Eggs-celent!

With summer well under way, it's the time of year for critters of all sorts to be laying their eggs. Whether bird, reptile, or amphibian, hear are some of the eggs I've come across in the past few weeks.

Killdeer eggs blend in nicely with the gravely areas they make their nests.

Four eggs are in the far right of this picture.

To start off, we have the fine-feathered shorebird, the Killdeer (Charadrius vociferus, "Noisy plover"). This bird doesn't have to be on the coast to be seen, and it is most well-known for its loud and frequent calling. Killdeer are ground-nesting birds, and their eggs are camouflaged for the gravel-like and sandy areas they like to lay. When threatened, a Killdeer guarding its nest will either fluff its feathers and tail to scare animals off, or it will pretend to have a broken wing so as to distract predators from its eggs.

Reptiles have been laying their eggs too. Instead of brooding eggs like birds, reptiles must lay their eggs in substrate that is warm enough to act like a natural incubator. This usually means sunny, dry, sandy areas. This common snapping turtle (Chelydra serpentina, "Snake-like turtle") exhibited an interesting behavior of shuffling her eggs around are depositing them each time. A snapping turtle's clutch can contain between 20-40 eggs.

As you know, I am a big fan of salamanders that breed in vernal pools. The Ambystoma genus of salamanders (Spotted, Jefferson's) laid earlier in April, and their eggs have been hatching over the patch few weeks. Unlike other eggs anywhere else, the eggs of Spotted salamanders have a unique symbiotic relationship with algae. So far, they are the only known vertebrate species that has a symbiotic relationship with algae. These algae, known as Oophila amblystomatis, not only invade the jelly of the egg, but they also invade the embryo and salamander tissue. The salamander benefits from increased oxygen and removal of ammonia waste during development, and the algae benefits excreted nutrients. Much is still not know about this relationship, but is clear that without the algae, eggs develop more slowly, have higher mortality rates, and produce smaller young upon hatching.

Algae covered Spotted Salamander larvae await to hatch at the end of May.

From a few months ago, underwater footage (couldn't help myself)

 of Jefferson's salamander eggs. Notice, they lack the algae their close cousin's have.

References
Kerney, R. (2011). Symbioses between salamander embryos and green algae. Symbiosis, 54(3), 107–117. 

Birds and the Bees, Sallies and the Streams

Well, not streams per se. But, with it being the season of pollen, green-up, and breeding comes the great breeding migration of the Spotted Salamander (Ambystoma maculatum) and the hatching of the Marble Salamander (Ambystoma opacum). Since the winter was so warm, breeding came early. In February, larvae of both species were swimming around in the vernal pools of Piedmont.

 A Spotted Salamander egg mass floating and hidden among vegetation.

The Marbled and Spotted Salamander have larvae that are deposited as eggs into vernal pools throughout the Southeast,  parts of the Midwest, and parts of New England. The Spotted Salamander's distribution also reaches into areas of Canada (Conant & Collins, 1998). Vernal pools, sometimes called ephemeral ponds, are seasonal wetland depressions found in woodlands. They fill during the winter and spring, and they dry during the summer and fall. Because they dry out, no fish can inhabit them--perfect breeding grounds for amphibians.

In the Piedmont of North Carolina, the hatching of the eggs for both species occurs simultaneously, and it can be difficult to distinguish between the two larvae. However, the Marbled Salamander larvae have black pigment on their throats and are typically larger (Mitchell & Gibbons, 2010). Both species have bushy external gills, tails for swimming, and two well developed forelimbs. Hind limbs develop during the larvae stage.

 Two Marbled Salamander larvae. 

Notice the tiny hind limbs and external gills.

The fascinating thing about these two species is not their aquatic larvae. Instead, it is the amazing journey the adults undergo in order to mate every year to two years. Both species are the only salamanders to mate on land. Marbled Salamanders migrate after mating occurs in October or November, and they lay their eggs in the dried ephemeral ponds. The eggs will only hatch after being inundated (Petranka, 1998).

 A Salamander larvae in its natural habitat, 

unaware of the looming net about to scoop it up!

Even more dramatic than that, Spotted Salamanders will migrate to breeding grounds during moist nights in late winter and early spring and will lay their eggs in flooded pools. It is unknown as to how salamanders orient themselves directionally, but they can travel great distances (200m-500m) to meet for the mating season (Petranka, 1998). For something only 22cm, that is a long way to go! Imagine having to go 900 to 2250 times our body size to find a mate.

 An adult Spotted Salamander. Found under a log

next to the vernal pool.

Unfortunately, given the migration patterns of the salamanders, there are great concerns for the survival and conservation of the two species. Besides the loss of ephemeral pools, habitat fragmentation by roads has isolated adult habitats from breeding grounds. With the small size and slow movement of salamanders, it is easy for them to be killed by motorists.

Hopefully you will have the chance to see one of these fantastic creatures! The best part is that they can be as far away as your backyard or local park.

Works Cited

Conant, R. and J.T. Collins. 1998. Reptiles and Amphibians of Eastern/Central North America. Houghton Mifflin Company, Boston, MA.

Mitchell, J.M. and W. Gibbons. 2010. Salamanders of the Southeast. University of Georgia Press, Athens, GA.

Petranka, J.W. 1998. Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C.