SALAMANDRA 46(1) 37–47 20 FebruaryEcology 2010 of RhacodactylusISSN 0036–3375 auriculatus

Ecological observations on the Gargoyle , auriculatus (Bavay, 1869), in southern

Joshua Snyder1+2, Leslie Snyder2 & Aaron M. Bauer1

1) Department of Biology, Villanova University, 800 Lancaster Avenue, Villanova, Pennsylvania 19085, USA 2) 883 South 630 West, Payson, Utah 84651, USA

Corresponding author: Aaron M. Bauer, e-mail: [email protected]

Manuscript received: 1 September 2009

Abstract. Ecological niches of squamate are delineated by diet, microhabitat use, and activity period. In the cur- rent study field data were gathered to characterize the ecology of Rhacodactylus auriculatus with regard to these three axes. Rhacodactylus auriculatus regularly consume a wide taxonomic and ecological variety of , lizard prey including and skinks, and various plant materials including floral parts and sap. Based upon the variety of dietary constituents and the regularity with which they are utilized, R. auriculatus may have the most atypical of all gekkonid diets. Rhacodacty- lus auriculatus partition their microhabitat with conspecifics based on perch height, presumably to avoid aggressive interac- tions. During winter in southern New Caledonia, R. auriculatus were most active from one to four hours after sunset. Key words. , Rhacodactylus auriculatus, New Caledonia, ecology, diet, activity, microhabitat.

Introduction is also known to utilize mangroves and strand vegetation (Bauer & Vindum 990, Bauer & Sadlier 2000). Within The , Rhacodactylus auriculatus, is a com- these areas, R. auriculatus is most frequently encountered monly kept and bred diplodactylid gecko. It is the small- on shrubs, saplings, and trees of small diameter. It is often est of six recognized in the , reaching only found within a few meters of these and is regularly active about 25 mm SVL (Sameit 986, Bauer & Sadlier 2000). on the ground, at least seasonally, in association with for- Rhacodactylus auriculatus occurs in both humid forest and aging and mating (Bauer & Sadlier 2000). maquis (a shrub-dominated habitat underlain by ultrama- In order to establish a more complete picture of the au- fic substrates) across the southern third of the New Cal- tecology of Rhacodactylus auriculatus, a field study was un- edonian mainland (Grande Terre) from sea level to nearly dertaken to quantify aspects of microhabitat use and activ- 000 m, but appears to be absent from the Isle of Pines and ity and to assess diet during the cool period of the austral its satellite islets (Bauer & Sadlier 994a, 2000). It has re- winter. cently been recorded from numerous isolated areas in the north of the island (Whitaker et al. 2004), and the tax- onomic status of these populations is under investigation Materials and methods (Bauer et al., unpublished). Study site and specimen documentation Although there is a large body of captive data about the species (e.g., Mertens 964, Rösler 988, Henkel 99, Rhacodactylus auriculatus were studied in Le Parc Provin- Pether 999, Tytle 2000, de Vosjoli et al. 2003, Bach cial de la Rivière Bleue (22°06’S, 66°39’E) in the southern 2004, Henkel & Schmidt 2007), field-based observa- part of the Province Sud on the Grande Terre of New Cale- tions are more limited, and have chiefly been based on op- donia (Figures –2). The park is a protected area with limit- portunistic data gathering (e.g., Roux 93, Meier 979, ed access. It was selected because of its location in the cent- Bauer & Vindum 990, Bauer & Sadlier 994b, 200, de er of the known contiguous distribution of R. auriculatus Vosjoli & Fast 995, Seipp & Henkel 2000). The infor- (Bauer & Sadlier 2000). The site contained both humid mation available, however, suggests that R. auriculatus has forest and maquis habitats (Figure 2). Other geckos in the a particularly diverse diet that is highly atypical for geckos, study area included septuiclavis, chiefly in maquis incorporating vertebrate prey, mollusks, and plant mate- and R. ciliatus, R. sarasinorum, symmetri- rial, as well as a broad range of arthropods (Bauer & Rus- cus, and Bavayia geitaina in forest. The study took place sell 990, Bauer & Sadlier 994b, Snyder et al. 2008). from 22 June 2004 to 4 August 2004 during the cool New The preferred habitats of this species are shrubby maquis Caledonian winter season. Data were recorded on a total vegetation, primary and secondary forest edges, and the of 30 nights within this interval as heavy rains occasion- ecotonal region between forest and maquis, although it ally precluded locating geckos by eye-shining. Transects

