Finding the elusive eastern spotted skunk

Screen Shot 2018-08-22 at 11.28.58 AM

Documentation of the mid-century eastern spotted skunk population decline by Gompper and Hackett (2005).

The eastern spotted skunk is an elusive, potentially rare and endangered species of skunk native to much of the eastern US between the Rockies and the Appalachian Mountains. The species was common throughout its range at the beginning of the twentieth century and people often saw eastern spotted skunks on family farms. During the 1940s and 1950s however, eastern spotted skunk populations crashed. The population decline is well documented, but reasons for the crash remain unclear. Hypotheses for the decline range from the expansion and modernization of agriculture to overharvest to disease. Likely, a combination of several concurrent factors lead to the decline. Eastern spotted skunk populations never recovered, remaining at low levels across much of their historic range.

Today, researchers are working with state wildlife agencies to identify where eastern spotted skunks are and determine which resources they need to maintain healthy populations. In some states, large-scale surveys for eastern spotted skunks resulted in no sightings, suggesting the species is locally extinct in parts of its historic range. Other states have identified populations and are working to understand whether the populations are at a healthy level.

In Arkansas, eastern spotted skunks were historically present across the entire state and recent surveys have revealed the species still has strongholds in the Ouachitas, or the western region of the state. It was with this knowledge the Arkansas Game and Fish Commission funded my research to determine whether eastern spotted skunks are present in the Ozarks, and if so, which resources they’re using. I conducted a large-scale camera trap survey in north-central Arkansas to answer these important questions. Although I recorded eastern spotted skunks at some camera trap sites, preliminary results suggest the species occurs at extremely low population levels in this part of the state.

ESS

An eastern spotted skunk visits a camera trap site in north-central Arkansas.

Using the information gathered from my camera survey, I decided to produce a species distribution model. This type of model uses presence-only data to evaluate where a species is most likely to be present based on characteristics of locations where we know eastern spotted skunks spend time. Using presence-only data means that I will only use camera trap locations where eastern spotted skunks were recorded. For example, from approximately 75 camera trap locations, eastern spotted skunks were photographed at only 4 sites. Failure to record an eastern spotted skunk at a camera trap site doesn’t necessarily mean the species is absent at that site; it simply means we don’t know for sure that eastern spotted skunks use that area. Thus, the locations where I recorded eastern spotted skunks on camera traps are “known locations.” I will use the 4 known locations where eastern spotted skunks were confirmed and exclude the remaining 71 camera trap locations for my species distribution model.

In addition to the 4 known locations from my camera trap survey, the eastern spotted skunk species distribution model will use an additional 72 known locations from eastern spotted skunk surveys by other researchers in Arkansas and southern Missouri. I will determine what the environment was like at the known locations, including how close they are to roads and other infrastructure, how close they are to water sources, and how dense the forest is at each location. Using this information, the species distribution model will predict where eastern spotted skunks are most likely to be across all of Arkansas and southern Missouri. For example, if most of the known locations are in areas where the forest is thick and dense, the model will predict that eastern spotted skunks are most likely to be in other thickly forested parts of the state and less likely to be in open fields.

Although the large-scale camera trapping survey I conducted resulted in limited eastern spotted skunk photographs, the species distribution model approach allows me to use these data. The final product will be a heat map of Arkansas and southern Missouri, with warm tones suggestive of eastern spotted skunk populations and cool tones meaning eastern spotted skunks are not likely to occur in those areas. The map will be useful for state wildlife agencies as they continue to determine where the species is and create management plans to prevent further population decline of this unique mammal.

 

Will you be at The Wildlife Society Annual Meeting in October 2018? Come to my talk on Tuesday, October 9 to see the results of the species distribution model.

Advertisements

The Tayra in a Changing Brazilian Landscape

mustelidae plate

Illustration of the Mustelidae Family from Handbook of the Mammals of the World: Volume 1 by Toni Llobet.

