was still lucrative by 1761 (Pingré, 1763), especially on Rodrigues. Introduced pigs that became with 30,000 tortoises exported in four vessels in 1759 feral on Mauritius and lowland Réunion wreaked havoc alone (Günther, 1898; North-Coombes, 1994). Due to Discovery of the First Cylindraspis Giant Tortoise Nesting Site on Rodrigues Island 113 their thin shells and hideous transportation conditions, Discussion with tortoises stacked one on top of the other, of 21,000 The nesting site at Petit Butte proved to be exceptional tortoises taken in six voyages during 1759–61 just in terms of preservation and abundance of fossil over 50% survived the voyage alive (Milne-Edwards, material, which adds much to our knowledge about 1875). The horticulturist and botanist Pierre Poivre the nesting behaviour of Cylindraspis tortoises. The (Froberville, 1848; Stoddart and Peake, 1979) noted nesting season runs from June–September on Aldabra that 4000–5000 animals per year in the period 1750–70 and July–November in the Galapagos, coinciding with were exported, each with an average mass of 9 the dry season and just before the start of the wet season kg. By 1767, Commander Yves Julienne and five slaves (Swingland and Coe, 1978; Swingland, 1989b). The dry remained on the island, but with the continued shortage season (austral winter) on Rodrigues, the driest of the of fresh meat on Mauritius, the Rodrigues settlement Mascarene Islands, extends from May–November, with increased to 23 with orders from Mauritius, specifically rainfall averaging from 800 mm on the Plaine Corail in to collect tortoises (North Coombes, 1971). The men the coastal southwest to > 1600 mm in the central-west scoured the island for the remaining animals, and a uplands (Cheke and Hume, 2008). Temperatures reach consignment of 1215 big carosses, the local name for a mean summer temperature of 25.9°C and the mean the large saddleback species C. vosmaeri, was shipped winter temperature is 22.3°C (Mauritius Meteorological to Mauritius (North-Coombes, 1971, 1994). This was Services, 2020). Presumably, Rodrigues tortoises nested the last mention of the saddleback. Just a year later, it during the dry season, with the hatchlings emerging just was difficult to collect just a few hundred animals for before or in November, ready for the wetter and warmer each of two shipments, so in 1769 the settlement was austral summer and in time to benefit from new plant withdrawn, bar a soldier and a few slaves left to husband growth. As on Aldabra, the hatchlings may have emerged the surviving tortoises (North-Coombes, 1971, 1994). at night to avoid the attention of diurnal predators, which Although data are lacking about the last remaining on Rodrigues included a rail, , starling, and individuals, North-Coombes (1994) estimated the two species of frigatebirds. collection of around 2000 tortoises in 1768–71, adding The location of the nesting site appears to be one a few subsequent smaller shipments to the total and any chosen specifically for the essential 300 mm depth of left alive on Rodrigues. Numbers must have been very sandy, free-draining soil and within close proximity to small, as a solitary individual collected on the Plaine the shoreline. The choice of coastal sand for nesting Corail in 1786 is the penultimate record (Hume et al., may also have been in response to abundant sandy soil 2015). In 1791, the few remaining settlers returned to deposits, maximising sunlight and taking advantage of Mauritius and left the island temporarily abandoned associated higher temperatures, as forested areas inland (North-Coombes, 1971), but the tortoise population on would be cooler; thus, egg temperature would be lower Rodrigues was by now beyond recovery. (Cheke and Hume, 2008). Some shade is necessary for The last observation of a living Rodrigues tortoise was Aldabra tortoise nest chambers, so if the same applied to by Philibert Marragon in 1795, who had started his term Cylindraspis, the original dense vegetation on Rodrigues as administrator in 1794 (North-Coombes, 1971; Bour provided sufficient protection, albeit stunted on the Plaine et al., 2014b). In a final statement on the matter, he not Corail (Pingré, 1763; Strahm, 1989). The presence of only bemoaned the fate of the species, but also the loss extinct and endangered terrestrial