Relationship of Diet and Prey Availability in Aristelliger Cochranae

NOTES 323

Direccioń Nacional de Parques, facilitated our work in Caribbean Journal of Science, Vol. 36, No. 3-4, 323–326, 2000 Copyright 2000 College of Arts and Sciences the Dominican Republic. R. E. Glor made helpful com- University of Puerto Rico, Mayaguëz ments on an early draft of this manuscript. Permits were issued by G. Santana, Departamento de Vida Sil- vestre, and K. Grasela, Direccioń Nacional de Parques. Relationship of Diet and Prey Field work was supported by Grant No. DBI-9732257 awarded by the National Science Foundation to Rob- Availability in Aristelliger cochranae,a ert Powell. Gecko from Navassa Island, West Indies

MATTHEW E. GIFFORD1,ROBERT POWELL2,3 AND WAR- LITERATURE CITED REN E. STEINER,JR.41Department of Biology, Avila Col- lege, Kansas City, Missouri 64145-1698; gif3 hotmail.com. Cast, E. E. et al. 2000. Natural history of an anoline 2Department of Biology, Avila College, Kansas City, Mis- lizard community in the Sierra de Baoruco, His- souri 64145-1698; [email protected]. 3Corresponding paniola. Carib. J. Sci. 36:258-266. author. 4Department of Entomology, NHB-187, Smithso- Curio, E. 1976. The Ethology of Predation. Springer- nian Institution, Washington, DC 20560; steiner.warren@ Verlag, New York. 250 pp. nmnh.si.edu. Greene, H. W. 1988. Antipredator mechanisms in reptiles. In C. Gans and R. B. Huey (eds.), Biology of Aristelliger cochranae Grant is a relatively small the Reptilia. Vol. 16, Ecology B. Defense and Life gecko with maximum snout-vent lengths (SVL) of 63 History, pp. 1-152. Alan R. Liss, Inc., New York. mm for males and 53 mm for females. It is endemic to Lenart, L. A., R. Powell, J. S. Parmerlee, Jr., A. Lathrop, Navassa Island, West Indies (Powell, 1999), and is and D. D. Smith. 1997. Anoline diversity in three typically arboreal, with individuals frequently found differentially altered habitats in the Sierra de within the twisted branches of Ficus trees or under Baoruco, Republica Dominicana, Hispaniola. Bio- bark. Thomas (1966) also noted their association with tropica 29:117-123. fan palms (Thrinax morrisii). In 1998, we collected this Losos, J. B., and D. J. Irschick. 1996. The effect of perch predator and its potential prey in fan palms on Na- diameter on escape behavior of Anolis lizards: labo- vassa. This tiny island, with an area of approximately 2 ratory predictions and field tests. Anim. Behav. 51: 5.2 km , is located about 60 km west of the southwest- 593-602. ern tip of the Haitian Tiburon Peninsula (Thomas, Rand, A. S. 1962. Notes on Hispaniolan herpetology 5. 1966). The natural history of three sympatric species of Although A. cochranae was described by Grant Anolis. Breviora (154):1-15. (1931) nearly 70 years ago, very little is known about its natural history (Lynxwiler and Parmerlee, 1993). Rand, A. S., and E. E. Williams. 1969. The anoles of La Because energy acquisition is a fundamental aspect of Palma: aspects of their ecological relationships. any species’ niche, we examined food habits in rela- Breviora (327):1-19. tion to potential prey present in the lizards’ habitat. Regalado, R. 1998. Approach distance and escape be- Previous studies of the West Indian geckos Hemidac- havior of three species of Cuban Anolis (Squamata, tylus haitianus (Powell et al., 1990), Aristelliger lar Polychrotidae). Carib. J. Sci. 34:211-217. (Burns et al., 1992), and Sphaerodactylus difficilis, S. al- Schwartz, A. 1974. A new species of primitive Anolis tavelensis, S. clenchi,andS. asterulus (Cunningham et (Sauria, Iguanidae) from the Sierra de Bahoruco, al., 1993) indicated that all of these lizards consume a Hispanolia. Breviora (423):1-19. wide range of prey. However, none of these studies SEA/DVS (Secretarı´a de Estado de Agricultura/ compared prey items taken by geckos with available Departamento de Vida Silvestre). 1992. Reconoc- prey. imiento y evaluacio´n de los recursos naturales en el Twenty-two (9 males and 13 females) geckos and Bahoruco Oriental. Sec. Estado Agric., Depto. Vida associated arthropods were collected on 29 July and 2 Silvestre. Sto. Domingo, Repu´ blica Dominicana. × August 1998 from fan palms in a savanna just south of + 141 pp. the lighthouse on Navassa. Predators and presumed Sifers, S. M., M. L. Yeska, Y. M. Ramos, R. Powell, and prey were acquired by shaking dead fronds over an J. S. Parmerlee, Jr. 2001. Anolis lizards restricted to insect net. Arthropods were placed in a killing jar and altered edge habitats in a Hispaniolan cloud forest. preserved in 80 % ethyl alcohol. Lizards were killed by lethal injection of T-61 (a veterinary drug no longer Carib. J. Sci. 37: in press. available), preserved in 10 % formalin, and transferred Williams, E. E. 1983. Ecomorphs, faunas, island size, to 75 % ethyl alcohol upon return to the laboratory. and diverse end points in island radiations of Ano- Stomachs were removed and contents identified to the lis. In R. B. Huey et al. (eds.), Lizard Ecology: Stud- lowest possible taxonomic level. Insect collections ies of a Model Organism, pp. 326-370. Harvard made during the biological inventory of Navassa fa- University Press, Cambridge, Massachusetts. cilitated identification of the often fragmented prey. Ydenberg, R. C. and L. M. Dill. 1986. The economics of Prey items were counted and volumes determined us- fleeing from predators. In J. S. Rosenblatt et al. ing the formula for the volume of a prolate spheroid (eds.), Advances in the Study of Behavior. Vol. 16, (Vitt and Zani, 1996). The intact size of lizard ova, pp. 229-251. Academic Press, New York. fragments of which were found in some stomachs, 324 NOTES was estimated by using the mean size of 11 intact eggs oviductal egg. Ova and hatchlings had importance (Powell, 1999). The resultant data were used to calcu- values of 0.271 and 0.082, respectively, in a pooled late dietary importance values (Powell et al., 1990; Birt sample of all lizards (Table 2). In females alone, ova et al., in press), which consider numbers, volumes, had an importance value of 0.318 and were the most and frequencies of occurrence for each type of prey. important item. Three stomachs were empty and two Prey types were defined as species for vertebrates and contained unidentifiable fragments. order for arthropods to facilitate comparisons with Consumed ova and hatchlings presumably repre- other dietary studies of West Indian lizards. Impor- sented the greatest energy source available. That they tance values then were used to calculate dietary niche were taken only by females is likely due to the high breadths standardized on a scale of 0-1 (Levins, 1968; energy demands of reproduction. At least 37 species of Hurlbert, 1978) and dietary niche overlaps (Pianka, geckos feed on other vertebrates (Bauer, 1990), with 1973) between males and females and between poten- other geckos and conspecifics (mostly juveniles) the tial prey found in palm fronds and actual prey con- most frequent victims. Consumption of intact eggs sumed by geckos. had not been reported previously (A.M. Bauer, pers. Statistical analyses were made using StatView 5.0 comm.), but we could not determine whether intact (SAS Institute, Inc., Cary, North Carolina). All means ova were consumed or hatching triggered a feeding are presented ± one SE; for all tests, ␣ = 0.05. Lizards response in the females. are in the Bobby Witcher Memorial Collection, Avila Standardized niche breadths of 0.612 for males and College, Kansas City, Missouri (BWMC 06199-220). In- 0.516 for females are substantially larger than for other sect specimens are deposited in the U.S. National Mu- West Indian geckos. Males consumed only 3 of 10 prey seum of Natural History, Smithsonian Institution, types (Table 2), but all were taken in large quantities. Washington, DC, and, in addition to locality informa- Females consumed 9 of 10 prey types. Dietary overlap tion, bear the label “Taken by beating dead leaves of between males and females (0.282) was surprisingly Thrinax in open rocky savanna and forest edges.” low, but it increased to 0.462 when ova and hatchlings A total of 576 arthropods was collected (Table 1). were excluded from the calculation. These low values The most abundant taxa were Psocoptera (32 %), Co- and a sexual size dimorphism index (M:F) of 1.19:1 leoptera (20 %), and Araneida (17 %). Psocoptera were (based on maximum male and female SVL; Roughgar- not found in lizard stomachs, but the combination of den, 1995) suggest resource partitioning. However, small size and soft bodies could have resulted in such the largest food items were taken by the smaller fe- rapid digestion that they appeared to be absent from males and mean food item size of males (26.7 ± 13.2 stomach samples. Araneida (20 %) and Coleoptera (12 mm3, 1.0-62.2 mm3, N = 5) and females (64.2 ± 19.9 %) were well represented in the lizards’ diets. The mm3, 0.8-202.0 mm3, N = 12) did not differ signifi- most common prey items were ants (Formicidae; 32 cantly when ova and hatchlings were included (Mann- %), which were far less commonly represented among Whitney U, Z = −0.95, P = 0.34) or excluded (Z = −0.11, potential prey (6 %). P = 0.92). Similarly, SVL and mean food item size were Hatchling A. cochranae, egg shell fragments, or both not significantly correlated (Spearman correlation; were found in five females, all of which contained an males: Z = 0.60, P = 0.55; females: Z = 1.89, P = 0.06;

