We are the @ColdBloodedHopsters, a group of McGill students in the class St Lawrence Ecosystems (ENVB222) studying amphibians at the Morgan Arboretum. Make sure to follow us on Twitter for more updates on our research!
Although they only occupy 0.5% of all animal species, amphibians are a large and diverse group with over 6000 species found across the world (Dodd 2010). Their main characteristics include highly permeable skin and eggs in gelatinous capsules (rather than hard shells), which make them vulnerable to water loss. For this reason, they are mainly found in moist environments. This class of organisms include the orders Anura (frogs and toads), Urodela (salamanders and newts) and Apoda (Caecilians).
The name amphibian means “two lives”, where amphi means two and bios means life (Dodd 2010), indicating that most, yet not all of these creatures, spend part of their lives in water and part on land. This emphasizes their need for a water source, such as a breeding pond. Breeding ponds are extremely important to amphibians, and those found in the Morgan Arboretum are no exception.
The species that can be found in the Arboretum are the Eastern Newt, Blue-spotted Salamander, Eastern Redback Salamander, Spring Peeper, Gray Treefrog, Wood Frog, and the American Toad. All of these species vary significantly in their life histories.
Figure 1: Species found in the Morgan Arboretum. Starting from upper left going clockwise: Wood Frog (Lithobates sylvaticus), Spring Peeper (Pseudacris crucifer), Eastern Newt (Notophthalmus viridescens), Eastern Redback Salamander (Plethodon cinereus).
For example, the Eastern Newt may remain in its aquatic phase of life permanently, unless food or water becomes limiting. In contrast, the Eastern Redback Salamander is completely terrestrial, laying its eggs in damp, rotten logs and hibernating underground. However, all amphibians aside from the Eastern Redback Salamander, depend on the presence of breeding ponds to begin their life cycle. Some return to the same breeding pond year after year, while others breed in any available patch of water (such as the American Toad). Amphibians such as Blue-spotted Salamanders are never found far from breeding ponds, whereas chorus frogs like Spring peepers and Gray treefrogs, reside in forested areas nearby (Bider and Matte 1996).
So why is it important to study amphibians? Amphibians play a key ecological role in energy flow and nutrient cycling as they are both predator and prey. Because they are cold-blooded, their energy is not wasted on generating body heat. As a result, they are able to convert 50% of the energy gained from food into new tissue, which in turn can be transferred down the food chain (Dodd 2010).
In the past, various experiments have been conducted to better understand the gap between breeding season and migratory patterns among amphibians. Several conclusions have been made thus far, each adding a piece of the puzzle in attempt to decipher the big picture. In 2015, a study in Alberta analyzed the correlation between beaver-built canals and Tree Frog abundance (both adult and newly hatched). It was discovered that these amphibians were nine times more abundant in areas with beaver canals (Anderson et al. 2015).
In 2006, a similar experiment to our own was conducted on forty-three North American Wood Frogs (Rana sylvatica) from April to November 2003. Monitoring their movements using radio-telemetry, scientists concluded that post-breeding movements away from a breeding pond were to closed-canopy forested wetlands, ranging from 102-340m (Baldwin et al. 2006). Furthermore, an Endangered Species Group at the University of Maine wrote a report on the effects of a roadside habitat and the abundance of anurans and salamanders. Surprisingly, anuran migratory patterns (frogs and toads) were unaffected by the 12m wide logging road. However, salamander populations were 2.3 times lower near a high traffic path compared to a forest control site (DeMaynadier and Hunter 2000).
Research Question and Hypotheses:
Evidently, it is important to understand the distribution of species and abundance of amphibians from critical habitats such as breeding ponds. This is why our research question is: How does the abundance and diversity of amphibians vary with distance from a temporary breeding habitat?
We predict that diversity will increase closer to the quarry, as not all amphibians can travel great distances, although some may cover more distance in a given day. Abundance will depend on what species we find, but we speculate that frogs will be found in abundance everywhere, since they are a regular sighting within the Arboretum. Our data will also vary depending on when we collected it, as hibernation will become more noticeable as the weather changes.
We conducted our data collection near the quarry of the Morgan Arboretum. To do so, we were provided with measuring and flagging tape with which we were able to set up our boundaries. We made 3 sections of 50 meters by 40 meters as presented below, moving away from the temporary water source (the quarry) and into the nearby maple-hickory forest. We then separated each section into 20 quadrants (10m by 10m) and picked 11 of the 20 squares by drawing numbers at random. The chosen squares are shaded below.
Figure 2: Map of the Morgan Arboretum and area of data collection (circled in blue) on the left and sampling method on the right.
For each one being analyzed, a corner is occupied by one person who then proceeds to turn over rocks and logs, heading towards the middle of the square. Squares are searched for approximately 15 minutes and any amphibians found are immediately noted to ensure that each individual is not counted twice.
Figure 3: In order to find amphibians, we had to search under leaf litter, logs, and rocks on the forest floor within each 10m by 10m square.
See this video for a typical day out in the field.
Our observation skills in the beginning of our data collection was less efficient than during our fourth day of observation. We had a better idea of what we were looking for and the best suited locations for finding the amphibians. Furthermore, a number of amphibians may have been hiding in obscure places and we could not turn over some rocks or logs due to their weight. In addition, the colder weather may have impeded the likeliness for the amphibians to come out of hiding.
Figure 4: Amphibians were often well camouflaged, like this Spring Peeper, presenting problems with data collection.
The amount of Redback Salamanders found remained more or less consistent across the three sections (slightly more near the quarry) and the amount of Spring Peepers noticeably increased as we moved further away from the quarry. We found that the second section (50-100m) held the most diverse range of amphibians, which included Redback Salamanders, Spring Peepers, a Wood Frog and a Red-Spotted Newt.
Anderson NL, Paszkowski CA, Hood GA. 2015. Linking aquatic and terrestrial environments: Can beaver canals serve as movement corridors for pond-breeding amphibians? Animal Conservation. 18(3):287-294. doi:10.1111/acv.12170
Baldwin RF, Calhoun AJK, Demaynadier PG. 2006. Conservation planning for amphibian species with complex habitat requirements: A case study using movements and habitat selection of the wood frog rana sylvatica. Journal of Herpetology. 40(4):442-453. doi: 10.1670/0022-1511(2006)40[442:CPFASW]2.0.CO;2
Bider, J. R. and S. Matte. 1996. The Atlas of Amphibians and Reptiles of Quebec. St. Lawrence Valley Natural History Society and the Ministère de l’environnement et de la faune, direction de la faune et des habitats: Québec, QC. 106p.
DeMaynadier PG, Hunter Jr ML. 2000. Road effects on amphibian movements in a forested landscape. Natural Areas Journal. 20(1):56-65.
Dodd, C. Kenneth, editor. 2010. Amphibian Ecology and Conservation: A Handbook of Techniques. New York: Oxford University Press.