Orangutans Count on Stats for Survival

ScienceDaily (Nov. 20, 2010) — Orangutans threatened with extinction could be brought back from the brink with help from a Queensland University of Technology (QUT) statistician.

Professor Kerrie Mengersen, from the School of Mathematical Sciences, is part of a study to guide efforts for saving the Indonesian primate whose name means "person of the forest."

Professor Mengersen said the study had found a quarter of villagers who lived side-by-side with orangutans did not know it was illegal under Indonesian law to kill the primates, and five per cent admitted to killing 1000 orangutans last year.

Professor Mengersen is participating in the study run by The Nature Conservancy (TNC) in their quest to protect orangutans in the Indonesian states of Borneo and Sumatra.

She designed and led the statistical analysis of the study's survey, which was completed by almost 7000 villagers.

In addition to learning about the location and abundance of remaining orangutans, the study investigated issues of conflict and hunting.

"Killing rates of more than one per cent of the orangutan population per year are thought to lead to certain extinction in local areas, but the survey results indicate rates of local killing may be much higher than this," Professor Mengersen said.

"Just over half of the killings were reportedly for food, followed by more than 10 per cent each for self-defence, crop protection and unspecified reasons.

"Very few reported killing for traditional medicine, selling orangutan babies for the pet trade, hunting for fun or being paid to kill."

Professor Mengersen said by identifying factors related to the killing, education campaigns could be tailored to specific areas and cultural groups.

"Not a single conservation program is effectively targeting orangutan hunting at present," she said.

"There appears to be a role for increased education about protection of orangutans under Indonesian law."

Professor Mengersen said the survey also found villagers felt overwhelming support for the forest, saying it contributed to their health and culture, but also appreciated the wealth, schools and health services provided where forest was cleared for industry, such as palm oil and eucalypt plantations.

"Through the work of TNC and others, and through the use of powerful statistical modelling, we can learn from the wealth of knowledge vested in these 'eyes and ears' of the forest and learn how to work more effectively towards goals for the conservation of orangutans," she said.

Professor Mengersen's findings have been published in the journal Significance, published by the Royal Statistical Society and the American Statistical Association.

El Origen de los Llamativos Patrones del Pelaje de Leopardos y Tigres

17 de Noviembre de 2010.

¿Por qué los leopardos tienen marcas en forma de rosetón pero los tigres tienen rayas? Rudyard Kipling sugirió que fue consecuencia de que el leopardo se trasladó hacia un entorno lleno de árboles y matorrales. ¿Pero hasta qué punto es cierta esta hipótesis?

Un equipo de investigadores en la Universidad de Bristol decidió analizar las marcas corporales de 35 especies de felinos salvajes en un intento de averiguar qué mecanismo exacto dirige la evolución hacia variaciones tan bellas como desconcertantes. Estos científicos profundizaron en los entresijos de las distintas pautas de coloración de los felinos, gracias a vincularlas a un modelo matemático de desarrollo de patrones.

Y han encontrado que los felinos que viven en entornos densos, como por ejemplo en los árboles, y están activos con niveles de iluminación bajos, son los que con mayor probabilidad acaban desarrollando esos patrones, sobre todo los complejos e irregulares. Esto sugiere que tales patrones surgen evolutivamente para que el animal se confunda mejor con su entorno. El análisis de la historia evolutiva de los patrones muestra que pueden evolucionar y desaparecer con bastante rapidez.

La investigación también explica por qué, por ejemplo, los leopardos negros (panteras) son comunes pero no se conocen guepardos negros. A diferencia de los guepardos, los leopardos viven en una amplia variedad de hábitats y tienen diversas pautas de conducta. La existencia de varios nichos ecológicos que individuos diferentes de la especie pueden explotar permite que patrones y colores atípicos se vuelvan estables dentro de una población.

El estudio también ha profundizado en la cuestión de la escasa cantidad de especies de felinos que tienen rayas verticales. De las 35 especies examinadas, sólo los tigres tenían siempre patrones alargados verticalmente, y estos patrones no estaban asociados con un hábitat de pradera, como se podría esperar. Sin embargo, los tigres parecen estar muy bien camuflados, así que esto conduce a la pregunta de por qué las rayas verticales no son comunes en los felinos y en otros mamíferos.