© 2010 Deutsche Gesellschaft für Herpetologie und Terrarienkunde e.V. (DGHT), Rheinbach, Germany All articles available online at http://www.salamandra-journal.com 37 Joshua Snyder et al. were followed along unpaved roads within the Parc Rivière altimeter, and measurements of vegetation were made with Bleu, typically from 8:00 to 22:30 h (although on warm- a tape measure (perch height) and digital caliper (perch er nights, when activity remained high, searching contin- diameter). Temperature was recorded each night at the ued until 0:00 h). Searches were not randomized but were beginning of each search period. Ambient light was cal- concentrated in areas found to be most productive. culated using data from the U.S. Naval Observatory site Geckos were located primarily by eye-shining and cap- (http://aa.usno.navy.mil/data/docs/RS_OneDay.html), tured by hand. For each specimen SVL (mm), total body which provides information about percent reflected visible mass (g), tail condition (original versus regenerated), sex, moonlight and moonrise/set time. and age class (juvenile [< 88 mm SVL] versus adult) were Single factor ANOVAs and regression analyses were recorded. A permanent black marker was used to write a performed in order to investigate the relationship between unique number on the ventral surface of the body so that perch height and diameter and gecko mass, SVL, and sex, individuals could be recognized when recaptured. Such and between temperature, ambient light, and precipitation markings are lost at ecdysis, but this occurs less frequently and average hourly capture rate. at cooler temperatures and lower metabolic rates (Alex- ander & Brooks 999) and none of the recaptured geckos shed during the period of the study. Nonetheless, to ensure Diet unambiguous identification of individuals digital photo- graphs were taken to record color pattern, which is highly Diet was determined through stomach flushing. Although variable in this species (Meier 979, Henkel 986, Bauer this method does not retrieve items that have passed below 990, Wirth & Peukert 2009; Figures 3A–B) and can be the pyloric sphincter, it has been found to be highly reli- used to identify individuals. able at recovering stomach contents and is non-destruc- tive (Legler 977, Legler & Sullivan 979). The mouth was held open by a plastic cuff and a human infant feeding Habitat and activity tube with sub-terminal holes to decrease pressure placed on the pyloric sphincter was connected to a 0 cc syringe For each specimen captured the following data were re- and passed down the throat to the center of the stomach corded: time of collection, latitude and longitude, eleva- (James 990). Approximately 0 cc of water (adjusted for tion, weather condition, phase of moon, vegetation type body size) was injected into the stomach. This was repeated (maquis or forest), perch height (m), and perch diameter 3–5 times unless stomach contents were regurgitated soon- (mm). Geographic coordinates were recorded with a Mag- er, in which case one additional flushing took place to en- ellan GPS, elevations were determined using a barometric sure the removal of all stomach contents. Stomach contents

Figure 1. Map of New Caledonia showing the position of the study site (Parc Rivière Bleue).

38 Ecology of Rhacodactylus auriculatus

Figure 2. Habitat of Rhacodactylus auriculatus. (A) View of the Rivière Bleue valley from an adjacent hilltop. (B) View of the Rivière Bleue from the Pont Germain showing humid forest trees flanking the banks. (C) Humid forest vegetation near a roadside in the Parc Rivière Bleue. Such roads served as transects for locating Rhacodactylus auriculatus. (D) Maquis vegetation, characterized by low canopy and generally small-diameter trees and shrubs along a roadside transect in Parc Rivière Bleue. were stored in 70% alcohol for subsequent identification. Results Specimens were released at the site of capture. Stomach Microhabitat flushing resulted in no fatalities or obvious damage to the geckos. Specimens weighing less than 2 g and those that One hundred and two captures, representing 88 unique had been stomach-flushed within the previous seven days specimens, were made (Figure 4). Six specimens were re- were not examined for dietary items. captured once and four were recaptured twice. Thirteen Dietary niche breadth for Rhacodactylus auriculatus Rhacodactylus auriculatus were found in humid forest and was calculated by number and volume of items in each 89 were found in maquis. All individuals found in the hu- food category using the Shannon index of diversity (Pian- mid forest were located along the roadside or at the ecotone ka 966, Peet 974, Pielou 977, Castanzo & Bauer 993, with maquis, where Bavayia septuiclavis was also common. 997, Vitt 995). Prey items were identified to the lowest The mean (+ S.D.) perch diameter for R. auriculatus re- taxonomic possible and larval coleopterans and lepidop- corded in humid forest was 40.0 ± 46.9 mm and the mean terans were treated as prey categories separate from adults. perch height was .6 ± 0.8 m. The mean perch diameter Calculations were based on the combination of results of and height for specimens recorded in the maquis was 2.0 the present study and previously published quantitative ± 23.2 mm and .8 ± . m, respectively. dietary data (Bauer & Devaney 987; Bauer & Sadlier Differences between mean perch height usage for males, 994b). females, and juveniles were statistically significant (P =

