Tuesday, April 28, 2015

Female chimps are more likely than males to use tools when hunting

The hunted (a galago). Credit: flickr user Robertsphotos1
Jill Pruetz and colleagues recently published a great study about sex differences in tool use in chimpanzees (Pan troglodytes verus). Pruetz works at Fongoli in southeastern Senegal. Fongoli is different than most chimpanzee study sites because it's actually a woodland-savannah. Most chimpanzee study sites, such as Gombe, are characterized by deciduous, woodland, or evergreen forests. Anyways, chimpanzees at Fongoli hunt bushbabies or galgoes (Galago senegalensis ) using sticks they've essentially sharpened into spears. The chimps will break off a branch and frequently use their teeth to sharpen the end of the stick. They're taking an object found in their environment and modifying it to suit their needs. This is the only site where chimpanzees have been observed hunting using tools. Recently and after years of data collection, Pruetz and colleagues discovered some interesting differences in hunting between the two sexes.

Over the course of the study, ninety-nine instances of chimpanzee hunting were recorded, including episodes during which tools were used. Both male and female chimpanzees hunt Galago more than any other vertebrate at Fongoli. After observing and documenting episodes of chimpanzees hunting with the use of tools, females were significantly more likely to use a tool than were males. Pruetz and colleagues (2015) report 170 instances of females using tools compared to 130 instances of males using them when hunting.

Uh oh fellas, does this mean female chimps are smarter than males? No, it doesn't. Let's not jump to any conclusions here.

Pan troglodytes. Photo credit: William Warby
There could be multiple reasons for females hunting with tools more than males. Perhaps females are smarter than males in this population and use tools to aid them when hunting. On the other hand, perhaps females use tools because they are weaker physically than male chimps, thus tool use makes hunting easier for them and compensates for this difference in strength. Both are possible answers and there are likely others. The study showed this difference in males and females is significant, thus it is not random that Pruetz and colleagues observed more females using tools when hunting than males. Pruetz and colleagues hypothesize that males may use tools less often when hunting Galago than females because males usually hunt larger prey, and thus when they flush out Galago individuals, it is opportunistic: they are not using tools to hunt baboons or other large prey they're targeting.

This isn't the only difference between the sexes when it comes to chimpanzee hunting. Males are known to hunt more than females (Fahy et al., 2013; Stanford, 1999). At Fongoli, Pruetz and colleagues also found while Galago made up 75% of females' prey, it accounted for only 47% of males'. Only male chimpanzees at Fongoli hunt patas monkeys (Erythrocebus patas). Successful hunters were more likely to be male than female. However, when both sexes used tools to hunt Galago, there was no difference in success rate between males and females.

As Pruetz and colleagues discuss in this paper, their study has implications for human evolution. Tools likely played a part in how our early human ancestors hunted, thus studying chimpanzees allows us to better understand what hunting may have looked like in early humans.

Food for thought: Can you think of any reasons why females use tools to hunt more frequently than males do?
Why might chimps use tools to hunt at Fongoli and not elsewhere?

Links of potential interest:
Video of Pruetz discussing chimps hunting bushbabies
Nat Geo article on Fongoli chimps
Tool Use, Hunting, and Other Discoveries

J. D. Pruetz , P. Bertolani , K. Boyer Ontl , S. Lindshield , M. Shelley , E. G. Wessling. New evidence on the tool-assisted hunting exhibited by chimpanzees (Pan troglodytes verus) in a savannah habitat at Fongoli, Sénégal. Royal Society Open Science, 15 April 2015
Fahy, G.E., Richards, M., Riedal, J., Hublin, J., Boesch, C. 2013. Stable isotope evidence of meat eating and hunting specialization in adult male chimpanzees. Proc. Natl Acad. Sci. USA 110, 5829-5833 
Stanford, C.B. 1999. The hunting apes:meat eating and the origins of human behavior. Princeton, NJ: Princeton University Press.

Wednesday, April 22, 2015

NY chimps NOT granted habeas corpus-not recognized as legal persons

A story received wide circulation yesterday stating that two Stony Brook University lab chimpanzees had been granted the writ of habeas corpus, thus effectively giving them the right to challenge their imprisonment and making them human in the eyes of the NY court. This is NOT the case.

The court document challenging the imprisonment of these two chimpanzees, Leo and Hercules, filed by The Nonhuman Rights Project, has the words "writ of habeas corpus" crossed out. See the document here. While the judge, Barbara Jaffe, originally did not strike out these words in the first document, she has since amended it.

Portion of the amended court document
However, this case is still ground-breaking, as it is the first time chimpanzees have ever been granted an Order to Show Cause. Chimpanzees now have the right to be heard (remember, this case still has to go to court). It will be interesting to follow this case and see what decision is made. Although chimpanzees (and any non-human animal) have never been granted legal personhood, it seems they might be getting closer.