snails in the sediments of a source of fresh meat, the ultimate reason for the that are open, exposed, coastal scrub inhabitants (Griffths tortoise’s demise: and Florens, 2006) strongly confirms that this of was preferred for nesting. As in Aldabra tortoises “The tortoises formerly so common seem to be completely destroyed. In more than a year since I have been here I have (Swingland and Coe, 1978), the same female may have only seen two, and those in almost inaccessible gorges. returned to the same nesting site, relocating the precise This is a great shame for, in addition to their goodness, they location by detecting the odour, and judging by the density would have been a great succour in this land totally without of eggshell fragments (30 mm depth), these return events butcher’s meat.” probably lasted decades. The nesting chamber was dug to a depth of approximately 300 mm using the hind feet, as in Aldabra and Galapagos tortoises (Swingland and Coe, 1978; Swingland, 1989a; Gerlach, 2004, 2014), and the loose sandy soil intermixed with urine and mucus to make 114 Julian P. Hume et al. a cement to harden the finished chamber. Residue of the Acknowledgements. We thank Denis Claude Milazar urine and cement are still present at the site (Fig. 2). The (landowner), Annabelle Agathe and Monica Young Kan Seong intact chambers were situated 2 and 2.5 m apart, but the (RRA); Stephen Kirsakye, Jenifer César, Anieta Shan-Yu, and Jean Alfred Bégne (MWF), and Rodney Severy (FLR) for their presence of broken eggshell elsewhere from successful help in excavating the tortoise nesting site, Jayshree Mungur- hatching suggests that destruction of all other chambers Medhi for support and permissions during the excavation, and was due to subsequent nest excavation. The nest chamber FLR for support on Rodrigues. We further thank an anonymous is sock-shaped and with a plug, as in Aldabra tortoise reviewer for helpful comments. (Swingland and Coe, 1978) (Fig. 4), and measured from 360–700 mm in length and 150–300 mm in depth, which References allowed an underground area for hatchling tortoises to Alexander, H.G.L. (1979): A preliminary assessment of the role of enter; thus, chamber size was variable and dependent the terrestrial decapod in the Aldabran ecosystem. on the size of the tortoise. Clutch size falls within those Philosophical Transactions of the Royal Society B, Biological recorded on Aldabra and Galapagos (Swingland and Sciences 286: 241–246. Coe, 1978; Swingland, 1989a,b), ranging from 8–13 in Arnold, E.N. (1979): Indian Ocean giant tortoises: their C. vosmaeri, but this may vary depending on season and and island . Philosophical Transactions of the Royal possibly the age of the adult. The eggs were spherical Society B, Biological Sciences 286: 127–145. Atkinson, I.A.E. (1985): The spread of commensal species of and averaged 51 mm in diameter (Table 1), but the Rattus to oceanic islands and their effects on island avifaunas. presence of one elongate example and two abnormal In: Conservation of Island Birds, p. 35–81. Moors, P.J., Ed., small eggs, shows that the Rodrigues tortoise was subject Cambridge, United Kingdom, International Council for Bird to extreme egg size and shape variation. In European Preservation. species, the elongate shape of eggs is due to Atkinson, I.A.E. (2000): Introduced and models for smaller-sized females rather than abnormalities (Hailey restoration. Biological Conservation 99: 81–96. and Loumbourdis, 1988). That three unhatched clutches Bonin, F., Devaux, B., Dupré, A. (2006): Turtles of the World. Baltimore, Maryland, USA, Johns Hopkins University Press. occurred in the nesting area demonstrates that they were 416 pp. at times subject to failure. Clutches primarily fail to hatch Bory de Saint-Vincent, J.B.G.M. (1804): Voyage dans les Quatre on Aldabra because of infertility, with 10–20% of all Principals Îles des Mers d’Afrique. Paris, France, F. Buisson. eggs infertile and 20–40% failing to hatch (Swingland Bour, R. (1979): Histoire de la tortue terrestre de Bourbon. Comptes and Coe, 1978); nest flooding, temperature deficiency or Rendus de l’Académie des Sciences, Paris 25: 97–147. fungal attack could also be a cause. It is very fortunate Bour, R. (1980): Systématiques des tortues terrestres des Îles that these clutches remained intact, despite the nesting Mascareignes: genre Cylindraspis Fitzinger 1835 (Reptilia, Chelonii). Bulletin du Muséum National d’Histoire Naturelle, area presumably turned over for decades, as the dense Paris 4(2A): 895–904. layer of eggshell fragments elsewhere in the nesting site Bour, R. (1981): Histoire de la tortue terrestre de Bourbon. Bulletin are indicative of breeding success. de l’Académie de Île de la Réunion 25: 98–147. The discovery of this remarkable tortoise-nesting site Bour, R. (2005): Type specimens of Testudo rotunda Latreille, provides an unprecedented insight into the life history 1801. 