Friday, July 25, 2014

A feeding aggregation of Boa constrictors

Boa constrictor (individual 1) predating Rufous-bellied Thrush 
on a trumpet tree. The black arrow indicates the bird's wing 
and the white arrow points out a conspecific (individual 2) on a 
parallel branch. Photo Gilson da Rocha Santos. 
Sit-and-wait predators remain motionless for long periods of time, waiting for prey to come within range of their reach. The choice of locations for the ambush can determine the success of the predator, and some snakes species (e.g., Boa constrictor;  Crotalus horridusEchis coloratus;  Epicrates inornatusGloydius shedaoensis) increase their chances of prey capture by selecting microhabitats that are frequently visited by the prey.

In a recent paper by Rocha-Santos et al. (2014) the authors reports on the Boa constrictor using fruiting Trumpet trees (Cecropia spp.). Cecropia are fast growing pioneers, associated mainly to secondary forests, found throughout the Neotropical area, from the south of Mexico to the north of Argentina. They can reach up to 22 meters and have long fruiting periods (up to 12 months) and they attract several omnivore and frugivorous species, including passerines, galliforms, parrots, marmosets, bats and coatis.

Boas are robust snakes that can reach up to 300 cm of total length. They are habitat generalists present throughout the Neotropics area, present in rainforests, savannas and wetlands. They are sit-and-wait strategists capable of detecting prey, probably using visual, thermal and chemical stimuli and they feed efficiently in terrestrial and arboreal environments. Published records suggest they prey on most major groups of vertebrates.

The authors observed the predatory behavior of boas during fieldwork in a Cerrado remnant of 50 ha belonging to Private Natural Heritage Reserve, Universidade Federal de Mato Grosso do Sul, Campo Grande, Brazil.  The reserve is located in an urban area, which is surrounded by boulevards and buildings of the UFMS campus. Vegetation is composed by trees reaching 15-18 m tall, smaller trees, shrubs, and herbaceous plants.

They observed the capture of a Rufous-bellied Thrush (Turdus rufiventris) by a boa on the branch of a 8 m trumpet tree. The Rufous-bellied Thrush landed on the branch, about 50 cm, from a snake probably in search of fruit, and was instantly captured and constricted. The snake touched the bird with its labial scales, inspecting it, and started ingesting by the bird’s head. Ingestion lasted about 14min, and the snake returned to its initial position (partially aligned on the branch). At the same time, we spotted two other snakes positioned on parallel branches in same tree.  The snakes were separated by 0.5 to 2 m of space.

The following morning the three snakes were in the same positions, probably the same individuals sighted in the previous day. And the authors observe another Rufous-bellied Thrush landing on a branch near the second individual. However, the bird managed to dodge the attack, escaping capture. Three minutes later the third snake captured a Great Kiskadee (Pitangus sulphuratus). No interactions among the snakes were observed.

Citation

Rocha-Santos, G. D., Barbier, E., & Bordignon, M. O. (2014). Sweet trap: Boa constrictor (Serpentes: Boidae) preying on passerines on Cecropia pachystachya (Urticales: Cecropiaceae) in fruiting periodBiota Neotropica, 14(2): 1-4.

No comments:

Post a Comment