UPDATED POPULATION AND HABITAT COMMENTS ABOUT THE REPTILES OF THE SWAN ISLANDS, HONDURAS JAMESR.MCCRANIE,1ALEXISHARRISON,2ANDLEONARDOVALDE´SORELLANA3 ABSTRACT. We discuss the results of a recent trip to situation regarding the Cnemidophorus the isolated Swan Islands, Honduras. We include from these islands. habitat notes for each of the reptilian species we Almost all authors who have discussed encountered. Also, we compare nine of the 13 reptilian species previously reported from these the reptilian species of the Swan Islands do islands with the only previous reptilian species list not give any information about habitats of that contains natural history notes. Comparisons the resident species, with the exception of between our 2012 experiences and those of a 1912 Lister (1976a,1976b). Also, besides Lister, trip demonstrate that the following changes have occurredinthepastcentury:threelizardspecieshave none of those authors had visited those been introduced by humans; two of the four island islands, or apparently even examined spec- endemic reptilian species remain common, as they imens. The main exception with regard to were in 1912; one endemic lizard species appears to have declined drastically in numbers; and the single habitat information and examination of endemic snake species remains as poorly known now specimens is Barbour (1914), although he asitwasin1912. did not visit the Swan Islands himself. Barbour (1914) described four new species Key words: Annotated Species List, Swan Islands, endemic to the Swan Islands, all of which CaribbeanSea,EnvironmentalNotes,Reptilia are consideredvalid herein. Barbour (1914) relied on the field notes of G. Nelson, the INTRODUCTION original collector of those species, to write The reptilian species known from the some brief but excellent field notes about Swan Islands (usually not including the three of the four species. marine turtles) have been listed several TheHonduranSwanIslandsconsistoftwo times, most recently by Powell and Hen- still-forestedislands,atleastpartiallyforested derson (2012), who failed to mention the inthecaseofBigSwanIsland,locatedinthe two species of Hemidactylus recently intro- CaribbeanSeaabout160kmto180kmnorth duced there (Sandoval et al., 2007; Ko¨hler of the northeastern Honduran mainland andFerrari,2011).Manyoftheexistinglists (Keith, 1985; Morgan, 1985) and about 350 have erroneously included a Cnemidopho- km southwest of Grand Cayman Island, the rus from the Swan Islands (last by Savage, closest non-Honduran island, making them 2002). McCranie (2017) discussed the ‘‘amongthemostisolatedislandsoftheWest Indies’’ (Morgan, 1985: 42). Aceituno and 1 10770 SW 164 Street, Miami, Florida 33157. Medina (2008) erroneously wrote that the Author for correspondence (jmccrani@bellsouth. SwanIslandswere250kmfromtheHonduran net). 2 Department of Organismic and Evolutionary mainland. The two islands that make up this Biology,HarvardUniversity,Cambridge,Massachu- island group are called Big Swan Island and setts 01238. 3 Colonia America, Bloque 9, Casa 1806, Co- Little Swan Island herein. The Swan Islands mayagu¨ela,MDC,Honduras. groupisalsocalledtheIslasdelCisneorIslas Bull. Mus. Comp. Zool., 161(7): 265–284, June, 2017 265 266 Bulletin of the Museum of Comparative Zoology, Vol. 161, No. 7 Figure1. TheHonduranNavalBaseandnearbyabandoned Figure2. EdgeofairstripandadjacentforestonBigSwan structuresonBigSwanIsland,asseenfromanairplane.Photo Island.Phototakenon9December2012byA.H. takenon9December2012byAlexisHarrison(A.H.) the Naval Base Headquarters on Big Swan Santanilla on some maps and by some were 17824.3330N, 83856.5100W (WGS84). inhabitants of northeastern Honduras. The The elevation was recorded as 8 m. Met Swan Islands have had a long and conflicted Office (1978) reported that the average historyandwereclaimedbytheU.S.untilthe