Olfactory Cues Aid in Prey Detection

Biological Strategy

White-chinned petrel

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Image: JJ Harrison / CC BY SA - Creative Commons Attribution + ShareAlike

Sense Chemicals (Odor, Taste, etc.) From the Environment

Chemicals are important for signaling and communication among living systems, either intentionally (such as when two living systems try to find one another) or unintentionally (such as when a plant emits a chemical signal that an herbivore can use to find a tasty bite). They are also important for other uses, such as navigating or finding sources for minerals. But chemical signals are often relatively weak and disperse when moving through water or gases. Therefore, detecting them requires specialized abilities, including a way to determine where they are coming from. A well known example of sensing chemicals can be seen in ants following a pheromone trail laid down by others in their colony to locate a quality and abundant food source.

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Navigate Through Air

Although free from many of the physical obstructions found on land and in water, organisms that move through the air must still avoid hitting each other and objects in their flight path, such as trees and mountains. They also need to navigate from one place to another, which presents a different challenge. They use one strategy to navigate around obstructions and another to move towards their destination. For example, bats use echolocation to detect both obstacles and prey. To navigate during migration, bats also use vision, sun orientation, and likely other strategies.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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The olfactory senses of seabirds help them locate prey via detection of dimethyl sulfide released by phytoplankton.

In ecosystems, phytoplankton contain high concentrations of DMSP (dimethylsulfoniopropionate), an osmolyte that helps marine algae regulate their internal osmotic environment and may also serve as a cryoprotectant. When phytoplankton are eaten by zooplankton such as crustaceans, DMSP is released into the water, where it is converted into DMS (dimethyl sulfide) and acrylic acid. DMS then travels to the surface of the water and is released into the atmosphere, where it gives off a distinct smell that attracts several procellariiform seabirds, including albatrosses, petrels, and shearwaters, which feed on crustaceans. This establishes a mutually beneficial relationship where phytoplankton release DMS, which seabirds use as a cue to find and eat prey, thereby reducing the grazing pressure on the phytoplankton. This relationship suggests that DMS serves as a “keystone” infochemical in marine trophic interactions.

In this tritrophic mutualism, phytoplankton are grazed by crustacea, catalyzing an enzymatic reaction that converts DMSP to DMS and acrylic acid. DMS, in turn, attracts procellariiform seabirds that forage on primary consumers (crustacea), thereby reducing grazing pressure on phytoplankton. Once attracted, the procellariiformes may benefit the phytoplankton by adding limiting nutrients via excretion.

Image: JJ Harrison / CC BY SA - Creative Commons Attribution + ShareAlike

White-chinned petrel flies low over the ocean surface, using DMS to locate prey.

Last Updated April 11, 2018

References

Dimethylsulfide (DMS) Iis ubiquitous in the surface waters of the ocean and appears always to be present in concentrations far in excess of the concentrations expected at atmospheric equilibrium. This large concentration gradient between the oceans and the atmosphere drives almost half the biogenic sulfur flux to the earth’s atmosphere. DMS constitutes about 90% of the flux of biogenic sulfur from the ocean to the atmosphere. As a result, considerable attention has been focused on the distribution and dynamics of DMS in ocean water in an effort to understand mechanisms controlling its flux to the atmosphere. The DMS in seawater appears to originate from algae, most likely produced by the decomposition of dimethylsulfoniopropionate (DMSP), a tertiary sulfonium compound analogous to the quaternary ammonium compounds (for example, glycinebetaine and proline) that are widespread in marine organisms. As with these ammonium compounds, DMSP may be involved in regulating cellular osmotic pressure in algae. Decomposition of DMSP appears to occur mainly by an enzymatically catalyzed elimination reaction, yielding DMS and acrylic acid” (Dacey et al. 1986:1314).

Journal article

Oceanic Dimethylsulfide: Production During Zooplankton Grazing on Phytoplankton

Science 19 Sep 1986: Vol. 233, Issue 4770, pp. 1314-131 | 19/09/1986 | John W.H. Dacey, Stuart G. Wakeham

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Reference

“Petrels, albatrosses and other procellariiform seabirds have an excellent sense of smell, and routinely navigate over the world’s oceans by mechanisms that are not well understood. These birds travel thousands of kilometres to forage on ephemeral prey patches at variable locations, yet they can quickly and efficiently find their way back to their nests on remote islands to provision chicks, even with magnetic senses experimentally disrupted. Over the seemingly featureless ocean environment, local emissions of scents released by phytoplankton reflect bathymetric features such as shelf breaks and seamounts. These features suggest an odour landscape that may provide birds with orientation cues. We have previously shown that concentrated experimental deployments of one such compound, dimethyl sulphide (DMS), attracts procellariiforms at sea, suggesting that some species can use it as a foraging cue. Here we present the first physiological demonstration that an Antarctic seabird can detect DMS at biogenic levels. We further show that birds can use DMS as an orientation cue in a non-foraging context within a concentration range that they might naturally encounter over the ocean” (Nevitt et al. 2005:303)

Journal article

Sensitivity to dimethyl sulphide suggests a mechanism for olfactory navigation by seabirds

Biol Lett. 2005 Sep 22; 1(3): 303–305. | 22/09/2005 | Gabrielle A Nevitt, Francesco Bonadonna

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Reference

Journal article

Evidence that dimethyl sulfide facilitates a tritrophic mutualism between marine primary producers and top predators

PNAS March 18, 2014. 111 (11) 4157-4161 | 18/03/2014 | Matthew S. Savoca and Gabrielle A. Nevitt

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Reference

Journal article

Dimethylsulfoniopropionate: Its Sources, Role in the Marine Food Web, and Biological Degradation to Dimethylsulfide

Appl. Environ. Microbiol. December 2002 vol. 68 no. 12 5804-5815 | Duane C. Yoch

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