(Cyclura Cychlura) in the Exuma Islands Kirsten N
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Natural Diet of Northern Bahamian Rock Iguanas (Cyclura cychlura) in the Exuma Islands Kirsten N. Hines [email protected] Introduction: Two subspecies of Northern Bahamian Rock Iguanas (Cyclura cychlura inornata and Cyclura cychlura figginsi) are endemic to the Exuma Islands of The Bahamas. They are considered to be primarily herbivorous; but, despite being the largest, native terrestrial vertebrates in the Exumas, there has been no comprehensive reporting of their native diet. Gaining a full understanding of their natural diet is particularly critical for the long-term management of this species now, given their increased popularity as a tourist attraction and the scientific communitiesʼ growing understanding of the impacts of associated food provisioning (Hines 2011; Knapp, Hines, Zachariah, White, Iverson, Buckner, Romero & Lattin, oral presentation this conference). This study presents data collected from non-feeding areas of 15 islands in the Exumas across 6 years in order to discern the natural diet of this species across its entire range. Methods: Islands where iguanas are known to reside across the Exumas were studied periodically between 2006 and 2013, including visits in winter, spring and summer. On each visit, scat samples were randomly collected across the entire island, recording the general location where each sample was retrieved. All samples were uniformly dried, then dissected into their distinct components. Each food item was identified, to species if possible, and classified descriptively (i.e., fruit, leaf, etc.). Individual items were then weighed and their proportion of the whole sample calculated. In this poster I report on frequency of occurrence of food type. Future reports will provide an analysis of proportional importance of food type. Results: A total of 387 scat samples collected from areas not affected by tourists on 15 islands in the Exumas have been processed to date. Pooling all analyzed samples across islands, 59 different food items were Table 1: observed (Table 1) with the most frequently consumed species being Seven Year Apple, Buttonwood, Natural food of Northern Bahamian Rock Iguanas in the Exumas. Sandfly Bush and Wild Dilly (Figure 1). Of these most frequently consumed species, all were observed in each sampling year and were found on 60-80% of the sampled islands (Table 1). Fruits, flowers and # Samples # Islands # Years Prey Item Scientific Name leaves (Figure 2) are the most common food items, but animal prey was present in 8.8% of the Observed in Observed On Observed samples. Seven Year Apple Casasia clusiifolia 148 12 6 Buttonwood Conocarpus erectus 115 11 6 Discussion: Sandfly Bush Rhachicallis americana 113 9 6 The native diet of Northern Bahamian Rock Iguanas in the Exumas consists primarily of four species of Wild Dilly Manilkara bahamensis 112 9 5 plant, with Seven Year Apple being the most commonly consumed food item. They are, however, Lignum Vitae Guaiacum sanctum 43 8 5 opportunistic foragers as indicated by the other 40 plant species observed in the samples, most noted in Bay Cedar Suriana maritima 36 9 6 less than 5% of the analyzed scat. Despite their proclivity for vegetarianism, their opportunistic Joewood Jacquinia keyensis 26 10 6 tendencies extend to animal protein and nearly 9% of the samples contained some animal remnant. Necklace Pod Sophora tomentosa 16 5 3 While some of these items were likely scavenged, these iguanas are also capable of hunting and have Organic Soil 15 7 4 been observed capturing live birds, mammals and marine invertebrates (Hines et al. 2002; Luther et al. Pigeon Plum Coccoloba diversifolia 12 4 3 2012; Pers. Comm.). These results are based on the currently analyzed samples, representing 34% of Darling Plum Reynosia septentrionalis 11 8 4 the total samples collected to date. The extent of their omnivory and proportional importance of various Golden Creeper