maximum daily temperature for the period U.S. dropped its claim during 1972 (see from 1917 to 1936 (some data incomplete) Weigel, 1973). The Swan Islands are part of was 868F and the average minimum daily the department of Gracias a Dios (Atlas temperature was 758F. In general, a dry Geogra´fico 2006), not the Islas de la Bah´ıa, season occurs from January to May, and a asstatedontheWikipediawebsite(http://en. wetseasonfromJunetoDecember(Weigel, wikipedia.org/wiki/Great_Swan_Island; last 1973). Weigel (1973) also provided much downloaded 4 June 2016). Although several information on the history of human pres- reptileshavebeenreportedfrombothislands, ence on Big Swan. Little Swan is uninhab- noamphibiansoccuroneitherisland. itable to humans and their domesticated No evidence indicates that the Swan animals because of its rocky cliffs that Islands were ever connected with the stretch from shoreline to shoreline. McCra- mainland or any other West Indian island nie (2011: 26–27) classified the forests on (Morgan, 1985, 1989). Big Swan has a land theseislandsas‘‘LowlandDryForest,West areaofabout3km2andLittleSwanabout2 Indian Subregion.’’ Figures 1–8 show some km2 (Morgan, 1985, 1989), although Powell of the habitat on the Swan Islands during and Henderson (2012) reported a land area December 2012, whereas Figure 9 shows of 5.5 km2 for Big Swan and 2.5 km2 for the field group. Little Swan. Some researchers consider a third island, called Cayo del Pa´jaro Bobo MATERIALS AND METHODS (BoobyCay),to be anisland inthe Islas del Cisne chain, but this tiny cay is too small to We conducted fieldwork and collected constitute an island (land area less than 0.1 tissues and some specimens on Big Swan km2) andis onlyslightly separatedfrom Big Island from 9 to 13 December 2012 and Swan. The highest elevation on Big Swan is during the morning of 12 December on only14mandthatonLittleSwanonly20m LittleSwanIsland.Wetargetedallreptilian (Keith,1985).Morgan(1985,1989)gavethe species on the islands, with A. H. primarily coordinatesforBigSwanIslandas178240N, focused on anoles. Powell and Henderson 838560W. Our readings with a handheld (2012) listed eight reptile species from the globalpositioningsystemfromthecenterof Swan Islands. We were able to collect and POPULATION AND HABITAT OF REPTILES OF THE SWAN ISLANDS (cid:2) McCranie et al. 267 Figure3. InteriorforestonBigSwanIsland.Phototakenon Figure5. CoastalforestonnorthernsideofBigSwanIsland. 14December2012byLeonardoValde´sOrellana(L.V.O.) PhototakenduringDecember2012byA.H. closely observe six of the species, only rapidly become abundant in all edificarian lackingtheextirpatedAmeivaandCubophis or non edificarian situations on Big Swan brooksi, which is endemic to Little Swan Island, including walls associated with the Island. Two introduced species of Hemi- naval base and in seminatural situations dactylus were overlooked by Powell and throughout Big Swan Island. It appears to Henderson (2012). Those two species of be rapidly eliminating the native and Hemidactylus were first collected during endemic Aristelliger nelsoni on Big Swan 2007 (Sandoval et al., 2007; Ko¨hler and (see below) despite being first collected on Ferrari, 2011, as H. brookii Gray, 1845). Big Swan in 2007 (Sandoval et al., 2007). Similar elimination of other Honduran endemic, arboreal gekkotan lizards by H. RESULTS frenatus has been documented on the Lizards Honduran Bay Islands (McCranie, 2017) Gekkonoidea and on islands in the Golfo de Fonseca in Gekkonidae southern Honduras (McCranie and Gut- Hemidactylus frenatus Schlegel (1836 IN sche, 2016; also see Powell, 2003 regarding A. M. C. Dume´ril and Bibron) that suspicion on Isla de Utila, Honduras). We collected a series of these nonnative Thisintroducedhousegecko(Fig.10)has geckos on Big Swan and deposited