Saturday, December 26, 2015

New research on vocalizations, grooming, and social bonds

Lemur catta Photo: author
Both grooming and vocalizing are linked to social bonds and relationships. Increases in the vocal repertoire of primates is correlated with group size and amount of time spent grooming (McComb and Semple, 2005). Previous research has shown that pairs of baboons (Papio cynocephalus) spend more time grooming one another (allo-grooming) and allo-groom more frequently if they are bonded socially (Silk et al., 2006). Dunbar first suggested that vocalizations may serve to act as a way of socially bonding when larger group sizes make grooming every member more difficult (1993; 2003; 2004).

A study published this December provides further insight into the reasons why small talk may have evolved and how it relates to social relationships. Studying ring-tailed lemurs (Lemur catta), Kulahci and colleagues (2015) examined vocalizations and grooming.  Four troops of free-ranging and semi-freeranging lemurs at the Duke Lemur Center and on St. Catherine's Island were studied. Vocalization and grooming network outdegrees were calculated to determine who each individual initiated vocalizations and grooming towards. The grooming network outdegree was simply the number of individuals the individual in question groomed. The vocalization network outdegree was   the number of individuals that the individual in question produced a vocal response towards upon hearing a call.

Kulahci and colleagues (2015) found that ring-tailed lemurs were more selective in who they vocalized to than who they chose to groom: as troop size increased, lemurs groomed more individuals but they did not vocalize directly towards more individuals. Regardless of troop size, vocalization network outdegrees were lower than grooming network outdegrees, showing that lemur are picky about who they vocalize to but less so about who they groom. Individuals responded to the vocalizations of lemurs they groomed more frequently than they did lemurs they groomed less often.

When audio playbacks were used, the same selectivity in vocalization responses was displayed. Thus, this selectivity in vocalizations is not due to olfactory or visual cues.

While this study agrees with previous work highlighting the connection between grooming and vocalizations, it does not align with Dunbar's hypothesis (1993; 2003; 2004) that vocalizations allow an individual to maintain more social bonds than grooming would. Whereas we would have expected to see vocalizations increase with group size, the opposite was true for this study. Rather than vocalize with more troop members as group size increases, L. catta selectively vocalize and groom all members. Thus, vocalizations may be a better indicator of social bonds than grooming, at least in L. catta.

Links of possible interest:
 Social grooming in primates
How the size of the neocortex and the size of grooming clusters relate
Derived vocal complexity of geladas


Dunbar, R. I. (1993). Coevolution of neocortical size, group size and language in humans. Behavioral and brain sciences, 16(04), 681-694.

Dunbar, R. I. (2003). The social brain: mind, language, and society in evolutionary perspective. Annual Review of Anthropology, 163-181.
Dunbar, R. I. (2004). Gossip in evolutionary perspective. Review of general psychology, 8(2), 100.
Kulahci, I. G., Rubenstein, D. I., & Ghazanfar, A. A. (2015). Lemurs groom-at-a-distance through vocal networks. Animal Behaviour, 110, 179-186.
Silk, J. B., Altmann, J., & Alberts, S. C. (2006). Social relationships among adult female baboons (Papio cynocephalus) I. Variation in the strength of social bonds. Behavioral Ecology and Sociobiology, 61(2), 183-195.

Monday, December 21, 2015

Another primate "sleeps" away hard times

Hibernation allows an organism to lower its metabolism, heart rate, body temperature, and breathing in order to expend less energy during what may be a difficult time, such as a cold winter.  Hibernation is a tactic commonly associated with rodents and polar bears but primates do it too. The fat-tailed dwarf lemur (Cheirogaleus medius) on the island of Madagascar hibernates during the dry season, using the fat in its tail to survive the winter. The Crossley's dwarf lemur (Cheirogaleus crossleyi) and the Sibree's dwarf lemur (Cheirogaleus sibreei) also hibernate. Some primates (Microcebus murinus, Allocebus trichotis, Galago moholi, and others) will enter what is called torpor, during which body temperature and metabolism is lowered but for a period less than 24 hours. Lemurs were thought to be the only primate that hibernated, until a close cousin changed the game.

Pygmy slow loris. Photo: David Haring at Duke Lemur Center
It has recently been reported that the pygmy slow loris (Nycticebus pygmaeus), a nocturnal primate living in Cambodia, China, Laos, and Vietnam does in fact hibernate (Ruf et al., 2015). The authors behind this study set out to find a hibernating primate outside of Madagascar and they succeeded.

Ruf and colleagues found it hard to believe that hibernation in primates would be restricted to only Madagascar, so they started thinking about what environmental conditions and physical characteristics would make an animal likely to hibernate. They hypothesized that a hibernating primate would be small, as most hibernating animals are (Ruf and Geiser, 2015), that the animal would live in an environment that is distinctly seasonal in temperatures and/or precipitation, and in an environment with seasonal changes in food availability. Given the primates known to use torpor, primates falling into the suborder Strepsirrhines seemed like their best bet.

The pygmy slow loris fit their criteria. It was logical that a small primate facing cold temperatures in winter and low food availability would adapt using hibernation. Thus lowering energy requirements during a period of limited resources. While previous descriptions of the pygmy slow loris were in accord with hibernation (Ratajszczak, 1998; Streicher, 2005), no measurements had been taken. Thus, Ruf and colleagues decided to take some.

After measuring temperature (but not metabolic rate) in five adults over 769 days total, animals hibernated for several days during midwinter interspersed with periods of activity and or torpor. On average, animals hibernated for 43 hours (± 3 hours with a range of 25.9-62.6 hours).

Thus, evolutionary mechanisms have not limited hibernation in primates to Madagascar. As more research is done, it is possible that hibernation will be found in other primate species inhabiting seasonal environments.

Links of possible interest:
Discovery of hibernation in fat-tailed dwarf lemur
Primate hibernation more common than previously thought
The costs and benefits of hibernation


Ratajszczak, R. (1998). Taxonomy, distribution and status of the lesser slow loris Nycticebus pygmaeus and their implications for captive management. Folia Primatologica, 69(Suppl. 1), 171-174.

Ruf, T., Streicher, U., Stalder, G. L., Nadler, T., & Walzer, C. (2015). Hibernation in the pygmy slow loris (Nycticebus pygmaeus): multiday torpor in primates is not restricted to Madagascar. Scientific reports, 5.

& Daily torpor and hibernation in birds and mammals. Biol. Rev. 90, 891–926, doi: 10.1111/brv.12137 (2015).

Streicher, U. (2005). Seasonal body weight changes in pygmy lorises Nycticebus pygmaeus. Verhandlungsber. Zootierkrk, 42, 144-145.

