Natural Diet of Northern Bahamian Rock Iguanas (Cyclura cychlura

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.
Table 1:
Natural food of Northern Bahamian Rock Iguanas in the Exumas.
Prey Item
Scientific Name
# Samples
# Islands
Observed in Observed On
# Years
Observed
Seven Year Apple
Casasia clusiifolia
148
12
6
Buttonwood
Sandfly Bush
Wild Dilly
Lignum Vitae
Bay Cedar
Joewood
Necklace Pod
Organic Soil
Pigeon Plum
Darling Plum
Golden Creeper
Ramʼs Horn
Wild Saffron
Silver Palm
Strumpfia
Black Torch
Iguana Skin
Turtle Grass
Wild Tamarind
Common Prickly-Pear Cactus
Bark
Thatch Palm
Twig
Bird Feathers & Wing
Gray Peanut Snail
Narrow-leaved Blolly
Sea Ox-eye Daisy
Beetle
Blue Crowngrass
Crabwood
Bug
Sea Purselane
Seagrape
Bushy Salmea
Dune Lily-thorn
Ghost Crab
Hermit Crab
Lancewood
Fly Maggots
Sargassum Weed
Sea Oats
Seashore Rush Grass
Whitewood
Balloon Seaweed
Bay Lavender
Buccaneer Palm
Caribbean Sea Spurge
Charcoal
Cocoplum
House Fly
Long-stalked Stopper
Morning Glory
Spanish Stopper
Tick
White Stopper
Worm
Ziziphus
Conocarpus erectus
Rhachicallis americana
Manilkara bahamensis
Guaiacum sanctum
Suriana maritima
Jacquinia keyensis
Sophora tomentosa
115
113
112
43
36
26
16
15
12
11
10
10
10
9
9
8
8
8
8
7
6
6
6
5
5
5
5
4
3
3
3
3
3
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
11
9
9
8
9
10
5
7
4
8
4
7
6
5
5
4
5
4
2
3
3
4
5
3
5
4
1
3
1
1
3
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
6
6
5
5
6
6
3
4
3
4
4
5
4
2
5
3
4
5
2
3
4
3
4
3
4
5
2
3
1
1
3
1
2
2
1
2
1
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Coccoloba diversifolia
Reynosia septentrionalis
Ernodea litoralis
Pithecellobium keyense
Bumelia americana
Coccothrinax argentata
Strumpfia maritima
Erithalis fruticosa
Cyclura cychlura
Thalassia testudinum
Lysiloma latisiliquum
Opuntia stricta
Thrinax morrisii
Cerion incanum
Guapira discolor
Borrichia arborescens
Coleoptera
Paspalum caespitosum
Gymnanthus lucidus
Hemiptera
Sesuvium portulacastrum
Coccoloba uvifera
Salmea petrobiodes
Catesbaea parviflora
Oxypode quadrata
Coenobita clypeatus
Nectandra coriacea
Brachycera
Sargassum sp.
Uniola paniculata
Sporobolus virginicus
Drypetes divserifolia
Colpomenia sp.
Argusia gnaphalodes
Pseudophoenix sargentii
Euphorbia mesemrianthemifolia
Chrysobalanus icaco
Musca domestica
Psidium longipes
Ipomea indica
Eugenia foetida
Amblyommatorrei sp.
Eugenia axillaris
Annelida
Ziziphus taylorii
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
observed (Table 1) with the most frequently consumed species being Seven Year Apple, Buttonwood,
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
leaves (Figure 2) are the most common food items, but animal prey was present in 8.8% of the
samples.
Discussion:
The native diet of Northern Bahamian Rock Iguanas in the Exumas consists primarily of four species of
plant, with Seven Year Apple being the most commonly consumed food item. They are, however,
opportunistic foragers as indicated by the other 40 plant species observed in the samples, most noted in
less than 5% of the analyzed scat. Despite their proclivity for vegetarianism, their opportunistic
tendencies extend to animal protein and nearly 9% of the samples contained some animal remnant.
While some of these items were likely scavenged, these iguanas are also capable of hunting and have
been observed capturing live birds, mammals and marine invertebrates (Hines et al. 2002; Luther et al.
2012; Pers. Comm.). These results are based on the currently analyzed samples, representing 34% of
the total samples collected to date. The extent of their omnivory and proportional importance of various
food types will be explored further as remaining samples are analyzed.
Figure 1:
Comparison of the 15 most frequently observed food items, based on percent presence in scat samples pooled across all
islands and years.
Seven Year Apple
Buttonwood
Sandfly Bush
Wild Dilly
Lignum Vitae
Bay Cedar
Joewood
Necklace Pod
Organic Soil
Pigeon Plum
Darling Plum
Golden Creeper
Ramʼs Horn
Wild Saffron
0
10
Wild Dilly fruit and seeds from scat sample
Figure 2:
Plant parts consumed of the most common food items of Northern Bahamian Rock Iguanas in the Exumas.
20
Percent (%) of Samples
30
40
Seven Year Apple Flower from scat (center) and fresh from
tree (surrounding)
Report Your Observations:
100
Fruit
Flowers
Leaves
Anecdotal accounts have been extremely valuable in documenting less common behaviors and
food items. Please contact me with observations of Rock Iguanas taking unusual food, hunting
or scavenging. I would greatly appreciate any information you might have to contribute and will
acknowledge all contributions. Thank you!
Percent (%) of Samples
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.
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.)
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.
50
25
Acknowledgements:
0
Seven Year Apple Buttonwood
Sandfly Bush
Wild Dilly
Lignum Vitae
Bay Cedar
Joewood
Permits were provided by the Bahamas Environment, Science and Technology (BEST) Commission and the
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.