El equipo de Will Allen, de la Universidad de Bristol, está ahora aplicando a otros grupos de animales el método que ha desarrollado para este estudio sobre los patrones del pelaje de felinos.

La Relación del Ser Humano con el Perro está Cambiando Drásticamente el Cerebro de este.

Por primera vez, se ha demostrado científicamente que la cría selectiva de perros domésticos no sólo está transformando radicalmente la apariencia de estos animales, sino que también está generando grandes cambios en el cerebro canino.

Según los investigadores, los cerebros de muchas razas de perros de hocico corto han rotado hacia delante tanto como 15 grados, mientras que la región cerebral que controla el olor, se ha reubicado.

Las grandes variaciones en el tamaño y la forma del cráneo del perro son el resultado de más de 12.000 años de cría en busca de características funcionales y estéticas.

El descubrimiento de esta importante reorganización del cerebro canino hace que nos preguntemos sobre su impacto en el comportamiento del perro.

El equipo del Dr. Michael Valenzuela, formado por investigadores de la Universidad de Nueva Gales del Sur, Australia, y la Universidad de Sídney, utilizó imágenes obtenidas por resonancia magnética para examinar los cerebros de una amplia gama de razas. Descubrieron correlaciones fuertes e independientes entre el tamaño y forma del cráneo de un perro, y la rotación del cerebro y el posicionamiento del lóbulo olfativo.

Ningún otro animal ha contado con el nivel de afecto y compañerismo humanos como el perro, ni ha sido sometido a una influencia sistemática y deliberada en su biología a través de la cría. La propia diversidad canina sugiere un nivel notable de plasticidad en el genoma canino.

Tal como el Dr. Valenzuela indica, los canes parecen ser increíblemente sensibles a la intervención humana a través de la cría. Es asombroso que el cerebro de un perro pueda adaptarse a diferencias tan grandes en la forma del cráneo a través de este tipo de cambios. Es algo que no se ha registrado en otras especies.

El siguiente paso obvio en esta línea de investigación, será tratar de averiguar si estos cambios en la organización cerebral también están vinculados a diferencias sistemáticas en las funciones cerebrales de los perros.

Simple Rubber Device Mimics Complex Bird Songs

ScienceDaily (Nov. 21, 2010) — For centuries, hunters have imitated their avian prey by whistling through their fingers or by carving wooden bird calls. Now a team of physicists at Harvard University in Cambridge, Massachusetts, has reproduced many of the characteristics of real bird song with a simple physical model made of a rubber tube.

"We wanted to know if you [could] build a simple device, which has minimal control but reproduces some non-trivial aspects of bird song," says L Mahadevan, a professor at Harvard. The work was presented at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, CA on November 21.

Bird song -- a complex sound full of intricate patterns and rich harmonics -- has long been studied by neuroscientists. Their research has explained much about how young birds learn these songs from adults and the complex neurological changes that allow them to control their voices.

But Aryesh Mukherjee, a graduate student in Mahadevan's laboratory, suggests that this neural control need not be as complicated as it could be. He suspects that the physics of a bird's vocal tract could explain much of the complexity of its voice, even with relatively simple neural control.

His bird call device consists of an air source, which creates a flow through a stretched rubber tube (modeled after a bird's vocal tract), and a linear motor that presses on the tube in a fashion analogous to a contracting muscle.

"Using this very simple device that pokes a tube, I see these beautiful sounds being produced without a sophisticated controller," says Mukherjee.

When analyzed on a spectrogram, the harmonics and other characteristics of the sounds made by the physical model closely resemble the songs of a zebra finch.

Another researcher in the lab, Shreyas Mandre, now an assistant professor at Brown University, is building mathematical models that seek to capture some of the underlying principles. His model, which represents the voice as a stretched string with dampened vibrations, creates digital bird calls that are also very similar to the real thing.

"Once we understand the physics better, we'll be able to mimic the sound much better," says Mandre.

The principles underlying the models aren't limited to single species of birds. The researchers believe that -- with a few tweaks -- their models could mimic a variety of bird calls.

Los Inusuales Colores de un Pingüino Extinto

5 de Noviembre de 2010.

Un equipo de paleontólogos ha desenterrado el primer pingüino extinto con vestigios de escamas y plumas lo bastante bien conservados como para desvelar con un grado razonable de certeza el color que tuvieron en vida del animal.