While many mammalian species found across Central and South America are declining due to habitat loss, forest fragmentation, and agricultural development, the tayra is trying something different: persistence. The tayra is a medium-sized omnivorous mammal that looks like a mix between a cute teddy bear and a giant weasel. In fact, it is a member of the weasel family (Mustelidae), which includes weasels, otters, wolverines, and a diverse range of other noodle-shaped mammals. It’s this fun-to-look-at species that brought me to Brazil this summer (or winter, depending on which hemisphere you’re reading from). With support from the Brown Graduate Research Fellowship Program through the College of Agriculture, Food, and Natural Resources at Mizzou, I partnered with Assistant Professor Rita Bianchi and her lab to analyze data they collected on the tayra.

The Bianchi Lab Group works extensively on mammalian ecology in Brazil. To achieve their varying objectives, many students use camera trap data. Camera traps are a remote-sensing technology that allow researchers to gather information on exactly where mammals are at specific dates and times. Over the past several years, the Bianchi Lab Group has methodically scattered camera traps throughout state parks and other natural areas in São Paulo State. These camera traps captured images of several mammalian species, including giant anteater, puma, agouti, and of course, tayra! Pairing the date and time stamp from the camera trap images with the camera trap location and species present in the photo, researchers can answer a breadth of questions about when and where animals spend time. Answers to these questions can help scientists and land managers understand the resources needed for species to thrive.

IMAG0041

Two tayra are captured on a camera trap in São Paulo State, Brazil.

Despite a growing shift from natural forest to agriculture throughout Brazil and other parts of Central and South America, tayra seem to be handling increasingly fragmented forests just fine. Why bother looking at data for an animal that we aren’t too concerned about? First, we must understand what a species needs if we are to keep it on the landscape. For example, what type of forests do tayra live in? When are they most active and what foods do they rely on? Can tayra survive in small forest fragments? Answers to these questions allow land managers to ensure tayra needs are met and prevent a future decline. Secondly, other species of mesocarnivore (medium-sized carnivorous and omnivorous mammals) are not faring as well as the tayra. Understanding the specific tayra traits that have allowed it to persist longer in this changing landscape could offer insights on why other species are declining.

Using camera trap data collected by the Bianchi Lab Group, we are working on two objectives: 1) Determine tayra habitat selection and 2) Evaluate tayra activity patterns. The first objective will help us understand where tayra are choosing to spend time, including which type, size, and structure of forest. We can also determine whether the presence of other species, like large predators or potential prey species, dictate where the tayra are on the landscape. The second objective will provide insight on when tayra move around the landscape and whether this activity changes by season. We anticipate this research will provide a much-needed update on tayra ecology in the current Brazilian landscape. Stay tuned to this blog for more insights on life in Brazil, tayra ecology, and other wildlife research.

A Turtle on a Tall Mountain

A couple of summers ago, I was trapping flying squirrels in the North Carolina mountains.  It was a normal day at work and I was mostly concerned with the squirrel trapping grid we had laid out atop Roan Mountain.  That was until we found a turtle.

The unassuming box turtle found atop Roan Mountain.

Box turtles are docile, adorable, and make for great photo ops, but rather than gather it up for some Instagram-worthy pics, we only looked at it, confused.  This turtle was hanging out in the middle of a spruce-fir forest 1,875 meters above sea level.

Let me put this in perspective.  Roan Mountain is one of the tallest mountains in North Carolina.  It reaches so high that many wildlife species common across North Carolina don’t dare venture to the peaks of the Roan Highlands.  Ticks are unheard of there, a unique scenario for anyone working summer months outside in the southeastern U.S.  When North Carolina experienced a massive heat wave that summer, the squirrel team switched from long-sleeved t-shirts to short-sleeved for a couple of weeks.  The temperatures are cooler and the forests different on a peak as tall as Roan’s.

When we found this turtle on Roan Mountain, we were simply stupefied.  We didn’t think box turtles as a species existed at such heights, but there it was—a turtle, on a tall mountain.  It offered no apology or explanation, so like any good scientist, we did some digging later that day and discovered what we already suspected—box turtles had never been recorded at such a high elevation in the southern Appalachians.  This turtle was a maximum elevation record.  This turtle was noteworthy.

