Doves, Dragonflies, and Frogs (Oh my!)
Quite the busy week this week!
Myself and my fellow interns spent just as much time at work on the refuge as we did off, visiting the Crosley Fish and Wildlife Area and Muscatatuck National Wildlife refuge to help out and gain experience with some new and different kinds of work!
We started our work week assisting with Mourning Dove banding at Crosley, with some biologists from the Indiana Department of Natural Resources (INDNR). This involved visiting several cage traps scattered around the property filled with sunflower seeds, collecting some bewildered (and well-fed) doves from them, and fixing them with some identifying bands!
This process involves first taking the doves from the cage and examining them to determine their age and sex. To do this, we ook at the outer (or primary) feathers. The primary feathers of a juvenile dove (under 3 years old) will have a light-colored, smooth margin, while the adult primaries will have margins that are frayed and dark colored.
Aging a Mourning Dove by its primary feathers! This male has white
margins along his primary feathers, meaning that he's a juvenile!
To determine sex, we can look for subtle differences in a variety of the dove's physical traits. For example, the female mourning dove has a rounder head compared to the male, and the male also has a more intense and vivid coloration than the female. The male mourning dove has a peculiar bluish-gray crown, light pink breast area, and bright purple-pink patches on the sides of the neck.
After we've gathered this demographic information from the bird, we fix a metal band onto its right leg that lets biologists identify the bird in the future (either when it is captured as part of another banding effort, or when it is shot down and retrieved by hunters, who then report it using the number provided on the band).
A mourning dove with a band on its leg! The metal bands have to be stretched open with pliers before being tightened around the dove's legs. Each band has an unique number used to identify the individual.
Wildlife biologists use survival rates, harvest rates, recruitment rates and population trends to help guide harvest management decisions. Banding is one of the most important tools used to obtain this information. Information gained from the current banding effort will be used in conjunction with previous information collected in Indiana and elsewhere to improve biologists' ability to manage doves at regional and national levels.
So the work was just as fun as it was essential!
Just a couple of days later we had the chance to visit Muscatatuck Wildlife Refuge to participate in their dragonfly survey! During this event, we worked under the refuge biologist and alongside Muscatatuck's own resident interns to identify, bag, and measure dragonfly larva (also known as nymphs) across several sites throughout the refuge.
Muscatatuck interns braving the murky depths! After sweeping the nets through the water, they examine their catch to see if there are any dragonfly larva present. The larvae are aquatic, and can be hard to spot due to their drab color. They are easily identifiable however by their six legs, large eyes, and small wing buds on the back of their thoraxes!
These sites typically border on wetlands and shallow bodies of water (streams, ponds, lakeshores, etc.). Both vegetative structure and hydrology are major mechanisms in determining dragonfly species richness and composition at these sites. Moist-soil units have a diversity of plant species and structure that likely provide the appropriate perch sites, territory boundary markers, and oviposition substrates for adults and adequate habitat for feeding and protection from predators for nymphs.
Performing these surveys involves sweeping the waters with nets while starting downstream and working upwards through the flowing water. This makes it more likely that the larvae will happen into our nets with the flowing currents, rather than flowing straight past us.
Moving on upstream!
When we encounter the larva, we use a spoon or a glove to place them individually into their own sample bags for identification and measuring. We measure the body length of the larva in millimeters (mm) with a plastic ruler, starting from their heads and measuring to the ends of their tail-spines. Most speciments are within the 10-40 mm range. Following this, we fill out a tag for the bagged individual, then slip the tag and the specimen back together into an outer bag for storage in our coolers.
After this is done, we record our findings on our data sheets and move onto the next individual (or the next site, if the area has already been thoroughly sampled, or is otherwise not experiencing much activity). Since narrowing down exactly what species of dragonfly we're looking at is difficult with larvae, our protocol only requires that we identify them as far as the taxonomic family (i.e. general group of species) that they belong to.
We try to choose at least 3 individuals from each family that was found to submit with our data, however we don't submit an individual if it's the only one of a certain family that we've discovered at a given site. We choose medium to larger samples (>15 mm) to submit over very small ones whenever possible, simply for sample quality and ease of indentification.
When working in different wetlands or even with different individual larvae, it's crucially important to make sure the equipment we're using (nets, spoons, boots, gloves, and buckets) are all clean, so as to not contaminate other samples or other bodies of water. Just like when we're working with the crawfish frogs at Big Oaks!
Speaking of the little guys, many of our tadpoles here are coming along the home stretch to becoming fully-fledged little froggies!
Towards the end of this week, we brought the Muscatatuck interns and the Youth Conservation Corps crew onto the refuge for a tour. We brought them to our final remaining active crawfish frog ponds and got a chance to show them how we do our monitoring, feeding, measuring, and releasing!
Muscatatuck interns and YCC Crew learning about our collection and data entry methods!
As many of our frogs are reaching the end stages of their metamorphosis, we've been measuring and releasing lots of succesful frogs, but we have also had to deal with many of our ponds experiencing extreme dieoff. We are waiting on lab results from the samples we collected in order to determine the exact cause, but we suspect that it may the results of some pathogen (possibly ranavirus, chytrid fungus, or a perkinsid parasite).
Metamorphosis is a very metabolically intense process for a tadpole that requires nearly all of the energy and resources that its body can spare to complete the transformation. Because of this, tadpoles are left highly vulnerable to infection by pathogenic agents that may be present in their ponds, which might be causing these mass deaths.
Regardless of the cause, the result is that the numbers of tadpoles in some of our cages have been dramatically reduced. The silver lining of this situation however is that our remaining tadpoles (i.e. the ones that we haven't yet released) are doing spectacularly well! Their legs are coming in quickly, and they have practically doubled in size over the past few weeks, as they're no longer competing with hundreds of their brothers and sisters for limited food resources.
One of our especially chunky tadpoles! Its hind legs are already out, and the
bumps along its front side mean that its front legs are due to emerge any day now!
Because our tadpoles are so far along in their growth and development, we're anticipating that this coming week will be our last week of feeding and monitoring the ones in our cages. They'll be released into the ponds they've been raised in, and then they'll be free to explore the wilds of Big Oaks! It'll only be a few short years before they return to the ponds to mate and lay their egg masses once again, starting the whole process all over.
Crawfish Frog metamorphs on their way to be measured and released!
Us interns might not be able to stick around to watch the final releases however, since this next week we'll be headed to a workshop in Minneapolis to meet with refuge staff from the midwest region, as well as with other interns and aspiring early-career biologists!
We'll be attending seminars, watching some presentations from our peers, and delivering some presentations of our own while we're there! It's sure to be a lot of fun, and you can bet that I'll be posting all about it as soon as I'm back home at Big Oaks.
Until then, as always, stay tuned!