El fósil, de 36 millones de años de antigüedad y proveniente de Perú, muestra que las plumas de este singular pingüino gigante, de una especie hasta ahora desconocida, eran de color gris y marrón rojizo. El aspecto de estos pingüinos antiguos era por tanto muy diferente del típico de los actuales, esencialmente con una coloración blanca y negra.

La nueva especie, Inkayacu paracasensis, tenía casi 1,5 metros de altura y era cerca de dos veces más grande que un pingüino emperador, el pingüino más grande de la actualidad.

Antes de este fósil, no había evidencias claras sobre las plumas, colores y formas de las aletas de los pingüinos del pasado lejano.

El fósil muestra que las formas de las aletas y plumas, que hacen que los pingüinos sean nadadores tan eficaces, evolucionaron tempranamente, y que los patrones de color de los pingüinos modernos son una innovación reciente.

Conocer los colores de un organismo extinto puede permitir obtener indicios sobre su ecología y conducta.

El Inkayacu paracasensis fue descubierto por Ali Altamirano en la Reserva Nacional de Paracas, Perú. Lo descubierto en esta nueva investigación se suma a los hallazgos hechos en trabajos anteriores por la paleontóloga Julia Clarke (Universidad de Texas en Austin) y sus colegas en Perú, que retan la teoría convencional sobre la evolución temprana del pingüino. El Inkayacu y otros hallazgos muestran que había una rica diversidad de especies gigantes de pingüino en el periodo Eoceno tardío (hace entre 36 y 41 millones de años aproximadamente) en las tierras bajas de Perú.

Además de Clarke, entre los paleontólogos que han llevado a cabo esta nueva investigación figuran Matthew Shawkey y Liliana D'Alba (Universidad de Akron) y Jakob Vinther (Universidad de Yale).

Bat Brains Offer Clues as to How We Focus on Some Sounds and Not Others

ScienceDaily (Nov. 15, 2010) — How do you know what to listen to? In the middle of a noisy party, how does a mother suddenly focus on a child's cry, even if it isn't her own?

Bridget Queenan, a doctoral candidate in neuroscience at Georgetown University Medical Center is turning to mustached bats to help her solve this puzzle.

At the annual meeting of the Society for Neuroscience in San Diego, Queenan reports that she has found neurons in the brains of bats that seem to "shush" other neurons when relevant communications sounds come in -- a process she suggests may be working in humans as well.

In her investigations, she has also found that "some neurons seemed to know to yell louder to report communication sounds over the presence of background noise."

"So we can now start to piece together how the cells in your brain are able to deal with the complex sensory environment we live in," Queenan added.

To understand auditory brain function, bats are especially interesting animals to study because they process sound through echolocation, which is a kind of biological sonar. Bats call out and then listen to their own echoes produced when those calls bounce off nearby objects. Bats use these echoes to navigate and to hunt.

Not only do the brains of bats have to process a constant stream of pulses and echoes, they have to simultaneously process the bats' social communication, Queenan says.

"What we are trying to figure out is how a bat can fly around echolocating -- screeching and listening to its own individual sounds bouncing back -- amidst a whole colony of hundreds of other echolocating bats -- and possibly hear another bat saying 'watch out! Bats actually do make these cautious calls quite a bit," she says. "In fact, bats have a whole host of communication sounds: angry sounds, warning sounds, and sounds that says 'please don't hurt me."

The auditory processing area in bats' brains is larger than other centers, just like the visual processing center in humans is large. "Humans operate predominantly by sight so a huge portion of our brain is devoted to vision processing. Bats, however, operate by sound," Queenan says.

In this study, Queenan and her colleagues presented different combinations of echolocation sounds with various communication sounds to awake bats to see how neurons in the bat brains were dealing with this incredible cacophony. The researchers found that some bats' neurons control the activity of other neurons when important sounds are perceived. These GUMC scientists also found other neurons that amp up perception of bat communication in the face of background noise. Working together, these clumps of neurons allow the bats to hear what is needed.

"All organisms are constantly assaulted by incoming stimuli such as sounds, light, vibrations, and so on, and our sensory systems have to triage the most relevant stimuli to help us survive," Queenan says. "As humans we are not only sensitive to a child's cry, but we notice flashing ambulance lights even though we are engrossed in something else. We want to know how that happens."