TABLE 1. Numbers of potential prey compared to prey consumed by A. cochranae found in dead, pendant palm fronds of Thrinax morrisii. Percentages are in parentheses; dashes indicate that a particular type of prey item was not found.

Prey Number present Number consumed Arachnida: Araneida 96 (16.7) 10 (20.0) Arachnida: Pseudoscorpionida 9 (1.6) 1 (2.0) Diplopoda: Polyxenida: Polyxenidae 2 (0.3) — Insecta: Cleoptera: Carabidae, Elateridae, Lathridiidae, Aderidae, Curculionidae, Anobiidae, Mordellidae, Oedemeridae, Melyidae, Bruchidae, Nitidulidae 116 (20.1) 6 (12.0) Insecta Diptera: Ceratopogonidae, Cecidomyiidae, Sciaridae 7 (1.2) 1 (2.0) Insecta: Heteroptera: Reduviidae, Anthocoridae 4 (0.7) — Insecta: Homoptera: Achilidae, fulgoroid (immature) 2 (0.3) — Insecta: Hymenoptera: Formicidae, Bethylidae, Halictidae, Agaonidae 37 (6.4) 16 (32.0) Insecta: Isoptera — 5 (10.0) Insecta: Lepidoptera: Gelechiidae, Tineidae, undet. larvae 35 (6.1) 5 (10.0) Insecta: Orthoptera: Gryllidae, Blattidae 61 (10.6) 1 (2.0) Insecta: Psocoptera 182 (31.6) — Insecta: Thysanura: Lepismatidae 1 (0.2) — Reptilia: Squamata: Gekkonidae (hatchling) 4 (0.7) 1 (2.0) Reptilia: Squamata: Gekkonidae (ova) 20 (3.5) 4 (8.0) NOTES 325

TABLE 2. Dietary importance values (I) (see text) of male and female A. cochranae taken from dead, pendant palm fronds of Thrinax morrisii on Navassa Island. Each entry contains four items: in line one the three figures represent relative numbers, relative volume, and relative frequency of occurrence, respectively; the figure in the second line is the importance value of that type of prey item in the diet. Dashes indicate that a particular type of prey item was not found.

Prey item I (all) I (males) I (females) I (females w/o ova) Arachnida: Araneida 0.200/0.092/0.300 0.444/0.556/0.400 0.146/0.030/0.261 0.167/0.307/0.462 0.197 0.465 0.145 0.312 Arachnida: 0.020/0.002/0.033 0.111/0.003/0.200 —— Pseudoscorpionida 0.018 0.104 Insecta: Coleoptera: 0.120/0.001/0.067 — 0.146/0.001/0.087 0.167/0.006/0.154 Anobiidae, Scolytidae, 0.063 0.078 0.109 Tenebrionidae Insecta: Diptera 0.020/0.004/0.033 — 0.024/0.001/0.044 0.028/0.012/0.077 0.019 0.023 0.039 Insecta: Hymenoptera: 0.320/0.029/0.200 — 0.390/0.036/0.261 0.444/0.347/0.462 Formicidae 0.183 0.229 0.418 Insecta: Isoptera 0.100/0.013/0.033 — 0.122//0.015/0.044 0.139/0.157/0.077 0.049 0.060 0.124 Insecta: Lepidoptera: 0.100/0.055/0.133 0.444/0.441/0.400 0.024/0.005/0.044 0.028/0.032/0.077 Gelechiidae and others 0.096 0.427 0.024 0.455 Insecta: Orthoptera: 0.020/0.011/0.033 — 0.024/0.013/0.044 0.028/0.138/0.077 Blatellidae 0.021 0.027 0.081 Reptilia: Gekkonidae 0.020/0.193/0.033 — 0.024/0.215/0.044 — (hatchling) 0.082 0.094 Reptilia: Gekkonidae 0.080/0.599/0.133 — 0.098/0.683/0.174 — (ova) 0.271 0.318