39 Joshua Snyder et al.

Figure 3. (A, B) Two representative Rhacodactylus auriculatus showing diversity in color and pattern at Rivière Bleue. (C) Bavayia sep- tuiclavis, the most common small gecko occurring at Parc Rivière Bleue and a confirmed dietary item for Rhacodactylus auriculatus.(D) Infrared video still of an adult female Rhacodactylus auriculatus licking sap from a Cunonia macrophylla (Cunoniaceae).

0.049; Tab. ). Female R. auriculatus occupied the highest .4 ± 0.7 m, respectively. Heavier were more likely perches on average (2.0 ± .2 m), whereas males and ju- to be found on higher perches (r2 = 0.065, f ratio = 6.7, veniles occupied average perch heights of .9 ± 0.9 m and degrees of freedom = , 97; P value = 0.0). The relation-

40 Ecology of Rhacodactylus auriculatus ship between perch height and SVL was non-significant (P Table 1. Relationships between attributes of Rhacodactylus au- = 0.077). Likewise, ontogenetic stage, body mass or SVL riculatus (sex/age class [male, female, or juvenile], mass, SVL) were not related to perch diameter (Tab. ). and microhabitat parameters (perch height and perch diameter). Statistically significant P values are indicated in bold.

Activity ANOVAs r2 f d.f. P Perch Height Class – 3.11 2,91 0.049 Specimens were captured from 43 minutes after sunset un- Perch Diameter Class – 1.66 2,84 0.196 til six hours and 38 minutes after sunset (local times be- tween 8:05 and 00:0 hrs). The highest capture rates oc- Regression Analyses curred between one and four hours after sunset, although Perch Height Mass 0.065 6.71 1,97 0.011 this is not necessarily indicative of peak activity as search Perch Height SVL 0.032 3.19 1,97 0.077 effort was not random. Nighttime temperatures during the Perch Diameter Mass 0.008 0.369 1,97 0.814 study period ranged from 4.3 to 2.9°C at the beginning of Perch Diameter SVL 0.002 0.639 1,97 0.221 field work each night. There were no significant relation- ships between hourly capture rate and temperature (r2 = 0.292, P = 0.394) or ambient light (r2 = 0.896, P = 0.08), al- though the highest average hourly capture rate (2.29 spec- and shrubs, the majority (87.3%) in maquis vegetation. The imens/hr) occurred at 90% ambient light. Field observa- primary use of maquis and humid forest edge habitats by tions suggested that light precipitation was also related to R. auriculatus appears to separate them spatially from their increased activity in R. auriculatus, but this was not found similarly sized congeners R. ciliatus and R. sarasinorum, to be statistically significant (P = 0.33). both of which also occur at Rivière Bleue, perhaps reduc- ing interspecific competition. Microhabitat may be utilized differentially based on a Diet variety of habitat features including substrate type, plant species, perch height and/or diameter, and retreat sites Sixty-six stomach flushings were performed, three on re- (James & M’Closkey 2002). In our study the difference in captured specimens. Food items were found in 4 of the 66 perch diameters used between habitats was not statistically (2.2%) stomachs flushed, yielding a total of 8 prey items significant due to small sample size in forest, but it is of (Tab. 2). Fifteen of the 8 items were prey, 3 of interest that humid forest specimens were found on much which were arthropods, comprising 86.7% by number and larger-diameter perches but at the same height as in the 93.9% by volume of the total animal prey items recovered. maquis. This suggests thatR. auriculatus may select perch- The majority of arthropods recovered showed little sign of es primarily based upon height rather than perch diam- digestion. Two vertebrate prey items, constituting 3.3% by eter and is consistent with our findings that perch height, number and 6.% by volume of the total animal prey, were but not diameter, is significantly related to size and sex in recovered. One was the forelimb of Caledoniscincus atrop- this species. Our results that heavier individuals were more unctatus and the other the thoracic region and humerus of likely to be found on higher perches than lighter individ- a small gecko (probably Bavayia septuiclavis; Figure 3C). uals parallels Seipp & Henkel’s (2000) observations that These were recovered from different adult male R. auricu- young R. leachianus occupied much lower perches than latus captured in open maquis. Remaining items included did adults and is consistent with the hypothesis that perch shed gecko skin, found in two stomachs, and an unidenti- segregation serves to reduce aggressive interactions among fiable gelatinous mass recovered from one stomach. Out- conspecifics (Pounds 988, Irschick et al. 2005). There is side of the context of the main study an adult female (36 g, little comparative information available for perch use by 22.8 mm SVL) was observed and filmed drinking sap from gekkotan lizards. Pianka & Pianka (976) reported height a Cunonia macrophylla (Figure 3D) over a period of three above ground for three species they considered to be arbo- nights (Snyder et al. 2008). real, but made no distinction between size, age, or sex. For Dietary niche breadth for Rhacodactylus auriculatus, the sphaerodactylid gecko Gonatodes humeralis, Miranda derived from cumulative data (multiple studies), based on & Andrade (2003) reported statistically significant differ- the number of prey items consumed per prey category was ences in perch height for males and females, but only dur- 2.43, and by volume .94 (Tab. 3). ing the rainy season. It is likely that perch use in Rhacodac- tylus auriculatus is also temporally labile and that seasonal variations in intraspecific segregation related to reproduc- Discussion tive activity, prey availability, or environmental conditions Spatial Use occur.