Wednesday, October 14, 2015

Potential trouble for the endangered Udzungwa red colobus monkey

Recent genetic analysis of the Udzungwa red colobus monkey (Procolobus gordonorum) indicates the species might be in trouble in the future. This endangered monkey is endemic to the Udzungwa Mountains in Tanzania with population numbers currently in decline due to habitat loss and fragmentation (Struhsaker et al., 2008).

Udzungwa red colobus monkey, credit:Stevage
Ruiz-Lopez and colleagues (2015) did genetic analyses on 121 individuals using DNA collected from fecal samples. Samples were collected from populations living in five forest fragments of varying size. Scientists then used what is termed, "landscape genetics," combining genetic analysis with geographic-information-science (GIS). Ruiz-Lopez and colleagues (2015) specifically looked at how fragmentation affects P. gordonorum's genetic variation and what landscape features explained genetic differences.

Results showed that the greatest genetic differences were found between monkeys that are separated by villages and/or by areas of land that experienced high densities of fires. Given that the red colobus monkey is arboreal, Ruiz-Lopez and colleagues were surprised forest coverage is not a significant factor contributing to genetic variation. Despite differences in forest fragment size and in population density of the monkeys themselves, genetic variation is not significantly affected by the forest fragment individuals inhabit. Forest fragmentation in this area is relatively new (Marshall, 2007), thus these populations have only recently been genetically isolated from each other. Perhaps not enough time has passed for differences to manifest.

Ruiz-Lopez and colleagues (2015) are careful in their conclusions though and state that their findings do not necessarily prove that human activities are the main cause of this genetic variation. Human habitation and human-caused fires are likely contributing to the genetic differences, but these differences may be natural in origin, with humans simply reinforcing and maintaining genetic variation (Ruiz-Lopez et al., 2015).

Although Ruiz-Lopez and colleagues are unable to show a direct cause-and-effect relationship, this work does highlight the importance of human activity on the landscape and its impact on genetic changes in primate populations. As of today, inbreeding is not a problem for the Udzungwa red colobus monkeys, but it could be in the future, given this new evidence suggests human impacts are contributing to genetic differentiation. This is one of the few studies to use landscape genetics in this region.

Links of interest:
IUCN Redlist Page
Why we need corridors

Works cited:
Marshall AR. (2007) Disturbance in the Udzungwas: Responses of monkeys and trees to forest degradation. PhD thesis University of York: UK.
Struhsaker, T, Butynski, T.M. & Ehardt, C. 2008. Procolobus gordonorum. The IUCN Red List of Threatened Species 2008: e.T40015A10302163.
Ruiz-Lopez, M. J., Barelli, C., Rovero, F., Hodges, K., Roos, C., Peterman, W. E., & Ting, N. (2015). A novel landscape genetic approach demonstrates the effects of human disturbance on the Udzungwa red colobus monkey (Procolobus gordonorum). Heredity.

Monday, October 5, 2015

Gregarious chimps have more grey matter in specific region of the brain

Chimpanzees with offspring, Photo credit: flickr user Valerie
As one of our closest living relatives, studying the behavior, ecology, and anatomy of chimps provides a look back in time as to what the last common ancestor of chimpanzees and humans may have been like. A recent study examined the brain structure of over one hundred chimpanzees to understand how personality and the brain are connected.

Latzman and colleagues (2015) studied 107 captive chimpanzees by using MRIs and an assessment composed of 41 questions about each individual chimp's personality that was conducted by staff members who care for the animals. The article did not state how long these staff members worked with the chimpanzees, only that they felt they could assess their personalities.

Latzman and colleagues (2015) showed that the volume of gray matter and asymmetry of various regions of the frontal cortex are correlated. Grey matter, found mainly on the outside of the brain, is composed on neuronal cells and unmyelinated axons. (To learn more about grey matter, click here.) Chimpanzees ranked as more dominant, open, and extraverted have greater average grey matter in the frontal cortex of their brains. Extraversion in this article is defined as "energetic approach orientated." Their research also shows that frontal cortex asymmetry, or lack of equality/symmetry, is associated (but not correlated) with dominance, extraversion, and unpredictability.
Source: Biological Psychology 6e via Wikipedia

There are limitations to this study, as Latzman and colleagues (2015) mention. It is impossible to determine the causal relationship. Do personality differences create these structural differences in the brain? Or do structural differences in the brain create these personalities differences? As of right now, we can't answer this question. Interpretations of these findings are also limited by our own understanding of the brain, and we have much to still learn about the structure and function of this complex organ.

Yet, because of this study we have a greater understanding of the biological bases of behavior and personality.  Latzman and colleagues (2015) are the first to study the frontal cortex of the brain and personality in chimpanzees. As we know, chimpanzees are an excellent model for human behavior and personality because they are so closely related to humans. Studies such as this one allow us to refine our understanding of the evolution of our own species.

Food for thought: Would we expect to see the same results in bonobos? Orangutans? Lemurs?

Links of interest:
Cooking chimpanzees
Female friendship in chimpanzees
Differences in tool use between males and females

Works cited:

Robert D. Latzman, Lisa K. Hecht, Hani D. Freeman, Steven J. Schapiro, William D. Hopkins. Neuroanatomical correlates of personality in chimpanzees (Pan troglodytes): Associations between personality and frontal cortex. NeuroImage, 2015; 123: 63 DOI: 10.1016/j.neuroimage.2015.08.041

Monday, September 21, 2015

Male squirrel monkeys made to see in living color

Squirrel monkey in Bolivia. Photo: author
Squirrel monkeys, like many New World Monkeys, are a bit unusual when it comes to their vision. Males are dichromatic, meaning that they do not have the ability to see red wavelengths but can see blue and green wavelengths. Females on the other hand, may be dichromatic or they may be trichromatic like us, able to see blues, greens, and reds. Males are dichromatic because trichromatic vision requires two copies of a certain opsin gene, a gene that is found on the X chromosome. Thus, females, who have two Xs, likely (but not always) carry two copies of the gene. The majority of female squirrel monkey can see shades of green and shades of red. Male monkeys have the gene that codes for seeing green colors but not the gene that allows them to see red.

When we refer to color blindness in humans, often what we really mean is that the person has dichromatic color vision. True color blindness in humans, where the person can only see in black and white, is very rare, although something similar does occur in another New World Monkey. Night monkeys have very poor color vision. As their name suggests, these monkeys are active only at night. Thus, seeing reds, greens, and blues isn't very advantageous given their environment. Over time, owl monkeys have evolved so that they have fewer cones, which allow the eye to see colors, and more rods, which allow the eye to distinguish blacks and whites. To further adapt for their mainly nocturnal lifestyle, the size of their eyes has also expanded. Again, being monochromatic is rare in humans, yet dichromatic color vision does occur in one out of twelve men.

Visible Wavelengths Dichromats lack red cones
Now, there may be hope for those who have dichromatic color vision and it's thanks to research done in squirrel monkeys. Two male squirrel monkeys have been made to see all three wavelengths.

Mancuso and colleagues injected the gene that would allow two male squirrel monkeys to see red into a virus, and then they injected that virus behind the retina. (Review your eye anatomy here.) Two years later, the monkeys have had no side effects and are able to see all three wavelengths. Squirrel monkey brains, like our own, are quite plastic, meaning they can change. These two animals can now distinguish reds from greens and their brains have apparently rewired themselves so that seeing and processing information about the red wavelength can be done.

Why do humans see in all three colors? There isn't a certain answer. Multiple hypotheses have been proposed. Peter Lucas, my former professor, believes our ability to see reds was advantageous in helping our ancestors see young red leaves, which are especially nutritious, against a background that is mostly made up of shades of green (Lucas et al., 1998). Our closest living relatives, chimpanzees and gorillas, consume a diet mainly composed of leaves. Or perhaps we see reds because red fruit is often ripe and therefore we can distinguish ripe  fruit against a green background (Allen, 1879; Mollon, 1989; Fleagle, 1999). Yet, if this were the complete answer, wouldn't we expect New World Monkeys, who consume fruit, to see red wavelengths? Another hypothesis suggests that our ability to see shades of red occurred so that male Old World Monkeys could more easily discern the sexual swellings of females that were in estrous (Liman and Innan, 2003).

Regardless of why trichromatic vision evolved in our ancestors, it seems that those humans unable to see all three wavelengths may one day be able to enjoy the Christmas colors following gene therapy. Trials in humans are underway and we have two male squirrel monkeys to thank for that.

Links of interest:
Color vision in primates
Color vision in humans 
Night monkeys and their morphology
A molecular view of how human color vision evolved

Works cited:
 Allen, G. 1879.  The colour-sense: its origins and development. Trubner, London.
Fleagle, J. G. 1999. Primate adaptation and evolution. 2nd ed. Academic Press, San Diego, CA. 
Liman, E. R., & Innan, H. (2003). Relaxed selective pressure on an essential component of pheromone transduction in primate evolution. Proceedings of the National Academy of Sciences, 100(6), 3328-3332
Lucas, P. W., Darvell, B. W., Lee, P. K. D., Yuen, T. D. B., & Choong, M. F. 1998. Colour cues for leaf food selection by long-tailed macaques (Macaca fascicularis) with a new suggestion for the evolution of trichromatic colour vision. Folia Primatologica, 69(3), 139-154.
Mancuso, K. et al. Nature advanced online publication, doi:10.1038/nature08401 (2009). 
Mollon, J. D. 1989. “Tho'she kneel'd in that place where they grew…” The uses and origins of primate colour vision. Journal of Experimental Biology, 146(1), 21-38.

Thursday, September 3, 2015

Female orangutans may prefer males with large cheekpads

Dominant male named Kiko at NZP. Photo: author
Orangutans display an interesting form of sexual dimorphism in that males have large cheek pads but females do not. Males are also larger and have large throat sacs that aid them when they make long calls, which advertise to females and tell other orangutans, "I am here!" However, not all males develop this large size, cheek pads, and throat sac. The cheek pads, large size and throat sacs are characteristic of dominant males. Thus, orangutan males display bimaturism, meaning the timing of development differs. Some males develop these dominant characteristics much sooner than others.  Because adult males aren't always large and with the distinguishing cheek pads and throat sacs, it can be quite difficult to tell non-dominant males and females apart.

These non-dominant males aren't juvenile or infertile. They are perfectly capable of reproducing and previously have been shown to produce about half of all wild orangutan offspring (Utami et al., 2002). These two forms of adult males have different strategies when it comes to mating. The dominant males defend their territory. Their homerange is very large and includes multiple females. Non-dominant males are able to gain access to females when the dominant male isn't around.

Bonnie(female) at NZP. Photo: author
A new study resulting from eight years of field research at Tanjung Puting National Park on the island of Borneo found that females prefer dominant males with cheek pads. This is the longest study to have been done at one site in a single population of individual orangutans in terms of orangutan paternity. Banes and colleagues (2015) determined parentage for orangutans inhabiting the homerange used by Kuasasi, a dominant male. They determined he produced far more offspring once he achieved dominance and that he fathered the majority of offspring in the area. This is in contrast to what Utami and colleagues found in 2002 in Sumatra in which unflanged males produced half of the offspring.

This more recent study is arguably limited by the fact that researchers determined the parentage of orangutans in one dominant male's range (Kuasasi). It is possible this is just one very successful male. Or, females are in fact choosing dominant, flanged males over unflanged males. The authors also point out that their study site may affect their results. Camp Leakey is characterized by both wild orangutans and individuals that were once captive but released to the area in the 70s. Orangutans at this site also receive medical treatment, which may mean that dominant males are surviving attacks that they otherwise would not, affecting the population.

Conducting studies on paternity and life history variables on orangutans is very difficult given that, other than humans, orangutan offspring take the longest to reach adulthood of any primate. Females will reproduce every eight years (Gladikas and Wood, 1990), thus answering these types of questions remains difficult.

Links of interest:
Encyclopedia of Life Page on Bornean Orangutans
 IUCN Redlist Page on Bornean Orangutan
Monopoly of the male orangutan
Orangutan long call


Galdikas BMF, Wood JW (1990) Birth spacing patterns in humans and apes. Am J Phys Anthropol 83:185–191

Graham L. Banes, Biruté M. F. Galdikas, Linda Vigilant. Male orang-utan bimaturism and reproductive success at Camp Leakey in Tanjung Puting National Park, Indonesia. Behavioral Ecology and Sociobiology, 2015; DOI: 10.1007/s00265-015-1991-0

Utami, S. S., Goossens, B., Bruford, M. W., de Ruiter, J. R., & van Hooff, J. A. (2002). Male bimaturism and reproductive success in Sumatran orang-utans. Behavioral Ecology, 13(5), 643-652.

Wednesday, August 26, 2015

Chimpanzee populations in Uganada greater than previously thought

 Chimpanzees (Pan troglodytes) are currently listed as endangered by the International Union for the Conservation of Nature (IUCN) due to threats from habitat loss and degradation causing a decrease in population numbers that will likely continue (Oates et al., 2008). However, a recent study examining chimpanzee numbers in Uganda gives us reason to hope for our close primate relatives. In the open access journal BMC Ecology, McCarthy and colleagues report that 15 months of data collection has lead them to determine that over two hundred and fifty chimpanzees live in a corridor that was previously assumed to hold ~seventy individuals.

Chimpanzees with offspring, Photo credit: flickr user Valerie
The Budongo and Bugoma Forest Reserves in Uganda are two large areas of protected land separated by an unprotected area that contains villages, agricultural fields, along with grasslands and forest. It's not your typical, ideal chimpanzee habitat. This corridor is dominated by humans, with 107 humans per square km (NPHC, 2014). Yet, studies like this one have obvious merit as we lose more and more pristine habitat.

Researchers collected fecal samples and genotyped those samples from 2011-2013. They then used models to determine the number of individuals. This noninvasive method is more accurate than counting the number of nests chimpanzees make at night in order to determine the number of individuals. (Chimpanzees make nests out of branches and forest materials every night that they sleep in. See a video here.) Using this method, they were able to determine that there are at least nine communities, each with anywhere between eight to thirty-three individuals. Because not all areas of the unprotected corridor were not sufficiently sampled in this study, it is possible this is a conservative estimate, and numbers may be even higher.

McCarthy and colleagues point out that chimpanzees exhibit a great deal of behavioral flexibility, which likely accounts for how they've coped with a less-than-ideal environment. Chimps are omnivores and can adapt their diet if they need to, including human-cultivated foods. Provided a lack of pressure from hunting, it is worth considering these stretches of land that previously may have been overlooked as viable areas worthy of conserving. The next steps will be understanding just how the chimps are doing so well in this habitat. What behavioral changes are they making?

Links of interest:
IUCN Redlist page on chimpanzees 
Map showing current range of chimpanzees 
The fate of western lowland gorillas and chimpanzees over the next decade
How human are chimps?

Works cited:

Maureen S McCarthy, Jack D Lester, Eric J Howe, Mimi Arandjelovic, Craig B Stanford, Linda Vigilant. Genetic censusing identifies an unexpectedly sizeable population of an endangered large mammal in a fragmented forest landscape. BMC Ecology, 2015; 15 (1) DOI: 10.1186/s12898-015-0052-x
NPHC 2014 provisional results report. Uganda Bureau of Statistics, Kampala; 2014.
Oates, J.F., Tutin, C.E.G., Humle, T., Wilson, M.L., Baillie, J.E.M., Balmforth, Z., Blom, A., Boesch, C., Cox, D., Davenport, T., Dunn, A., Dupain, J., Duvall, C., Ellis, C.M., Farmer, K.H., Gatti, S., Greengrass, E., Hart, J., Herbinger, I., Hicks, C., Hunt, K.D., Kamenya, S., Maisels, F., Mitani, J.C., Moore, J., Morgan, B.J., Morgan, D.B., Nakamura, M., Nixon, S., Plumptre, A.J., Reynolds, V., Stokes, E.J. & Walsh, P.D. 2008. Pan troglodytes. The IUCN Red List of Threatened Species. Version 2015.2. <>.  OpenURL

Wednesday, July 15, 2015

How hurricane severity affects extinction probabilities for howler monkeys

Howler on Barro Colorado Is. Photo: Vince Smith
Howler monkeys are known for their long, bellowing calls that can be heard in the forests of Central and South America. There are five subspecies, the taxonomic rank below species, of howler monkeys. Alouatta palliata mexicana is a critically endangered subspecies found in parts of Mexico and Guatemala. Ameca y Juárez and colleagues had the idea to examine how hurricanes affect population numbers of this arboreal, New World primate. Using data from 1988 to 2002, the authors modeled how hurricane intensity affects extinction likelihood of local populations of this New World primate. They also wanted to know which human disturbance, hunting or habitat loss, had a greater impact when combined with different intensities of hurricanes.

Previous studies have examined how other species of howler monkeys have been impacted by hurricanes on a short-term basis, but this study is the first to look at the effects over a long period of time. The area in which A. p. mexicana inhabits is experiencing more hurricanes lately (Manson et al., 2009; Portilla-Ochoa et al., 2006), thus this study is of increasing relevance.

Studying A. p. mexicana living on Agaltepec Island in Mexico, which is isolated and predator-free (including human predators),  Ameca y Juárez and colleagues estimated predator, hunting, and habitat loss pressures from other A. p. mexicana populations in the area. They used population viability analysis (PVA) to determine the impact of different hurricane intensities on howler monkeys' quasi-extinction risk, or the probability of reaching a population size in which additional threats could cause the loss of the entire population.

The lowest degree hurricane disturbance result in a 28% quasi-extinction risk forty years later. Baseline estimates of hurricane intensity result in a 74% risk. Overall, the authors found that hurricanes have the ability to exceed the risk of human impacts. The combination of hurricanes and habitat loss have a substantially faster effect than when hurricanes and hunting are paired together.  It is the decrease in survival of adults that most affects the quasi-extinction rates, with adult males having an especially significant effect on the population.

The authors do point out that recurrent exposure to disturbances, including hurricanes, can be expected to affect the adaptability over time, thus reducing the likelihood the species will go extinct from the disturbance. Thus, the relationship between quasi-extinction risk and hurricane intensity won't be lineal in reality, as populations frequently exposed to hurricanes over time will adapt to lessen or moderate the negative effects.

As more frequent and intense hurricanes are expected in the future, studies such as this one allow us to determine how primate populations might be affected. Future modelling of hurricane intensity and frequency may incorporate other factors likely to affect population numbers, such as inbreeding.

Food for thought:
How might conservation biologists use information from this study to protect A. p. mexicana?
How might this study apply to other species of primates and other animal species in general?

Links of interest:
IUCN's page on A. palliata
How animals survive hurricanes
Why we should expect more extreme weather
Howler monkeys' call

Works cited:
Ameca y Juárez EI, Ellis EA, Rodríguez-Luna E. 2015. Quantifying the severity of hurricanes on extinction probabilities of a primate population: Insights into “Island” extirpations. American Journal of Primatology 77:786-800.

Manson RH, Jardel Pelaez E, Jimenez Espinosa M, et al. 2009. Perturbaciones y desastres naturales: impactos sobre las ecorregiones, la biodiversidad y el bienestar socioeconomico, en: Capital natural de Mexico, vol II: Estado de conservacion y tendecias de cambio. Conabio, Mexico, pp. 131-184. 

Portilla-Ochoa E, Sanchez-Herdandez AI, Hernadez-Meza D. 2006. El impacto de los huracanes en la biodiversidad del estado de Veracruz. In: Inundaciones 2005 en el estado de Veracruz. pp. 101-119. Universidad Vercruzana, Veracruz Mexico. 

Tuesday, July 7, 2015

A look inside an ancient primate's brain yields surprises

Fifteen million years ago the earliest known member of the subfamily cercopithecine roamed the planet. Victoriapithecus is the most ancient old world monkey scientists have discovered to date. This frugivorous primate was found on an island in Lake Victoria (Benefit, 1999). What we know about this species is a result of one fossil, a skull. A recent study by Gonzales and colleagues studied the inside of this monkey's skull (also called an endocast) to learn more about the brain structure of Victoriapithecus.

Endocast of A. sediba, Photo credit: Lee Berger
Using high-resolution X-ray imaging, researchers were able to create a 3D model of what Victoriapithecus's brain looked like. The results were surprising. At only 35.6cm3, this monkey had a brain about the size of a plum: small when compared to the animal's body size.  Most primates this size have a brain that's about the size of an orange.

The olfactory bulb, the part of the brain in which sense of smell is processed, was three times larger than expected. It was along the lower end of what we see for strepsirrhines, a group of primates with a greater reliance on sense of smell when compared to haplorhines (new and old world monkeys, tarsiers, and apes).

Despite having a small brain and a greater reliance on smell, characteristics typically seen in the so-called lower primates, there is more to Victoriapithecus than meets the eye. Micro CT scans were able to show the wrinkles and folds in the brain.  Given that this animal had quite a small brain, the numerous ridges and folds (sulci and gyri) show that this species was complex.  Folds on the brain are generally linked to greater intelligence. The organization of Victoriapithecus's brain and the sulci and gyri are what we see in present-day cercopithecines. Thus, it looks like a having a large brain is not a prerequisite for having a complex brain.

Links of interest:
Brain size and evolution
Developmental pattern of primate brains
How snakes may have influenced primate brain evolution

Literature cited:

Benefit, B. R. Victoriapithecus: the key to Old World monkey and catarrhine origins. Evol. Anthropol. 7, 155174 (1999). 

Gonzales, L., Benefit, B., McCrossin, M., Spoor, F. Cerebral complexity preceded enlarged brain size and reduced olfactory bulbs in Old World monkeys. Nature Communications, 2015; 6: 7580 DOI: 10.1038/ncomms8580

Tuesday, June 30, 2015

Olive baboons can be democratic when it comes to troop movement

Olive baboons (Papio anubis) live in a world where social rank matters. They live in troops that can have over one hundred individuals, with females remaining in their natal group and males dispersing. Males are dominant over females but females have a strict linear dominance hierarchy, meaning who your mother is matters. A lot. Related females groom each other and have each others backs in agonistic meetings.

Photo credit: Nevit Dilmen
A new study out in Science by Strandburg-Peshkin and colleagues shows that, much to everyone's surprise, olive baboons are democratic when it comes to troop movement. Yep, these primates, which can be known for their aggression (just look at those canines), don't bully when it comes to choosing where to go.

What we'd expect in a primate with such a strict social system is that the group would go where dominant individuals want to go. Those lower on the social totem pole aren't going to act against a more dominant individual's decision nor are they going to attempt to make these decisions themselves. However, using GPS technology, researchers found that the troop tends to go where multiple initiators want to go and individuals who move in a directed manner are more likely to be followed.

When two groups within a troop are moving in different directions, the larger group is more likely to win, and this likelihood grows as the difference in size between the two groups of initiators grows. The authors failed to clarify if, of those decisions with multiple initiators, the number of dominant individuals within groups of initiators made a difference. I'd like to know if five low-ranking individuals could top two high-ranking individuals, when determining which direction to go. Does social rank really have no effect? I'm not sure I'm entirely convinced that it doesn't, but I also don't study baboons.

Now, this study was conducted by studying 33 out of 46 members of one baboon troop over nine days, so it'd be interesting to see if results differ in other troops, in troops of differing sizes, or during different times of the year (for example, when food resources are low). It'd also be interesting to see if this finding holds true for other species of baboons. For example, previous research has shown chacma baboons (Papio ursinus) do pay attention to social relations when deciding which patches of food to target (Marshall et al., 2012).

Food for thought:
Strandburg-Peshkin and colleagues didn't find any differences based on sex when it came to an individual initiating troop movement. Why is this surprising?
Why might this system (in which the troop is democratic in deciding where to go) be adaptive to baboons? When might it not be?

Links of potential interest:
Olive baboon behavior and social organization
Chacma baboon study

Literature cited:
Ariana Strandburg-Peshkin, Damien R. Farine, Iain D. Couzin, and Margaret C. Crofoot. Shared decision-making drives collective movement in wild baboons. Science, 19 June 2015 DOI: 10.1126/science.aaa5099

Harry H. Marshall, Alecia J. Carter, Tim Coulson, J. Marcus Rowcliffe, Guy Cowlishaw. Exploring Foraging Decisions in a Social Primate Using Discrete-Choice Models. The American Naturalist, 2012; 180 (4): 481 DOI: 10.1086/667587

Thursday, June 25, 2015

Potential innate difference in tool use between chimps and bonobos

Young chimpanzee. Photo credit Sabine Bresser
Koops, Furuichi and Hashimoto published a paper recently on the innate ability to use tools in chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). Both species are our closest living relatives, thus providing opportunities to study the evolution of our species and determine what makes humans human. Tool use has long fascinated biological anthropologists, ever since it was first recorded by Jane Goodall at Gombe in 1960.

The authors tracked both species for three months each and recorded all instances of tool use and all instances they thought had potential for tool usage. Fourteen chimps and sixteen bonobos were studied.

Koops and her colleagues determined the available opportunities to harvest army ants and termites (insects that required tool use), nut trees and stones available below those nut trees (used to crack open the nuts) at each of the two sites. The authors determined that the opportunities for dipping for termites and/or army ants was present at both sites. Opportunities for nut cracking were available but limited.

Bonobo young spent more time with their mothers than did chimpanzees. Bonobos also spent more time in close proximity to each other in feeding contexts. Bonobos also had more individuals in close proximity and more social partners than chimpanzees did, thus bonobos had increased opportunities for social learning. Neither ape cracked nuts. Interestingly, bonobos did not fish for termites or army ants whereas chimpanzees did. Both species were more likely to manipulate objects in a resting context than in a feeding context. The most convincing evidence that there is an innate difference between these two species is that chimpanzees less than one year old were observed manipulating objects. These young animals have had few opportunities for social learning, the authors argue, thus their object manipulation is intrinsic.

I'd like to see this study replicated and expanded. Studying each species for only three months doesn't yield a very large amount of data when we're talking about behavioral studies. The more data the better, and given that chimpanzees and bonobos don't reach maturity until around age eight, it's possible study these young apes for more than a few months. I also think it'd be ideal to see this study replicated across numerous sites, incorporating different habitats. Because neither species cracked nuts, we're really only talking about using tools to fish for ants and termites. Given the diverse tool use we see in animals, I wonder if it is a bit premature to declare that chimps are inherent tool users compared to bonobos given the limits of this study. Nonetheless, Koops and her colleagues certainly made an interesting discovery, and it'll be exciting to see what they discover next, as at least one more publication on this topic appears to be in the works.

For now, chimps have a more innate propensity to use tools for army ants and termites. In the future, we very well may prove chimpanzees have more of an innate propensity for tool use than bonobos or at least a different type of innate ability to use tools.

Links of interest:
Chimps that cook
Female chimps more likely to use tools when hunting
Are bonobos more peaceful than chimps?
How human are chimps?

Literature cited:

Kathelijne Koops, Takeshi Furuichi and Chie Hashimoto. Chimpanzees and bonobos differ in intrinsic motivation for tool use. Scientific Reports, 2015 DOI: 10.1038/srep11356

Wednesday, June 10, 2015

Chimpanzees understanding cooking and choose to do it

We can add another skill to the long list of what chimpanzees are able to do: cook. A study was published last week on a series of cooking related experiments done with semi-free-ranging chimpanzees from the Tchimpounga Chimpanzee Sanctuary and the results are fascinating. This was a very cool series of experiments!

Warneken and Rosati first tested sixteen chimpanzees on whether they would choose to delay and receive a larger portion of food that was either raw or cooked or if they would choose an immediate but smaller portion of food. The chimps chose to wait (and thus consume a larger quantity) 60% and 84.4% of the time for the raw and cooked food respectively, showing that the chimps are more willing to suffer the delay to consume a cooked item than a raw item. This finding isn't surprising, as any zookeeper can tell you apes prefer many cooked foods to raw ones. It gets much better though.

The next experiment tested whether or not the chimpanzees understood cooking. Subjects chose between a container that "cooked" the item and bowl that did not cook the item. Raw food was placed in both the container and the bowl, the experimenter shook both of them, but only the container resulted in cooked food. The chimps chose the container with cooked food over 87% of the time. The next test was to determine whether chimps would immediately consume a piece of available food or place it in either the cooking device or the bowl (that didn't cook the item). Thirteen out of twenty-one chimps chose the cooking device at least one time. Chimps that chose a device chose the cooking device more than 80% of the time. The next experiment gave the chimps carrots, which they had not seen in the context of the cooking devices, and the chimps chose to cook the carrots more often than not. When given non-edible items, the chimps didn't try to cook those. All of these experiments point to chimps having the ability to comprehend cooking on a very basic level. They're not cooking everything and they're choosing to cook items that make sense.

Photo credit: Neil McIntosh
Warneken and Rosati then upped the stakes and placed the cooking device further away to determine if the subjects would travel in order to cook their food. All but one of the thirteen chimps successfully transported food to the cooking device that was far away at least once. And when the cooking device was far away, chimps still chose to visit it 60% of the time.

This study is impressive because the sample size is quite robust for a primate cognition study. (Usually you get sample sizes that are smaller because zoos don't have the ability to house so many animals). Because this study was done with semi-free-ranging chimps at a rehabilitation center, the sample size is larger. We're not talking about one ape that knows some sign language, although that's amazing too. We're talking about roughly thirteen individual chimps that are now probably wondering where that magical container went that cooked all of their food.

Links potentially of interest:
BBC Horizon Video-Did cooking make us human?
How human are chimps?

Literature cited:
Felix Warneken, Alexandra G. Rosati. Cognitive capacities for cooking in chimpanzees. Proceedings of the Royal Society B., June 2015 DOI: 10.1098/rspb.2015.0229

Thursday, June 4, 2015

Rank affects a female's likelihood to seek out "friendships"

Photo: Chris Allen
Chimpanzees (Pan troglodytes) are social creatures, living in a fission-fusion society, meaning one large group often breaks into smaller ones to form feeding parties. In the chimp world, males outrank females and there is a strict linear hierarchy to male relationships (Goldberg & Wrangham 1997). Whereas males can remain in their natal group, females migrate around the time when they reach adolescence (years 9-14) (Nishida et al. 2003). Thus, females eventually need to make new friends, whereas males have the benefit of life-long buddies. In most chimpanzee populations, females spend a lot of time by themselves (Williams, Liu, and Pusey, 2002). At Gombe, the famous site where Jane Goodall first went to the wild and studied chimpanzees, females spend the majority of their time alone or with a few other family members (Wrangham and Smuts, 1980; Goodall, 1986).

Gombe National Park in Tanzania, Google Earth
A study due to be published next month in the journal Animal Behaviour reports new insights into the "friendships" of female chimpanzees. (Friendship may very well be too strong of a word. Acquaintance or association is likely more accurate.) Foerster and colleagues used thirty-eight years of data from Gombe National Park and show that female chimpanzees aren't just bonding randomly with each other. Unsurprisingly, mothers, daughters, and sisters form the strongest bonds. However, among unrelated females, those of a low rank were more likely to seek out other females than were mid or high-ranking females. They also sought out other low-ranking females. 

There are multiple reasons low-ranking females might seek out others of the same rank. As Foerster and colleagues suggest, perhaps having an additional low-ranking pal makes competing for food easier or perhaps they seek others to dissuade higher-ranking members from bullying. The reason for their increased likelihood to seek out other female friends remains unknown at the time. It would be interesting to know how long these partnerships last. If they're temporary, why? What circumstances or events cause the end of the partnership?

 Finally, the presence or absence of offspring affects the likelihood a female will seek out other unrelated females. Females with young female offspring associate with other females less than expected, but females with young male offspring seek each other out. This may because it is especially important for males to interact socially with each other and bond, given that those bonds have the potential to last a life time. The same cannot be said for young female chimpanzees because they will eventually leave and find a new troop. Thus, it apparently is worth forming relationships with other young females within the troop.

Food for thought: What are the benefits and disadvantages to spending time with others (if you're a chimpanzee)?
How might this study differ if the study species had been bonobos? Remember, they have a very different social system!

Links of interest:
ScienceDaily article
Chimpanzee social systems
Chimps create traditions video clip
IUCN Redlist page on chimpanzees
Female chimps more likely to use tools
How human are chimps?

Foerster, S, McLellan, K, Schroepfer-Walker, K, Murray, CM, Krupenye, C, Gilby IC, Pusey, AE. Social bonds in the dispersing sex: partner preferences among adult female chimpanzees. Animal Behaviour, 2015; 105: 139 DOI: 10.1016/j.anbehav.2015.04.012
Goldberg TL, Wrangham RW. 1997. Genetic correlates of social behavior in wild chimpanzees: evidence from mitochondrial DNA. Anim Beh 54: 559-70. 
Goodall J. 1986. The chimpanzees of Gombe. Cambridge (MS): Belknap Pr.
Nishida T, Corp N, Hamai M, Hasegawa T, Hiraiwa-Hasegawa M, Hosaka K, Hunt KD, Itoh N, Kawanaka K, Matsumoto-Oda A, et al. 2003. Demography, female life history and reproductive profiles among the chimpanzees of Mahale. Am J Prim 59(3): 99-121. 

Williams, J. M., Liu, H. & Pusey, A. E. 2002. Costs and benefits of grouping in female chimpanzees at Gombe. In: Behavioral Diversity in Pan. (Ed. by Boesch, C., Hohmann, G., and Marchant, L. F.) pp. 192-203. Cambridge: Cambridge University Press.
Wrangham, R. and Smuts, B.B. (1980). Sex differences in the behavioural ecology of chimpanzees in the Gombe National Park, Tanzania. Journal of Reproduction and Fertility. Supplement, 28, 13-31.

Wednesday, May 27, 2015

New consequence of grooming discovered

Macaca fuscata grooming, Photo: Noneotuho
When primates groom each other, they improve their health and hygiene by removing parasites, dirt, and dead skin. This practice is also known as allogrooming. If a primate lives in a group, you'll likely observe allogrooming. (Note: this is not a term restricted to primates: other animals allogroom as well.)

The benefits of allogrooming extend beyond hygiene though, as evidenced by a study on mangabeys (Cercocebus torquatus lunulatus) that found difficult to reach areas were not groomed as often as one would expect if hygiene were the sole purpose of grooming (Perez and Baro, 1999). The practice also maintains and betters affiliative bonds (Seyfarth and Cheney, 1984; Stammbach and Kummer, 1982). Allogrooming promotes cooperation over food in Japanese macaques (Ventura et al, 2006). It reduces tension in Macaca fascicularis (Schino et al., 2005) and M. mulatta (Aureli, Preston, and de Waal, 1999).

During allogrooming, the primate doing the grooming is obviously focused on another individual, thus it is not entirely surprising that there's a tradeoff between allogrooming and vigilance. Macaque mothers that engage in allogrooming glance at their infants significantly less and those infants are the victim of harassment more often than when mothers are present (Maestripieri, 1993). In general, the costs of allogrooming are less well understood than the benefits. Energetic, cognitive, and other opportunity costs have all been suggested to exist (Russell and Phelps, 2013).

Brown spider monkey, Photo credit: Fir0002
A new study by Rimbach and colleagues describes a previously unknown consequence of allogrooming in the critically endangered brown spider monkey, Ateles hybridus. Studying sixteen individuals, Rimbach and colleagues found that the more connected monkeys had a greater richness of gastrointestinal parasites than monkeys that were less connected. This relationship is based on physical contact, as when the authors examined proximity alone, there was no such relationship. The authors concluded that the largest parasite risk to this particular community of brown spider monkeys is in fact social grooming.

Given that this species is critically endangered due to habit loss and hunting, identifying other potential threats to their health and survival is crucial. I'm not positive what the applications of this new study would be though, as it's impossible to stop primates from grooming each other, thus parasite transmission will continue to occur. If these monkeys aren't negatively affected by their parasites in a significant manner though, the threat posed may be small. One of the parasites found in this study, Strongyloides, has cased moderate to severe disease in grey wooly monkeys though (Lagothrix cana) (Mati et al., 2013), so it seems reasonable to assume a negative effect in brown spider monkeys as well. 

Food for thought: How might the adaptive benefits of allogrooming counter the effects of increased gastrointestinal parasites? Is it possible allogrooming no longer acts as a benefit to this particular primate population given their low numbers?

Further reading:
Sciencedaily article
IUCN Redlist page on Brown spider monkeys
What are they picking at?
Baboons groom in the morning to reap benefits in afternoon

Aureli F, Preston S.D, de Waal F.B.M. Heart rate responses to social interactions in free-moving rhesus macaques (Macaca mulatta): a pilot study. J. Comp. Psychol. 1999;113:59–65. doi:10.1037/0735-7036.113.1.59 
Russell, Y. I., & Phelps, S. (2013). How do you measure pleasure? A discussion about intrinsic costs and benefits in primate allogrooming. Biology & Philosophy, 28(6), 1005-1020.
Rimbach, R., Bisanzio, D., Galvis, N., Link, A., Di Fiore, A., Gillespie T.R.,. Brown spider monkeys (Ateles hybridus): a model for differentiating the role of social networks and physical contact on parasite transmission dynamics. Philosophical Transactions of the Royal Society B: Biological Sciences, 2015; 370 (1669): 20140110 DOI: 10.1098/rstb.2014.0110
Schino G, Scucchi S, Maestripieri D, Turillazzi P.G. Allogrooming as a tension reduction mechanism: a behavioral approach. Am. J. Primatol. 1988;16:43–50. doi:10.1002/ajp.1350160106
Seyfarth, R. M., & Cheney, D. L. (1984). Grooming, alliances and reciprocal altruism in vervet monkeys. Nature, 308, 541-543.

Wednesday, May 20, 2015

Questions every biologist should ask before starting research

It's getting to be that magical time of year again! No, it's not Christmas. I'm talking about the time of year when most professors and students have time off from coursework and can venture out to do fieldwork! Whether you're spending the better part of a full day traveling to Madagascar or driving a few minutes from home to your field site, field work is arguably the best part of being a biologist. That said, there are a few things I've learned from my own experiences that I think are worth sharing. Here are ten questions I think everyone should ask themselves before they head to the field.

1. What's the point? No really, what is the significance of your research? This matters because you're probably going to have to include a significant portion of your write-up, whether it's a thesis, academic paper, or paper for class, to what makes your research matter. Knowing the significance of your research also helps you if you're applying for any type of grant or funding because it will definitely be a major factor when considering if your research is worth funding.

Photo credit: US Fish and Wildlife
2. What are the applications of your research? Can anyone use your results? If you're working in a national or state park, are those officials going to use what you've learned in their practices? Or will your results make a difference to future research projects?

3. What's the minimum you need to accomplish this research? Stuff goes wrong. Plans fail. Something you never could have imagined happens and completely changes your plan. Can your research survive? What part of your methods is essential?

4. How much data do you want to collect? What's the least amount of data you need to collect in order for your project to be successful?

5. Who can you rely on for help? You'll likely have questions. Maybe something will go terribly wrong or maybe you'll think of a great idea while in the field. You might not have the time or resources to research that new idea or alternative plan fully, so who can you call? Who can you email for advice? Are there experts out there you haven't met personally, but who may be worth mustering up the courage to shoot an email to? I'm a big fan of collaboration and scientists helping scientists. Chances are, if you're polite and the person you're requesting help from isn't a total jerk, that person will extend a hand or point you in the direction of someone who can answer your question.

6. How excited you are about this research? Because you're going to encounter bumps in the road,
you're probably going to work on this project more than you ever imagined, and your project is going to be questioned and scrutinized, so you better love it. You better be invested. You're going to have a much harder time if this was really your advisor's idea and it's not your baby, it might be a long road.

Me observing sifakas
Photo credit: Saotra Rakotonomenjanahary
7. How can you connect with nonprofits and conservation organizations to make your research have a significant impact? Yes, your research probably has a very important indirect effect on conservation biology. Sure, studying the reproduction of the Vences' chameleon will help us understand more about the species, thus conserving it. But wouldn't it be better if you could pair with WWF for example and attach a more direct conservation project to your research, collaborate with a partner outside of academia, and make more of a difference?

8. What's the best way to collect data, knowing you're going to eventually enter it all into an Excel sheet and run statistical analyses on it? Think about how you're going to analyze your data. Think about how you're going to arrange your observation sheets and your field notebook so that it's painless (relatively) to enter it all into your computer. You also want your data to go smoothly from your Excel or FileMaker Pro or whatever to a statistical software package. Reformatting your data because you didn't take the time to think about it beforehand is painful and can be very time-consuming. If you're not sure about your statistics or data entry, go talk to a statistician (your advisor should also be able to help you with this).

9. Think about how you're going to present your final product and what details you might want to collect or note while you're doing research that aren't essential to your research question, but that might be nice to have. For example, it's hard to show a slide with a photo of everyone in your lab if you never took that photo. For your study on behavior and daily activity budget, it's impossible to determine if humidity might have had an effect on how much time your giraffes spent resting if you didn't measure humidity. Think about the little things.

10. What photos are you going to wish you had taken when you return home/finish your research? There's always at least one...

Wednesday, May 13, 2015

The rights of great apes around the world

Pan troglodytes in cage
A few weeks ago, it appeared that a New York judge had granted chimpanzees habeas corpus for the first time in the United States, which would have effectively declared chimps legal persons who could challenge their own imprisonment. It turned out this wasn't true. Great apes (gorillas, orangutans, bonobos, and chimpanzees) have not been awarded the same legal rights as humans in NY or in any other state. What rights do great apes have in the United States and how do these rights compare to other countries?

Currently, different states have different laws and punishments for animal abuse and cruelty. In Washington state for example, a person can face one year in prison and/or a $5,000 fine for animal cruelty in the second degree, with animals defined as nonhuman mammals, birds, reptiles, and amphibians. The only federal law to address animals used in laboratories, research, and in exhibitions is the Animal Welfare Act, which was signed in 1966 and has since been amended seven times. The Act also covers animal transport and how animals are treated by dealers. The Animal Welfare Act basically sets a minimum standard. States can then create stricter rules or not. Take a look at this link to see the best and worst states for animal rights according to the Animal Legal Defense Fund.

There are multiple organizations lobbying for more rights for great apes. In addiction to the Animal Legal Defense Fund, the Great Ape Project and the Nonhuman Rights Project both fight for great ape rights. The Nonhuman Rights Project argues that great apes and other highly intelligent animals such as dolphins and elephants should have legal rights, including personhood. The Nonhuman Rights Project have attempted multiple times to have chimpanzees and other animals are recognized as a person by expanding what common-law defines as a person. They are the group behind the most recent New York ruling mentioned earlier lobbying for the rights of two chimpanzees.

The Nonhuman Rights Project previously attempted to lobby for one of the two chimpanzees mentioned earlier. On December 5, 2014, a NY judge ruled that the chimpanzee, Tommy, was not entitled to legal personhood because no animal has been awarded this right previously and there is no precedent for this case. The judge cited Cupp's argument that rights are connected to "moral agency and the ability to accept societal responsibility in exchange for rights." Judge Sise stated that chimpanzees do not have responsibilities and cannot be held responsible for their actions as a human would. Sise did conclude that chimpanzees are not defenseless and that it is possible to press for further protections for chimpanzees, but the writ of habeas corpus does not apply. To read the full ruling, see here. The Nonhuman Rights Project is currently in the process of appealing this decision.
Chimpanzee named Enos going into space, Public Domain

In what would been a step forward for great ape rights, The Great Apes Protection Act generated interest and controversy when it was first introduced in 2011 (see here and here). This bill would have ended invasive research on great apes. However, it was never voted on before the end of the 2011-2012 session of Congress, thus it must now be reintroduced.

To summarize, while there have been many attempts to grant legal personhood to great apes, these attempts are repeatedly denied. The Great Apes Protection Act would have been a milestone for these animals, but sadly it did not pass. Thus, the only federal protection great apes have is through the Animal Welfare Act. Otherwise, the protection and laws governing what can and cannot be done to apes varies by state.

Let's move on and look at what rights great apes have in other countries.

In 2007, the Balearic Islands (an autonomous community and providence of Spain) became the first in the world to grant legal personhood to great apes. As of today, this remains the only place in the world where great apes are legally recognized as people. While great apes don't enjoy legal personhood in Spain, they can no longer be used in experiments, circuses, and television shows and commercials.

In Belgium, great apes can no longer be used in research since 2008. The same is true for Austria (2006), Sweden (2003), the Netherlands (2002), and the European Union (2010). Japan no longer permits invasive chimpanzee research as of 2006. See a review of the international laws passed here.

Sign for Lucy at National Museum of Ethiopia, Photo Adam Jones
There are those who very strongly believe chimpanzees and bonobos should not be in the genus Pan but in Homo (see Wildman et al., 2003 for a review of the genetics), an argument that would significantly strengthen the case for granting chimpanzees and bonobos the same rights as humans. Placing chimps and bonobos in the same genus as humans would be a large shake up in our evolutionary tree. Lucy, the famed human ancestor shown to the right, is not even in the genus Homo but in Australopithecus. As of now though, chimps and bonobos remain firmly in the genus Pan and are quite far from achieving the same rights as humans.

While other countries have taken significant steps towards protecting great apes, the United States affords these animals no more protection than other primates and animals on a federal level. If something such as the Great Ape Protection Act were to be passed, distinct and ape-specific rules would apply to these intelligent cousins of ours, but no such legislation has been passed. Great apes and other primates in the US are still used in biomedical research, kept privately in some states, and are not awarded any special legal considerations. There are many groups working hard to change this, but it remains to be seen if the US will ever follow the likes of the Balearic Islands and award legal personhood to apes.

Food for thought:

Should humans and great apes both be entitled to the same rights under federal law? What would the implications for this be? Would this change our perception of what defines what it means to be human or would we draw a line between the legal term and our everyday meaning behind what makes us human?

Links of interest:
The Great Apes Project is another organization that seeks to defend the rights of non-human great apes. 
Video from NY Times, "Animals are Persons Too"
Federal laws governing animal care
Should a chimp be able to sue its owner?-NY Times article
A History of Chimps in Medical Research 
Study finds one third of Americans believe animals deserve the same rights as humans

Richard L. Cupp Jr., Children, Chimps, and Rights: Arguments from "Marginal" Cases, 45 Ariz, St LJ 1, 13 (2013)
Wildman, D. E., Uddin, M., Liu, G., Grossman, L. I., & Goodman, M. (2003). Implications of natural selection in shaping 99.4% nonsynonymous DNA identity between humans and chimpanzees: enlarging genus Homo. Proceedings of the national Academy of Sciences, 100(12), 7181-7188.