herpetology

The Impacts of Global Warming on the Common Toad

Common Toad. Photo Taken by Karamel. https://upload.wikimedia.org/wikipedia/commons/9/93/Common_Toad_%28Bufo_bufo%29.jpg

Over the last couple of decades, amphibians globally have experienced huge population declines that have resulted in the extinction of some species (AmphibiaWeb, 2017). Amphibians are ectothermic, meaning they cannot regulate their own body temperature. They instead rely on external sources like the sun to thermoregulate. This means that amphibians are particularly sensitive to changes in their environment. With global temperatures rising due to global warming, the summers are becoming longer and the winters are becoming shorter and milder (Reading, 2006). The hibernation periods of toads are disrupted in the process, leading to detrimental and even fatal health complications for toads. 

In a study on Common Toads, a widespread species in Europe, Jorgenson (1986) found that female toads who were given unlimited access to food during the winter and prevented from hibernating, grew slower and died at higher rates than female toads that hibernated. He also found that female toads reached reproductive age younger and at a smaller size than female toads that hibernated. A study conducted by Reading (2006) on the same species yielded the same results and found that mild winters caused female toads to reach breeding age at smaller sizes. This can be detrimental to toad populations because the amount of eggs a mother toad lays is dependent on how big she is. 

Amphibians have structures called fat bodies that allow them to store energy that can be used while they hibernate (Reading, 2006). When the winters are cold, metabolism slows down and energy usage is minimal. However, when the winters are only mild, the toad’s metabolism doesn’t slow down enough to minimize energy usage. The toads emerge hibernation with less energy availability and their body condition is decreased. In some cases, the toads’ energy reserves are depleted before they emerge from hibernation and they die in the process (Reading, 2006). 

Unfortunately, global mean temperatures are expected to rise by 1-7 in the coming years (IPCC, 2001). The Common Toad and other amphibian species populations will likely face more challenges as temperatures continue to rise. In order to help these species see the future, we can continue to study them and their physiological limitations further. Although amphibians may not seem important enough to preserve, we must remember that they help control mosquito populations that can reduce our risk of disease exposure (Morris, 2020).

References

AmphibiaWeb: Worldwide Amphibian Declines (2024). https://amphibiaweb.org/declines/ (last accessed 12 February 2024).

External and internal control of patterns of feeding, growth and gonadal function in a temperate zone anuran, the toad Bufo bufo – Jørgensen – 1986 – Journal of Zoology – Wiley Online Library (2024). https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.1986.tb03631.x?casa_token=mZ2kbsVtPwQAAAAA:WkOXqMUoUJ2XXl-546g0FEczyBwOPNJxCTVoN7fRJk5ghTBgPCo6SseiegGljrfTahwqCbLqSivC4bM (last accessed 12 February 2024).

Kerlin KE (2020) Amphibian Declines Affect Human Health. UC Davis. https://www.ucdavis.edu/climate/what-can-i-do/amphibian-declines-affect-human-health (last accessed 12 February 2024).

Reading CJ (2007) Linking global warming to amphibian declines through its effects on female body condition and survivorship. Oecologia 151: 125–131.

Watson RT, Albritton DL, Intergovernmental Panel on Climate Change, Intergovernmental Panel on Climate Change, Intergovernmental Panel on Climate Change, eds. (2001) Climate Change 2001: Synthesis Report. Cambridge University Press, Cambridge ; New York.

Hellbenders Deserve Love Too

My #scicomm story is about the eastern hellbender (Cryptobranchus alleganiensis). Aptly nicknamed the ‘snot otter’ (I mean, just look at it), the hellbender is North America’s largest salamander species. Fun fact, it was recently named as Pennsylvania’s state amphibian.

Eastern hellbender (Photo: USFWS Midwest)

Side note: Before doing research for this post, I didn’t realize state amphibians were even a thing.

Thanks to anthropogenic effects, the hellbender is also in serious decline. One study held over the course of twenty years observed a 77% decline in hellbender populations (Wheeler et al, 2003).

So, what is causing such a sharp downturn for the lowly ‘lasagna lizard’? Unfortunately, like most of the declining populations that we see in ecosystems today, the ‘Allegheny alligator’ suffers from an acute case of humans. We’ve screwed up their habitats pretty badly.

The hellbender conducts gas exchange completely through their skin. As a result, they require oxygen-rich, shallow, fast-flowing streams for their habitats. Because of their strict habitat requirements, hellbenders are extremely sensitive to environmental changes. One of the biggest contributors to the ‘devil dog’s’ decline is siltation of their habitat via roadways, agriculture runoffs, pollution, and damming of waterways (Unger et al, 2017). All of these things muddy up their native stream systems. This reduces oxygen availability in the environment and can smother the animals.