Queenan says her next task is to record brain neurons in bats that are not only awake, but flying

El Terrible Chupacabras es Tanto Víctima Como Villano

10 de Noviembre de 2010.

Con la llegada de Halloween suelen abundar las historias de monstruos y criaturas macabras. Entre los más temidos se cuenta la bestia legendaria conocida como “chupacabras”.

Pero el monstruo real no es el animal pelado y con colmillos que, supuestamente, ataca al ganado y chupa su sangre, sino una criatura pequeña, de ocho patas, que convierte a un animal salvaje y sano en un “chupacabras”, dijo el biólogo de la Universidad de Michigan, Barry O’Connor.

La existencia del “chupacabras” se mencionó por primera vez después de ataques contra el ganado en Puerto Rico donde se encontraron ovejas muertas y con heridas punzantes, sus cuerpos totalmente drenados de sangre. Informes similares empezaron a acumularse de otros sitios en América Latina y Estados Unidos. Provinieron de personas que decían haber visto animales de aspecto maligno, descritos tanto como parecidos a perros como a roedores, o reptiles, con largos hocicos, enormes colmillos, una piel correosa o con escamas verdosas y un olor muy desagradable. Los lugareños juntaron una y otra cosa y llegaron a la conclusión de que las alimañas feas eran responsables por las muertes.

Los científicos que estudiaron algunos cadáveres de chupacabras llegaron a la conclusión de que los temidos monstruos eran realmente coyotes con casos extremos de escabiosa o sarna, una condición de la piel causada por ácaros que se alojan debajo de la piel. O’Connor, que estudia los ácaros que causan el escabio, está de acuerdo y tiene una idea de por qué los diminutos atacantes afectan a los coyotes salvajes con tanta gravedad, convirtiéndolos en atrocidades.

En una reciente emisión por Internet titulada “Hablando de monstruos”, que apareció en el sitio de la revista Skeptic, O’Connor explicó que los ácaros responsables de la extrema pérdida de pelo que se ve en el “síndrome del chupacabras”, es el Sarcoptes scabiei, que causa también el escozor conocido como sarna en los humanos. El escabio humano es una molestia, pero no llega a ser habitualmente un grave problema de salud o para la apariencia, en parte porque nuestros cuerpos ya casi carecen de pelo y en parte porque la población de ácaros en una persona es relativamente pequeña, apenas 20 á 30 ácaros.

Los estudios de evolución hechos por O’Connor y su ex estudiante de grado Hans Klompen, quien ahora es un profesor asociado en la Universidad de Ohio, indican que los ácaros del escabio han estado con nosotros a lo largo de toda la historia de la evolución, dando a los humanos tiempo de sobra para que desarrollaran defensas. Cuando los humanos empezaron a domesticar animales, el Sarcoptes scabiei encontró todo un contingente nuevo de víctimas potenciales. Los perros domésticos, al igual que los humanos, han sido anfitriones de los ácaros el tiempo suficiente como para haber evolucionado la capacidad de combatir la sarna, pero cuando la condición se propaga a los miembros salvajes de la familia canina —zorros, lobos y coyotes— ahí hay que tener gran cuidado.

“Siempre que aparece una nueva asociación de anfitrión y parásito, lo que ocurre es bastante malo”, dijo O’Connor, profesor de ecología y biología evolutiva y curador en el Museo de Zoología de la UM. “Causa un gran daño y la mortalidad puede ser relativamente elevada porque esa especie anfitriona no ha tenido historia evolutiva alguna con el parásito, de manera que no ha podido evolucionar defensas como las que tenemos nosotros”.

En estos animales desafortunados el gran número de ácaros que se alojan bajo la piel causan inflamación y esto lleva a un engrosamiento de esta última. El suministro de sangre a los folículos del pelo se interrumpe, y cae el pelambre. En casos especialmente malos la condición debilitada del animal deja abierta la entrada a las bacterias que causan infecciones de piel secundarias, las cuales a veces producen un muy mal olor. Ponga todo esto junto y ya tiene una monstruosidad fea, pelada, correosa y maloliente: el chupacabras.

¿Las infecciones con ácaros también alteran el comportamiento de los animales convirtiéndolos en asesinos sedientos de sangre? No exactamente, pero hay una explicación acerca de por qué pueden ser particularmente propensos a atacar animales del ganado menor como las ovejas y las cabras.

“Dado que estos animales están muy debilitados tienen mucha dificultad para cazar”, dijo O’Connor. “Por eso se ven forzados a atacar el ganado, porque es más fácil que perseguir un conejo o un ciervo”.

Si bien el chupacabras ha alcanzado status de leyenda, otros animales salvajes sufren lo mismo a causa de los ácaros de la sarna, dijo O’Connor. En Australia se sabe que los ácaros están matando a los vombátidos. “Presumiblemente los ‘wombats’ recibieron los ácaros de los dingos, los perros salvajes, que a su vez los recibieron de perros domésticos que los recibieron de los humanos”, señaló.

Otro ácaro relacionado e igualmente insidioso puede llevar a la autodestrucción de las ardillas. En sus años en la escuela de grado en la Universidad Cornell, O’Connor observó ardillas debilitadas por la sarna que caían de los árboles. Aquella observación le llevó a realizar una encuesta informal para determinar si las ardillas sarnosas también eran más propensas que las sanas para terminar muertas, aplastadas en las calles. Y obtuvo una respuesta afirmativa, la cual indica que, al ser torturadas por los ácaros de alguna manera las ardillas eran menos adeptas a esquivar los vehículos automotores. (U. Michigan)

Researchers Zero in on Protein That Destroys HIV

ScienceDaily (Aug. 25, 2010) — Using a $225,000 microscope, researchers have identified the key components of a protein called TRIM5a that destroys HIV in rhesus monkeys.

The finding could lead to new TRIM5a-based treatments that would knock out HIV in humans, said senior researcher Edward M. Campbell, PhD, of Loyola University Health System.

Campbell and colleagues report their findings in an article featured on the cover of the Sept. 15, 2010 issue of the journal Virology, now available online.

In 2004, other researchers reported that TRIM5a protects rhesus monkeys from HIV. The TRIM5a protein first latches on to a HIV virus, then other TRIM5a proteins gang up and destroy the virus.

Humans also have TRIM5a, but while the human version of TRIM5a protects against some viruses, it does not protect against HIV.

Researchers hope to turn TRIM5a into an effective therapeutic agent. But first they need to identify the components in TRIM5a that enable the protein to destroy viruses. "Scientists have been trying to develop antiviral therapies for only about 75 years," Campbell said. "Evolution has been playing this game for millions of years, and it has identified a point of intervention that we still know very little about."

TRIM5a consists of nearly 500 amino acid subunits. Loyola researchers have identified six 6 individual amino acids, located in a previously little-studied region of the TRIM5a protein, that are critical in the ability of the protein to inhibit viral infection. When these amino acids were altered in human cells, TRIM5a lost its ability to block HIV-1 infection. (The research was done on cell cultures; no rhesus monkeys were used in the study.)

By continuing to narrow their search, researchers hope to identify an amino acid, or combination of amino acids, that enable TRIM5a to destroy HIV. Once these critical amino acids are identified, it might be possible to genetically engineer TRIM5a to make it more effective in humans. Moreover, a better understanding of the underlying mechanism of action might enable the development of drugs that mimic TRIM5a action, Campbell said.

In their research, scientists used Loyola's wide-field "deconvolution" microscope to observe how the amino acids they identified altered the behavior of TRIM5a. They attached fluorescent proteins to TRIM5a to, in effect, make it glow. In current studies, researchers are fluorescently labeling individual HIV viruses and measuring the microscopic interactions between HIV and TRIM5a.

"The motto of our lab is one of Yogi Berra's sayings -- 'You can see a lot just by looking,'" Campbell said.

Campbell is an assistant professor in the Department of Microbiology and Immunology at Loyola University Chicago Stritch School of Medicine. His co-authors are Jaya Sastri, a Stritch graduate student and first author; Christopher O'Connor, a former post-doctorate researcher at Stritch; Cindy Danielson and Michael McRaven of Northwestrn University Feinberg School of Medicine and Patricio Perez and Felipe Diaz-Griffero of Albert Einstein College of Medicine.

The study was supported by a grant from the National Institutes of Health.

How the Songbird's Brain Controls Timing During Singing

ScienceDaily (Nov. 8, 2010) — A team of scientists has observed the activity of nerve cells in a songbird's brain as it is singing a particular song. Dezhe Jin, an assistant professor in the Department of Physics at Penn State University and one of the study's authors, explained that understanding how birds string together sets of syllables -- or notes in a song -- may provide some insight into how the human brain learns language and produces speech.