12(6): 23–27. of a tortoise species now extinct for more than two Bour, R., Mourer-Chauviré, C., Ribes, S. (2014a): Morphology and centuries. It is very likely that C. peltastes and the other palaeontological (up to 2000) of the extinct tortoises of the Mascarene islands. In: Western Indian Ocean Tortoises: species on Mauritius and Réunion had similar ecologies, Ecology, Diversity, , Conservation, Palaeontology, but despite the wealth of fossil material discovered on p. 121–202. Gerlach, J., Ed., Manchester, United Kingdom, each island (Hume, 2014a), the nesting site at Petit Butte Siri Scientific Press. is unique. The Mascarene endemic genus Cylindraspis Bour, R., Frétey, T., Cheke, A.S. (2014b): Philibert Marragon is now extinct, and its former existence evidenced only (1749–1826) and the Mémoire sur l’Isle de Rodrigue (1795). by documented accounts, illustrations, and physical Bibliotheca Herpetologica 10(2): 5–32. remains. Conversely, the tortoises of Aldabra and Bourn, D. (1977): Reproductive study of giant tortoises on Aldabra. Journal of Zoology, London 182: 27–38. most of those in the Galapagos survived the massacre Bourn, D., Coe, M.J. (1979): Features of tortoise mortality and that took place in the Mascarenes, solely because the decomposition on Aldabra. Philosophical Transactions of the discovery of these islands by humans occurred much Royal Society B, Biological Sciences 286: 189–193. later and conservation efforts prevented potential Bourn, D.M., Gibson, C., Augeri, D., Wilson, C.J., Church, J., (Stoddart and Peake 1979; Swingland, Hay, S.I. (1999): The rise and fall of the Aldabran giant tortoise 1989a,b; Bourn et al., 1999; Chambers, 2005). population. Proceedings of the Royal Society of London B, Biological Sciences 266: 1091–1100. Discovery of the First Cylindraspis Giant Tortoise Nesting Site on Rodrigues Island 115

Caccone, A., Gentile, G., Gibbs, J.P., Fritts, T.H., Snell, H.L., Ecology, Diversity, Evolution, Conservation, Palaeontology, Betts, J., Powell, J.R. (2002): Phylogeography and history of p. 229–251. Gerlach, J., Ed., Manchester, United Kingdom, giant Galapagos tortoises. Evolution 56(10): 2052– 2066. Siri Scientific Press. Caccone, A., Gibbs, J.P., Ketmaier, V., Suatoni, E., Powell, Griffiths, O.L., Florens, V. (2006): A Field Guide to the Non-marine J.R. (1999): Origin and evolutionary relationships of giant Molluscs of the Mascarene Islands (Mauritius, Rodrigues Galapagos tortoises. Proceedings of the National Academy of and Réunion) and the Northern Dependencies of Mauritius. Sciences 96(23): 13223–13228. Mauritius, Bioculture Press. 185 pp. Chambers, P. (2005): A Sheltered Life: the Unexpected History of Günther, A. (1898): Recent progress on our knowledge of the the Giant Tortoise. Oxford, United Kingdom, Oxford University distribution of the gigantic land tortoises. Proceedings of the Press. 306 pp. Linnean Society 110: 14–29. Cheke, A.S. (1987): An ecological history of the Mascarene Islands, Hailey, A., Loumbourdis, N.S. (1988): Egg size and shape, clutch with particular reference to extinctions and introductions of land dynamics, and reproductive effort in European tortoises. vertebrates. In: Studies of Mascarene Island Birds, p. 5–89. Canadian Journal of Zoology 66: 1527–1536. Diamond, A.W., Ed., Cambridge, United Kingdom, Cambridge Herbert, W., Nichelson, W. (1780): A New Directory for the East University Press. Indies. Fifth Edition. London, United Kingdom, Henry Gregory. Cheke, A.S., Bour, R. (2014): Unequal struggle – how humans 554 pp. displaced the dominance of tortoises in island ecosystems. In: Hermann, J. (1903): Colonisation de l’Ȋle Bourbon et Foundation Western Indian Ocean Tortoises: Ecology, Diversity, Evolution, du Quartier Saint-Pierre. Paris, France, C. Delagrave. 