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how do penguins find food

Can Penguins Smell?

Gentoo Penguin

Can Penguins Smell?

By Abigail Pietrow, Penguin Keeper

There are lots of common questions that I’m often asked as a Penguin Keeper at the Aquarium of Niagara:Can Penguins Breathe Underwater?”  “What do penguins eat?”Why are penguins black and white?” It sometimes seems like the curiosity directed towards our flightless feathered friends is endless, but is generally directed towards some common topics from day to day. I was surprised this past week by an uncommon question that came from two different individuals within the span of a couple of days: Can penguins smell? In order to answer that question I had to do a little digging, and what I found was pretty interesting!

What do seabirds smell?

Up until the mid-1900s it was widely assumed that birds did not have a sense of smell. This belief was based on the results of a few small studies, differences in nasal anatomy, and the fact that the olfactory bulb in most bird species (the organ in the brain responsible for the sense of smell) was much smaller than that of mammals when examined. More recently, scientists specifically studying this sense in birds have uncovered a very different truth – many birds have a well-developed sense of smell.

Tube-nosed seabirds in particular (Order Procellariiformes), like Albatrosses and Shearwaters, have highly developed olfactory systems. These systems are tuned to search out dimethyl sulfide (DMS), a very particular compound released when krill consume phytoplankton. Krill is an important food source for many seabirds, and following the scent trail of this compound can help these birds locate patches of food in the vast distances of the open ocean.

Consequences of DMS (Dimethyl Sulfide) Sensitivity in Birds

Unfortunately, feasting krill are not the only source of DMS in our oceans today. Plastic and micro-plastic pollution in our oceans is an ever-increasing environmental issue. An analysis performed in 2015 extrapolated that if pre-existing plastic ingestion studies from 1962-2012 were conducted under current oceanic conditions, then the percentage of seabirds surveyed with plastic in their digestive system would likely be closer to 90% compared to the 29% from previous decades.

It has been theorized in the past that the basis for this phenomenon is primarily visual – that plastic is eaten when it is mistaken for prey species while foraging.

A study conducted in 2016 sought to investigate other explanations for why seabirds ingest so much plastic debris. They tested the three most common types of plastic found in marine debris and found that after only one month in the ocean, these samples were coated in a biological film that produced DMS at a level detectable by tube-nosed seabirds. Their results suggest that part of the reason seabirds are eating so much plastic is because it smells like food to them too!

Sense of Smell in Penguins

Tube-nosed seabirds are generally considered to be some of the closest living relatives to modern penguins. While these evolutionary relationships are still under investigation, penguins do share some of the same adaptations for smell as other seabirds. African Penguins have been shown to have a similar sensitivity to DMS, as well as being attracted by the scent of this compound both on land and at sea.

They posses a single nostril called a “nare” on either side of their beak, and while their olfactory bulbs are relatively small compared to other seabirds, the organ is still larger than many land-based bird species. This reduction in size is paired with a reduction in the amount of olfactory receptor genes in their DNA and likely a reduced sense of smell compared to other waterbirds. However, some scientists hypothesize that this reduction in reliance on smell correlates with evolution of other adaptations penguins developed to hunt effectively under the surface like spherical lenses and flattened corneas for improved underwater vision.

Sniffing out Friends and Family

Penguins may also use their sense of smell for another important task. While many have now studied how birds can use their sense of smell for important functions like navigation and foraging, one fascinating study looked at how Humboldt Penguins (Spheniscus humboldti) might use their sense of smell to recognize mates or family members.

The scientists used oil samples from the preen gland of penguins to test whether individuals reacted differently to the scent of unfamiliar penguins than they did to family or neighbors.  They found that the studied penguins preferentially investigated unfamiliar and non-kin smells when presented with a choice. This could have implications for how penguins avoid inbreeding when choosing a mate in their natal colony!

What action can you take?

While penguins seem to be less likely to ingest plastic at the same rate as other seabird species, ingestion is not the only risk that plastic pollution in our oceans poses. Plastic entanglement is an issue facing many marine species, penguins included.

African Penguin entangled in discarded plastic.
Source: Avery, 2018.

Reducing your use of single-use plastics is one of the most effective ways to reduce your plastic footprint and helps keep plastic out of the world’s landfills and oceans! Instead of single-use items, reusable alternatives can be a planet-friendly way to make a difference for wildlife!