Rhacodactylus auriculatus has been recorded from open and closed maquis as well as humid forest (Bauer & Sadlier Activity 2000), usually on trees and shrubs at heights of 3–5 m, al- though specimens have also been found on fence posts, on In the present study, the highest capture rates occurred the ground, under rocks, and under the loose bark of trees from one to four hours after sunset (900–2200 h). This is (Bauer & Vindum 990, Seipp & Henkel 2000). In the consistent with qualitative statements by Bauer & Sadli- present study all specimens were found perched on trees er (2000) that R. auriculatus are most active from sunset

41 Joshua Snyder et al.

42 Ecology of Rhacodactylus auriculatus

Table 2. Stomach contents from the 14 specimens of Rhacodactylus auriculatus from Parc Rivière Bleue that contained food items during the austral winter of 2004. Prey, by category, are listed by absolute number and percent of: total items consumed, stomachs containing prey type, volume of all items consumed, and mass (blotted dry) of all items consumed. Shed skins and amorphous plant material consumed are not included in the percentages calculated but are indicated below the main table. Note that the values under “stomach” exceed the total animal prey values because a single specimen may contain more than one prey type.

Prey Taxon Items Stomachs Volume Mass number % total number % total cm3 % total g % total Araneae 1 6.7 1 7.1 0.15 12.6 0.09 17.6 Diptera Tupulidae 2 13.3 2 14.3 0.03 2.5 0.04 7.8 Coleoptera adult 3 20.0 3 21.4 0.05 4.2 0.05 9.8 larvae 3 20.0 3 21.4 0.23 19.3 0.17 33.3 Lepidoptera adult 2 13.3 2 14.3 0.22 18.4 0.06 11.8 larvae 1 6.7 1 7.1 0.05 4.2 Phasmotidae 1 6.7 1 7.1 0.39 32.7 0.07 13.7 Scincidae Caledoniscincus atropunctatus 1 6.7 1 7.1 0.01 0.8 0.02 3.9 Diplodactylidae Bavayia spp. 1 6.7 1 7.1 0.06 5.3 0.01 2.0 Total Animal Prey 15 100 14 100 1.19 100 0.51 100 Other Shed gecko skin 2 2 14.3 2.26 0.79 Gelatinous mass 1 1 7.1 0.30 to 2:00–22:00 h. Although diurnal activity was not moni- change their behavior under such conditions, presumably tored in this study, a radiotelemetered female R. auricula- to avoid predators. However, at least some species, such as tus studied opportunistically at the same time (Snyder et Crossobamon e. eversmanni, serve as counter examples and al. 2008) was found to rotate around its perch, following are inactive during bright nights (Szczerbak & Golubev the sun. Such limited diurnal activity, presumably related to 996). basking, has also previously been noted in gargoyle geckos (Meier 979, Bauer 990, Bauer & Vindum 990). We did not find a relationship between capture rate and Diet either precipitation or ambient light. Higher ambient light could facilitate prey location by nocturnal reptiles, but may In the present study, conducted during the austral winter, also subject them to higher risk of predation themselves 2.2% of stomachs flushed contained food items, which is (Perry & Fisher 2005). Native nocturnal predators of R. comparable to Bauer & DeVaney’s (987) results for sam- auriculatus are few, but barn owls (Tyto alba) are a poten- ples collected in May–June 985, in which two of nine (22%) tial threat and do occur in the study area. The few studies R. auriculatus contained prey. In contrast, 9 of 2 (90.5%) that have been done on nocturnal geckos suggest that most specimens contained food items in Bauer & Sadlier’s are more active under higher light conditions. Bouski- (994b) dietary examination of R. auriculatus specimens la et al. (992) and Reichmann (998) found that Sten- collected in the austral spring–summer (although some odactylus doriae (a terrestrial, nocturnal, desert-dwelling prey items were retrieved from the hindgut, which was not gecko) is most active during moonlit nights, although they accessed in the present study). Such a seasonal difference is expected as cooler temperatures reduce the activity lev- els of both ectothermic predators and their prey, reducing Left page: Figure 4. Capture sites of Rhacodactylus auriculatus both the likelihood of obtaining prey and the need to do so within the Parc Rivière Bleue. Each numbered locality represents (Huey et al. 200). The generally high proportion of empty a capture site. (A) Topographic map (Serie Orange 1:50000 4834 stomachs in R. auriculatus, regardless of season, is not un- St. Louis, Institut Géographique National, Paris) of the north- expected as Huey et al. (200) found that gekkonids had western portion of the Parc Rivière Bleue. Course of the Rivière Bleue indicated in blue. Outlined rectangle indicates the main the highest percent of empty stomachs of all lizards they area of capture sites and corresponds to the area shown in greater reviewed. In addition, they found that regardless of phyl- detail in B. (B) Satellite image (Google Earth) of the main study ogeny, a high proportion of empty stomachs was associated area, showing the course of the Rivière Bleue and park roads and with species occupying higher trophic levels and with noc- trails used for sampling transects. turnality, both traits characterizing R. auriculatus.

43 Joshua Snyder et al.

Table 3. Diet of Rhacodactylus auriculatus. Data derived from have either escaped or been consumed. Based on compar- multiple sources; superscripts denote data sources: (1) Bauer & isons with museum specimens, an entire Caledoniscincus DeVaney (1987), (2) Bauer & Sadlier (1994), (3) this study. atropunctatus of comparable forearm length would be ap- Data presented by percent by number and percent by volume proximately 97 mm in total length and have a volume of .8 of total prey items recorded. Total number and total volume are cm3. This value would represent 62.4% by volume of the to- listed parenthetically Previous studies did not provide prey vol- umes, thus all data in the volume column are derived from the tal animal prey consumed. Likewise, the gecko consumed present study. Unlike Tab. 2, shed skins and unidentified material would have also accounted for a much higher percentage are included in the totals calculated. *Note that Bauer & Sadlier by volume of the total animal prey had its whole body been (1994) reported 14 anthers, 20 stamens, and one leaf from their recovered. sample of R. auriculatus gut contents, but we have treated these Lizard prey in the diet of R. auriculatus have previous- plant parts as three items for the purposes of our calculations See ly been reported by Bauer & DeVaney (987), Bauer & text for details of calculation of niche breadth. Sadlier (994b), and Seipp & Henkel (2000), who ob- served a R. auriculatus stalk and consume a Bavayia sep- Prey Taxon Number Volume tuiclavis in the wild. Seipp & Henkel (2000) also claimed Chilopoda 0.92 (1)2 – that “wild R. auriculatus have proved to be partly cannibal- Araneae 11.01 (12)2,3 4.00 (0.15) istic.” Our results document that both geckos and skinks are consumed by R. auriculatus in winter, although only Hemiptera: Cicadidae 0.92 (1)2 – 23 3.0% (present study) of gargoyle geckos examined during Coleoptera (adult) 13.76 (15) 1.33 (0.05) the cool season contained lizard prey compared to 23.8% of 3 Coleoptera (larvae) 2.75 (3) 6.13 (0.23) specimens collected in warmer months (Bauer & Sadlier Diptera: Tupulidae 2.75 (3)2,3 0.80 (0.03) 994b). The regular consumption of vertebrates by geckos Lepidoptera (adult) 2.75 (3)2,3 5.87 (0.22) is rare (Bauer 990). Notable exceptions include Cyrto- Lepidoptera (larvae) 29.36 (32)2,3 1.33 (0.05) dactylus cavernicolus (Harrison 96), and Gekko gecko Hymenoptera undetermined 1.83 (2)2 – (Boulenger 92, Smith 935), and especially pygopodids Hymenoptera: Formicidae 0.92 (1)2 – of the genus Lialis (Patchell & Shine 986). Whether all Phasmatodea 1.83 (2)2,3 10.40 (0.39) R. auriculatus include lizards in their diets is unknown, but Orthoptera: Gryllidae 1.83 (2)2 – Bauer & Russell (990) argued that the dentition of this Orthoptera: Gryllacridoidea 3.67 (4)2 – species was unique among gekkotans and consistent with a diet of soft-bodied prey items, such as vertebrates. Orthoptera: Ensifera 1.83 (2)2 – 2 The ingestion of flower parts by R. auriculatus has long Blattidae 3.67 (4) – been known (Bavay 869) and has been confirmed by the 1,2 Unidentified Insecta 2.75 (3) – recovery of anthers, stamens, and possibly pollen from Total Arthropoda 82.57 (90) 29.87 (1.12) the stomach of preserved specimens (Bauer & Sadlier Mollusca: Pulmonata 0.92 (1)2 – 994b), and by recent observations (Bauer & Sadlier Plant Material* 2.75 (3)2 – 200) of feeding on Geissois sp. (Cunoniaceae) in the field. Vertebrata: Bavayia 1.83 (2)1,3 1.60 (0.06) Feeding on the sap of Cunonia macrophylla was also doc- Vertebrata: Caledoniscincus 5.50 (6)2,3 0.27 (0.01) umented during the period of this study and previously Total Vertebrata 7.34 (8) 1.87 (0.07) (Snyder et al. 2008). Although the regular use of plant ma- Shed skin 5.50 (6)2,3 60.27 (2.26) terial of any kind is rare in lizards (King 996), and geckos Unidentified 0.92 (1)3 8.00 (0.30) in particular (Cooper & Vitt 2002), it is most often asso- ciated with insularity (Bauer 990, Perez & Corti 993, Total Ingested Material 100.00 (109) 100.00 (3.75) Van Damme 999). Other geckos known to regularly to Niche breadth 2.43 1.94 opportunistically ingest nectar, sap, and other plant parts include Hoplodactylus spp. and Naultinus spp. from New Zealand (Eifler 995, Whitaker 987a, 987b), Phelsu- Arthropods were the most numerous dietary constitu- ma spp. from the Mascarenes and Seychelles (Vinson & ent recovered, as is typical for virtually all geckos (Pian- Vinson 969, Gardner 984, McKeown 993), and Lepi- ka & Pianka 976, Pianka & Huey 978, Snyder 2007). dodactylus (Perry & Ritter 999) and Gehyra (Gibbons However, the large size of some prey items, particularly the & Clunie 984, Dell 985, Couper et al. 995, Letnic & single phasmid consumed (32.7% by volume of the total an- Madden 998) in Australia and the tropical Pacific. imal prey), is noteworthy and corroborates the tendency of The majority of gecko species are small nocturnal insec- this species to take large prey noted by Bauer & Sadlier tivores (Loveridge 947, Kluge 967, Bustard 968, Pi- (994b). anka & Pianka 976, Pianka & Huey 978, Vitt & Zani As expected based on earlier studies (Bauer & Dev- 997, Miranda & Andrade 2003), but geckos have been aney 987, Bauer & Sadlier 994b), vertebrate prey items reported to consume diverse prey items such as tadpoles, were also recovered from R. auriculatus, although they birds, mice, bats, snakes and other lizards, often conspecif- constituted only 6.% by volume and 3.3% by number of ics (Roux 93, Polis & Myers 985, Mitchell 986, Bau- the total prey items. The low volume of the vertebrate prey er 990). However, many of these observations are based is a reflection of their fragmented condition and the con- on animals in captive conditions or are anecdotal records servative means by which the volume of vertebrate prey of anomalous single events rather than evidence of regular was calculated. The volume of the single skink prey was patterns of consumption. The regular acquisition of both based only on the arm recovered, as the skink itself may lizard prey and plant materials, along with arthropods,