these Figure4. Coastalforestonsouthwestern sideofBigSwan Figure 6. Damaged structure from U.S. time on Big Swan Island.Phototakenon17December2012byL.V.O. Island.Phototakenon14December2012byL.V.O. 268 Bulletin of the Museum of Comparative Zoology, Vol. 161, No. 7 Figure8. North-central coast ofLittle SwanIslandshowing theraggedcliffsandforestsofthatisland.Phototakenon12 December2012byL.V.O. Sphaerodactylidae Aristelliger nelsoni Barbour (1914) This species is apparently being quickly replaced by the introduced gecko H. frenatus. This native and endemic Aristel- liger (Fig. 12) proved difficult to find during our trip, but H. frenatus was extremely common in all parts of Big Swan, including nonedificarian forest types. We Figure7. InteriorforestonLittleSwanIsland.Phototakenon found one A. nelsoni inside a termite nest 12December2012byL.V.O. during the day (MCZ R-191121), one beneath tree bark during the day (MCZ specimens in the Museum of Comparative R-191165), and two others (MCZ R- Zoology collections (MCZ R-191070, 191071, 191146) were active on an old 191124, 191127–30, 191136, 191140–41, fence post at dusk. These two specimens 191147–54). were collected at the same time. Other Hemidactylus mabouia (Moreau de crepuscular and nighttime searches did not Jonne`s, 1818) reveal additional individuals. However, all walls associated with the naval base and This is another introduced house gecko previous structures left by the Americans (Fig. 11), also first found on Big Swan were heavily populated with H. frenatus during 2007. As is the case in other during the night. Clearly, H. frenatus is a Honduran localities (McCranie, 2017), H. serious threat to the native nocturnal and mabouia was apparently being replaced by arboreal gecko fauna on Big Swan as well H. frenatus by the time of our 2012 visit. as the remainder of Honduras (McCranie, The single H. mabouia we collected (MCZ 2017). Barbour (1914) discussed the natu- R-192116) was found on the wall of an old ral history of A. nelsoni from both Swan building near the naval base. We note that Islands on the basis of the collector’s field both H. frenatus and H. mabouia were notes of 1912 and wrote: ‘‘Mr. Nelson erroneously reported from Big Swan as H. states that the species is extremely common brookii by Ko¨hler and Ferrari (2011). on both Swan Islands. It is frequently POPULATION AND HABITAT OF REPTILES OF THE SWAN ISLANDS (cid:2) McCranie et al. 269 Figure9. Theauthorsontheleft(J.R.M.,L.V.O.,A.H.)andthepilotgassinguptheairplanetoleave.Phototakenon12 December2012byanunknownsoldier. heard croaking at dusk both among the Sphaerodactylus exsul Barbour (1914) coconut palms, in the houses (on [Big] In December 2012, this tiny lizard (Fig. Swan Island), and in the woods. On Little Swan Island the species occurs only in the 13) endemic to the Swan Islands was jungle since this island is and always has common beneath ground debris on Big been uninhabited and is without any Swan and easily seen under leaves and cleared land.’’ Those 1912 observations loose rocks wherever forested areas oc- clearly contrast to what we found on Big curred. Individuals of this diurnal Sphaer- Swan Island 100 years later. odactylus move rapidly when uncovered, Figure10. Hemidactylusfrenatus(MCZR-191070).PhotobyJ.R.M. 270 Bulletin of the Museum of Comparative Zoology, Vol. 161, No. 7 Figure11. Hemidactylusmabouia(MCZR-192116).PhotobyJ.R.M. and are difficult to capture without damag- lizards are very abundant in the accumula- ing their fragile skin. This was an abundant tions of humus and fallen leaves in the lizard during 1912 (Barbour, 1914: 265) on cavities and depressions so very common in Little Swan (also see Barbour, 1921: 256), the sharply eroded aeolian limestone of the but remarkably was not found on Big Swan island.’’ We collected a series on Big Swan at that time. Barbour (1914: 264–265) Island (MCZ R-191069, 191089–92, wrote: ‘‘Mr. Nelson says that these little 191125–26, 191142–45). Figure12. Aristelligernelsoni(MCZR-191146).PhotobyJ.R.M. POPULATION AND HABITAT OF REPTILES OF THE SWAN ISLANDS (cid:2) McCranie et al. 271 Figure13. Sphaerodactylusexsul(MCZR-191125).PhotobyJ.R.M. Neoiguania umber’’ to ‘‘clay color’’ (McCranie and Kohler,2015:116–117).Sexual dimorphism Dactyloidae in this species is very pronounced, possibly Norops nelsoni (Barbour, 1914) as a consequence of ecological release in a population with no anoline competitors The anoles of the Swan Islands are (Lister, 1976a, 1976b). On average, the members of the Norops sagrei species maleswemeasuredhadasnout–ventlength complex. This anole is abundant on both (SVL) of 71.2 mm (SD of 64.9) and a mass Big and Little Swan islands, and occurs at of 8.3 g (62.1) and females were 52.4 mm the highest density of any lizard species (63.4) and 2.9 g (60.6), respectively. J.R.M. has seen in all of Honduras. A.H. The anoles on Big Swan Island were postedseveraldiscussionsaboutthisspecies found in a wide range of habitats. Males on Anole Annals during 2013 (see Appen- were found primarily on tree trunks and dix). This anole was prominent in all branches (32/33 observations), whereas forested and deforested areas on both females used a wider range of substrates, islands. Everywhere one would sit down including trunks and branches (27/38), the for a break, numerous individuals would ground (6/38), man-made wood and metal appear within a few minutes. Barbour posts (3/38), rocks (1/38), and leaves (1/38). (1914: 287 from G. Nelson’s 1912 field Maleswerefoundatanaverageheightof94 notes) called it ‘‘exceedingly abundant in all cm (648) on perches averaging 8 cm (64) situations on both islands’’ during 1912. in diameter. Females used perches averag- Thishasnotchangedduringthesubsequent ing 51 cm (639) above the ground, with a 100 years. diameter of 8 cm (67). Most animals were The anoles on Big Swan Island (Figs. 14, observed in full or partial shade: 20/33 15) are similar in appearance to N. sagrei males and 25/38 females were in full shade, except notably larger, with a darker dewlap whereas 12/33 males and 10/38 females described as ‘‘deep olive-gray’’ (Barbour, were in partial shade, and only 1/33 males 1914: 287; Ruibal, 1964: 493) or ‘‘burnt and 3/38 females were in full sunlight. This 272 Bulletin of the Museum of Comparative Zoology, Vol. 161, No. 7 Figure14. AdultmaleNoropsnelsonifromBigSwanIsland(MCZR-192108).PhotobyJ.R.M. preference for shade corresponded to an perched with their head oriented toward averageof97%(65)canopycoverformales the ground (18/20 and 14/20 observations, and 95% (616) for females. A series was respectively). When approached, both collected on Big Swan for future taxonomic males and females tended to flee up into study (MCZ R-192031–42, 192059–79, the canopy (16/18 and 14/16 observations, 192108–12, 192114). respectively). This species appears to con- Both males and females on Big Swan form to a trunk–ground ecomorph in most Island were most frequently observed respects, but the tendency to flee upward Figure15. AdultmaledewlapofNoropsnelsonifromBigSwanIsland(MCZR-192114).PhotobyJ.R.M. POPULATION AND HABITAT OF REPTILES OF THE SWAN ISLANDS (cid:2) McCranie et al. 273 Figure16. AdultmaleanddewlapofNoropsnelsonifromLittleSwanIsland(MCZR-194190).PhotobyJ.R.M. into the canopy is more typical of trunk– otherstrikingdifferencewasthepresenceof crown anoles (e.g., Williams, 1972, 1983). vivid yellow and green longitudinal stripes The N. nelsoni collected on Little Swan and reticulations against a dark background Island (Figs. 16, 17) had very distinctive onthebodiesofmales,comparedwithsolid coloration in life relative to the anoles on body coloration