Although it may not feel like spring yet, especially with this recent blast of cold and snow, it will soon be here before we know it. While we remain inside to stay warm and dry from the outside elements, many organisms will start to move out of their winter shelters. As we mentioned in a previous post, many amphibians will be on the move to their breeding pools; however, we didn’t mention all the stream salamanders that will be moving about this spring as well. Though stream salamanders don’t make spectacular mass migrations over a series of warm rainy nights, they move about the seeps and stream banks to breed and lay their eggs. As the spring and summer progresses, some salamanders will remain near the streams while others will move into surrounding areas to forage and take refuge under rocks or logs on the forest floor. As the salamanders move from place to place, they face an imminent threat of predators. However, many salamanders have special ways of outsmarting their predatory counterparts.
While in my senior year at Houghton College, I completed a senior honors research thesis in which I had to design a research project, write a research paper indicating my methods and results, present the project at a science conference, and formally defend it before my council of professors. It was a yearlong process in which I spent several late nights in the lab staring at salamanders, drank lots of hot apple cider (since I’m not a coffee drinker), consumed countless hours of researching primary literature and writing, and prepared my final draft for publication. Although staring at salamanders may not seem too appealing to some, I was quite surprised, as well as my advisor, to see what these simple tetrapods are capable of doing. For my project, I specifically studied the Allegheny Mountain Dusky Salamander (Desmognathus ochrophaeus) which is an abundant stream species ranging throughout eastern Canada and the United States. These common salamanders don’t look too attractive or seem to have any elaborate displays or behaviors; however, they are well equipped with a special olfactory organ called the vomeronasal organ. This organ along with the nasolabial grooves enables them to detect even the slightest concentrations of chemical scents released from other salamanders or predatory species. With that in mind, we questioned whether these Dusky salamanders could differentiate between the different types of chemical scents or “cues” that may be produced and respond with specific behaviors rather than responding indiscriminately.
This is an example of the nasolabial groove. The groove extends from the tip of the upper lip to the nostrils. Salamanders pick up chemical cues by tapping their nose to a substrate. The chemical then travels up the nasolabial groove via capillary action and goes into the vomeronasal organ. This olfactory organ is utilized by salamanders within the Plethodontidae family such as this Red-Backed salamander (Plethodon cinereus) as well as Allegheny Mountain Dusky Salamanders.
Many salamanders produce chemicals within their skin in a variety of situations. Dusky salamanders will produce a mixture of pheromones indicating their stress when startled or harassed by a predator. If a predatory event escalates, causing injury to the skin or tissue, a different set of chemicals is released by the salamander. Also, in areas where no predatory event has occurred rather a predator has just passed through, the predator will leave a chemical signature as well. In areas where predators have alarmed or attacked a salamander, chemical cues indicating the situation will be left on the substrate. Other salamanders moving through the area can pick up the chemical cues left behind using their vomeronasal organ and react by either avoiding the area where a predator may still be present or defend itself if the predator attempts to get itself another meal.
Interestingly, we found that the Allegheny Mountain Dusky Salamander responds differently to each chemical cue according to the level of threat perceived. Simply put, a salamander can detect whether the predator was just in the area, harassed another salamander or successfully consumed a salamander by just “smelling” the chemical cues left on the substrate. Once the cues are detected, a salamander can then determine how it will respond. If a predator is in the area, the salamander may be more likely to lower its activity level so that it may go undetected. To the salamander, being detected by a predator is a major risk and remaining motionless but alert raises its chances of survival. If a fellow salamander was eaten in a particular location, the salamander may then decide to high tail it out of there and escape from the area. Rather than hanging around where a hungry predator may be, the most beneficial response for the salamander may be to leave. Lastly, if the salamander detects that another was startled or harassed by a predator but was unharmed, the salamander may be alert but continue to forage or pass through the area as the level of threat is relatively low. By responding in such ways, these little salamanders can outsmart a nearby predator.
Allegheny Mountain Dusky Salamander (Desmognathus ochrophaeus)
In finding this information through this project, we can gain a better understanding of how predators and their prey interact; and, how one species must adapt to avoid being eaten, while the other must adapt in order to successfully procure food resources. In addition, we can also use this information to gain some insight into energy management as well as the costs and benefits of particular behaviors. Although salamanders may be small, they are certainly complex and the things we learn from them can help us further understand other processes in broader contexts such as population dynamics as well.
Lastly, in doing all this research and finding these interesting behaviors, I am happy to report that my work on the Dusky salamanders has recently been accepted for publication in an internationally known scientific journal. Furthermore, we hope that from our conservation projects here at RTPI, we can publish our important findings and provide knowledge to scientists, land managers, students and others. So stay tuned throughout this spring and summer as we plan to get out into the natural world and see what else we can discover!
Elyse Henshaw
Conservation Technician
Photos © Elyse Henshaw
