Wandering albatrosses (Diomedea exulans), with a wingspan of 3.2 meters, they can travel thousands of kilometres in open ocean, foraging on one of the most demanding marine environments of the world. Their large oceanic journeys, indicate an impressive navigation skill and show a highly developed and finely honed sensory mechanisms (vision, smell or navigation by magnetic field). Prey detection mechanisms and sensorial response in foraging behaviour of wandering albatrosses are still not fully understand. Wandering albatrosses seem to use a combination of visual and olfactory strategies to navigate and to detect productive areas in wide ocean. They have one of the largest olfactory bulbs of seabirds and results from foraging behaviour models, performed in pelagic environments, suggest an attraction to fishing and squid smelling odorants.
Albatrosses are able to recognize and follow odors emanating from a distant source, like dimethyl sulfide (DMS) [1] to identify foraging hotspots at open ocean, thousands of kilometers away. Albatrosses, and other procellariforms (albatrosses, petrels and shearwaters), seems to use odor cues at two spatial scales. At a large spatial scale albatrosses may use olfactory mechanisms to identify productive areas of the ocean where prey is likely to be found. Once the productive region is located, albatrosses switch to a small-scale visual detection mode, performing area-restricted search (ARS) [2] within areas where they identify prey patches. Wandering albatrosses first respond to the odour plumes emanating for example by DMS, and once the prey is detected, they take the most direct path to capture the prey.
Were identified four different movement patterns according to their different shapes: direct (without changes of flight direction), turn/zigzag (one or more turns of >45° flight direction changes), circle (bird surround’s prey capture point event) and water (bird remains on the water between prey captures).In-flights movement patterns occur upwind in response to the olfactory cues in the ocean. The crosswind flight increases the possibility of found an odour plume and was tested this prediction for each movement pattern, linking the flight direction with wind direction. Movement pattern of turn kind were preferentially oriented upwind, whereas direct movement pattern are oriented downwind.
These results and the movement patterns features reflect a multimodal strategy where olfactory cues alert wandering albatrosses to a particular ocean productive area or leads the bird to the neighbourhood prey where lately it is visually spotted.
[1] DMS: Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur and is a water-insoluble. DMS is the most abundant biological sulfur compound emitted to the atmosphere. Emission occurs over the oceans by phytoplankton that produces DMS. DMS has a characteristic smell commonly described as cabbage-like and has been characterized as the “smell of the sea” though it would be more accurate to say that DMS is a component of the smell of the sea, others being chemical derivatives of DMS and algal pheromones.
[2] ARS: In a continuous patchy environment, it is expected that predators should increase search effort after detecting a prey item because of the high probability of encountering other prey items nearby, before continuing a wider-range exploration and moving from one spatially delimited resource patch to an other.
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Source: Nevitt, G.A., Losekoot, M. & Weimerskirch, H. (2008). Evidence for olfactory search in Wandering albatross Diomedea exulans. Proceedings of the National Academy of Sciences, 105(12). doi: 10.1073/pnas.0709047105
Author: Jorge Pereira