This morning I am preparing to step into a highly-publicized movement and declare my love for science to the world.  I am participating in the March for Science in Columbia, Missouri.  This public space is not commonly occupied by scientists.  It is true that science has had its moments, but we largely stay out of sight, fueled by our own curiosity.  We sit in our labs and offices running experiments, recording data, and writing papers.  But, this movement has been brewing for months and unlike a quiet turtle on a tall mountain, we are stampeding into this unexpected space, unified and loud.

I anticipate today will be easy.  I am marching with friends and fellow scientists and we will be surrounded by smiling faces who support the work we do.  After the march, we will discuss our research with the science-loving public at a local festival.  But then what?  Are the ears on Capitol Hill listening?  Are climate change deniers opening their minds to real scientific evidence?  Are we really making strides in how the public perceives science?

Today is not a challenge.  Today we collectively throw ourselves into the public eye, a space where we aren’t expected.  Where we go from there is the challenge.  Perhaps we scientists belong in everyday life the way a box turtle belongs in a spruce-fir forest on top of a mountain.  It’s unexpected, not wrong.  So here’s my suggestion: don’t leave this public space we’ve come crashing into.  Stay visible.  Keep talking about your work, keep putting it out there in a way that anybody can digest.  And don’t apologize about being in that space.  Don’t offer an explanation.  Be present in that space until it’s expected.  Be noteworthy.  Be a turtle on a tall mountain.

You.

Read the turtle note here.

This one’s for the women: thank you

Wildlife biology. As someone immersed in the field now, those words mean many things: research, conservation, exploration. When I declared them as my major at North Carolina State in 2010, I was naive to the path women before me paved in my field. But it didn’t take long to realize most of the core wildlife faculty, most of my classmates were male. Still, I never felt out of place, less than, or in the wrong being a woman in wildlife. Let me tell you why.

At freshman orientation, it was a woman (Rebecca) who grabbed my arm and forged a lifelong friendship fueled on dining hall food, late night study sessions, and a mutual love of the outdoors. As a junior working in a lab at the nature museum, it was a woman (Morgan) graduate student and woman (Ariel) research assistant who showed me the ropes. That summer, the women (Alex, Danie, Lauren, Lindsey, Julie, Erica, Elysha, Elizabeth) of wildlife camp formed a sisterly bond over morning bird quizzes and evening beers by the river.

When senior year rolled around, a woman (Dr. Gardner) professor taught the class notorious for being the most difficult in the wildlife curriculum. A woman (Lisa) interviewed me for my final internship as an undergraduate student that year, too and became a lasting mentor; she still challenges, “Are you doing what you want? Pursue only what you want.”

In my post-graduation internship, a woman (Stephanie) proved that glamour has a place in wildlife and a team of women (Troi, Mary, Natalia, Christina) interns lent helping hands on the others’ projects. Toward the end of that summer, I interviewed with a woman (Marcella) professor who hired me for my first real technician job. When I got to work, a woman (Jenna) trained me. The woman (Dana) graduate student on the project heard when I asked for more and gave me the opportunity to present and publish research on the data I helped collect. When that work was done, it was a woman (Cordie) graduate student who offered a job on her squirrel project. During her brief absence to attend a conference it was a woman (Emily) technician who came to assist me in the field.

When I moved to Missouri, I first worked for a woman (Rami) in a wildlife physiology lab, then with a woman (CJ) on a deer capture crew. The woman (Chloe) graduate student on the deer project balanced her responsibilities with the capture crew and coursework flawlessly. Later, I was hired by a woman (Roxie) to head up an invasive plant removal crew, where I worked with women (Michaela, Hannah) crew members.

When my graduate position on spotted skunks was still only maybe going to happen, it was a fellow woman (Colleen) mesocarnivore adorer who offered excitement. I ultimately accepted that graduate position and when I requested help from my lab prepping field equipment, it was two women (Lauren, Abby) who volunteered. The only woman (Lori) on my committee was the most enthusiastic of four members to join my thesis efforts.