females without ova and hatchlings: Z = 0.73, P = LITERATURE CITED 0.46). Overlap between potential prey available and actual Bauer, A. M. 1990. Gekkonid lizards as prey of inver- prey taken (0.182) was much lower than anticipated, tebrates and predators of vertebrates. Herpetol. although the overlap is greater (0.475) when ova and Rev. 21:83-87. hatchlings are excluded. However, overlap was zero Birt, R. A., R. Powell, and B. D. Greene. In press. Natu- when prey were identified to species. In addition, the ral history of Anolis barkeri, a semi-aquatic lizard species actually consumed by geckos are known to be from southern Me´xico. J. Herpetol. 35: in press. associated with dead standing wood and were not Burns, J. K. et al. 1992. Lizards of the Cayos Siete Her- found in the palm frond assemblage. These data sug- manos, Dominican Republic, Hispaniola. Bull. Chi- gest that lizards forage away from the palm fronds, a cago Herpetol. Soc. 27:225-232. conclusion that raises the question of why geckos Cunningham, C. A., J. S. Tulloch, and R. Powell. 1993. would forage elsewhere when the palms offer so Food habits of four Hispaniolan species of Sphaero- much potential prey and shelter from predators. dactylus (Lacertilia: Gekkonidae). Herpetol. Nat. Hist. 1(2):91-93. Acknowledgments.—Jil Swearingen helped collect Grant, C. 1931. A new species of Aristelliger from Na- specimens. Aaron M. Bauer commented on an earlier vassa. J. Dept. Agric. Porto Rico 4:399-400. draft of this manuscript. Field work by RP and WES Hurlbert, S. H. 1978. The measurement of niche over- took place during an expedition organized by the Cen- lap and some relatives. Ecology 59:67-77. ter for Marine Conservation, with major support of the Levins, R. 1968. Evolution in Changing Environments: Luce Foundation, the U.S. Department of the Interior’s Some Theoretical Explorations. Princeton Univ. Office of Insular Affairs, and the U.S. Coast Guard. The captain and crew of the U.S.C.G. Legare arranged Press, Princeton, New Jersey. ix + 120 pp. access to the island, and the captain and crew of the Lynxwiler, J. R. and J. S. Parmerlee, Jr. 1993. Aristelliger U.S.C.G. Valiant facilitated our return to civilization. cochranae. Cat. Amer. Amphib. Rept. (567):1-3. Chief Sharon Patterson provided logistical support Pianka, E. R. 1973. The structure of lizard communi- and exceedingly gracious hospitality during our stay ties. Ann. Rev. Ecol. Syst. 4:53-74. at the U.S. Naval Base at Guantanamo, Cuba. S. Blair Powell, R. 1999. Herpetology of Navassa Island, West Hedges (Pennsylvania State University) and the Mil- Indies. Carib. J. Sci. 35:1-13. waukee Public Museum provided funds to offset per- Powell, R., J. S. Parmerlee, Jr., M. A. Rice, and D. D. sonal expenses incurred by RP. Smith. 1990. Ecological observations of Hemidacty- 326 NOTES

