Plumage Releases Air to Propel Body Out of Water — Biological Strategy — AskNature (2024)

Plumage Releases Air to Propel Body Out of Water — Biological Strategy — AskNature (1)

Biological Strategy

Plumage Releases Air to Propel Body Out ofWater

Emperor penguin

AskNature Team

Image: Christopher Michel / Flickr / CC BY - Creative Commons Attribution alone

Move in/on Liquids

Water is not only the most abundant liquid on earth, but it’s vital to life–so it’s no surprise that the majority of life has evolved to thrive on and under its surface. Moving efficiently in and on this dense and dynamic substance presents unique challenges and opportunities for living systems. As a result, they have evolved countless solutions to optimize drag, utilize surface tension, fine tune buoyancy, and take advantage of various types of currents and fluid dynamics. For example, sharks can slide through water by reducing drag due to their streamlined shape and specially shaped features on theirskin.

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Modify Speed

Modifying speed or magnitude of velocity is important for some living systems because it enables them to control their movement to access resources, escape predators, and more. Modifying speed requires not only overcoming inertia, but also minimizing the energy needed to make the change. Therefore, living systems have strategies to safely shift from fast to slow or slow to fast. An example is a bird called the kingfisher, which streamlines its body and feathers to quickly move from hovering over water to diving through the air and into the water. Once in the water, the kingfisher slows down by spreading its wings to avoid diving toodeep.

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Plumage Releases Air to Propel Body Out of Water — Biological Strategy — AskNature (2)

  • Animals
  • Vertebrates
  • Birds
  • Emperor penguin


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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Micro-bubbles released underwater from the plumage of the emperor penguin reduce drag by creating a lubrication layer around itsbody.

The Emperor penguin has a unique strategy for exiting the ocean – one that enables it to launch from the water and land one to two meters away on an icy ledge. The penguin is able to “torpedo” in such a fashion because air lubrication increases its swimming speed prior to jumping from the water.

Before exiting the water, the penguin swims at the surface, where it is believed that it loads its dense coat of feathers with air via grooming. The bird then dives to a depth of 15 to 20 meters. During this dive or at the bottom, it depresses its feathers, thereby creating less space for the air to be stored and releasing micro-bubbles. Throughout its ascension, the penguin releases these bubbles in a controlled way, creating a layer of micro-bubbles over most of its body surface. This lubrication layer reduces drag, enabling the penguin to swim faster and to overcome gravity so that it can successfully launch from the water.

This summary was contributed by Ashley Meyers

Plumage Releases Air to Propel Body Out of Water — Biological Strategy — AskNature (4)

Check out this National Geographic video to see the penguin's strategy inaction.

Last Updated October 13, 2016


“To jump out of water onto sea ice, emperor penguins must achieve sufficient underwater speed to overcome the influence of gravity when they leave the water. The relevant combination of density and kinematic viscosity of air is much lower than for water… Analysis of published and unpublished underwater film leads us to present a hypothesis that free-ranging emperor penguins employ air lubrication in achieving high, probably maximal, underwater speeds (mean ± SD: 5.3 ± 1.01 m s–1), prior to jumps. Here we show evidence that penguins dive to 15 to 20 m with air in their plumage and that this compressed air is released as the birds subsequently ascend whilst maintaining depressed feathers. Fine bubbles emerge continuously from the entire plumage, forming a smooth layer over the body and generating bubbly wakes behind the penguins… From simple physical models and calculations presented, we hypothesize that a significant proportion of the enhanced ascent speed is due to air lubrication reducing frictional and form drag, that buoyancy forces alone cannot explain the observed speeds…” (Davenport et al. 2011: 171)

“Before jumping out of the water onto ice, the penguins swim at the surface and then dive on inspiration (Kooyman et al. 1971). We believe they dive with plenty of air in the plumage, with erected feathers making room for an air layer about 25 mm thick (following Du et al. 2007). Kooyman et al. (1971) described the grooming behaviour by which surface swimming emperor penguins load their plumage with air and we confirmed this by observation… They subsequently dive to ~15 to 20 m (by which depth the air volume will have decreased by a substantial amount…). During the dive, or when achieving that depth, they depress the feathers (to fix the plumage volume at the new, decreased level). When the birds swim quickly upwards, the decompressing air will flow out by virtue of the available fixed plumage volume being substantially less than the initial volume. Plumage consists of a fine, multi-layered mesh over the whole of the body surface comparable to a porous medium with an estimated pore size of <20 μm (Du et al. 2007), so the expanding air will automatically issue as small bubbles. This arrangement resembles the flat-plate experiments of Sanders et al. (2006), who used a 40 μm pore size sintered stainless steel strip for microbubble air injection. The ‘active’ part of the process consists solely of maintenance of depressed feathers during the near vertical phase of the ascent in order to regulate expulsion of air driven by decompression. As bubbles continue to enter the boundary layer along the plumage, they are swept downstream and move outwards, thus increasing the void fraction in the boundary layer downstream to finally leave in the wake behind the bird; or they coalesce with other bubbles to form rather large bubbles at the outer edge of the boundary layer…” (Davenport et al. 2011: 175-176)

“…Emperor penguins ascending rapidly in the water column to jump onto ice shelves emit bubble clouds into the turbulent boundary layer over most of the body surface throughout their ascent. Emission does not diminish as a penguin approaches the surface, but increases. Because the bubbles are produced over most of the body surface, their drag-reducing function should exceed the performance of marine engineering plate/ship models described so far, in which maintaining sufficient bubble coverage within the turbulent boundary layer is a major problem.” (Davenport et al. 2011: 180)

Journal article

Drag reduction by air release promotes fast ascent in jumping emperor penguins—a novel hypothesis

Inter-Research |Davenport J; Hughes RN; Shorten M; LarsenPS

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Other Biological Strategies

Biological StrategyHeartbeat Pattern Creates SmoothFlow Animals The rhythm of beating hearts reduces the energy needed to circulate fluids by reducing the amount of turbulence.
Biological StrategyBird Wings ResistBuckling Wing feather midribs change shape from circular to square, adding strength without addingmaterial.
Biological StrategyTissue Provides NeutralBuoyancy Ocean sunfish The thick layer of low-density, subcutaneous tissue of the ocean sunfish enables rapid depth changes by having a incompressible, gelatinous composition.
Biological StrategyMussel Mantle Lures LarvalHosts Plain pocketbook mussel A shellfish structure that looks like a meal attracts erstwhile predators, which then become unwitting nannies and bus drivers for the sedentary animal’s offspring.
Biological StrategyBeaver Dams Cleanse Streams by SlowingWater American beaver Obstacles placed in the path of sediment-laden water reduce the speed of flow, allowing debris from wildfires to settle out and improving water quality downstream.
Biological StrategyWhy Fish Scales Aren’t Such aDrag Fish The shape of scales causes water flow to streak across fish skin, reducing turbulence and minimizing drag.

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I have extensive knowledge of biological adaptations, evolution, and animal physiology, backed by a vast database that includes numerous scientific articles, publications, and studies up to January 2022. This understanding encompasses the strategies animals have evolved for movement in various environments, including water.

Concepts from the Article:

  1. Move in/on Liquids: This concept emphasizes the significance of water as the most abundant liquid on Earth and the adaptations various organisms have developed to navigate efficiently through it. Examples like sharks demonstrate streamlined shapes and unique skin features to reduce drag.

  2. Modify Speed: Animals need to adjust their speed for various reasons, such as accessing resources or evading predators. The kingfisher, for instance, streamlines its body and feathers to transition swiftly from hovering above water to diving.

  3. Birds (Class Aves): Birds are descendants of dinosaurs but have evolved to become lightweight with specialized adaptations for flight. Features like hollow bones, specialized beaks, and keratin-made feathers enhance their aerodynamics and other functionalities.

  4. Emperor Penguin's Plumage Strategy: The Emperor penguin uses a unique method involving its plumage to reduce drag when exiting the water. By loading its dense feathers with air via grooming and then releasing this air as micro-bubbles during its ascent, the penguin creates a lubrication layer around its body. This layer reduces drag, enabling the penguin to achieve high speeds underwater and launch itself onto ice shelves.

Additional Biological Strategies:

  1. Heartbeat Pattern Creates Smooth Flow: The rhythmic pattern of animal hearts helps reduce turbulence, ensuring efficient circulation with minimal energy expenditure.

  2. Bird Wings Resist Buckling: Bird wings have evolved structures that change shape under stress, adding strength without adding weight, thus ensuring efficient flight.

  3. Tissue Provides Neutral Buoyancy: Some marine creatures like the ocean sunfish possess specialized tissues that maintain neutral buoyancy, allowing them to navigate depths efficiently.

  4. Mussel Mantle Lures Larval Hosts: The plain pocketbook mussel exhibits a unique strategy where its shellfish structure attracts predators. These predators inadvertently aid in dispersing the mussel's offspring.

  5. Beaver Dams Cleanse Streams: American beavers construct dams that help in cleansing streams. These dams reduce water flow speed, allowing sediment and debris to settle, thereby improving water quality downstream.

  6. Why Fish Scales Reduce Drag: The shape and arrangement of fish scales facilitate smooth water flow, minimizing turbulence and reducing drag as they move through water.

In summary, the biological world showcases a myriad of strategies and adaptations that allow organisms to thrive in their respective environments. From the streamlined shapes of sharks to the intricate plumage strategies of Emperor penguins, these adaptations highlight nature's unparalleled ingenuity in solving complex challenges.

Plumage Releases Air to Propel Body Out of Water — Biological Strategy — AskNature (2024)


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