Ernodea litoralis 10 4 4 food types will be explored further as remaining samples are analyzed. Ramʼs Horn Pithecellobium keyense 10 7 5 Wild Saffron Bumelia americana 10 6 4 Silver Palm Coccothrinax argentata 9 5 2 Figure 1: Strumpfia Strumpfia maritima 9 5 5 Comparison of the 15 most frequently observed food items, based on percent presence in scat samples pooled across all islands and years. Black Torch Erithalis fruticosa 8 4 3 Iguana Skin Cyclura cychlura 8 5 4 Seven Year Apple Turtle Grass Thalassia testudinum 8 4 5 Wild Tamarind Lysiloma latisiliquum 8 2 2 Buttonwood Common Prickly-Pear Cactus Opuntia stricta 7 3 3 Sandfly Bush Bark 6 3 4 Wild Dilly Thatch Palm Thrinax morrisii 6 4 3 Twig 6 5 4 Lignum Vitae Bird Feathers & Wing 5 3 3 Bay Cedar Gray Peanut Snail Cerion incanum 5 5 4 Joewood Narrow-leaved Blolly Guapira discolor 5 4 5 Sea Ox-eye Daisy Borrichia arborescens 5 1 2 Necklace Pod Beetle Coleoptera 4 3 3 Organic Soil Blue Crowngrass Paspalum caespitosum 3 1 1 Pigeon Plum Crabwood Gymnanthus lucidus 3 1 1 Bug Hemiptera 3 3 3 Darling Plum Sea Purselane Sesuvium portulacastrum 3 2 1 Golden Creeper Seagrape Coccoloba uvifera 3 2 2 Bushy Salmea Salmea petrobiodes 2 2 2 Ramʼs Horn Dune Lily-thorn Catesbaea parviflora 2 2 1 Wild Saffron Ghost Crab Oxypode quadrata 2 2 2 0 10 20 30 40 Hermit Crab Coenobita clypeatus 2 2 1 Percent (%) of Samples Lancewood Nectandra coriacea 2 2 2 Fly Maggots Brachycera 2 2 2 Sargassum Weed Sargassum sp. 2 2 2 Sea Oats Uniola paniculata 2 2 2 Seashore Rush Grass Sporobolus virginicus 2 2 2 Whitewood Drypetes divserifolia 2 2 2 Balloon Seaweed Colpomenia sp. 1 1 1 Bay Lavender Argusia gnaphalodes 1 1 1 Buccaneer Palm Pseudophoenix sargentii 1 1 1 Caribbean Sea Spurge Euphorbia mesemrianthemifolia 1 1 1 Charcoal 1 1 1 Cocoplum Chrysobalanus icaco 1 1 1 House Fly Musca domestica 1 1 1 Long-stalked Stopper Psidium longipes 1 1 1 Morning Glory Ipomea indica 1 1 1 Spanish Stopper Eugenia foetida 1 1 1 Tick Amblyommatorrei sp. 1 1 1 White Stopper Eugenia axillaris 1 1 1 Worm Annelida 1 1 1 Ziziphus Ziziphus taylorii 1 1 1 Wild Dilly fruit and seeds from scat sample Seven Year Apple Flower from scat (center) and fresh from tree (surrounding) Figure 2: Plant parts consumed of the most common food items of Northern Bahamian Rock Iguanas in the Exumas. Report Your Observations: 100 Fruit Anecdotal accounts have been extremely valuable in documenting less common behaviors and Flowers food items. Please contact me with observations of Rock Iguanas taking unusual food, hunting Leaves or scavenging. I would greatly appreciate any information you might have to contribute and will acknowledge all contributions. Thank you! 75 Literature Cited: Hines, KN. 2011. Effects of ecotourism on endangered Northern Bahamian Rock Iguanas (Cyclura cychlura). Herpetological Conservation and Biology 6(2):250-259. 50 Hines, KN, JB Iverson and JM Valiulis. 2002. Cyclura cychlura inornata (Allen Cays Rock Iguana): Bird predation. Herpetological Review 33(4):306. Knapp, CR, KN Hines, T Zachariah, CLA White, JB Iverson, SD Buckner, LM Romero and CR Lattin. In Prep. Physiological impacts of tourism and food supplementation on endangered insular iguanas. (Oral presentation this conference.) Percent(%)of Samples 25 Luther, B, CR Knapp, D Greene, SD Buckner, and JB Iverson. 2012. Cyclura cychlura figginsi (Exuma Island Iguana), Rodent Kill. Herpetological Review 43(3):483. Acknowledgements: 0 Permits were provided by the Bahamas Environment, Science and Technology (BEST) Commission and the Seven Year Apple Buttonwood Sandfly Bush Wild Dilly Lignum Vitae Bay Cedar Joewood Bahamas Department of Agriculture with assistance from the Bahamas National Trust. I would like to thank the following for their various forms of support: Keith Bradley, Sandra Buckner, Eric Carey, Bruce Dunham, George Gann, Louis Harts, John Iverson, Chuck Knapp, Andrew Kriz, James Kushlan, Darcy Lesh, Predensa Moore, John Thompson, Sheila Young, and numerous volunteers in the field..