44 Ecology of Rhacodactylus auriculatus suggests that Rhacodactylus auriculatus may have one of Acknowledgements the most diverse of all gekkotan diets. Compared with 9 other gekkotans for which data were available (Snyder Funding for this project was provided by the Department of Bio- 2007), R. auriculatus had the highest dietary niche breadth logy, Villanova University. We express our special gratitude to the Direction des Ressources Naturelles of the Province Sud, and by prey category. Mean dietary niche breadth for the other specifically to J. Manaute, J. Delafenetre, and J.-M. Meriot; taxa was .59 ± 0.8 (range 0.00–2.40), whereas in R. au- who provided not only permission to conduct field research but riculatus it was 2.43 (Tab. 3). By volume R. auriculatus had also accommodations and transportation within the Parc Provin- a dietary niche breadth of .94 compared to a mean dietary cial de la Rivière Bleue. J. Delafenetre also assisted in fieldwork niche breadth of .74 ± 0.78 (range of 0.06–2.62) in other on several occasions. R. Ross and the late K. Ross supplied trans- gekkotans. The comparatively lower dietary niche breadth portation to Nouméa on several supply trips as well as accommo- by volume as compared to number may, in part, be due dations in Nouméa and most importantly their friendship. Ap- to the propensity of R. auriculatus to take large soft-bod- preciation is also expressed to R. Curry, L. Gray, V. Iyengar, ied prey items, but is also partly an artifact of the lower and T. Jackman for their constructive comments. number of prey categories (0 versus 2) for which volu- metric data were available (these were not reported in ear- References lier studies). Dietary niche breadth comparisons are use- ful in comparing diets (Pianka 966, Castanzo & Bauer Alexander, G. J. & R. Brooks (999): Circannual rhythms of 993, 997, Vitt 995), but account only for the number of appetite and ecdysis in the elapid snake, Hemachatus haem- categories utilized and not for the taxonomic or ecological achatus, appear to be endogenous. – Copeia, 999: 46–52. diversity of the categories. However, in the case of R. auri- Bach, S. (2004): Haltung und Nachzucht des Höckerkopfgeckos, culatus, the prey categories certainly are reflective of a wide Rhacodactylus auriculatus Bavay, 869. – DRACO, 5(8): 82– taxonomic and ecological range of dietary constituents. 87. Bauer, A. M. (990): Gekkonid lizards as prey of invertebrates and predators of vertebrates. – Herpetological Review, 2: 83– Resource Partitioning 87. Bauer, A. M. & K. D. DeVaney (987): Comparative aspects of Diet, microhabitat use and activity period (Pianka 973, diet and habitat in some New Caledonian lizards. – Amphibia- Schoener 977, Howard & Hailey 999) are the three Reptilia, 8: 349–364. main resource-partitioning axes along which lizards seg- Bauer, A. M. & A. P. Russell (990): Dentitional diversity in regate. In the relatively simple lizard communities of New Rhacodactylus (Reptilia: Gekkonidae). – Memoirs of the Caledonia, the arboreal Rhacodactylus auriculatus is clearly Queensland Museum, 29: 3–32. ecologically segregated from most skinks, which are chiefly Bauer, A. M. & R. A. Sadlier (994a): The terrestrial herpeto- terrestrial or subfossorial, diurnal, and strictly insectivo- fauna of the Ile des Pins, New Caledonia. – Pacific Science, rous (Bauer & DeVaney 987). Although it is probable 48: 353–366. that gargoyle geckos share the same basic activity period Bauer, A. M. & R. A. Sadlier (994b): Diet of the New Caledo- with most other New Caledonian geckos, significant size nian gecko Rhacodactylus auriculatus (, Gekkoni- differences from the endemic species of Bavayia and Eury- dae). – Russian Journal of Herpetology, : 08–3. dactylodes, as well as all