Saturday, December 4, 2010

Gentle Giants and Graceful Grazers; A Look at the Florida Manatee

The Florida manatee, Trichechus manatus latirostris, is known for its gentle nature and lumbersome ways. Its nickname, the sea cow, comes with good reason. This mammal spends nearly 8 hours out of its day doing nothing but eating, yes nothing but eating. During these 8 hours of munching, the manatee can consume about 7.5% its own body weight in food per day. Their diet consists of over 60 different types of aquatic plants including turtle grass, mangrove leaves, and types of algae. That is a lot of food considering adult manatees can reach nearly 10 feet long weighing in at around 1,500 lbs. That is a big cow! A unique aspect of the manatee is that it is the only herbivorous mammal that is specifically designed to live the entirety of its live in the water.

The Florida manatee is found in the southeastern part of the U.S. mainly in Florida. Its main habitat consists of coastal wetlands and the warm waters of shallow rivers, bays, and estuaries. They can be found in several different parts of Florida including the North and Southwestern Florida, the Atlantic coast, and St. Johns River along with the Gulf. In these areas, not all of the water is salt water and the sea cows can survive in saltwater as long as there is freshwater nearby and available. They are also found in brackish areas. During the winter months, they will travel further into the gulf and gather in the rivers and the natural springs located there. The internal temperature of a sea cow is 97.5 degrees Fahrenheit and if the temperature of the water that they are in reaches below 65 degrees Fahrenheit, they can get "cold stress syndrome" and can possibly die.

While in the water, manatees have been clocked at swimming nearly 20 miles an hour, however they typically only swim at around 3-6 miles per hour, doing somersaults and barrel rolls and can be seen gliding through the water upside-down. To swim, the manatee uses its forearms that are reduced to simple paddles that are used for steering and also are flexible enough to help bring food towards its mouth and to scratch their eyes and face. These paddles each have 4 nails at the tip of each and the rear paddle, or tail, is where the manatee gets its power while swimming. Although the manatee is designed to live in the water for its entire life, it does take breaks from eating and sleeping to come to the surface and take a breath. In fact, the manatee takes a breath every 3 to 4 minutes during activity but can hold its breath for up to 20 minutes during rest. The reason that a manatee can hold its breath for so long is because the lungs in an adult can reach nearly 3 feet in length and when it takes a breath, it can replace up to 90% of the air versus humans who only replace 10%. This air also aids in buoyancy.

Another really cool aspect of the manatee is that its bones are solid and do not contain any marrow or hollow cavities and this is too help the manatee be able to sink to eat the aquatic plants off of the river bed. The bones help to indicate age as well with the growth layers. In the wild, a manatee can live upwards of 50-60 years and in captivity just short of around 65 years. Their lifespan is so long because the manatee has not natural predators and its only threat are people and the cold weather. Boat propellers and jet skis are a huge threat to the manatees along with habitat destruction. The numbers of manatees is declining in the wild because of those previously mentioned and also because they have a very slow reproduction rate. They only have one calf every 5-7 years with a 12 month gestation period. Females also do not typically breed until the age of 6-10 years.

Sea cows are gray to brown in color with small, widest set eyes and they have ears that lack external lobes. Since they eat so many plants, they are hind-gut fermenters with a very long digestive tract. Because they are constantly eating, they need to have great teeth to withstand the grinding. With this wear and tear on the teeth, they continuously replace their back molars. The molars erupt from the back of each jaw and pushes forward, forcing out old teeth at the front .

I looked at a study done at the University of Florida on the material properties that make up the rib in manatees. This is so interesting because the ribs in manatees are completely solid to help with the density to sink the bottom to graze without using mush energy. However, even though they sink to eat, they still get hit by boats and other water craft. This is analyzing what kind of impact these bones can withstand to be able to better mark speeds that boats can travel in manatee areas. The results show that manatee bone is not as strong and tough as other mammalian bone. Their bones cannot absorb much in the way of energy or impact leading to more fatalities of these creatures when hit by boats. This decrease in energy absorption is because of the density and mineral content of the bone. This was tested by examining the strength, modulus, work of fracture and fracture toughness.




Sources-

Tuesday, November 30, 2010

The Red Panda

Red Panda

Ailurus fulgens

Habitat:

Red pandas live in the Himalayan Mountains in bamboo forests, spanning across Nepal, India, Bhutan, and Myanma. They enjoy the moist cool air at elevations of 7000-15500 feet.

