This week’s BEACON Researchers at Work blog post is by University of Washington students Sarah Hammarlund and Katie Dickinson.
The existence of the Sasquatch (also referred to as Bigfoot) has been debated for centuries. Alleged witnesses have described the forest-dwelling ape-like creature as being covered in hair, with large eyes, a pronounced brow, and a large, low-set forehead. Most scientists discount the existence of Bigfoot and consider it to be a combination of folklore, misidentification, and hoax, rather than a living animal, because of the lack of physical evidence and the large numbers of creatures that would be necessary to maintain a breeding population. However, indigenous groups in the Pacific Northwest have long told legends of the creature, and more recently researchers in the PNW may have identified what makes Sasquatch such an elusive creature.
A Sasquatch sighting in the lab
Deep in the Hoh rainforest on the Olympic peninsula in Washington State, researchers have discovered a remote population of Sasquatches. Interestingly, the population can actually be divided into two types: Sasquatches that produce a strong unpleasant odor, and those that do not produce any odor. The odor appears to have the amazing ability to obscure the population from humans by both repelling and disorienting the humans. Scientists stumbled upon this remarkable phenomenon when a team of researchers studying the Olympic marmot included a scientist who is anosmic, lacking the ability to perceive odor. While all other members of the research team became confused and retreated from the area, the anosmic researcher came upon a family of scent-producing individuals, and began studying them. Recent evidence suggests that rare mushrooms must be gathered in order for Sasquatches to produce the oily foul-smelling compounds. In addition, it has been argued that the odor can be considered a “public good” – the Sasquatch population as a whole can benefit from the protection provided by odor producers because non-producers in the neighborhood of producers are also shielded. Researchers therefore consider scent producers to be “cooperators.” Sasquatch sightings have occurred periodically for decades and it has been observed that these are always solo creatures. It is now believed that all of the Bigfoot sightings are of “social cheats” – types that do not incur the cost of producing the scent, and are protected as long as they are in the vicinity of odor producer. However, when the cheaters become isolated, they are vulnerable to Bigfoot hunters and researchers. It is suggested that the cooperative Sasquatch stench has allowed large populations of the creatures to exist for years and yet remain a mystery.
Investigating the social context of odor-production
According to social evolution theory, a fundamental first step in the study of any trait is to demonstrate its fitness consequences in a social context (West et al., 2006). If the Sasquatch odor is a cooperative public good and odor-negative individuals are social cheaters, then the following predictions (Zhang & Rainey, 2013) should hold:
- Populations of odor producing Sasquatches should be more successful (less likely to be captured by scientists or hunters) than populations of non-producers when types are separated.
- Non-producers should outperform producers in mixed populations.
- Populations of non-producers should perform better than populations of producers when environmental conditions change such that scent production is not required (i.e. no scientists/hunters present).
- When rare, producers should not invade a population of non-producers.
Unfortunately, the discoverer of the Sasquatch population has since disappeared, but a notebook was found at a field site containing some interesting observations. One hypothesis is that the stress due to habitat fragmentation in the rainforest may actually favor odor producers. This may be because population fragmentation can isolate cooperators and cheaters from one another, allowing only cooperators to benefit from public good production. Additional anosmic scientists have been contacted to aid in the investigation of this hypothesis in the natural Sasquatch population.
Using microbes to explore public good production
Pseudomonas aeruginosa grown in minimal media. The green culture is the wild-type ‘cooperator’ and the white is our ‘cheater’ strain.
Sarah Hammarlund and Katie Dickinson in the Kerr lab at the University of Washington are using microbes as a model system to address some of the ecological and evolutionary factors involved in the public good production reported in the Sasquatch population. We are using two strains of the bacterium Pseudomonas aeruginosa: a quorum sensing “cooperator” that produces protease (a public good) and a quorum sensing-defective “cheater” which benefits from public good production without incurring the cost of production. We are currently exploring how the environment affects the relationship between the cooperator and cheater. Specifically, we are investigating whether stress can benefit cooperation. In a spatially structured environment, stress may favor cooperation, since public goods become localized around cooperators (Hamilton, 1964; Fletcher & Doebeli, 2009). Furthermore, when public good producers are isolated from cheaters, this may allow for further adaptation to the stressful environment in the cooperator background.
Pseudomonas aeruginosa colonies on skim milk agar. The protease-producing wild-type strain has large ‘halos’ where casein proteins have been broken down.
Cooperation has puzzled evolutionary biologists since Darwin. We are interested in understanding not only how cooperative behaviors evolve but also how they are maintained, particularly in the face of cheaters. Recently, with the help of fellow BEACONite Brian Connelly, we entered the world of computer modeling to create a simulation of our system. In addition, Sarah has applied for
a Fulbright scholarship with the hopes of researching the evolution of cooperation between species at Oxford with Kevin Foster before beginning graduate school. Katie, in addition to her BEACON administrative work, plans to continue studying cooperation and altruism in the Kerr lab while debating the costs and benefits of grad school. We both enjoy photography and the great PNW outdoors, but despite being camera-at-the-ready hikers we have yet to cross paths with a Sasquatch.
For more information about Sarah and Katie’s work, you can contact Sarah at sarahham at uw dot edu and Katie at katiejd8 at uw dot edu. BEACON would like to caution that Sarah and Katie are not a reliable source for information about Sasquatches.