In December of 2014, a court in Argentina appeared to give an orangutan, named Sandra, human rights, but once the court document was properly translated into English, it became clear the media originally erred and this was not the case. Whether or not Sandra is entitled to human rights is now a confusing matter, but this no longer looks like the landmark case it was made out to be.

As of today, it appears that apes have not been granted the same rights as humans in the United States. They have not been declared non-human persons and have never been granted the writ of habeas corpus. 

Links of interest:
How human are chimps?
The Nonhuman Rights Project
Jane Goodall's stance on chimpanzees and their rights

Tuesday, April 14, 2015

Mountain gorilla genome sequenced

Mountain gorillas (Gorilla beringei) are arguably the cutest species of gorilla. They're especially fuzzy but they're also especially scarce. There are fewer than 800 individuals left on the planet and they are found only in the Virunga Volcanoes in Uganda, Rwanda, and The Democratic Republic of Congo (IUCN). That's it. There are zero individuals in zoos right now.

Juvenile mountain gorillas, Photo credit: Philip Milne
Because there are so few individuals left, mountain gorillas are at risk of genetic inbreeding.  This is when there are so few individuals that mating opportunities are limited. One of the greatest benefits of sexual reproduction is genetic diversity, creating new gene combinations in your offspring that you don't have. With inbreeding, individuals mate with those closely related genetically. This can be damaging to a population because diversity protects us: one disease can't wipe out the entire population if we're all different. (Check out UC Berkley's excellent explanation of inbreeding depression here for a refresher on the topic or to learn it for the first time.) With less than 800 individuals remaining, the risk of inbreeding is much higher in mountain gorillas than in other great ape populations.

A paper by Xue and colleagues (2015) published in Science last week details the genetic consequences of prolonged population decline in eastern lowland and mountain gorillas. Completing a whole-genome sequence on this species has led to some fascinating and some surprisingly optimistic findings.

Xue and colleagues report homozygosity, or having two forms of the same gene that are identical, is higher in mountain and eastern lowland gorillas than in western lowland gorillas and even the most inbred populations of humans. Within the study populations, chromosomes were found to be homozygous on over one third of their total length, indicating that the parents of these individuals are related. The degree to which this homozygosity extends suggests that mountain gorillas have experienced several recent doses of inbreeding.

Mountain gorilla adults and infant. Photo credit: Derek Keats
The effective population size of mountain gorillas is currently 273 individuals (plus or minus 54). A term used in genetics, effective population size refers to the number of breeding individuals in an ideal population that would display the same gene frequencies as would occur randomly due to genetic drift. This is a good measure of genetic diversity.

The study also found that mountain gorillas have a lower rate of the harmful loss-of-function variants than do their more populous relatives, western lowland gorillas. Loss-of-function variants can be fatal. Mountain gorillas also appear to have survived at low population numbers for a long time, thousands of years. This is excellent news! Although it's certainly doesn't mean we should relinquish our conservation efforts.  The authors of this study find further evidence to suggest that the last great environmental change (tropical forests to savannah) caused a collapse in mountain gorillas and western lowland gorillas.

While inbreeding usually makes for a risky situation as environmental changes or disease, for example, could wipe out substantial parts of a population, it seems mountain gorillas are doing better than expected. They are inbred but they're doing well.

Food for thought: How does this new study relate to gorilla conservation issues? How might a better understanding of population genetics help combat poaching and the illegal wildlife trade?

Links of interest:
IUCN Redlist overview of species
Gorilla Doctors Website
Paper, "Great ape genetic diversity and population history"

Xue, Y., Prado-Martinez, J., Sudmant, P. H., Narasimhan, V., Ayub, Q., Szpak, M., ... & Scally, A. (2015). Mountain gorilla genomes reveal the impact of long-term population decline and inbreeding. Science, 348(6231), 242-245.

Friday, April 10, 2015

The fate of western lowland gorillas and central chimpanzees over the next decade

The International Union for the Conservation of Nature (IUCN) recently published a new report detailing what threats central chimpanzees (Pan troglodytes troglodytes) and western lowland gorillas (Gorilla gorilla gorilla) face and identifying conservation priority areas for the next ten years.

Central chimpanzees are currently listed as endangered whereas western lowland gorillas are considered critically endangered. The new regional action plan identifies three main threats to the survival of both great apes including 1) poaching (forbidden by national laws but still a serious problem), 2) disease and 3) habitat loss. These main forces threatening central chimps and western lowland gorillas are aided by increased habitat access, a growing demand for bushmeat, and a lack of law enforcement as well as corruption.

Obstacles detailed in the regional action plan include a lack of solution to the Ebola endemic and mining and logging in forests that were once remote and inaccessible. Mining and logging aren't directly threatening to apes, but these industries create access through roads or railroads to great ape habitat. These animals and others can then be poached. Another obstacle is the growth of agriculture, specifically palm oil, which will mean the loss of forested areas that are presently home to chimps and gorillas. The report also details an overall lack of management, law enforcement, adequate monitoring and research. A legal system with substantial corruption is making matters worse.