Food Source:

Like there giant panda relative the red panda survives mostly on a diet of bamboo. They must constantly eat in order to maintain their body weight, even eating up to 200,000 bamboo leaves a day.

Intriguing Facts:

They have an incredibly low metabolic rate, similar to that of a sloth. So this animal rests up in the trees for almost 15 hours a day. They spend almost all of their waking time eating. They are solitary creatures, only coming in contact with other red pandas during mating season. Due to habitat loss the red panda is one of the most endangered species on the planet, it is estimated only 2500 individuals remain.

Resent Research:

The current phylogeny of the red panda is debated. Some scientist debate that it is more closely related to the raccoon, while others suggest it is more closely related to the bear. Others still suggest that it should be placed in a family all its own. The research done by the Chinese University of Science seeks to better understand the red pandas elusive phyologeny. They analyzed the: “interchromosomal rearrangements and amplic-cation of repetitive sequences have played a major role in differentiating the karyotypesof the mustelid species.” Their results showed that the red panda is closely related to the mustelids, or weasel family. This is certainly an interesting find and more genomic research is currently being done, fossil analysis must also be done to confirm the phylogeny thoroughly.

Sources:
General info- http://www.edgeofexistence.org/mammals/species_info.php?id=19 and http://www.centralparkzoo.com/animals-and-exhibits/animals/mammals/red-panda.aspx

Research- http://www.springerlink.com/content/uvnvj8x37ytcmnkt/

Special Little Swimers


The otter is one of my favorite animals not only because its cute but because it is interesting. The otters we saw at the zoo are North American River Otters(Lontra Canadensis) which obviously live in North America as the name says. They can be found in most rivers throughout the entire continent and exist here in Ohio. They usually eat fish, crayfish, and crabs since they spend most of their time in the water but can occasionally eat small birds and rodents. They are very specialized for water life and are able to close their ears and nose, have a clear third eyelid called a nictitating membrane, webbed feet, and they can hold their breath for up to 8 minutes. They also have claws that are useful if they happen to venture onto land or need to build their dens.

In a recent study researchers studied the patterns of these otters moving throughout Minnesota. A group of otters was monitered for multiple seasons and things such as time of day, temperature, weather etc. were observed. The otters were most active in the evening and least active around mid-day. It was also found that there was more activity during mating season and less during winter. Although there was less winter activity in general there was more foraging for food probably because of the increased energy needs for temperature regulation. There was also increased activity in males compared to females. Although the authors hypothesize that it may be because of differing diets, or different energy needs
they did not test these hypotheses.


Zoo otter info
Otter research study

The North American River Otter (Lontra canadensis)

Basic Information
These very social, playful aquatic animals are members of the weasel family of the order Carnivora. Their bodies are highly modified for a life spent mostly in and around the water. These modifications include a streamlined body, webbed feet, thick, water-repelling, insulating fur, a tapered tail, and small ears and nasal openings that can close underwater!

Habitat and Range
These river otters live in mainly the northern U.S., the coastal states, and parts of Canada in and close by any inland waterways.

Diet
River otters will eat many different types of freshwater creatures including fish, crayfish, small mammals, frogs, mollusks, and other small invertebrates.

Life History
Females give birth to one to six young in their underground burrows. Males do not take part in the care of the young. After about 2 months of mainly being in the burrow, the mother pushes the young otters into the water, forcing them to learn how to swim while she supervises.

Primary Research
I looked at two current research articles on the North American River Otter, one explored the impact of an invasive trout species on the otter populations in Yellowstone National Park and the other was written about an attempt to reintroduce the river otters to waterways in Indiana.

The paper about the invasive species of Lake trout being found in increasing amounts in several lakes in Yellowstone National Park, revealed that although some other species of piscivores (fish-eaters) such as the grizzly bear and some birds are being impacted by the replacement of the endangered Yellowstone cutthroat trout with the invasive lake trout, the river otter is doing fine. The river otter eats a variety of different fish, so replacing one of its major food types with the invasive species of trout does not change anything except now more of the river otter's diet is made up of lake trout rather than the cutthroat trout.