Hellbenders aren’t prolific breeders, either. A relatively long-lived species, hellbenders have slow growth and developmental rates and an extremely low number of offspring live long enough to join the breeding population (only around 1% in the wild). With their recruitment rates practically crawling along and full-grown adults dying thanks to damaged habitat, things aren’t looking good for the lowly ‘ground puppy’. It isn’t hard to see how their population numbers dropped so drastically

But it isn’t all over yet. Hellbenders have been getting a helping hand recently thanks to joint efforts from state agencies, zoos, and university research. Captive breeding programs and scouting areas for appropriate habitats alongside PR campaigns for public support (Mullendore et al, 2014) have helped the hellbender slowly make a comeback.

Check out this video by the Toledo Zoo to learn more about conservation efforts for these guys:

https://www.youtube.com/watch?v=ufA8ZjsUhQw

Reference:

  1. Mullendore N, Mase AS, Mulvaney K, Perry-Hill R, Reimer A, Behbehani L, Williams RN, Prokopy LS. Conserving the eastern hellbender salamander. Human Dimensions of Wildlife. 2014 Mar 4;19(2):166-78.
  2. Wheeler BA, Prosen E, Mathis A, Wilkinson RF. Population declines of a long-lived salamander: a 20+-year study of hellbenders, Cryptobranchus alleganiensis. Biological Conservation. 2003 Jan 1;109(1):151-6.
  3. Unger SD, Williams LA, Groves JD, Lawson CR, Humphries WJ. Anthropogenic Associated Mortality in the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis). Southeastern naturalist. 2017 Jun;16(2).
  4. Toledo Zoo (2014)

*Nicknames provided by the US Fish and Wildlife Service: https://www.fws.gov/southeast/wildlife/amphibians/eastern-hellbender/

Snake X-ing: Massasaugas and the dangers of sunbathing

I’ve decided to stick with herps for my second #scicomm post. This time we’ll be talking about rattlesnakes, specifically the Eastern Massasauga (Sistrurus catenatus) which is currently listed as threatened throughout its entire range.

 Figure 1: Range map for the Eastern Massasauga

The massasauga, like all other reptiles, is an ectotherm meaning that they need to use outside forces to regulate their internal temperature (thermoregulation). This strategy for thermoregulation becomes a problem when the environment they require for that action has been changed. Yes, we’re taking about habitat degradation again. Humans are really good at it.

Massasaugas primarily live in wetlands, lowlands, and riparian areas. These areas have perfect basking sites – regions where an individual can intentionally go out and warm up under the sun (Harvey and Weatherhead, 2010).  Unfortunately for the massasauga, a lot of these spaces have been taken by humans for urbanization and agriculture.

A lot of reptiles live in warm, typically sunny environments that provide plenty of basking sites regardless of human interference. However, the massasauga is a temperate species, ranging through the American Midwest region. Because of the area’s lower average temperature and natural geography – more forests and woodlands rather than open prairie and scrubland – the basking sites they do have are crucial. Loss of these important sites causes massasaugas to look for other alternatives, which in this case means roads. Where there are roads, there are cars and in the fight of snake vs F-150, the truck wins. Every time. Roadkill accounts for a very large proportion of human related deaths for massasaugas (Jones et al, 2012).

And that’s not the only human problem that massasaugas face.

Historically, public opinion has not been on the side of snakes. Rattlesnakes get a particularly bad rep. It’s understandably hard to be considered beneficial or cute when you’ve got a mouth full of venom. However, human fear leads to aggressive action when it comes to massasaugas. The first response of many people when confronted with a massasauga is to kill it and this practice along with habitat loss is what has severely depressed the massasauga’s population numbers. In order to combat this, local DNRs and the federal government have been attempting to educate the public on their importance. Massasaugas eat small mammals, birds, and other vertebrates, making them an important source of pest control in their ecosystems. They also serve as an important source of food for larger predators. This, along with making snake removal an option in more regions has helped cut down on direct human mortality. There has also been a recent management effort to create new basking sites in protected areas to reduce their roadkill mortality.

Learn more about massasauga research here: https://www.youtube.com/watch?v=xe2e1d38LyQ

  1. Jones PC, King RB, Bailey RL, Bieser ND, Bissell K, Campa III H, Crabill T, Cross MD, Degregorio BA, Dreslik MJ, Durbian FE. Range‐wide analysis of eastern massasauga survivorship. The Journal of Wildlife Management. 2012 Nov;76(8):1576-86.
  2. Weatherhead PJ, Prior KA. Preliminary observations of habitat use and movements of the eastern massasauga rattlesnake (Sistrurus c. catenatus). Journal of Herpetology. 1992 Dec 1:447-52.
  3. Harvey DS, Weatherhead PJ. Habitat selection as the mechanism for thermoregulation in a northern population of massasauga rattlesnakes (Sistrurus catenatus). Ecoscience. 2010 Dec 1;17(4):411-9.
  4. US Fish and Wildlife Service
  5. Photos: USFWS, Creative Commons, and New York State Conservation Site