The report identified six new priority landscapes in addition to the twelve first identified in 2005. Fifty-one percent of central chimpanzee and western lowland gorilla geographic range is now included in these eighteen landscapes, covering 77% of chimp and gorilla population. These priority landscapes are not all protected areas however. In fact, the protected areas within these landscapes currently protect 21% of the population.

The IUCN report recommends the following actions to ensure the survival of central chimpanzees and western lowland gorillas: law enforcement and better regulations, national and regional land-use planning, and outreach to all sectors that deal with protecting natural resources and land.

Monitoring the cause and effect of responses in reducing pressures that are detrimental to great ape populations will allow researchers to determine the success of this regional action plan. The first year will be about implementation with reports that are fully accessible to the public available in year ten.

The action plan concludes by stating that much has been accomplished since 2005. However, more needs to be done as the region continues to experience population growth (humans) and an increasing and global demand for extracting natural resources from the area also creates new problems. The report is optimistic that holistic solutions that allow biodiversity protection and the well-being of humans can be found and reached if governments make thoughtful decisions that look far into the future.

You can read the full regional action plan here.

Links of interest:
A.P.E.S. Portal
IUCN Primate Specialist Group
Ebola and Primates
SMART-Wildlife Conservation Tool 
In Situ Conservation I and II

Friday, April 3, 2015

Locals knowledgable of ecosystem are more likely to conserve

A study by Sawchuck and colleagues (2015) published in the journal Marine Policy explores how angler understanding of the ecosystem and fishing practices affects their views on conserving Puget Sound rockfish (Sebastes spp.). Multiple species of Puget Sound rockfish were listed under the Endangered Species Act in 2010 (Drake et al., 2010). The current study conducted by Sawchuck and colleagues (2015) found that fisherman with knowledge of the Puget Sound rockfish support conservation efforts, and individual preference on conservation efforts are influenced by where those individuals fish. Clearly, knowledge is power when it comes to conservation.

While this study is specific to conserving rockfish in Puget Sound, something I admittedly know little about, the results are applicable to many conservation biologists. Those who live closely alongside and act as part of the ecosystem are more likely to develop an attachment and appreciation of it. I know the more time I spend surrounded by nature, the more I both understand and love it. As wildlife increasingly comes into contact with humans, studies like this one that examine how people view conservation initiatives are important. They help us better understand what makes people want to conserve certain species.

Yelloweye rockfish, Sebastes ruberrimus
As the authors state in this paper, there are many factors (economic, social, cultural) that influence a person's beliefs, support, and compliance with conservation efforts. This holds true whether we're discussing fish, primates, or wild cats. Sawchuck and colleagues (2015) also state that while the Puget Sound rockfish has been studied previously, "...few have engaged recreational anglers in the recovery process and examined the underlying knowledge and perceptions that may ultimately affect support for recovery measures."

Scientists can declare that we need to protect a certain species and go through all of the hoops and bureaucracy associated with getting that species attention on a national or state level, but if there isn't local support and cooperation for conservation plans, it seems obvious to me that those plans will be less successful. People live alongside these animals and ecosystems and interact with them on a regular basis, something we're beginning to understand and appreciate more as scientists. Granek and colleagues (2008) found that commitment to conservation is higher when recreational fisherman are involved in protecting their fish from external threats to recreational fishing (commercial fishing or habitat destruction), which may simply be a matter of protecting self-interest but maybe not. The more recent study conducted by Sawchuck and colleagues (2015) shows that knowledgeable local stakeholders are more likely to support conservation.

Food for thought:

How do you think local knowledge should influence policy decisions?
When is it appropriate for scientists to include the beliefs and ideologies of locals? When might it not be appropriate or logical?

Drake JS, Berntson EA, Cope JM, Gustafson RG, Holmes EE, Levin PS, et al. Status of five species of rockfish in Puget Sound, Washington: Bocaccio (Sebastes paucispinis), Canary Rockfish (Sebastes pinniger), Yelloweye Rockfish (Sebastes ruberrimus), Greenstriped Rockfish (Sebastes elongatus) and Redstripe Rockfish (Sebastes proriger). U.S. Department of Commerce, NOAA Technical Memorandum; 2010. NMFS-NWFSC-108, 234 p.
E.F. Granek, E.M.P. Madin, M.A. Brown, W. Figueira, D.S. Cameron, Z. Hogan, et al. Engaging recreational fishers in management and conservation: global case studies Conserv Biol, 22 (5) (2008), pp. 1125–1134
Sawchuk, Jennifer Heibult, et al. "Using stakeholder engagement to inform endangered species management and improve conservation." Marine Policy 54 (2015): 98-107.