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Rivas, J. A., Molina, C. R & T. M. Avila 1998. Iguana iguana (Green iguana): juvenile predation. Herp. Review. 29 (4) : 238-239  pdf

Iguana iguana (Green iguana): Juvenile predation. The green iguana has been reported to nest communally as a strategy to decrease predation by terrestrial vertebrates (Rand & Dugan 1983. Copeia 1983: 705-711). Iguana nest can be taken by several predators (Rand & Robinson, 1969. Herpetologica. 25:172-174) and juveniles can also suffer heavy predation (Greene et al., 1978 J. Herp. 12: 169-176.).

During the dry season of 1988 we documented the emergence of hatchlings in several breeding aggregations during in April and May at Hato Masaguaral, a cattle ranch at Guárico State (8º 34' N, 67º 35' W). We recorded the animals that were seen preying on hatchlings by systematically patrolling the breeding aggregations. Patrols were conducted from 8:00 to 9:30 and from 16:30 to 18:00. We totaled 51 hours of observation in 17 days. We also recorded other events of predation that we saw along with data from the stomach content of road killed animals that we collected on the highway.

The predated animals were classified in three different group based upon their estimated snout-vent length (mm): Size I, animals smaller than 180 mm; size II, from 180 to 239 mm; and size III, 240 mm or larger (Rivas unpublished)

In table 1 we present the species documented preying on iguanas with the estimated size of the prey and the relative frequency. The class found preying most frequently on iguanas were birds (22 species), followed by reptiles (8 species) and mammals (6 species). Even though we did not try to quantify the predation pressure, judging by the number of events recorded, it seems like birds make the highest effect. Nevertheless the predation pressure made by mammals could be underestimated due to their secretive nature and nocturnal habits.

The lapse between the first animal that hatched and the last one was 14 days. We estimated that 120 nest (4800 hatchlings approximately) in a dune approximately 8 ha. This synchrony produced a brief invasion of hatchling to the area. High encounter with this item explains the high number of predators found.

Our data suggest that juvenile iguanas suffer high predation from aerial vertebrates. This seems to be in agreement with the behavior of juveniles at the tree tops where they stay motionless for a long time synchronizing their movements with the winds that blows through the canopy (Henderson 1974. Herpetologica. 30:327-332) as well as the habit of sleeping in burrows (Brust 1985. Amer. Zool. 25(4):7A).

Acknowledgment: We are in debt to Tomás Blohm for allowing us work in the ranch and the use of the facilities. We also thank J. Thorbjarnarson, B. Thomas, for providing useful information. L. Levin and Renee Owens provided useful comment on early versions of the manuscript. This research was sponsored by Wildlife Conservation Society (Formerly New York Zoological Society).

 

 

Table 1: shows the list of predators documented preying on iguanas or with remaining of them in the stomach content. The ones with a start were seen chasing, stalking or holding pieces of the tail. Animals marked with and "f’" were seen preying on iguanas more than ten times. Piaya Cayana was seen in two opportunities with embryos of a lizards in advances stage of development, full comprobation about the identifications of the embryos was not possible. The records of Crocodylus ocurred in outdoor cages where they are kept.

REPTILES:

Size I

Size II

Size III

Alligatoridae

 

 

 

Caiman crocodilus

 

1

 

Boidae

 

 

 

Eunectes murinus

 

2

1

Colubridae

 

 

 

Chironus sp.

 

1*

 

Crocodilidae

 

 

 

Crocodylus acutus

 

1

 

Crocodylus intermedius

 

1

1

Teidae

 

 

 

Ameiva. ameiva.

4

1

 

Cnemidophorus sp.

1

 

 

Tupinambis sp.

1*

1

 

Birds:

 

 

 

Accipitridae

 

 

 

Buteo albicaudatus

3

 

 

Buteo magnirostris

6

 

 

Buteogallus urubitinga

f

3

1, 1*

Elanoides fortiscatus

1

 

 

Elanus leucurus

1

 

 

Gampsonyx swainsonii

1

 

 

Geranospizia caerulencens

1

 

 

Heterospizia meridionalis

f

 

 

Parabuteo unicintus

1

1

 

Ardeidae

 

 

 

Ardea cocoy

 

1

 

Casmerodius albus

1

 

 

Tigrisoma sp.

1

 

 

Cuculidae

 

 

 

Crotophaga ani

1*

 

 

Crotophaga mayor

1

 

 

Piaya cayana

2

 

 

Falconidae

 

 

 

Falco femoralis

f

 

 

Falco sparverius

f

 

 

Milvago chimachima

1

 

 

Polyborus plancus

f

 

 

Icteridae

 

 

 

Icterus icterus

4

 

 

Tyrannidae

 

 

 

Pitangus sulphuratus

2*

 

 

Tytonidae

 

 

 

Tyto alba

1

 

 

mammals:

 

 

 

Canidae

 

 

 

Canis familiaris

 

 

6

Cerdocyon thous

f

1

1

Cebidae

 

 

 

Cebus nigrivitatus

 

1

1

Felidae

 

 

 

Felis pardalis

 

 

1

Felis domesticus

f

 

 

Procyonidae

 

 

 

Procyon cancrivorus

1