The second paper spoke about the attempt to reintroduce the North American river otter to Indiana after the species had disappeared from the state in 1942 due to fur trapping, loss of habitat, and food. The attempt had mixed results in that many of the original otters introduced from surrounding states were killed by various means just as they were before. However, some good was achieved and many of the otters did begin breeding and establishing themselves in certain regions of the state. The paper stated that the researchers conducting this experiment did need to look further into ways to protect, maintain, and regulate these restored populations as well as defining the exact occupied regions and certain age-specific reproductive patterns.

Resources

1. http://animals.nationalgeographic.com/animals/mammals/american-river-otter.html
2. Kelt, D; Johnson, M. (2010) Ecological consequences of invasive lake trout on river otters in Yellowstone National Park. BIOLOGICAL CONSERVATION, 143, 5, p. 1144-1153.
http://journals.ohiolink.edu/ejc/pdf.cgi/Wengeler_William_R.pdf?issn=00063207&issue=v143i0005&article=1144_ecoiltroiynp
3. Walker, H; Hudson, C; Hewitt, T; Thompson, J. (2007) Prospects for restoring river otters in Indiana. Proceedings of the Indiana Academy of Science, 116, 1, p. 71-83.
http://web.ebscohost.com/ehost/pdfviewer/pdfviewer?hid=18&sid=a7a05636-c0b2-4db4-b24a-160dd978c61a%40sessionmgr15&vid=2

Monday, November 29, 2010

This Should Lure You In.....


The alligator snapping turtle, Macrochelys temminckii, is found in lakes and streams in the south eastern region of the United States and can be found into Canada. The largest specimen ever formally recorded was a 236 pound alligator snapper at the Brookfield Zoo in Chicago. On average, these turtles generally grow to a carapace length of 26 inches and weigh up to 175 pounds. These turtles got their name from the three pronounced ridges that are on the carapace which resemble those of the alligator. Often called the dinosaur of the turtle world, these interesting turtles are very primitive in appearance. These turtles can live anywhere from 50-100 years!

Alligator snapping turtles are scavengers by night and hunters by day. During the day, the use a specialized section of their tongue, which resembles a worm, to lure in prey. When the lure is in use, it fills with blood giving it the red color of a worm. To help with camouflage, the deep ridges of the turtle's shell become covered with algae helping to blend their shell into the substrate. The inside of the turtles mouth is grey in color and also blends in with its surroundings.

These turtles mate in early spring and nest 2 months later. The female will lay her eggs about 50 yards from the water's edge and this is the commonly the only time these turtles will leave the water. A clutch of eggs can contain 8-52 eggs and incubation lasts anywhere from 100 to 140 days. Sex is determined by the temperature of each individual egg during incubation.

A study produced by the Louisiana Department of Wildlife and Fisheries in 2006 titled "Food Habits of Macrochelys temminckii from Arkansas to Louisiana" includes interesting information on the food habits of these interesting turtles. This experiment was carried out by investigating the stomach contents and intestinal tracts of 109 alligator snapping turtles from both Arkansas and Louisiana. One of the first findings of the study was that a positive correlation between body mass and stomach content was discovered. This means that the larger a turtle was, the more food it consumed. Contents of the stomach and intestinal tracts included the following in order of most common: fish, crayfish, mollusks, turtles, insects, and nutria. Most surprisingly mammals were found in the digestive tracts of these primitive looking turtles. It is just another connection to the alligators from which they got their common name. Mammals that were found in their stomach include; Dasypus novemcinctus (armadillo), Didelphis virginiana (Virginia opossum), Sciurus sp. (squirrel), and Sus scrofa (hogs). The take home message from this study is that alligator snapping turtles are opportunistic scavengers and have the ability to consume a wide variety of prey.


Sources:
Turtle info: http://animals.nationalgeographic.com/animals/reptiles/alligator-snapping-turtle/
http://www.tortoise.org/archives/snapping.html
Louisiana Study:http://web.ebscohost.com/ehost/pdfviewer/pdfviewer?vid=4&hid=17&sid=9c803ba8-173d-4f22-82b9-5300ed2f3730%40sessionmgr12

Caribbean flamingo


Caribbean flamingo
Phoencopterus ruber ruber

Habitat: North and South America; mud flats, shallow lakes, and salt lagoons

Food source: Filter feed on algae, crustaceans, seeds, small fish, insects, and mollusks

Interesting facts: Both male and female flamingos produce crop milk which is used to feed the juvenile flamingos while they are young. Flamingos typically only lay one egg at a time.