408 pp. Conservation, Palaeontology, p. 31–120. Gerlach, J., Ed., Hoeck, H.N. (1984): Introduced fauna. In: Key Environments. Manchester, United Kingdom, Siri Scientific Press. Galápagos, p. 233–245. Perry, R., Ed., Oxford, United Kingdom, Cheke, A.S., Hume, J.P. (2008): Lost Land of the Dodo. London, Pergamon Press. United Kingdom, T. & A.D. Poyser. 464 pp. Hubbard, C.E, Vaughan, R.E. (1940): The Grasses of Mauritius Cheke, A.S., Pedrono, M., Bour, R., Anderson, A., Griffiths, C., and Rodriguez. London, United Kingdom, Waterlow & Sons. Iverson, J.B., Hume, J.P., Walsh, M. (2016): Giant tortoises 127 pp. spread to western Indian Ocean islands by sea drift in pre- Hume, J.P. (2005): Contrasting taphofacies in ocean island settings: times, not by later human agency – response to Wilmé the fossil record of Mascarene vertebrates. Monografies de la et al. (2016). Journal of 44: 1426–1440. Societat d’Història Natural de les Balears 12: 129–144. Ciofi, C., Wilson, G. A., Beheregaray, L.B., Marquez, C., Gibbs, Hume, J.P. (2014a): Fossil discoveries on Mauritius and Rodrigues. J.P., Tapia, W., et al. (2006): Phylogeographic history and gene In: Western Indian Ocean Tortoises: Ecology, Diversity, flow among giant Galápagos tortoises on southern Isabela Evolution, Conservation, Palaeontology, p. 203–228. Gerlach, Island. Genetics 172(3): 1727–1744. J., Ed., Manchester, United Kingdom, Siri Scientific Press. Coe, M.J., Bourn, D., Swingland, I.R. (1979): The biomass Hume, J.P. (2014b): Systematics, morphology, and ecological production and carrying capacity of giant tortoises on Aldabra. history of the Mascarene (Aves: Sturnidae) with the Philosophical Transactions of the Royal Society B, Biological description of a new genus and species from Mauritius. Zootaxa Sciences 286: 163–176. 3849(1): 1–75. Cooper, J.E. (1983): Preliminary studies on the eggs of three Hume, J.P. (2017): Extinct Birds. Second Edition. London, United species of chelonians. Testudo 2(2): 33–35. Kingdom, Helm. 608 pp. Cruz, F., Donlan, C.J., Campbell, K, Carrion, V. (2005): Conservation Hume, J.P. (2019): Systematics, morphology, and ecology of action in the Galapagos: feral (Sus scrofa) eradication from rails (Aves: Rallidae) of the Mascarene Islands, with one new Santiago Island. Biological Conservation 121: 473–478. species. Zootaxa 4626(1): 1–107. Dupon, J.F. (1974): Relation de l’Isle Rodrigue. Text attributed to Hume, J.P., Steel, L., André, A.A., Meunier, A. (2015): In the Tafforet, circa. 1726. Proceedings of the Royal Society of Arts footsteps of the bone collectors: nineteenth-century cave & Sciences of Mauritius 4(1): 1–16. exploration on Rodrigues Island, Indian Ocean. Historical Freycinet, L.C.D. (1825): Voyage Autour du Monde Exécuté sur Biology 27(2): 265–286. les Corvettes de S.M. l’Uranie et la Physicienne Pendant les Leguat, F. (1708): Voyages et Avantures de François Leguat & de Années 1817, 1818, 1819, et 1820. Volume 1. Paris, France, Ses Compagnons en Deux Îles Désertes des Indes Orientales. Pillet Ainé. 734 pp. Amsterdam, The Netherlands, Jean Louis de Lorme. Fritts, T.H. (1984): Evolutionary divergence of giant tortoises in Lougnon, A. (2006): Sous le Signe de la Tortue. Voyage Anciens à Galapagos. Biological Journal of the Linnean Society 21(1–2): l’Ile Bourbon, (1611–1725). Saint-Denis, La Réunion, France, 165–176. Editions Orphie. 284 pp. Froberville, E. de (1848): Rodrigues, Galega, Les Sechelles, Les MacFarland, C.G., Villa, J., Toro, B. (1974): The Galápagos giant Almirantes, etc. In: Iles de Afrique. Part 3. Iles Africaines de tortoises ( elephantopus). I. Status of the surviving la Mer des Indes. Volume 2, p. 65–114. Avezac, M.A.P. d’, Ed., populations. Biological Conservation 6(2): 118–133. Paris, France, Firmin Didot Freres. Mauritius Meteorological Services (2020): Climate of Rodrigues Gerlach, J. (2004): Giant Tortoises of the Indian Ocean. Frankfurt & Islands. Available at: http://metservice.intnet.mu. Accessed am Main, Germany, Chimaira. 207 pp. on 10 June 2020. Gerlach, J. (2014): Ecology and status of Western Indian Ocean Miers, E.J. (1879): Crustacea. Philosophical Transactions of the Aldabrachelys giant tortoises. In: Western Indian Ocean Tortoises: Royal Society of London 168: 485–496. 116 Julian P. Hume et al.

