*Blood Disclaimer: Images from veterinarian surgery below.
A long while ago, I wrote about surveying for timber rattlesnakes (Crotalus horridus) in
the Midwest. Last summer I had the opportunity to visit those sites again,
although this time it was for a different purpose. Working with a Department of
Natural Resource’s contractor, our goal was to survey known rattlesnake
populations in an effort to characterize the prevalence and distribution of
snake fungal disease (SFD), a recently documented wildlife disease.
Basking amongst the warm rocks. The snake bag was poised and ready!
While scattered reports of the disease have been surfacing over the past several years, SFD is still surrounded by a shroud of mystery. It is
currently hypothesized that the fungus Ophidiomyces
ophiodiicola (From Greek “ophio” meaning serpent, and “myces” meaning
fungus) is the agent of the infection, but the evidence remains unclear. The disposition of a snake does not improve matters.
Generally, snakes are solitary creatures, making it difficult to
understand how the disease is transmitted. One possibility is transmission during hibernation. In this region timber rattlesnakes have community hibernacula, so the disease may be spread when several individuals come into contact during the winter. Another possibility is that the fungus is ubiquitous throughout the environment and only becomes pathogenic under certain conditions.
Since long-term population monitoring is rare, and since SFD is so new, it is challenging for scientists to get a clear picture on how SFD is impacting snake populations. Nonetheless, there is compelling evidence that SFD has harmed and will continue to impede snake conservation (Sutherland et al., 2014). Currently, reports of SFD have
occurred mainly in the eastern United States. Several snakes species have had
reported signs of SFD infection; however, SFD first gained attention due to its
impacts on northeastern populations of timber rattlesnakes and eastern
massassauga populations in Illinois. Within a single year, SFD played a
clear role in the 50% decline of the last New Hampshire population of rattlers in 2006 (Clark et al., 2011). To shed some light on the situation, research is currently being done to understand the disease's dynamics. So, let’s get back to the Midwest!
To avoid being bitten, venomous snakes are
measured and handled while safely stuck in a tube.
On a sweltering day in June, with the mayfly hatch swarming, we spent the morning hours scouring prairie hillsides. Whether basking at the edge of cover or hiding under shelf-rock, we found several rattlesnakes during our search. Once we captured them with snake tongs and safely deposited them into a snake bag, we moved to a convenient place to work each individual up (somewhere not at a 45 degree slope!). We determined their weight, length, gender, and body condition. Several snakes looked healthy, but one individual had a conspicuous node on its side. Since SFD causes a variety of skin defects (blisters, lesions, swellings), we took it in to have the node removed and biopsied.
The types of infections caused can SFD can vary greatly,
from nuisances like this node to severely damaged respiratory tissue.
This snake can't avoid being stuck in a tube! Here, it enters the
apparatus to receive a constant air flow that contains the anesthesia.
Throughout the surgery, the snake's breathing and vitals are closely monitored.
Here the dilated pupils indicate that the snake is nice and relaxed.
I just recently learned the node's biopsy came back positive for O. ophiodiicola, so it was considered to be a SFD infection. At this point some might ask, “why let the potentially infected snake back out into the
wild?”. Too little is currently known about SFD to know how to effectively
combat it. Most likely, if the disease had already infected that one snake, the
fungus was present throughout the whole area. Considering timber rattlesnakes
are having a tough time in many parts of their range, removing an individual
would be more detrimental than releasing the infected snake--especially since the mortality rate of SFD varies dramatically.
It was great to re-visit these timber rattlesnake populations once more. I can only hope the researchers working on this project will not only get a better sense of where SFD occurs but also its underlying cause so that proper disease management can be undertaken.
The surgery area is prepped.
Doc said "scalpel", so I handed him a scalpel.
Here, the node has successfully been removed. The tissue was
then divided and placed in a vial for further analysis.
To finish the surgery, the wound was stitched closed and it was given fluid to rehydrate.
Once the snake appeared responsive from coming out of the anesthesia, it was placed back
in its transportation container.
It was great to re-visit these timber rattlesnake populations once more. I can only hope the researchers working on this project will not only get a better sense of where SFD occurs but also its underlying cause so that proper disease management can be undertaken.
If you think you have come into contact with a snake that
may be showing signs of SFD, call your state wildlife agency. Also, clean your
shoes and any other gear with soap and water. Then soak in a 10% bleach
solution.
All surveys were done with appropriate permissions, permits, and humane handling protocols.
References
Clark, R. W., Marchand, M. N., Clifford, B. J., Stechert,
R., & Stephens, S. (2011). Decline of an isolated timber rattlesnake
(Crotalus horridus) population: Interactions between climate change, disease,
and loss of genetic diversity. Biological Conservation, 144(2), 886–891.
doi:10.1016/j.biocon.2010.12.001
Northeast Partners in Amphibian and Reptile Conservation.
2013. Snake Fungal Disease: Frequently Asked Questions. http://www.northeastparc.org/products/pdfs/NEPARC_SnakeFungalDiseaseFAQ.pdf
Sutherland, W. J., Aveling, R., Brooks, T. M., Clout, M., Dicks, L. V., Fellman, L., … Watkinson, A. R. (2014). A horizon scan of global conservation issues for 2014. Trends in Ecology and Evolution, 29(1), 15–22.