© Abigail Pietrow 2020

Abigail Pietrow is a penguin keeper at the Aquarium of Niagara, and works extensively with Humboldt Penguins. Any views or opinions expressed in this article are the author’s own, and do not necessarily represent those of the Aquarium of Niagara.

Did you know that penguins could smell? Let us know in the comments what you found most interesting! Please help us continue to learn more about penguins by donating to Penguins International.

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References

Coffin, H R, J V Watters, J M Mateo. 2011. Odor-based recognition of familiar and related conspecifics: a first test conducted on captive humboldt penguins (Spheniscus humboldti). PLoS ONE 6(9): e25002. doi:10.1371/journal.pone.0025002

Dell’Ariccia, G., Phillips, R. A., Van Franeker, J. A., Gaidet, N., Catry, P., Granadeiro, J. P., … & Bonadonna, F. (2017). Comment on “Marine plastic debris emits a keystone infochemical for olfactory foraging seabirds” by Savoca et al. Science advances, 3(6), e1700526.

Lu, Q. et al. 2016. Penguins reduced olfactory receptor genes common to other waterbirds. Sci. Rep. 6, 31671; doi: 10.1038/srep31671

Nevitt, G A. 2008. Sensory ecology on the high seas: the odor world of the procellriiform seabirds. The Journal of Experimental Biology (211) 1706-1713. doi:10.1242/jeb.015412

Pinto, M. B., Siciliano, S., & Di Beneditto, A. P. M. (2007). Stomach contents of the Magellanic penguin Spheniscus magellanicus from the northern distribution limit on the Atlantic coast of Brazil. Marine Ornithology, 35, 77-78.

Ryan, P. G. (2018). Entanglement of birds in plastics and other synthetic materials. Marine pollution bulletin, 135, 159-164.

Savoca M, M E Wohlfeil, S E Ebeler, G A Nevitt. 2016. Marine plastic debris emits a keystone infochemical for olfactory foraging seabirds. Sci Adv 2 (11) e1600395. DOI: 10.1126/sciadv.1600395

Watanabe M, et al. 2006. New candidate species most closely related to penguins. Gene (378) 65-73. https://doi.org/10.1016/j.gene.2006.05.003

Wilcox C, E Van Sebille, B D Hardesty. 2015. Threat of pollution to seabirds is global, pervasive, and increasing. PNAS 112 (38) 11899-11904. https://doi.org/10.1073/pnas.1502108112

Wright, K L B, L Pichegru, P G Ryan. 2011. Penguin are attracted to dimethyl sulfide at sea. The Journal of Experimental Biology (214) 2509-2511. doi:10.1242/jeb.058230

 

Sources:

Averett, N. (2014). Birds Can Smell, And One Scientist is Leading the Charge to Prove It. [online.] Audubon Magazine. Available from: https://www.audubon.org/magazine/january-february-2014/birds-can-smell-and-one-scientist [Accessed 07 October 2020].

Avery, M. (2018). Guy Shorrock – Plastic Perils and Penguins. [online]. WordPress. Available from: https://markavery.info/2018/01/28/guy-shorrock-plastics-perils-penguins/ [Accessed 07 October 2020].

Fish Beware! – Penguins Adapt Effective Means of Capturing Prey

Photo of King Penguin. Photo credit: saname777 [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons

Fish Beware! – Penguins Adapt Effective Means of Capturing Prey

By Mike King

Scientists currently split the penguin family into 18 different species that occur all over the Southern Hemisphere. As these penguin species evolved from a common ancestor, they each gained unique traits. One of the most important traits that penguins have adapted is how they eat. Most people know that penguins swim underwater and catch marine prey instead of flying like other birds, but there is actually a lot of variation in the specific feeding behaviors exhibited between separate penguin species. From krill to fish, sea to shore, and even day to night; there is a lot to learn about how different penguins keep themselves, and their chicks, happy and healthy.

Scientists are not sure how long ago penguins lost the ability to fly, but it’s thought that as the birds’ wings became more adapted for swimming, they lost the lengthy surface area of feathers needed to hold the birds aloft. It is more difficult for flightless birds to escape from predators like leopard seals; but the reward is well worth the risk. Since the wings of the penguins have evolved into streamlined flippers, they are able to swim with incredible grace and agility through great depths of water in search of food. Emperor Penguins (Aptenodytes forsteri) can routinely dive well over 200 meters while holding their breath for up to 20 minutes! This can be very helpful for catching Antarctic Silverfish, which spends most of its time between 200 and 300 meters below the surface. This is just one example of how penguins evolved alongside their food source, enabling them to keep up with their prey as the fish began to swim deeper and faster.

Penguins porpoising in the ocean
Gentoo Penguins

How do penguins find food?

While Emperor Penguins spend their time diving to great depths in search of fish, other penguin species have their own methods for finding food. Gentoo Penguins (Pygoscelis papua) are extremely fast swimmers, although it’s important to note that reports of top speeds on various websites of 22 miles per hour are unsubstantiated and their top speed is currently unknown. Galapagos Penguins (Spheniscus mendiculus) utilize a technique where they dive beneath schools of fish, then swim upwards and drive the fish toward the surface. This traps the fish between the penguins and other species of seabirds at the surface that cannot dive so they have nowhere to escape. Many species, like Little Penguins (Eudyptula minor) stay in the water all day to find enough fish to feed themselves and their offspring.

Penguins almost always live in close proximity to other vertebrate species. Whether it’s seals, fish, or even other penguins, there is bound to be some competition for food. This is why penguins have evolved many ways to fill their own ecological niche.A niche is an organisms place in the ecosystem, where most of the resources they need to survive are readily available to them. Ecological niches help animals ensure the survival of their own species by avoiding harmful interactions with other species. A good example of this is Gentoo and Emperor penguins. While both species live and hunt in Antarctica, they do not compete for resources. Emperor Penguins make deep dives in search of fish, while Gentoo Penguins speedily cruise near the surface of the water in search of krill. This division of foraging techniques is the line between the ecological niches of the two species.

Sometimes, when resources are scarce, animals must adapt new techniques to continue providing enough food for themselves and their offspring. Until just this year, scientists believed that male Emperor Penguins fasted for 115 days while they incubate their eggs. This would be a monumental task for these birds who, like all organisms, need energy to metabolize and survive. If an adult Emperor Penguin dies of starvation while incubating, his offspring also would not survive. A recent research article written by Gerald L. Kooyman et. al. in January 2018 may shed some light on how Emperor Penguins survive this long period of incubation. There is a colony of penguins near the Ross Sea in Antarctica that is one of the strongest of all Antarctic populations. A team of researchers set out to examine why, at a latitude much farther south than most other Emperor Penguins, this group was faring so well. It turns out, the males in this colony do not participate in the 115-day annual fast. In the dead of winter, when days are very short, these penguin males relinquish their parental duties to the females for one night; to dive for fish–in the dark. Prey becomes harder to see at night, as do predators. These Emperor Penguins, however, have taken advantage of the underutilized populations of fish found in the Ross Sea after dark. This adaptive trait has allowed their population to become one of the most stable of any penguin species in the world.

Photo credit: https://nauticallog.blogspot.com/2010/12/ross-sea-whaling.html

Penguins have to constantly adapt to survive, however.

Much like penguins developing different foraging behaviors, animals are constantly adapting to the challenges presented to them by nature. As problems arise, organisms must find ways to overcome them. This incredible race for survival drives all living things to further evolutionary advancement, and results in the splendid array of biodiversity we know in our world today. However, for the first time ever, one species has advanced itself so greatly that it threatens to irreversibly tip the balance of nature toward destruction. Because of climate change, illegal hunting and fishing, and over-exploitation of natural resources, humans are at risk of causing the largest mass extinction in the history of the world. Although animals, like the Emperor penguins of the Ross Sea, are capable of rising above challenges presented by nature, it can be difficult or impossible for them to evolve quickly enough to face challenges brought on by human industry. In order to halt this catastrophic extinction event that has already begun, immediate action is needed. Legislation must be passed to protect natural habitats, awareness must be raised for issues affecting wildlife around the world, and small changes must be made in each of our lives to benefit the Earth instead of exploiting it. It is up to humans to help the ecosystem return to its natural state, for the benefit of ourselves and all other organisms that call the Earth home.

What do you think about penguins and how they capture prey? Would love to hear what you think, what you learned, and more!

 

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