The research will be published in the journal Nature.

"Unlike dogs and cats, whose vocalizations are innate and unlearned, songbirds learn a song in much the same way as humans learn a language -- through cultural transmission," Jin said. "So we decided to study exactly what is going on -- at the level of brain cells -- in a songbird called the zebra finch." Jin explained that both humans and zebra finches arrange sets of learned syllables to communicate. This arrangement of syllables is known as syntax. Jin said that, although finch syntax is much less complicated than human syntax, finch syntax can still provide a model for human speech.

Jin described the area of the brain responsible for a zebra finch's song production as a clump of neurons, which, if absent, renders the bird incapable of singing. To determine exactly how this clump is involved in syntactic production, Jin and his colleagues used special electrodes to monitor the brain cells in this neuronal clump. The electrodes recorded the pattern of neuronal firings that occurred while the finches were repeating a song. The scientists found that when a zebra finch produces its song, a specific set of neurons in this clump fire at precisely the moment when a particular syllable is being sung. "The result is a kind of domino or cascade effect," Jin said. "We saw that when one syllable was sung, a specific set of neurons in the clump fired, which in turn caused the next set of neurons to fire, and that was associated with the next syllable in the song being sung." Jin explained that the ordered firing of specific sets of neurons can be likened to a musical score. "The sequential bursts of brain-cell activity represent the sequential notes on the same piece of music," he said.

Jin also explained that Darwin's theory of sexual, as opposed to natural, selection could explain the songbird's musical prowess. Sexual selection is the theory that an animal chooses a member of the opposite sex based on some observable feature that signals good health and superior genes. The classic example is the male peacock's elaborate and calorically expensive tail, which attracts the female peahen. In male songbirds, an elaborate tail has been replaced by an elaborate song. "A skilled singer will win the attention of more females, and, as such, he will produce more offspring," Jin explained. "It's not that the song itself varies, just the skill with which it's sung. Imagine different pianists playing the same Chopin piece. What sets one apart from the others is his sense of timing and rhythm. In the zebra finch, we found that the timing precision of singing was controlled by bursting properties of individual neurons."

Jin and his colleagues believe that the next step in their research will be to perform similar studies in other species of songbirds, including the Bengalese finch. "The zebra finch is a simple model because the bird perfects just one song during its lifetime," Jin explained. "However, other species learn several distinct songs. They have a larger repertoire."

Along with Jin, the study's co-authors include Michael A. Long and Michale S. Fee of the Massachusetts Institute of Technology's McGovern Institute for Brain Research.

Support for this research is provided by the National Science Foundation, the National Institutes of Health, and the Alfred P. Sloan Foundation.

Group of adult zebra finches. (Credit: Liza Gross)
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Gene Implicated In Human Language Affects Song Learning In Songbirds

ScienceDaily (Dec. 5, 2007) — Do special "human" genes provide the biological substrate for uniquely human traits, like language?

Genetic aberrations of the human FoxP2 gene impair speech production and comprehension, yet the relative contributions of FoxP2 to brain development and function are unknown.

Songbirds are a useful model to address this because, like human youngsters, they learn to vocalize by imitating the sounds of their elders.

Previously, Dr. Constance Sharff and colleagues found that, when young zebra finches learn to sing or when adult canaries change their song seasonally, FoxP2 is up-regulated in Area X, a brain region important for song learning.

Dr. Sebastian Haesler, Dr. Scharff, and colleagues experimentally reduce FoxP2 levels in Area X before zebra finches started to learn their song. They used a virus-mediated RNA interference for the first time in songbird brains.

The birds, with lowered levels of FoxP2, imitated their tutor's song imprecisely and sang more variably than controls.

FoxP2 thus appears to be critical for proper song development.

These results suggest that humans and birds may employ similar molecular substrates for vocal learning, which can now be further analyzed in an experimental animal system.

Journal citation: Haesler S, Rochefort C, Georgi B, Licznerski P, Osten P, et al. (2007) Incomplete and inaccurate vocal imitation after knockdown of FoxP2 in songbird basal ganglianucleus Area X. PLoS Biol 5(12): e321. doi:10.1371/journal.pbio.0050321

Zebra finch. (Credit: iStockphoto/David Gluzman)