Recent research: There has always been a common question surrounding the way that flamingos rest. Flamingos are known for resting on one leg. The common question is: Why do the flamingos only stand on one leg and not two. Recently studies (Anderson 2009) have found that resting on one leg may help the flamingos in thermoregulation.

Because flamingos are filter feeders, they heavily rely on the health of their beak and tongue to survive. Another fairly recent study (Hammer 2007) showed that if flamingos eat foods that are too greasy, they can have a build-up that will hinder their filter feeding ability.


Anderson, Matthew J. and Sarah A. Williams. “Why do flamingos stand on one leg?” Zoo Biology 29:365-374 (2009).

Hammer, Sven, Simon Jenson, Raffy Borjal, and Marcus Clauss. “Bill impaction in a group of captive Caribbean flamingos (Phoenicopterus ruber).” Journal of Zoo and Wildlife Medicine 38(3): 465-470 (2007).

Alligator snapping turtle

Physical description
With large heads and powerful jaws, alligator snapping turtles (Macrochelys temminckii) are the largest freshwater turtles in the world.  They can be easily distinguished by the three large pronounced ridges that run from front to back on the carapace. The fact that they have eyes on the sides of their heads makes them unique.


[Picture of an alligator snapping turtle (M. temminckii) that I took while at the Columbus Zoo]

Habitat
Alligator snapping turtles live in freshwater areas in the southeastern United States. Adults live in deep lakes and ponds, while juveniles are usually found in smaller rivers and streams.

Diet
Alligator snapping turtles are hunters and sometimes scavengers. They sit still with their mouth open, using their tongue to lure in fish. Alligator snapping turtles will also eat molluscs, crayfish, insects, leaves, roots, tubers, nuts, and seeds, and aquatic plants, but their diet mainly consists of fish. They may even eat other turtles; in one Louisiana study, turtles were found in the stomachs of just under 80% of all alligator snapping turtles.

Habitat Study
By attaching radio transmitters to alligator snapping turtles in Arkansas, Howey and Dinkelacker found how they choose habitats throughout the year. Both males and females showed a high preference for aquatic sites with large amounts of submerged debris and canopy cover. This may be due to increased prey abundance near debris and higher chance of nuts and seeds falling from canopy cover. Also, more cover allows for more places for the alligator snapping turtles to hide from predators. Howey and Dinkelacker also found that both sexes prefer deeper water or stream banks during the summer months for easier thermoregulation. This allows them to sun themselves to warm up, and go underwater to cool off.


Sources:

AnimalDiversityWeb. (2010, November).  Macrochelys temminckii. Retrieved November 29, 2010, from

Howey, C. A. F. & Dinkelacker, S. A. (2009). Habitat Selection of the Alligator Snapping Turtle (Macrochelys temminckii) in Arkansas. Journal of Herpetology, 43(4), 589-596. doi:10.1670/08-105.1

The Cause of the Extinction of the Australian Megafauna is...



...Humans!?!

Yes, several findings and papers link the migration of humans to the Australian continent to the eventual extinction of many of Australia's existing megafauna, including giant marsupials such as the gigantic kangaroo, Procoptodon, the two ton wombat-like marsupial, Diprotodon, and the half ton Palorchestes azael, an extinct Australian giant marsupial which was similar to a ground sloth, giant reptiles, and flightless birds.

Humans arrived on the Australian continent between 60,000 and 45,000 years ago and fossil records place the megafauna extinctions to have completed by around 46,000 years ago. For some time, the large Australian animals and humans might have coexisted but eventually most of the megafauna were driven to extinction. Researchers believe this was because humans were hunting the megafauna for a food source. The conflicting argument that other scientists have is that climate caused the extinctions, similar to many of the other extinctions that have occurred in history.

There is supporting and conflicting evidence for both hypotheses. The fact that the large animals went extinct shortly after the supposed arrival of humans supports the theory that humans were a driving force for the extinction of these great animals. However, several sites, especially one particular controversial site known as Cuddie Springs (it is controversial because some researchers have said the layers of rock may have moved or been moved, with some much older fossil rock pushing up into more recent rock with human tools), have shown sedimentary rock layers with both prehistoric man-made tools and megafauna fossils in the same time period, showing that humans and these large Australian animals may have coexisted for several thousand years before some other event occurred or maybe until humans eventually hunted them to extinction anyway. That other event could have been a climate change, because evidence has shown that that period of the Last Ice Age had above average aridity. However, evidence against climate being a factor was that these animals were already evolved for the drier conditions since the climate had been fairly arid for several thousand years, and when these animals went extinct, the climate was fairly calm and tolerable.