lus brooki haitianus Meerwarth (Sauria: Gekkoni- lian amphibians and reptiles. Apparently, small local- dae) from Hispaniola. Carib. J. Sci. 26:67-70. ized populations had been established prior to the Roughgarden, J. 1995. Anolis Lizards of the Car- documented arrival of container-borne frogs in 1999. ibbean: Ecology, Evolution, and Plate Tectonics. The resident populations, supplemented by recent Oxford Univ. Press, New York and Oxford. arrivals, took advantage of conditions during an un- Thomas, R. 1966. A reassessment of the herpetofauna usually wet year (1999) that culminated with the land- of Navassa Island. J. Ohio Herpetol. Soc. 5:73-89. fall of two major hurricanes—Jose´ in October and Vitt, L. J. and P. A. Zani. 1996. Ecology of the elusive Lenny in November. Population sizes increased explo- tropical lizard Tropidurus [=Uracentron] flaviceps sively due to the benefits of inundation and corre- (Tropiduridae) in lowland rain forest of Ecuador. sponding large-scale increases in reproductive activity Herpetologica 52:121-132. (Meshaka, 1993; in press). During such events, breeding activity is not limited to larger, more fecund females. Instead, the more plentiful small-to-medium sized females are incorporated into the breeding Caribbean Journal of Science, Vol. 36, No. 3-4, 326–328, 2000 population, dramatically enhancing recruitment (Me- Copyright 2000 College of Arts and Sciences University of Puerto Rico, Mayagu¨ez shaka, in press). In addition, frogs moved or were transported throughout much of the western half of the island. Cuban Treefrogs (Osteopilus With the resumption of drier conditions, frogs re- treated into available refuges (Schwartz and Hender- septentrionalis) in Anguilla, son, 1991; Meshaka, 1996). By February 2000, the Lesser Antilles Health Department had received many calls about frogs and tadpoles in cisterns. A program was insti- tuted to screen cistern openings where frogs had been JOSIAH H. TOWNSEND, Department of Biology, Miami- reported. Between February and June, 33 complaints Dade Community College, Kendall Campus, Miami, were investigated and 144 frogs were collected (J. Parr, Florida 33157 (current address: Department of Wildlife pers. comm.). An additional 81 cisterns were screened Ecology and Conservation, University of Florida, Gaines- as a precautionary measure. ville, Florida 32611, [email protected]); JAMES In June 2000, we searched 20 sites (water tanks, M. EATON, Department of Biology, St. Louis University, freshwater springs, gardens, and resorts) across the St. Louis, Missouri 63103 ([email protected]); ROBERT island (Fig. 1). Voucher specimens were collected at POWELL, Department of Biology, Avila College, Kansas ten sites, and frogs, tadpoles, or eggs were observed City, MO 64145 ([email protected]); JOHN S. PAR- but not collected at two additional sites. No evidence MERLEE,JR., Department of Biology, Avila College, Kansas of frogs was found at the remaining sites. Eighteen City, Missouri 64145 and Department of Biology, Johnson metamorphosed frogs and three tadpoles were col- County Community College, Overland Park, Kansas 66210 lected and are deposited in the Bobby Witcher Memo- ([email protected]); AND ROBERT W. HENDER- rial Collection (BWMC) at Avila College. The Health SON, Section of Vertebrate Zoology, Milwaukee Public Mu- Department reported an additional 24 sites (J. Parr, seum, Milwaukee, WI 53233 ([email protected]). pers. comm.; Fig. 1). All sites with frogs, except one, were near areas of human activity. The exception was Since late 1999, the Cuban Treefrog, Osteopilus sep- an abandoned well near Katouche Bay, in which frogs tentrionalis, has become firmly established in Anguilla were observed calling and in amplexus at the water’s (Fig. 1). Anguilla is a xeric island (∼900 mm annual surface approximately3mbelowground level. rainfall) and its primary habitat is dry thorn forest, Osteopilus septentrionalis is well known for its ability most of it degraded by feral goats. Twenty-three salt to successfully colonize areas by exploiting man-made ponds and marshes constitute the only natural surface structures and water supplies (Meshaka, in press). The water. Sites where treefrogs have been recorded in- populations on Anguilla certainly have followed this clude water storage tanks, old wells, private cisterns, pattern, but methods of dispersal are unknown. Aside and areas in resorts and gardens that are watered from active dispersal during the rainy season, frogs regularly. might be dispersed passively via plants transported Most Anguillians believe that these frogs were in- from one site to another. In addition, we heard nu- troduced in 1999 via container shipments of decora- merous anecdotal accounts of dispersal by cars or by tive plants from Miami, Florida (USA) that were the trucks that distribute water to cisterns during the bound for a resort hotel in the final stages of construc- dry season. Assuming that dispersal and subsequent tion. Workers at several resorts and nurseries reported colonization of new areas are facilitated by wet con- that they had opened shipping containers from Miami ditions, we predict that, when hurricanes strike An- and found frogs inside. However, several of these guilla again, frogs are likely to occupy almost every same workers, in addition to officials with the Health suitable habitat on the island. Care and Water departments, reported seeing occa- Meshaka (in press) listed 10 factors that allow Os- sional frogs as early as the late 1980s. Although the teopilus septentrionalis to be successful in a situation earlier arrivals were not documented with voucher that seems less than ideal for supporting a widespread specimens, photographs of Cuban Treefrogs were anuran population (i.e., an extremely xeric island). Al- taken in 1997 (K. V. D. Hodge, pers. comm.) and Dal- though the Anguillian population exhibits most of try (1998) included O. septentrionalis in a list of Anguil- these factors, four appear to be particularly important: