What you may not have read about the scary decline in Grauer's Gorilla numbers

Cover of the WCS and FFI Report

Over a week ago, a report from Wildlife Conservation Society and Fauna and Flora International hit the press about Grauer's gorillas (Gorilla beringei graueri).  Grauer's gorillas, previously known as eastern lowland gorillas, are one of four subspecies of gorillas. Consuming fruits and vegetation, Grauer's gorillas are the largest subspecies. They are listed as endangered and are found only in the Democratic Republic of Congo (DRC).

They made the headlines, and not just on the science news sources, because the latest data shows their numbers have declined dramatically. Over the past twenty years, Grauer's gorilla numbers have declined by an astonishing 77%, with only 2, 585 animals estimated alive today. Their range has been reduced by 84-93%. If you saw this on the news, you probably also saw that civil unrest and other human pressures are the reasons behind the sudden decline. This is hardly surprising.

What you may have missed are some of the more nuanced details behind these numbers, details that can be found in the report itself, which also covers chimpanzees in the same area. In their report titled, "Status of Grauer's Gorilla and Chimpanzees in Eastern Democratic Republic of Congo: Historical and Current Distribution and Abundance," we learn that increases in agriculture and the availability and use of shot guns caused habitat loss and extinctions of local populations in the 60s and 70s. Surveys done in the 90s also suggested species decline due to expanding human populations and hunting. The late 90s and early 2000s saw these threats exacerbated when refugees from civil war in Rwanda, internally displaced people, and armed groups in the DRC put further pressure on DRC forests and wildlife. This influx of people needed fuel for firewood, land for agriculture, timber, and also hunted wildlife and mined.

The main threats to Grauer's gorillas are hunting for bushmeat and habitat loss due to the spread of agriculture. Hunting practices are related to artisanal mining though. These mines are found adjacent to or even in protected areas, are illegal, and are controlled by armed militias (Kirkby et al., 2015). They allow people an economic opportunity to earn an income quickly and attract people from multiple social classes(Kirkby et al., 2015). Once working at these remote mines, miners rely on bushmeat for food and consume primates and other large mammals(Kirkby et al., 2015). The miners aren't evil people though, as many said they wouldn't hunt bushmeat if alternatives were available and also said they wanted to leave the mining industry.

SMART patrols, reconnaissance surveys, transects, and occupancy surveys were used to determine gorilla decline and show that one of the areas with the highest number of animals, Kahuzi-Biega National Park saw a decline of 87% in gorilla density, and this is with a portion of the Park protected reasonably well. Seven of the eleven sites surveyed through encounter rates show an average decline of 94%. These findings are enough to support raising the IUCN status of Grauer's gorillas to critically endangered.

Occupancy probability model from report. Blue areas
mean high likelihood and red very low likelihood of gorillas

Behind these alarming numbers, a story emerges of people pushed beyond their limits and forced to use the forests available in order to survive. Civil war, changes in government, and general civil unrest gives the DRC its tumultuous historic timeline, the effects of which not only impact people but also the flora and fauna of the region. Some may find it easy to forget, but humans and nature are intricately linked.

You may think you have no connection to this story other than one as an innocent bystander, but the resources mined from the DRC are part of an industry many of us play into. Most of the mines are for cassiterite, gold, coltan, and wolframite. The first is an important source of tin, the second you may be wearing now, coltan is used in electronics such as our cell phones, and the last is an important source of tungsten. Given that mining is one of the main reasons Grauer's gorillas are threatened, chances are many of us are connected to this problem, as uncomfortable as that may make us feel.

Links of potential interest
IUCN Page for Grauer's Gorillas
IUCN Categories and Their Criteria
BBC's Country Profile of the DRC

Works cited:

Kirkby, A., Spira, C., Bahati, B., Twendilonge, A., Kujirakwinja, D., Plumptre, A., ... & Nishuli, R. (2015). Investigating artisanal mining and bushmeat around protected areas. Unpublished report to USAID and Arcus Foundation.

Plumptre, A.J., Nixon, S., Critchlow, R., Vieilledent, G., Nishuli, R., Kirkby, A., Williamson, E.A., Hall, J.S. & Kujirakwinja, D. (2015). Status of Grauer’s gorilla and chimpanzees in eastern Democratic Republic of Congo: Historical and current distribution and abundance. Unpublished report to Arcus Foundation, USAID and US Fish and Wildlife Service.

Bonobos focus on the positives: humans focus on the negatives

Photo: Mark Dumont

A recent study done on captive bonobos (Pan paniscus) reports that these apes focus on images that are of a more positive nature (compared to images of danger or aggression). Using a test designed to understand attentional bias in humans, researchers from various institutions in The Netherlands studied attentional bias in bonobos, our close relatives.

Four female bonobos each completed either twenty-five or twenty-six trials in total over thirteen separate testing sessions. They were briefly shown two images and then a dot appeared on the screen which remained there until the individual tapped the dot. Upon tapping the dot, the individual is rewarded with a food item. In half of the trials, the images briefly shown were of a bonobo in some sort of emotional state, such as pant hooting, playing, or in distress. In the other half, the images were of a bonobo in a neutral state.

By looking at the reaction time, Kret and colleagues (2016) were able to determine that bonobos are more captivated by images of other bonobos that are affiliative or protective rather than images with bonobos in distress or aggression, which has found to be the case most often for humans (Vuilleumier and Schwartz, 2001; Williams et al., 2004; Tamietto et al., 2005; Flaisch et al., 2009).

