FROM THE VICE PRESIDENT
Campus research efforts now expend more than $67 million annually.
A rundown of science stories during the past year
THE OUTER LIMITS
New University research center studies the edge of human endurance.
THE ROOTS OF SOCIAL INEQUALITY
Digs in British Columbia offer a groundbreaking view of hunter-gatherer societies.
Research reveals another public health threat from asbestos contamination.
A young UM researcher studies flying rhinoceros beetles in Taiwan.
The Milltown Dam removal allows trapped sediments to travel.
How do prey species react when predators are returned to ecosystems.
THE NEW NOTE-TAKING
UM develops new software to aid college students.
A UM legal scholar reveals Constitution's original intent.
FLIP THROUGH CURRENT ISSUE
Cover: Jeff Cincoski, a triathlete and UM employee, puts a research bike through its paces in a 100-degree, temperature-controlled room at the Montana Center for Work Physiology and Exercise Metabolism.
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Studying big beetles in Taiwan
Interview by Brianne Burrowes
|UM doctoral student Erin McCullough, working in Taiwan, poses with two rhinoceros beetles she had marked with paint pens.
Erin McCullough, a second-year doctoral student in UM’s organismal biology and ecology program, spent last summer studying the Japanese rhinoceros beetle, also known as Allomyrina dichotoma. Her research, funded by the National Science Foundation East Asia and Pacific Summer Institutes, focused on determining whether there is a relationship between a beetle’s horn size and the aerodynamic and energetic cost of flying with horns. For three months she tracked the beetles at two different sites in Nantou County, a mountainous region in central Taiwan.
What sparked your interest in studying beetles, and more specifically, rhinoceros beetles?
I’ve been interested in animal behavior for a really long time. As a little girl I used to play in tide pools and just watch birds and squirrels. I’ve always loved the animal kingdom. As an undergrad I studied navigation and decision-making in honeybees and bumblebees. After I graduated college, I spent a year studying feeding behavior in primates in Thailand. When I was applying for grad schools, I wasn’t specifically looking to study rhinoceros beetles but, more broadly, animal signals. I have always been fascinated by how elaborate and
bizarre some animals can be. I interviewed at a whole bunch of different schools around the country, and Montana was the last place that I interviewed. I just sort of fell in love with Missoula, and the professors and the program. My adviser, Doug Emlen, has been studying horned beetles for the last 15 years. Only recently has he switched to the rhinoceros beetles. He’s done most of his work on dung beetles, which are much smaller but also have really interesting and elaborate horn morphologies.
What was your first step when you arrived in Taiwan?
I wanted to do my research at a field station. Unfortunately, when I got to Taiwan at the beginning of June, there were no beetles. I’m not sure if I was there early. Usually beetles are out by May. The whole life span of a beetle is about a year. They spend most of it as larvae. The adults will emerge in May, maybe even the end of April, and then they’ll live through August. The field station is a popular destination among tourists, and the beetles there have been heavily harvested. Tourists will take them home to sell, or kids will take them home as pets. Because of this the population is dwindling. So there I was at the research station with no beetles. I was only in Taiwan 10 weeks, and I couldn’t wait around for the beetles to possibly come and then have tourists take them, because my project hinged on the fact that I needed to see beetles over consecutive nights. I needed to know how far they’re moving from night to night in order to measure flight distance. If they were getting collected by tourists, this wasn’t going to work. I went to National Chi Nan University in Puli, Taiwan, and there was a large population of beetles. This ended up being one of my research sites. It had a large population of beetles that wasn’t getting harvested. Then I had a second study plot on the side of a mountain road about four kilometers southwest of campus.
What was the focus of your research in Taiwan?
I’m interested in the aerodynamic and energetic costs of flying with these horns. If you have a big horn sticking on the front of your head, how hard is it to maneuver? How hard is it to turn? How does this differ if you have a horn sticking straight out in front of you or if you have several different horns around your head? I’m interested in how the shape of the horn might affect the way that you fly, so how a horn of one shape might cause more drag than a horn of a different shape, or how the horn of one shape might shift the beetle’s center of mass more. The horns can be more than half the length of the body. It would be like humans having a leg sticking out of their head. This is a large appendage. It can be very heavy and, I assume, very awkward. It is likely to cause imposed aerodynamic drag. So, if flying with the horn is costly, I would predict that big males with big horns would fly slower, or that maybe they just won’t fly as far or as often.
How did you test your hypothesis?
The beetles are nocturnal. I was active at night. I used headlamps because the beetles are light sensitive. If you are staring at beetles for long periods of time, you don’t want to be shining a bright light on them. But they can’t detect red light, so I would put red cellophane over my headlamp and then stare at them as long as I wanted. I would find each beetle, and then I would mark them with paint pens. I would give each beetle four dots -- two dots on the left elytra (the hard wings on a beetle) and two dots on the right elytra. And, I would give each beetle a number. I then measured the horn length, the horn width, the prothorax width and the elytra length as measures of body size. Then I put the beetle back on the ground, and I would wait for it to take off. Some beetles were ready to go and would take off right away, and some beetles were extremely reluctant to fly. I think I waited three hours for one beetle to take off. Sometimes they just don’t want to go. Actually, it’s interesting because they are much more eager to fly from 7 to 10 p.m., and then there’s a lull from 11 p.m. to 3 a.m. where they don’t want to do anything. Then right before the sun comes up, they’re ready to go again.
How did you measure flight speed?
I used a radar gun, which is the same instrument that police use to measure speeding cars. The males are fighting on trees over these sap sites and whoever loses gets knocked off the tree, and then they fall down to the ground. Then they take off from the ground and fly back onto the tree or onto another tree. I would use the radar gun and track takeoff speeds as the beetles were coming off the ground, which was much easier than I thought. I started off the trip thinking there was no way that I was going to be able to measure flight speeds. But if I know where the beetle is, and I’m following it, then I can take the speed as they take off easily.
When you clocked their speeds, what was the average speed?
They’re going anywhere from 1.5 to 3.5 meters per second. Most of them are going between 2 and 3 meters per second, which is pretty fast. My adviser thought that I could run after them, but there is no way I would be able to run 3 meters per second after a tiny insect in the dark. (Laughs)
How did you measure flight distances?
I did scans every two hours. I had two study plots. At these sites I had all of my trees marked, and every two hours I would scan all of the trees and see which beetles were in which trees. Again I had all of the beetles marked. I would go up and down (the tree trunk) with my big light, and I would see which beetles were on the trees. If there were any beetles that I hadn’t marked, I would mark them.
What did your study find?
I actually haven’t finished analyzing all of the data, but it looks like there’s no difference in flight speeds, which I find surprising. Big males, small males and females are all flying about the same speed. So I’m actually beginning to wonder how costly the horns actually are, which is pretty amazing because these structures are huge, and rhinoceros beetles are a prime example of something with a sexually selective trait. Here’s this male with this gigantic horn, and if I find that the horns aren’t costly at all, that’s a pretty surprising result. But there’s a lot of lab work and flight lab work that I hope to do to test that specifically.
What is next in your research?
One cost that I want to test is how the horn, or how this big structure on your head, might change your center of mass. The reason I want to test this is because when the beetles were taking off more than once, I saw a male try to take off and his head would run into the ground. His horn would get stuck in the ground. Sometimes he would just sit there with his head in the ground trying frantically to take off, or the horn would get stuck in the vines as he was taking off. I really think that center of mass seems costly. So that’s a next step that’s in the near future.
|Powerfully strong for its size, this beetle has no problem carrying the transmitter attached to it.
|McCullough and some of the specialized equipment she used to track the beetles at night