Do invasive rodents impact endangered insular iguana populations?
- 424 Downloads
Ample evidence confirms that large invasive mammalian competitors and predators can devastate endangered insular iguana populations. However, the impact of invasive rodents, particularly rats (Rattus rattus), has remained elusive. Tail autotomy occurs frequently in lizards, often as an antipredator tactic, but sometimes from intraspecific aggression. Tail autotomy can incur substantial locomotor, behavioral, energetic, and survival costs. Furcation (i.e., dividing into branches) of regenerated tails may also result from attempted predation but occurs much more rarely, and with unknown costs. To evaluate the potential impact of invasive rodents—primarily rats—on West Indian rock iguanas (genus Cyclura), we compared tail-break and tail-furcation frequencies among 19 insular iguana populations (3,537 individuals) representing three species in the Bahamian Archipelago (including the Turks and Caicos Islands). The findings supported our three hypotheses: (1) that tail-break and tail-furcation frequencies are significantly higher in populations coexisting with invasive rodents; (2) that tail-furcation results primarily from failed predation attempts rather than intraspecific aggression; and (3) that frequencies of tail breaks and tail furcation are associated with each other, suggesting a degree of commonality in cause-effect (i.e., failed predation attempts). Tail furcation, in contrast to tail breakage, never occurred on islands lacking invasive mammalian predators. We conclude that invasive rodents, particularly rats, may have a greater impact on endangered insular iguana species than previously recognized.
KeywordsInvasive mammals Rats Lizards Tail autotomy Tail furcation Predation
We thank the many students and colleagues without whose support this work could not have been accomplished. Research by Hayes and Carter was supported by the Bahamas Ministry of Agriculture, Chicago Zoological Society, Denver Zoological Society, Disney Foundation, Insular Species Conservation Society, and International Iguana Foundation. Iverson’s studies were funded by the Test Fund, the Cope Fund, and the Professional Development Fund, all of Earlham College. Knapp’s work was funded by the John G. Shedd Aquarium’s citizen scientist iguana research program. All authors were also supported by their host institution(s), with research approved by their respective institutional animal care and use committees, and authorized by Bahamas research permits.
- Bates MF (1990) Bifid, trifid and branched tails in lizards. African Herp News 14:19–22Google Scholar
- Bellairs Ad’A, Bryant SV (1985) Autotomy and regeneration in reptiles. In: Gans C, Billett F (eds) Biology of the reptilia, vol 15., Development B. Wiley, NY, pp 301–410Google Scholar
- Carter RL, Hayes WK (2004) Conservation of an endangered Bahamian iguana. II. Morphological variation and conservation recommendations. In: Alberts AC, Carter RL, Hayes WK, Martins EP (eds) Iguanas: biology and conservation. University of California Press, Berkeley, pp 258–273Google Scholar
- Cohen J (1988) Statistical power analysis for the behavioral sciences, 2nd edn. Erlbaum, HillsdaleGoogle Scholar
- Haneke B (1995) A study of Mona rock iguana (Cyclura cornuta stejnegeri) nesting sites on Mona Island, Puerto Rico. J Int Iguana Soc–Iguana Times 4(4):61–71Google Scholar
- Hayes WK, Carter RL, Cyril S, Thornton B (2004) Conservation of an endangered Bahamian iguana. I. Population assessments, habitat restoration, and behavioral ecology. In: Alberts AC, Carter RL, Hayes WK, Martins EP (eds) Iguanas: biology and conservation. University of California Press, Berkeley, pp 232–257Google Scholar
- Henderson RW (1992) Consequences of predator introductions and habitat destruction on amphibians and reptiles in the post-Columbus West Indies. Caribb J Sci 28:1–10Google Scholar
- Iverson JB (1979) Behavior and ecology of the rock iguana Cyclura carinata. Bull Florida State Mus 24:173–356Google Scholar
- Iverson JB, Smith GR, Pieper L (2004) Factors affecting long-term growth of the Allen Cays rock iguana in the Bahamas. In: Alberts AC, Carter RL, Hayes WK, Martins EP (eds) Iguanas: biology and conservation. University of California Press, Berkeley, pp 176–192Google Scholar
- Knapp CR (2000) Home range and intraspecific interactions of a translocated iguana population (Cyclura cychlura inornata Barbour and Noble). Caribb J Sci 36:250–257Google Scholar
- Mata-Silva V, Rocha A, Gandara A, Johnson JD (2010) Cophosaurus texanus (Greater Earless Lizard). multiple tails. Herpetol Rev 41:352–353Google Scholar
- Mitchell NC (1999) Effect of introduced ungulates on density, dietary preferences, home range, and physical condition of the iguana Cyclura pinguis on Anegada. Herpetologica 55:7–17Google Scholar
- Mitchell N, Fulford M, Haeffner R (2000) Turks and Caicos iguana (Cyclura carinata carinata). West Indian Iguana Specialist Group News 3(1):7–13Google Scholar
- Sood MS (1939) A peculiar case of caudal abnormality in Hemidactylus flaviviridis Rüppell. Proc Plant Sci 9:316–322Google Scholar
- Tolson PJ (2000) Control of introduced species. In: Alberts AC (ed), West Indian iguanas: status survey and conservation action plan. IUCN—the World Conservation Union, Gland, pp 86–89Google Scholar