Images of yawning, grooming, and sexual behavior caught the bonobo's attention the most. Reaction time was longest for yawning, followed by grooming and then sexual behaviors. Yawning is a contagious behavior in humans and also for bonobos (Palagi et al., 2014). Grooming and sexual behavior are both types of behavior that reduce tension (Manson et al., 1997; De Waal, 1997; Crockford et al., 2013).

The increased attention devoted to these social behaviors suggest that they are of greater importance to bonobos than aggressive behaviors or actions associated with a threat. Given that this isn't the case with humans and what captures our attention, this study highlights another intriguing difference between the two species.

Links of potential interest:
Paper in PNAS 
Are bonobos more peaceful than chimpanzees?
IUCN page on bonobos


Works cited:
Crockford, C., Wittig, R. M., Langergraber, K., Ziegler, T. E., Zuberbühler, K., & Deschner, T. (2013). Urinary oxytocin and social bonding in related and unrelated wild chimpanzees. Proceedings of the Royal Society of London B: Biological Sciences, 280(1755), 20122765.

De Waal, F. B. (1997). The chimpanzee's service economy: food for grooming. Evolution and Human Behavior, 18(6), 375-386.

Flaisch, T., Schupp, H. T., Renner, B., & Junghöfer, M. (2009). Neural systems of visual attention responding to emotional gestures. Neuroimage, 45(4), 1339-1346.

Kret, M. E., Jaasma, L., Bionda, T., & Wijnen, J. G. (2016). Bonobos (Pan paniscus) show an attentional bias toward conspecifics’ emotions. Proceedings of the National Academy of Sciences, 201522060.

Manson, J. H., Perry, S., & Parish, A. R. (1997). Nonconceptive sexual behavior in bonobos and capuchins. International Journal of Primatology, 18(5), 767-786.

Palagi, E., Norscia, I., & Demuru, E. (2014). Yawn contagion in humans and bonobos: emotional affinity matters more than species. PeerJ, 2, e519.

Tamietto, M., Latini Corazzini, L., Pia, L., Zettin, M., Gionco, M., & Geminiani, G. (2005). Effects of emotional face cueing on line bisection in neglect: a single case study. Neurocase, 11(6), 399-404.

Vuilleumier, P., & Schwartz, S. (2001). Emotional facial expressions capture attention. Neurology, 56(2), 153-158.

Williams, M. A., & Mattingley, J. B. (2004). Unconscious perception of non-threatening facial emotion in parietal extinction. Experimental Brain Research, 154(4), 403-406.

The latest puzzling chimpanzee behavior

Young chimpanzee. Photo credit Sabine Bresse

Of the animal kingdom, chimpanzees, Pan troglodytes, are one of the well-known tool users. All populations of wild chimpanzees studied have been observed using leaves to obtain food and some populations have been observed modifying branches to forage for termites and even fashioning spears to hunt bushbabies (Shumaker et al, 2011; Boesch, 2012).

As is the case with studying many primates, our knowledge of tool use and how it is passed from generation to generation is limited by the number of field sites where long-term research occurs. Chimpanzees must first become used to human presence (or habituated) before their natural behavior can be studied, and this can take a great deal of time.

Theorizing that the repertoire of chimpanzee behavior is much wider than what is currently known, Kühl and colleagues used camera traps to study multiple populations of chimpanzees in West Africa that are not habituated. This is when they noticed some very interesting behavior. Researchers first noted unusual piles of rocks in trees and used camera traps to determine what was behind this puzzle. They observed chimpanzees picking up rocks from piles around or in trees and then throwing them at the tree.

Through the camera trap footage, researchers were able to determine that chimpanzees would throw the stones at the trees and vocalize a long-distance pant-hoot at the same time. The stones are mainly thrown by adult males and they seem to be independent of any sort of foraging behavior. The same chimpanzee was often observed returning to the tree and engaging in the behavior. This strange accumulative stone-throwing has only observed in West Africa and was seen in four populations of chimpanzees.

Stone throwing may be a type of male display, during which the individual attempts to draw attention to one's strength and impress other chimps. Kühl and colleagues theorize that using the stones in this manner may produce a loud sound resulting in a greater display. Another theory the authors present is that this may be a symbolic behavior. In either case, obviously more data is needed. Stone-throwing chimpanzees raises more questions than it does answers in terms of behavior and possibly cognition in the case of the latter theory.
 
This work goes to show that you can still learn a great deal about a comparatively well-studied primate species even if you're not Jane Goodall and haven't been working at the same research site for decades. Kühl and colleagues have captured some truly fascinating behavior that raise a series of new questions using technology to their benefit.

Links of potential interest:
Video of behavior
Pan African Programme: The Cultured Chimpanzee
How human are chimps?
Females more likely to use tools when hunting



Works cited:

Boesch, C. Wild Cultures: A Comparison between Chimpanzee and Human Cultures. (Cambridge University Press, 2012).

Kühl, H. S. et al. Chimpanzee accumulative stone throwing. Sci. Rep. 6, 22219; doi: 10.1038/srep22219 (2016).

Shumaker, R. W., Walkup, K. R. & Beck, B. B. Animal Tool Behavior: The Use and Manufacture of Tools by Animals. (JHU Press, 2011).