The argument goes both ways on how these great megafauna went extinct: climate or humans, and many scientists see the situation as unresolved. So, maybe it was not the Australian ancestors who had the major role in the extinction of the Australian megafauna?

(The image above is an artist's reconstruction of the half-tonne Palorchestes azael, an extinct Australian giant marsupial which was similar to a ground sloth. (Credit: Courtesy of Peter Schouten))

Source Articles
http://www.sciencedaily.com/releases/2010/01/100121141109.htm
http://www.nature.com/news/2010/100123/full/news.2010.30.html

Captive female Koala's are bisexual


Queensland Koala (Phascolarctos cinereus adustus)
Diet: Eats about one pound of leaves a day (from both eucalyptus and non-eucalyptus trees)
Habitat: Eucalyptus forests in Australia
Reproduction: Breeding season is between October and February, males mate with several females, gestation lasts 34 to 36 days after which a single koala baby is born, the 2 ounce baby stays in it's mothers pouch for another 7 months.
Notes: Sleep about 18 hours a day, males are up to 50% larger than females and have broader faces
Homosexuality has been observed in many classes of vertebrates. Interestingly, a study by Feige et. al (2007) found that female koalas exhibit both heterosexual and homosexual behaviors in captivity. However, in the wild only heterosexual mating has been observed. Homosexuality in solitary mammals, like the koala, is usually only seen under two conditions: one, limited numbers of a certain sex dictates the need for reproductive success through homosexuality; and two, when kept in captivity, homosexuality is used to relieve stress and exhibit dominance. In the wild, male koalas make a loud acoustic bellow to attract mates or defend their territory from other males. Female bellows have not been recorded in the wild. In captivity, this bellowing sound is made by both males and females. In captivity, female bellows may be used to alert males when she is ready to mate, or to warn males when she is not ready to mate. In this study, a total of 43 homosexual and 15 heterosexual interactions and were made by females. Copulation behavior with other females is very similar to the behavior exhibited by heterosexual mating. One factor to consider in this study is females were housed in single-sex enclosures, where more than one female may be ready to mate and competition for males is high. Studies have found that homosexual behavior in koala's is not spontaneous, but is usually in response to the presence of a male. However, homosexual behavior is not used to attract a male, because males are not drawn to homosexually engaged females. Some females in this study rejected the males only to begin mating behaviors with other females. This is not unique to Koalas, and seems to be in response to increased stress or increased frequency of sexual encounters. Another study reported that homosexual interactions made up 11% of the interactions of captive female koalas, and is most likely due to the skewed sex ratio among the captive population. "It is likely, therefore, that rather than having adaptive significance which is unlikely in a short-lived captive population, the homosexual behaviour observed is an expression of a hard-wired behavior that is stimulated in the hypothalamus in the presence of elevated oestradiol concentrations." It seems that homosexual activity may serve as a stress release for captive female koalas.



Sources:
Feige, S., Nilsson, K., Phillips, C. J., , & Johnston, S. D. (2007). Heterosexual and homosexual behaviour and vocalisations in captive female koalas Phascolarctos cinereus. Applied Animal Behaviour Science, 103(1-2), 131-145. doi:10.1016/j.applanim.2006.03.014
http://www.thebigzoo.com/Animals/Queensland_Koala.asp
image from: http://abundancesecrets.com/motivational-posters/index.php?item=3160767

Zoo Post: Manatee



The manatee (Trichechus manatus) also know as the sea cow is a large herbivorous aquatic mammal, and the largest surviving member of the aquatic mammal order Sirenia (which also includes the Dugong and the extinct Steller's Sea Cow). The weights of these creatures can range from 880lbs to 1200lbs and are usually between 9 and 10 feet long. They can max out at almost 12 feet and 4000 lbs! They have a large flexible prehensile upper lip that acts in many ways like a shortened trunk, somewhat similar to an elephant's. They use the lip to gather food and eat, as well as using it for social interactions and communications. Their eyes are small and widely spaced, and are covered by eyelids that close in a circular manner. The adults have no incisor or canine teeth, just a set of cheek teeth, which are not clearly differentiated into molars and premolars. Uniquely among mammals, these teeth are continuously replaced throughout life, with new teeth growing at the rear as older teeth fall out from farther forward in the mouth (like sharks). At any given time, a manatee typically has no more than six teeth in each jaw of its mouth. Like horses, they have a simple stomach, but a large cecum, in which they can digest tough plant matter. In general, their intestines are unusually long for animals of their size.

