1 Tahrcountry Musings: Sharks and “mental maps”

Thursday, March 03, 2011

Sharks and “mental maps”


Now, this is amazing. Sharks making mental maps” that allow them to pin-point destinations up to 50km away. I read this in a new paper by Yannis P. Papastamatiou ,Daniel P. Cartamil, Christopher G. Lowe, Carl G. Meyer, Brad M. Wetherbee and Kim N. Holland titled “Scales of orientation, directed walks and movement path structure in sharks” published in Journal of Animal Ecology

The researchers analysed tracking data from three shark species tagged with acoustic transmitters, and found that they took directed paths from place to place. This shows a capacity to store maps of key sites. The researchers used statistical techniques to show that the journeys were not made by accident.
Blacktip reef sharks (Carcharhinus melanopterus), although widespread around the Pacific, appear to have small ranges within their home reef system.
On the other hand, tiger sharks (Galeocerdo cuvier) can cover huge distances. Tags have been recovered from individuals more than 3,000km away from where they were attached
The researchers say animal search patterns reflect sensory perception ranges combined with memory and knowledge of the surrounding environment. Random walks are used when the locations of resources are unknown, whereas directed walks should be optimal when the location of favourable habitats is known. However, directed walks have been quantified for very few species.
Tiger sharks performed directed walks at large spatial scales (at least 6–8 km). Thresher sharks also showed directed movement (at scales of 400–1900 m), and adult threshers were able to orient at greater scales than juveniles, which the researchers say suggest that learning improves the ability to perform directed walks. . Blacktip reef sharks had small home ranges, high site fidelity and showed no evidence of oriented movements at large scales.
The researchers conclude that Sharks can perform directed walks over large spatial scales, with scales of movements reflecting site fidelity and home range size. The researchers signs off saying “Understanding when and where directed walks occur is crucial for developing more accurate population-level dispersal models.”

Scales of orientation, directed walks and movement path structure in sharks
Yannis P. Papastamatiou ,Daniel P. Cartamil, Christopher G. Lowe, Carl G. Meyer, Brad M. Wetherbee and Kim N. Holland
Article first published online: 1 MAR 2011
DOI: 10.1111/j.1365-2656.2011.01815.x
Journal of Animal Ecology

1 comment:

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