Fido’s Big Feat: Human Communication
By Bio 94 Student Megan Ha
You have had a long day from school or work, or maybe both. You pull up to your house drained, mentally and physically, but when you open the door, you forget it because your furry friend is ecstatic to see you and greets you with slobbery kisses. The fact that your dog can relieve even a little bit of stress is due to that strong loving bond you two share, similar to that of a mother and child. Many people say dogs are therapeutic companions, but are they really? Science says yes! There is biological evidence supporting this. Higher levels of oxytocin have been found in urine of individuals with strong bonds with their dogs. Oxytocin is a hormone important in the bonding between mother and child, and when given to animals (including humans), aid in relaxation and coping with stress. However, dogs were not always bred for companionship. So where did man’s best friend come from?
Dogs, (Canis lupus familiaris) are descendants of wolves (Canis lupus). What does that mean? Long ago, perhaps about fifteen to thirty thousand years ago, wolves were incorporated into human civilization. How this came to be still remains unclear. However, what is clear is that over that span, the appearance, personality, and cognitive and physical abilities have been altered significantly. Although your typical dog may not be able to take down a moose, it has traded in its physical abilities for a new set of skills, human social skills.
The key factor here is domestication. Living among humans does not necessitate domestication. It can be purely experiential, in which case, is called habituation. When alteration of the genetic code is involved, it is then called domestication. We say dogs are domesticated animals. Does that mean dogs are genetically predisposed to have the ability to socially communicate with humans? Does this mean wolves raised in a human social environment will not have the same communication abilities as dogs?
Scientists at Eotvos University in Budapest wondered those exact questions and designed two experiments in which the social ability of dogs and wolves would be tested. Four to six day old wolf pups and dog puppies were assigned to be raised by humans in very similar experiences, both spending most of the day and night with their human caregiver. In the first experiment, five week-old puppies, nine week-old puppies, and nine week-old wolf pups were tested by a simple experiment. The objective was for the animal to get food from an inaccessible plate which would require human assistance. All the animal had to do was simply make eye contact with their human, and they would be rewarded with food from the plate. By the second minute of unsuccessfully trying to get the food, dog puppies began to look to their human for help. By the fourth minute, dogs had already established the key to getting the food while the wolves still attempted to reach the food on their own. At the end of the experiment, wolves still failed to realize that eye contact was the key to unlocking the food.
In the second experiment, dogs and wolves were presented with a task of retrieving food by pulling a rope with food tied to the end to reach the food. After mastering the task, both were presented with a rigged version of the experiment in which it was impossible for them to obtain the food. Dogs looked back at their caregiver for help and wolves did not. This concludes that although wolves were fully socialized, they still treated the situation as a physical obstacle. These experiments show that dogs’ social ability to communicate with humans is a direct result from domestication.
Bacteria Mediate Communication Between Hyenas
By Bio 94 Student Ava Pournejad
Mammalian evolution has occurred hand in hand with microbes. It is known that microbes outnumber human cells in our bodies. Along with aiding in digestion, microbes are also required for social communication among animals. A study conducted by Theis et al at the Michigan State University showed that bacterial species present in the scent glands of hyenas are responsible for their social behavior, including mating, same and different species recognition and territorialism. The results obtained by the authors confirmed the fermentation hypothesis of chemical recognition. According to this hypothesis, which was introduced over 30 years ago, microbial species exist in the scent glands of mammals and their aromatic by-products provide the characteristic odor to animal scent. In addition, the microbial species present in the scent of one species or social group differ significantly from other species or groups (Theis et al, 2012).
Hyenas usually live in large groups or ‘clans’ within which subgroups form, intermingle and dissolve every day. For the purposes of communicating with each other and within each subgroup; for protecting the clan from other hyenas and larger animals and for mating purposes, these mammals employ a large number of specific social behaviors. One of the most common is the act of ‘pasting’, which refers to the rubbing of the secretion of their scent glands onto plants or other surrounding fixtures to mark a scent trail (Theis et al, 2012). The ‘paste’ is a lipid rich compound and contains large numbers of microbes. The paste is the byproduct of fermentation that happens in these microbial species.
The authors collected paste samples from four hyena clans living in the Masai Mara National Reserve, Kenya (Southern Comfort, Fig Tree, Mara River and Emarti Hill). Animals sampled included males, females, pregnant females and lactating females. Paste samples were collected directly from the anal scent pouches of these animals following tranquilization. They were then analyzed by scanning electron microscopy that showed the presence of lipid droplets and rod shaped bacterial cells. The bacterial species were indentified and it was found that along with 78 established genera, there were a significant number of cells that could not be identified with confidence, suggesting the presence of as yet unidentified species.
The bacterial species identified showed a great degree of overlap between members of the same clan. The overlap in microbial species could be from sharing the same plant or object for pasting. This also has the added effect of generating more intense scent trails for better communication, especially for marking territories (Theis et al, 2012). In addition, the type of species that were present on males was different from females. Even among females, lactating mothers had a different subset of bacteria unique to their scent. In this study, spotted hyenas belonging to one clan showed 54 species unique to lactating females and 46 to pregnant females. Species identification and comparison was done by high-throughput sequencing of their 16s RNA.
The findings present in this study suggest the credibility of the fermentation hypothesis of chemical recognition. In addition, it can be assumed that hyenas are not the only mammalian species benefitting from such a relationship with bacteria. Further studies that aim to grow some of these identified bacterial species from paste in a lab setting and show the generation of paste components by these microbes is needed as a validation of these results.
Darwin’s Frogs Decline
By Bio 94 Student Melody Sayrany
Charles Darwin embarked on a journey on the HMS Beagle in 1831 whereby he came to discover numerous species, one of which were the rhinodermatid frogs, also known as Darwin’s frogs, which are native to Chile and Argentina. These frogs are unique in that they can camouflage to look like a leaf to avoid being eaten. They are mainly a diurnal species, but they exhibit mating calls during both night and day where the males court the female then give rapid “pip” sounding calls. The rhinodermatids exhibit a very clever strategy to avoid predators. When threatened, the immediately play dead, lying on their backs, and if near a stream they hop in and float away.
In recent discoveries it has been noticed that a skin infection caused by a fungus, known as Batrachochytrium dendrobatidis or Bd, has spread and is killing countless amphibians. By DNA examination of over a hundred preserved amphibian species from the years between 1835 through 1989, it was proven that amphibian chitridiomycosis is causing mortality by causing morphological damage. Such damage includes convulsion of limbs, a medical condition resulting in rapid and repeated contraction and relaxation of muscles causing involuntary shaking, and reddening of skin. Lethargy, lack of energy, and failure to seek shelter and protect oneself as other normal frogs would do is also associated with the disease. The two most affected species of frogs are the now extinct Rhinoderma rufum and endangered Rhinoderma darwinii. Scientists believe the death and decline of these frogs are related to Bd skin disease, however they cannot conclude this relationship for sure for habitat destruction is also a major influencing factor. Some may ask, well why is amphibian extinction such a tremendous deal when so many other animals are also extinct? Well the answer to that would be that these species serve an immense purpose in sustaining ecological balance in the environment. Without them humans would be exposed to diseases carried by plagued insects, for there are no longer any frogs that prey on them, and this would result in an increase in the rise of diseased humans as well as damaged agriculture.