Of course my journey in this “male-dominated” field included men too. An undergraduate advisor, for example, who believed my language-learning, study-abroading, non-wildlife-related pursuits were valuable. A boyfriend, who in response to whatever new dream job I discover, asks how, not whether we will achieve that dream. A professor and supervisor who will always write that letter or pick up the phone and call his contacts to vouch for me when I apply for a new job. A family that just wants to hear my stories, to know why I love the work I do.

womensmarch-expect-usIt’s a gift to be surrounded by men who can’t fathom the type of person who would sexually discriminate or harass a woman in our workplace. But they know as well as we do, ladies, that our work isn’t done. Women don’t represent half of the wildlife field yet; the stats are even worse for women representing other minorities as well. Multiple women mentioned in this story told me experiences of sexual discrimination at work. That’s what today is about. Thousands of women are gathered in Washington, D.C., standing strong in the face of an uncertain future. Still thousands more are walking in sister marches worldwide. Today is about us standing in solidarity, in celebration, standing together.

To every strong woman in the wildlife field: thank you. You are proving to me, and the world, that we belong where we go. We are carving a space for ourselves and we’re not here just to look good or just for fun or just until our babies are born. We know our work, our contributions aren’t done. That’s why we’re here. Proudly. Unapologetically. For good.

This slideshow requires JavaScript.

Signage from the January 21, 2017 Women’s March on Washington sister march in Columbia, Missouri.

These Aren’t The Poops You’re Looking For

Researchers have been using animal scat (read: poop) for decades, and for good reason.  Bits of identifiable food not fully ingested by the animal offer insights into diet, while many parasites pass eggs through feces.  More recently, physiologists have defined methods for extracting stress hormones from fecal samples, providing information on when animals become stressed and whether that stress is chronic.  Collecting scat is a great way to answer basic ecological questions on a given species.  Cool story, right?  Well, we’ve got a bit of a problem.

If you read through old research papers on carnivore diet, you’ll find that in many diet studies, researchers collected scats from live traps.  Say the target species is a grey fox.  The researchers set live traps, capture a grey fox, and discover a scat inside the trap.  It’s pretty clear that scat was made by the grey fox.  Easy identification.

field-guide-scatOne of the major benefits to studies utilizing scat today, however is that they are “non-invasive.”  That means researchers don’t need the animal in hand to conduct the study.  In turn, studies are cheaper and logistically easier.  The data (poops) are out there on the landscape, scientists just have to find them.  As long as they know the animal exists in the study area, they know its scat exists there too.

Until recently, a typical researcher conducting one of these non-invasive studies would carry a field guide on her poop collecting journeys.  When she wandered upon a scat sample, she could observe its shape, size, odor, and any associated tracks to determine who made the poop.  That’s right, a handy dandy field guide could tell her whether she was looking at the digested dinner of a bear, coyote, bobcat, red fox, grey fox, or domestic dog.  Or could it?

A team of researchers at Virginia Tech decided to test how handy that guide really was when it came to assigning appropriate species identifications to scat samples.  In other words, do carnivores leave scat samples different enough that a researcher can tell them apart, or is the researcher simply making an educated guess?  If the latter is true, how much are those guesses altering the study results?

They started by – you guessed it – collecting scats.  Every time they found a sample, they gave a species identification based on field guide descriptions of the most common carnivores found in their study area: the Virginia mountains.  Then, partnering with a lab at the University of Idaho, they used DNA left behind by the predator on the outside of each poop to confirm identifications.  These genetically based identifications were reliable; they identified the true pooper, and it wasn’t always the same as the field guide suggested.

Now the scientists decided to test if those incorrectly identified samples mattered.  Were they altering study results?  To find out, they conducted a diet study.  They looked at bobcat, coyote, and bear diet when the samples were identified using only field guides, then looked at diet for the three carnivores using the true, genetically confirmed identifications of the scat samples.  Details on using scat to discover dietary patterns in carnivores can be found in my Scoop on Poop series.

