A Tiny Salamander Appears

As winter draws near, it will be time for many terrestrial salamanders to reduce their surface activity and switch to their underground retreats. While some salamanders will use underground burrow networks created by small mammals, others will create their own.

Some members of the red-backed salamander species (Plethodon cinereus) will especially need to find a retreat soon. Starting in August, neonates hatched from eggs suspended in crevices inside logs, under rocks, and underground. These tiny salamanders are barely 25mm long. After an average of 6 weeks of gestation in eggs, the salamanders (depending on latitude) have only a few months before winter sets in. During this time, they disperse from the nest, forage, and find areas to overwinter.

Female P. cinereus typically lay their eggs (collectively called a clutch) in late spring and early summer; however, it isn't uncommon for females to oviposit later in the year. The number of eggs in the clutch ranges from 1-14 and is often correlated to the size of the female. Unlike males that mate each year, female P. cinereus reproduce biennially. Developing eggs, and eventually brooding them, is energetically expensive. Clutches that aren't brooded have a higher chance of being eaten, as the brooding female will lunge, bite, and snap at other salamander intruders. In some cases, conspecifics (members of the same species) will cannibalize eggs due to their energy content and nutrients.

Here in the Northeast, winter is quickly approaching, so lets hope this year's neonates are able to find retreats deep enough that they don't freeze.

References
Petranka, J. W. 1998. Salamanders of the United States and Canada. Smithsonian Institution Press, Washington, DC. 576 pp. 

On the Road Again

(Disclaimer, if you don't like animal guts, skip this post).

Also, double post this weekend, so don't miss “Quoth the Marsh”

Most normal people would not consider any road kill all that special, particularly if it is a snake. Even though I am human, I most likely wouldn't fit the bill for being normal. Naturally, when I saw a Eastern Common Garter Snake (Thamnophis sirtalis sirtalis) dead on the road, I had to pull over and snag it.

 The specimen in question. Depending on the subspecies,

it can take two the three years before females can reach reproductive maturity

Now, even further from being normal, I decided to dissect the snake so that I could try and get a whole snake skeleton to put together as a model. It was also a unique opportunity because she was gravid, and you could feel the embryos in her gut.

Common Garters are not having too hard of a time compared to most snakes, but it is still sad to see a gravid female killed by a car. There were a total of five embryos inside her. Garters are ovoviviparous, meaning that they produce offspring within an amniotic sac and give live birth. It takes 80 to 90 days for gestation to occur (depending on environmental temperature), and a female can birth between 1 and 101 offspring depending on size and maturity. Females will only breed bi-annually or tri-annually. 

One of five embryos inside the snake. It's rare to get to see offspring

mid-development. The top picture shows the developing snake inside its own membrane.

The second shows it outside of the membrane.

Interestingly, the Common Garter snake is the northernmost snake species in North America. This is because it can tolerate a wide range of temperatures and can even survive being frozen for brief periods of time. Found in a variety of different habitats, the snake is most commonly found near wet areas. As there are many subspecies of this snake, coloration, diet, and behavior can vary drastically.

The Common Garter Snake is also the most deeply studied snake in North America.

For more info, see Snakes of the United States and Canada by Ernst and Ernst