Wood Ducks in the Vernal Pool

Some may remember a post from March detailing the installation of a wood duck box in our nearby vernal pool. There has been a game camera monitoring the box 24/7 since it was put in. It has documented raccoons, gray foxes, mallard ducks, and wood frogs but until recently no wood ducks. Last Thursday, the camera finally captured the species we had been targeting.

A pair of wood ducks in the vernal pool near the nesting box. 

Vernal pools provide important habitat for more than just amphibians. There are a variety of reptiles, birds, and mammals that rely on these seasonal areas for food and shelter. It is also easy to overlook the countless species of invertebrates that live in and around the pool. Wood ducks use vernal pools as secluded areas to feed and rest. This pair was busy feeding on the plant material and invertebrates in the pool. The drake (male) was captured later on in the foreground feeding amongst the vegetation. 

A handsome drake wood duck feeds in the vernal pool.

The drake wood duck is considered by many to be one of the most beautiful birds in North America. They are acrobatic in the air and just as comfortable flying through the forest as they are over an open marsh. I often use this species in class when teaching about Sexual Dimorphism. This occurs males and females of the same species look strikingly different. The male wood duck has evolved its colorful plumage over the eons in response to traits sought after by hens (females) while selecting a mate. The healthiest and most colorful drakes are more likely to pass on their genes continuing mother nature's slow motion race to perfection. The hen's drab coloration helps her to blend in with the surroundings while rearing ducklings. To date, there has been no interest in the nest box but I will be sure to keep you posted if that is to change. 

Signs of Spotted Salamanders

I took advantage of some nice weather before break to get out with my Maine Fish and Wildlife classes and check in on our local vernal pool. Along the way we made some great discoveries. The duck-like vocalizations of the wood frogs that were so easy to hear a week or two ago are now few and far between. Most have likely completed their reproduction and are in the process of moving back into the nearby forest for the remainder of the year. We came across the wood frog shown below resting in a puddle adjacent to the main vernal pool.

This wood frog hid at the bottom of the puddle upon our arrival but posed for some pictures under water. 

The wood frogs left plenty of egg masses in their wake. Most of them seem to have made it through the recent periods of cold. Only the eggs that were near the surface when the pool froze over were killed. It looks like most of the eggs that were fully submerged and insulated by the water have made it through. No tadpoles hatching yet but we are getting close!

The most glaring change in the vernal pool was the the addition of spotted salamander egg masses. At some point in the week between our last visit the salamanders arrived and completed their life cycle. Much like the wood frog, by now they have mostly moved back into their upland habitats for the remainder of the year. .

A spotted salamander discovered during a past vernal pool trip.

The salamander egg masses are easily distinguishable from the wood frog eggs. They are generally a bit smaller in overall size but he individual eggs within the mass are larger and more distinct. The jelly that surrounds them is thick and much more firm to the touch. While wood frog eggs are typically laid near the surface, salamander eggs are often seen attached to debris deeper in the pool.

Spotted salamander egg masses are typically found deeper in the vernal pool.

Lifting this overhanging tree exposed a large number of salamander egg masses initially hidden by the glare on the water. 

One of our coolest finds on the day was salamander spermatophores (seen below). Salamanders have an elaborate mating ritual that involves almost no contact with one another. Males adhere small spermatophores to debris at the bottom of the pool. The female later uses this tiny packet of genetic material to fertilize her eggs internally. All of this takes place in a mirky vernal pool under the cover of darkness! Leftover spermatophores are typically visible for a short time near the egg masses. It takes a keen eye to spot them at the bottom of the pool but my students did a great job.

Leftover salamander spermatophores.

The Power of Scent

Cody Harris, a talented senior wildlife student and avid trapper, recently whipped up a batch of "lure" and asked if I would be willing to test its effectiveness in the T.A. forest. Testing the lure with the game camera offers the opportunity to not only keep track of the species drawn in but also observe their reactions to this potent concoction. Trapping lure is a scent laden substance used to attract a variety of furbearers (creatures whose fur is commercially valuable). Cody's recipe reminded me a lot of a halloween witch's brew including things like beaver tail, dear meat, and fox urine. I have been using small amounts of the lure in front of the game cameras around the TA forest for the past couple of weeks and the verdict is in. This stuff works!

The species captured over the past few weeks stopping in to give the lure a sniff include gray squirrel, gray fox, red fox, porcupine, opossum, raccoon, and coyote. Some of the most notable videos are shown below.

This porcupine spent a while investigating the scent lure left on the upright stick. 

This red fox surely picked up some the pheromones from the fox urine in the lure and left a scent mark of its own. 

The coyote shown in the video strikes a perfect pose while remaining wary of any danger. 

A pair of coyotes arrive on the scene later on the same night to investigate the scent lure. 

One of the most notable observations from the use of the lure was the territorial behaviors it generated from some of the species. The red fox shown above leaves a scent mark of its own before departing. It is certainly possible that the presence of fox urine in the lure could signal the arrival of an intruder on its territory. The pair of coyotes shown in the last video is another highlight. The individual seen in the background seems a little rotund for the time of year and it is possible that this could be a female late in her pregnancy. Coyotes in Maine generally have their pups between late March and May making the timing almost perfect. 

Vernal Pool Fun

My spring semester wildlife students have been working hard for the past week learning all about vernal pools and the amphibians that call them home each spring. These ephemeral ponds in the woods are one my favorite topics to teach to high schoolers. It is one of the few instances in my Maine Fish and Wildlife course where we can learn in detail about a group of species and then march outside as a class and observe them in person. That is exactly what we did last week on Thursday (3/31).

Listening as a class for the duck-like chuckle of the wood frog.

Seasonal pond in the forest must satisfy three basic requirements before they can be classified as "vernal pools" and receive some extra protection. 

       1. Vernal pools are temporary bodies of water and typically dry up by late summer or early 

            fall.

       2. There must be no fish present. 

       3. Vernal pools should show signs of use by one or more of the indicator species listed 

            below.

              a. Wood frog (Rana sylvatica)

              b. Spotted salamander (Ambystoma maculatum)

              c. Blue-spotted salamander (Ambystoma laterale)

              d. Fairy Shrimp (Anostraca)

On our most recent visit, students got to witness two of the four indicator species in their natural environment. Wood frogs were both heard and seen floating around in the pool. Their softball sized egg masses were also visible clinging to vegetation in the water. A haul of a trap left overnight yielded two male spotted salamanders. The spotted salamanders are a real treat for the students as their size (up to 7") and striking coloration is unforgettable. These members of the mole salamander family are rarely seen outside of their springtime march to the vernal pool as they spend the remainder of the year deep underground in small mammal burrows or natural crevices in the forest. 

A close-up look at a wood frog, the first arrivals at vernal pools in the spring. 

A spotted salamander fresh from the vernal pool. 

The activity around the vernal pool as come to yet another screeching halt as winter refuses to release its grip on the landscape. The vernal pool ecosystems and their fragile amphibian inhabitants immediately come to mind whenever I see a springtime cold snap in the weather forecast. The good news is that wood frogs and spotted salamanders have existed on the Maine landscape for a lot longer than I have been worrying about them. They have evolved systems to handle brief dips in the mercury like the one we are currently experiencing. As long as temperatures don't get too cold for too long, they are able to wait out the snow and ice at the bottom of the pool or in nearby leaf litter before resuming their breeding activity again.