The researchers found they weren’t too good at assigning correct scat identifications using only field guides.  Coyote scats were only identified correctly in the field 54% of the time and bobcats had a similarly dismal field accuracy rate at only 57.1% of true bobcat samples identified correctly in the field.  Black bear scats, on the other hand, were easier to identify; almost all (95.2%) bear samples were identified correctly in the field, likely because they are much larger in size when compared to coyote and bobcat samples.

Sometimes the researchers incorrectly called bobcat scats coyote scats and vice versa…so what?  They’re probably after the same prey anyways, right?  As it turned out, that “sometimes” really influenced the results of the diet study.  When bobcat scats were misidentified, they were classified as coyote scats 98% of the time.  Similarly, bear scats called something other than bear in the field were called coyote 75% of the time.

Because they were classifying some bobcat scats as coyote in the field, it appeared that coyote diet was similar to bobcat diet (0.95 niche overlap, where 1 means identical diets and 0 means completely different diets).  In contrast, coyotes and bears appeared to have quite different diets (0.5 niche overlap) when using the field identification method.  In reality, bobcats and coyotes were tapping into some of the same prey resources, but not at the same frequencies.  Their true niche overlap, calculated based on those reliable genetic identifications, was 0.73; bears and coyotes actually shared more diet items than it seemed with a true niche overlap of 0.69.  The incorrectly identified scat samples provided a picture of how the carnivores were interacting on the landscape, just not the right one.

Scientists make a living on asking questions, and sometimes that means questioning their own methods.  In this case, it’s a good thing they did!  Moving forward in the realm of scat studies, the authors of the study suggest always corroborating field identifications of scat samples with genetic methods in the lab.  Read the complete study here.  The data are strong with this one.

How to Catch a Deer

Several years ago, I was having a relaxing morning at my parents’ house when my little brother walked inside, apparently exhausted. He went straight for the cabinet, plucked a cup off the shelf, filled it with water, and chugged the full cup…twice. Breath caught, he looked at me. “I tried to catch a deer.”

White-tailed deer are a fairly common site near our suburban North Carolina home. They make regular early morning appearances—regular enough, in fact, that our garden is now fully fenced in an effort to keep them out. They are fun to watch from the window, coffee in hand, but they tend to make haste when we step outside. Apparently my brother took their fleeing as a challenge. He chased a group of deer through our backyard and into the neighboring woods and if you ask him, “I almost touched one.” He admittedly didn’t know what he would have done with an entire live deer, but he knew he’d figure it out in the moment. Classic.

Sometimes deer biologists need to catch deer and needless to say, my brother’s methods are not the most effective. Instead, they use clover traps, rocket nets, and dart guns to safely capture live deer and conduct research. Reasons for catching live deer include deploying GPS or radio collars to track movements and survival, collecting blood, inserting individual identification tags, and to help answer a variety of other research questions.

Clover Traps

Clover traps are rectangular, netted traps with a door that closes when a trip wire is triggered by the deer. The traps are baited with corn behind the trip wire. The trip wire is high enough that critters like squirrels, raccoons, and birds can enter and exit the trap without getting caught. Researchers check clover traps at least once daily. If there is a deer inside, they open the door, pull it out, and process the deer in whatever way is relevant to the specific project. Some clover traps are designed so that researchers can collapse the trap on the deer when they arrive, helping immobilize the deer while they remove it from the trap.

Researchers with the Missouri Deer Project remove and process a captured deer from a clover trap.

Rocket Nets

Rocket nets are used to capture a variety of wildlife, including wild turkeys, waterfowl, and deer. A rocket net set-up consists of rockets, or cylindrical tubes with a series of holes on the back end, tied to the front end of a large net. Rocket charges (black powder) inside the rockets are connected to a long wire that links all rockets in the series. The far end of the long wire connects to a detonator in a waiting researcher’s hands. Deer are attracted to a bait site in front of the net. When the rockets are deployed, they soar over the deer, pulling the net with them. Heavy anchors on the back end of the large net prevent the rockets from pulling the net completely over and beyond the deer. The tug from the anchors causes the rockets to drop and the net entraps the deer. Researchers waiting nearby race to the rocket net site and rapidly untangle and process the deer according to the project objectives.