in males on Big Swan. The Big Swan. Male dewlap coloration was less most striking difference, however, was the dark with more yellow-orange tones. An- yellow pigmentation of the heads of both Figure17. AdultfemaleofNoropsnelsonifromLittleSwanIsland(MCZR-194191).PhotobyJ.R.M. 274 Bulletin of the Museum of Comparative Zoology, Vol. 161, No. 7 sexes on Little Swan, though somewhat seawaters. A. H. also observed Iguana more prominent in the females. Both males diving into the ocean when approached. and females on Big Swan lacked yellow Iguana was also common in forested areas heads. The anoles of Little Swan were also ofBigSwanandwasregularlyseeninopen smaller, on average, than the anoles of Big areas around the naval base and associated Swan: males averaged 65.2 mm (67.6) SVL old structures left by the Americans. and5.3g(61.6)mass,andfemales50.9mm Barbour (1914) reported this iguana from (61.6) SVL and 2.2 g (60.3) mass. Males ‘‘Swan Island’’ (as I. delicatissima Lauren- from Little Swan were significantly smaller ti, 1768), but gave no habitat information. than males from Big Swan with respect to Moyne(1938:82)stated‘‘Landiguanasare bothSVL(t¼(cid:3)2.8,df¼22.5,p¼0.010)and far more numerous than I have ever seen body mass (t¼(cid:3)5.2, df¼38.1, p , 0.001). them [on the Swan Islands], even on Femalesalsodifferedsignificantlyinmass(t Galapagos,andaresoindifferenttohuman ¼(cid:3)3.4,df¼17.8,p¼0.003),butnotinSVL approach that they can easily be seized by (t¼(cid:3)1.6796,df¼8.341,p¼0.130).Aseries the tail.’’ Lowe (1911) and Moyne (1938) of Little Swan anoles was also collected provided photographs of Swan Island (MCZ R-192043–58, 192091–92, 192113, Iguana in their natural habitats. Because 194190–91). of theirConvention onInternational Trade Given the differences in coloration and in Endangered Species of Wild Fauna and size between the anoles of Big and Little Flora (CITES) classification, and our lack Swan islands, the results of future work on of permits, the geographic origin of these genetic differences between these two iguanas could not be studied using molec- populations and others in the N. sagrei ular methods. species complex will be interesting. Might two populations in such proximity and so Leiocephalidae isolatedfromtherestoftheCaribbeanhave Leiocephalus varius Garman (1887) divergedenoughtomeritstatusasadistinct species or as two distinct species? The data This species (Fig. 18) appears to be a we were able to collect in our short time on rather recent introduction to Big Swan the islands are insufficient to answer this Islandfromthe CaymanIslands. Itwasfirst question, but they do suggest that there reported from ‘‘Swan Islands’’ by Schwartz might be an interesting evolutionary story and Thomas (1975: 128), who called it hidden there. Leiocephalus carinatus varius (McCranie, 2017 suggested elevating L. varius to the Iguanidae species level). Leiocephalus varius is other- Iguana iguana (Linnaeus, 1758) wiseendemictoGrandCaymanIsland.The firstindividualstocollectthisspeciesonthe This iguana was still common on the SwanIslandsweretworesearchersfromthe rocky cliffs on Big Swan near the sea SmithsonianInstitution,Washington,DCin during2012,eventhoughitisregularlyand February 1974 (USNM 494801–08, illegally collected for its meat and eggs by 570244). Ferrari, in Sandoval et al. (2007), nonregulated lobster fisherman that fre- reported this population as ‘‘Sceloporus quently visit the Swan Islands. J.R.M. spp.’’ Individuals of Leiocephalus on Big watched, with binoculars, adult Iguana Swanshowlittlefearofhumans,eventothe voluntarily entering the shallow marine extent that, in J. R. M.’s opinion, a person waters near those cliffs and appearing to hadtostepoveralizardforfearofstepping enjoypassivelyfloatingintheshallow,calm on it while walking around the naval base.