Lurking beneath the trash laden leaf litter of the 5 boroughs lurks a secretive little amphibian that exemplifies the struggle between the forces of urbanization and the biological need to adapt or face extinction. The Eastern Red-backed Salamander (Plethodon cinereus) is a unique kind of caudate with numerous traits that make it well equipped to navigate the unseen parts of the urban jungles of NYC.
Inhabiting many of the parks and green spaces of the city, this amphibian is one many people have passed or even stepped over if they have been within the city limits, but it is so seldom seen that many people can go their entire lives without ever seeing one… unless you know where to look! These salamanders are fossorial, spending much of their time beneath the leaves and other cover objects. The individual pictured above was found in northern Manhattan in a seldom visited park only a dozen meters or so away from a highway, and moreover as seen in the photograph, human debris in the form of a discarded tissue is present in the living space of the salamander.
These organisms are known to have quite small home ranges, usually spending their lives within the approximately 0.16 square meter bounds of their territory (Mathis 1991). Additionally they are known to be quite territorial and are intolerant of conspecifics within their living area (Jaeger et al 1982). This information tells us that these salamanders, known to respond violently to other salamanders, are living only a short walk from one of the most highly traveled highways in the region, are surrounded by trash, and are somehow thriving. On a cold spring day you might be surprised to flip logs and find upwards of a dozen salamanders beneath! A look into their physiology will tell us that there is much more than meets the eyes when it comes to these caudates.
Firstly, Eastern Red-backed Salamanders belong to a group known as the Woodland Salamanders. These differ in a huge way from the other more common northeastern clade known group known as ambystomatidae. The difference lies in how they breathe, plethodontid salamanders actually lack lungs, breathing almost entirely through their skin and the specialized surfaces of their buccopharyngeal cavity! This is a huge departure from the ambystomatid relatives as they possess lungs. This difference likely evolved as part of the life history of these complex creatures, as plethodontid salamanders do not require a water source to breed! Instead during the spring and fall months they reproduce and lay their eggs under the ground, adhering the gelatinous egg masses to the surfaces of rocks and debris like larger logs. Where they undergo direct development. Skipping the larval phase that most other amphibians undergo.
These salamanders play an important role in the cycle of energy within the eastern deciduous forests of the United States. They take part in a plethora of critical functions that facilitate the breakdown of leaf litter, soil aeration, invertebrate population control, and function as an important food source for a diverse array of predators that range from birds, to skunks, and even bears!
This terrestrial life history has also afforded the redback protection against the complex issues many amphibians must face when it comes to having a clean, fish-free water source to live or breed. Ambystomatidae are reliant on vernal pools and a total absence of fish predators, whereas the redback instead has no need for such fragile habitat. But this adaptation to thrive in the leaf litter of the northeast has also afforded these amphibians a unique resistance to what is otherwise a global amphibian threat.
Chytridiomycosis, or chytrid for short, is a fungal disease that has led to widespread amphibian decline across the world. Batrachochytrium dendrobatidis (Bd) in specific is responsible for infecting over 700 species with lethal consequences for many of them (Lips 2016). However, on account of the skin microbiota, the diverse community of microorganisms that live on the surface of these woodland salamanders, Eastern Red-backed Salamanders are actually resistant to some of the effects of the pathogen! Studies have found that the presence of the skin microbial community helps the salamanders avoid the weight loss otherwise associated with infection by the pathogen (Becker et al 2010).
The grim truth of the matter is that this pathogen is heavily influenced and spread by human activity. Each step we take, each dirty footprint we leave behind has a chance of releasing the motile spores of this fatal fungus. It also remains to be seen how human trash and litter affect the disease dynamics of urban amphibians so all of the tissues, plastic bottles, and discarded waste products could be having detrimental effects on these unseen communities.
With this in mind we begin to see the sad lining to the dominance of the redback in our urban forests. Where are the other salamanders and anurans? Human development and urbanization have extirpated huge quantities of different species and we are left with the one that is most able to survive amidst the chaos.The presence of debris like the tissue seen above could possibly affect the skin microbiome of these salamanders that come into contact with it and this could hypothetically impact their ability to resist chytrid. We must be more cognizant of our potential impacts on the environment.
I say we need to appreciate the red-back while it is here, and do what we can to keep our local amphibians safe. Sources like The Wisconsin Department of Natural Resources recommend using a 10 % bleach solution or 70% alcohol wipe on items when moving between field sites to prevent the spread of chytrid, but this may not be feasible for most people. Instead we can reduce our contribution to the spread of chytrid by sunning our items for a few days after returning from an area of importance for amphibians. Shoes, poles, tools, balls, strollers, and anything that makes significant contact with the ground should be carefully handled to prevent the spread of this disease.
If we do nothing, we may lose this abundant amphibian, and then our quiet urban forests may truly stand empty.
References:
Mathis, A. Territories of male and female terrestrial salamanders: costs, benefits, and intersexual spatial associations. Oecologia 86, 433–440 (1991). https://doi.org/10.1007/BF00317613
Robert G. Jaeger, Donna Kalvarsky, Naomi Shimizu, Territorial behaviour of the red-backed salamander: Expulsion of intruders, Animal Behaviour, Volume 30, Issue 2, 1982, Pages 490-496, ISSN 0003-3472, https://doi.org/10.1016/S0003-3472(82)80061-4.
Lips KR. Overview of chytrid emergence and impacts on amphibians. Philos Trans R Soc Lond B Biol Sci. 2016 Dec 5;371(1709):20150465. doi: 10.1098/rstb.2015.0465. PMID: 28080989; PMCID: PMC5095542.
Becker MH, Harris RN. Cutaneous bacteria of the redback salamander prevent morbidity associated with a lethal disease. PLoS One. 2010 Jun 4;5(6):e10957. doi: 10.1371/journal.pone.0010957. PMID: 20532032; PMCID: PMC2881031.
I am interested in how the anthropocene has swayed the forces of evolution, specifically through understanding urban adaptation and population disease ecology.
I want to be a voice for victims of environmental racism, systemic injustice, and the legacy of colonialism.
We all have our roles to play in life's collective struggle against the universe's call to entropy.
Currently researching: Gray Tree Frogs (Hyla veriscolor) in NYC.
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