Researchers with the Missouri Deer Project deploy a rocket net to trap a doe.

Dart Guns

Dart guns are exactly what they sound like—guns that shoot darts. The darts are filled with an immobilization drug, which varies by species and project, though there are guidelines, regulations, and approval processes governing how immobilization drugs can be used. When a deer is shot with a dart gun, ideally in a meaty part of the body like the ham, the drug releases into the deer. Researchers process darted deer while they are chemically immobilized and reverse the drug before letting the deer go on its way. Researchers use dart guns from tree stands over baited sites or even while driving around in a truck, so long as the deer will stand in range of the dart gun. Like other guns, dart guns must be cleaned and sighted in regularly to ensure accuracy.

I got the opportunity to practice with several dart gun models while learning to safely immobilize wild animals at a Safe-Capture workshop.

I got the opportunity to practice with several dart gun models while learning to safely immobilize wild animals at a Safe-Capture workshop.

These methods tend to be the most common in North Carolina and Missouri where I am familiar with deer research. Other states may deploy different methods to catch deer, however. Drop nets rest on poles above a bait site and fall at the will of the researcher when deer are present. Box traps are like a fully enclosed clover trap. In areas with long swaths of open ground without timber, some research projects hire helicopters to find and capture deer using a net gun. Regardless of the capture method, research allows state and federal agencies to better manage our deer herds. With a thriving deer population, nature enthusiasts from hunters to adorable animal lovers (to backyard deer chasers) will enjoy their presence for years to come.

Scoop on Poop: Ungulates

Predator poop tells researchers about diet, but it’s not all about carnivores in the scat world. Ungulates like elk and mule deer leave data-rich pellets for scientists to collect across the landscape. It is possible to determine food items from ungulate scat, but when I started working in the University of Missouri’s Wildlife Physiology Lab, we were using scat samples for a different reason: to determine stress levels.

To understand how we’re getting to those stress levels using a couple of scat pellets, let’s take a step back. Ungulates (and lots of other animals, including humans) have something called the hypothalamus-pituitary-adrenal axis (HPA axis) that, among other things, responds to stressors. One HPA axis reaction to stress is an increase in glucocorticoid production. Glucocorticoids, also known as stress hormones, signal the body to produce glucose faster than normal and distribute it primarily to the heart and brain, resulting in a fight-or-flight response.

Researchers can find these stress hormones in scats, and a higher concentration means a more stressed animal. It isn’t a big deal for occasional spikes in stress hormones. For example, we might see an increase in glucocorticoids in an elk as it notices and runs from a predator or in a human before a big speech. But, a long-term increase in stress hormone production can have negative results, including immune system suppression, issues with reproduction, and ulcers, all of which reduce the overall fitness of an individual. It is important to understand if and why ungulates are chronically stressed so we can better manage the herd.

Ungulates like elk have pellet-shaped scats. (Image credit: Colter Chitwood)

Ungulates like elk have pellet-shaped scats. (Image credit: Colter Chitwood)

After we received scat samples in the lab, we mushed together the pellets in each sample and collected a small subsample in a vial. We completely dried the subsample and I then had the glorious job of turning that clump of dried poop into what I referred to as “poop dust” using a small mesh sieve. We mixed the poop dust with an ethanol solution that pulled those stress hormones from the samples. Then, we used a special kit to determine the glucocorticoid concentrations in each sample.

We can use those concentrations to get an idea of how stressed the herd is as a whole. Take the Missouri elk herd as an example. Elk were recently reintroduced into the state from Kentucky (you can read more about Missouri’s elk here and here). We can imagine that the move was a high-stress time for the elk. But after spending several years in Missouri, we would expect their stress levels to be lower overall. They might still experience seasonal changes in stress, however. For example, the increase in disturbance caused by humans during white-tailed deer hunting season might trigger an increased stress level that time of year.

Researchers can use these same methods to test various potential stressors in other ungulate herds, too. So, the next time you come across a deer scat, skip the “Ew!” and consider how cool that pile of pellets really is!