The manatee spends most of its time either sleeping, or grazing in shallow waters. They usually surface for air close to every 20 mins, and have been know to live close to 60 years. Their average speed is around 5 mph but can reach a top speed of 20 mph, but only short bursts. Manatees are capable of understanding discrimination tasks, and show signs of complex associated learning and advanced long term memory. They demonstrate complex discrimination and task-learning similar to dolphins and pinnipeds in acoustic and visual studies. They enjoy warmer waters and are known to congregate in shallow waters, and frequently migrate through brackish water estuaries to freshwater springs. Manatees cannot survive below 15°C. Their natural source for warmth during winter is warm-spring fed rivers.

Current research on this mammal is mainly geared toward studying social interactions and behaviors. The sea cow is dieing more and more each day due to habitat loss and human interactions. Colder water temperatures are killing these creatures, and many are found with large cuts and gashes on their backs from boat engines. Since they feed in shallow water they are easy hit by propeller blades. They study I looked at watched the behavior of captive manatees in Mexico, They studied 2 adults, 1 sub adult, and 1 calf. The behavioural strategies of the manatees included (1) during the day, mainly foraging, feeding, and remaining inactive, and (2) evening activities were divided among social interaction, environment exploration, and resting activities. All the behaviour patterns of the captive manatees seemed to be influenced by the feeding schedule during the day. The number of contacts between manatees increased strongly at night, each individual having a preferred partner for social interaction. The cow-calf dyad showed the highest intensity of contacts, whereas subadults showed the lowest.

Refernces

Hénaut, Yann. "Activities and social interactions in captive Antillean manatees in Mexico." Mammalia. 74.2 (2010): 141-146.

Sunday, November 21, 2010

Takin' a Penguin to prom? He already has a Tux!


Melanosomes are organelles–cell parts–responsible for producing the pigment melanin. These tiny bits of biology can be preserved in fossils, which have led to some really cool papers. Scientists have now recovered melanosomes from dinosaur fossils, for instance; the pigment allowed researchers to determine how certain dinosaurs were colored.
Fossilized feathers from an ancient penguin species, Inkayacu paracasensis

A new study, reveals another neat use for fossilized melanosomes–tracing the evolutionary history of the penguin. The birds have remarkable feathers, perfectly designed not only to allow the penguins to glide through the water at high speeds but also to insulate them from the breathtaking cold. For these reasons, and others, penguins’ feathers are radically different than those of other birds.

The new research begins to reveal how these multitasking feathers evolved. The scientists studied the 36 million year old fossilized feathers of Inkayacu paracasensis, a newly discovered species of giant penguin that stood five feet tall. From the outside the feathers looked just like those of modern penguins, with the same streamlined shape and dense packing.

But the melanosomes told a different story, revealing that the ancient penguin would have displayed gray and reddish-brown patterning. Today’s penguins, on the other hand, have melanosomes that make them look black. The findings suggest that the exterior of penguin’s feathers evolved first and that only later did the interior of the feathers, with their melanosomes, change.

Artist's reconstruction of Inkayacu paracasensis

Among the coolest things of this paper is the very end, when the researchers write about what could have driven the color change. Previous studies have suggested that melanin can protect feathers from breakage and damage. Penguins swim underwater at incredible speeds (in what’s known as “aquatic flight”) and their feathers must withstand enormous pressures and forces. Birds with more melanin–and, therefore, darker feathers–may have had a survival advantage. That cute black suit that makes us flock to the theaters to see movies about penguins? Perhaps that’s just an unintended–if handsome–side effect.

REFERENCES:

Julia A. Clarke, Daniel T. Ksepka, Rodolfo Salas-Gismondi, Ali J. Altamirano, Matthew D. Shawkey, Liliana D’Alba, Jakob Vinther, Thomas J. DeVries, Patrice Baby (2010). Fossil Evidence for Evolution of the Shape and Color of Penguin Feathers. Science : 10.1126/science.1193604