gekkonine geckos, almost certain- Bauer, A. M. & R. A. Sadlier (2000): The Herpetofauna of New ly force differences in both microhabitat use (particularly Caledonia. – Society for the Study of Reptiles and Amphib- ians, Ithaca. oviposition sites and retreats) and, concomitantly, in diet. Among its congeners on Grande Terre, R. auriculatus is Bauer, A. M. & R. A. Sadlier (200): New data on the distribu- certainly separated from R. chahoua, R. leachianus, and R. tion, status, and biology of the giant New Caledonian geckos (Squamata: Diplodactylidae: Rhacodactylus spp.). – Amphib- trachyrhynchus by microhabitat. These species are typically ian and Conservation, 2: 24–29. exclusively arboreal, and tend to occupy perches relatively Bauer, A. M. & J. V. Vindum (990): A checklist and key to the high in the canopy (Bauer & Sadlier 2000), descending herpetofauna of New Caledonia, with remarks on biogeogra- only for specialized activities, such as oviposition (Henkel phy. – Proceedings of the California Academy of Sciences, 47: 99). For R. sarasinorum and R. ciliatus, similarly-sized 7–45. congeners that occur in sympatry with R. auriculatus and Bavay, A. (869): Catalogue des reptiles de la Nouvelle-Caldonie are also often active at lower levels within the vegetation, et description d’espèces nouvelles. – Mémoires de la Société diet may serve as the primary resource partition. Linnéenne de Normandie, 5: –37. Relatively little is known about the ecology of arboreal Boulenger, G. A. (92): A Vertebrate Fauna of the Malay Penin- night-active geckos (Vitt & Pianka 994, Pianka & Vitt sula: Reptilia and Batrachia. – Taylor and Francis, London. 2003). The information gathered in this study helps eluci- Bouskila, A., D. Ehrlich, Y. Gershman, I. Lampl, U. Motro, date the natural history of R. auriculatus and provides the E. Shani, U. Werner & Y. L. Werner (992): Activity of a context within which further studies may be conducted. nocturnal lizard (Stenodactylus doriae) during a lunar eclipse Given the many threats to these geckos, including habitat at Hazeva (Israel). – Acta Zoologica Lilloana, 4: 27–275. destruction through mining and deforestation, predation Bustard, H. R. (968): The ecology of the Australian gecko, Ge- by introduced animals including rats, dogs, and cats, and hyra variegata, in northern New South Wales. – Journal of Zoo- exploitation by the illegal pet trade, such studies, which logy, London, 54: 3–38. may provide invaluable data for use in the management Castanzo, R. A. & A. M. Bauer (993): Diet and activity of of these magnificent geckos and their habitats, should be Mabuya acutilabris (Reptilia: Scincidae) in Namibia. – Herpe- a priority. tological Journal, 3: 30–35.

45 Joshua Snyder et al.

Castanzo, R. A. & A. M. Bauer (997): Comparative aspects of Loveridge, A. (947): Revision of the African lizards of the fam- the ecology of Mabuya acutilabris (Squamata: Scincidae), a ily Gekkonidae. –Bulletin of the Museum of Comparative Zoo- lacertid-like skink from arid south western Africa. – Journal logy, 98: –469. of African Zoology, 2: 09–22. McKeown, S. (993): The General Care and Maintenance of Day Cooper, W. E. & L. J. Vitt (2002): Distribution, extent, and evo- Geckos. – Advanced Vivarium Systems, Lakeside. lution of plant consumption by lizards. – Journal of Zoology, Meier, H. (979): Herpetologische Beobachtungen auf Neukale- London, 257: 487–57. donien. – Salamandra, 5: 3–39. Couper, P. J., J. A. Covacevich & S. K. Wilson (995): Sap feed- Mertens, R. (964): Neukaledonische Riesengeckos (Rhacodac- ing by the Australian gecko Gehyra dubia. – Memoirs of the tylus). – Der Zoologische Garten (N.F.), Leipzig, 29: 49–57. Queensland Museum, 38: 396 Mitchell, J. C. 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