Milne-Edwards, A. (1875): Nouveaux documents sur l’époque de Stoddart, D.R., Peake, J.F. (1979): Historical records of Indian Ocean la disparition de la faune ancienne de l’Île Rodrigue. Annales giant tortoise populations. Philosophical Transactions of the Royal des Sciences Naturelles 6S(2): 1–20. Society of London B, Biological Sciences 286: 147–161. Mondini, E. (1990): Les tortues géantes terrestres et le choc de Strahm, W. (1989): Plant Red Data Book for Rodrigues. Königstein, l’histoire. Cahiers d’Outre Mer 43: 555–559. Germany, Koeltz Scientific Books. 241 pp. Moore, J., White, W.M., Paul, D., Duncan, R.A., Abouchami, Swingland, I.R. (1989a): Geochelone elephantopus. Galapagos W., Galer, S.J. (2011): Evolution of shield-building and giant tortoises. The conservation biology of tortoises. Occasional rejuvenescent volcanism of Mauritius. Journal of Volcanology Papers of the IUCN Species Survival Commission 5: 24–28. and Geothermal Research 207: 47–66. Swingland, I.R. (1989b): Geochelone gigantea. Aldabran giant Moree, P.J. (1998): A Concise History of Dutch Mauritius, 1598– tortoise. The conservation biology of tortoises. Occasional 1710. London, United Kingdom, Kegan Paul International. Papers of the IUCN Species Survival Commission 5: 105–108. 127 pp. Swingland, I.R. (1991): Environmental sex determination, North-Coombes, A. (1971): The Island of Rodrigues. Mauritius, migration, and regulation in the Aldabran giant tortoise. The Standard Printing Establishment. 337 pp. Proceedings of the Council Symposium 1987– North-Coombes, A. (1994): Histoire des Tortues de Terre de 1991: 43–50. Rodrigues. Second Edition. Mauritius, Mauritius Printing Swingland, I.R., Coe, M.J. (1978): The natural regulation of giant Specialists. 100 pp. tortoise populations on Aldabra Atoll: reproduction. Journal of Pingré, A.-G. (1763): Voyage à l’Isle Rodrigue. Ms 1804. Zoology, London 186: 285–309. Bibliothéque Ste-Geneviève, Paris, France. 470 pp. [edited and Swingland, I.R., Coe, M.J. (1979): The natural regulation of rearranged version of MS 1803 (1761), a day-to-day diary from giant tortoises on Aldabra Atoll: recruitment. Philosophical 1760–1762]. Transactions of the Royal Society of London B, Biological Pitot, A. (1905): T’Eylandt Mauritius. Esquisses Historiques Sciences 286: 177–188. (1598–1710). Précédés d’une Notice sur la Découverte des Tafforet, J. (1725-26): Relation de l’Isle Rodrigue. Ms, Archives Mascareignes et Suivies d’une Monographie du Dodo, des Nationales, Paris, Fonds des Colonies, Correspondence de I’île de Solitaires de Rodrigue et de Bourbon et de l’Oiseau Bleu. Port France, C4, Volume 12, no 48: ex Ministère de la Marine, no 29, 1. Louis, Mauritius, Coignet Frères & Cie. 496 pp. Temple, R.C., Ed. (1914): The travels of Peter Mundy in Rostal, D.C., Robeck, T.R., Grumbles, J.S., Burchfield, P.M., and , 1608–1667. Hakluyt Society SII 35(2): 1–437. Owens, D.W. (1998): Seasonal reproductive cycle of the Terahara, M., Moriyama, S. (1998): Breeding the Aldabra giant Galapagos Tortoise (Geochelone nigra) in captivity. Zoo tortoise. Animals & Zoos 12: 404–407. Biology 17: 505–517. Vries, T.J. de. (1984): The giant tortoises: a natural history disturbed Safford, R.J., Hawkins, A.F.A. (2013): The Birds of . by man. In: Key Environments: Galapagos, p. 145–156. Perry, Volume VIII. The Malagasy Region. London, United Kingdom, R., Ed., Oxford, United Kingdom, Pergamon Press. Christopher Helm. 1024 pp. Standford, C.B. (2010): The Last Tortoise: a Tale of Extinction in Our Lifetime. Cambridge, Massachusetts, USA, Belknap Press of Harvard University Press. 240 pp.

Accepted by Hinrich Kaiser