Squirrel! (Skulls, That Is)

So often what we picture ourselves doing in college is not the reality. We know we’ll be studying, attending class, maybe hanging out in a place where students gather. Some of us even envision working on a research project (something many Penn State Altoona students experience). So when Mallory Harold was a freshman, she went looking for research opportunities at Altoona. What she found was a wide variety of experiences looking inside rodent skulls on a computer screen and collecting bees in the bright sunshine.

A pre-med major, Harold knew she wanted to be involved in research but had no idea what she wanted to pursue. “I had heard about research opportunities involving squirrels, but I didn’t know who would want to research squirrels all the time.” Just the same, she knocked on Professor Carolyn Mahan’s office door. Harold says, “Dr. Mahan said, ‘I have something for you. It’s not squirrels, but I was looking for students.’ I was a freshman. We both needed each other at the same time.”

Deermouse skull

What Harold ended up doing was measuring rodent skulls. She explains: “The project I originally started working on with Dr. Mahan was measuring the cranial cavity of small rodents. The purpose of this was to see if their cranial size increased, and therefore their intelligence, over time with exposure to humans.” Thanks to a loan from the Carnegie Museum’s collection of small mammals from Allegheny County, dated from the late 1800s to the present, “we had skull samples of four different mammals—big brown bat, deer mice, a short-tailed shrew, and a meadow vole.”

Scanning the skulls was handled by technicians at Penn State Hershey, and then Harold took over. “I measured their skull length and actual area using a program called Avizo, commonly used in the medical field for CAT and CT scans to measure tumor diameters. I had to take the imagery of the skull—top view, side view, bottom view—and put them in one file to make a 3D image (they were sliced). I had to click around the circumference for every third slice of about 300 slices and then put it together and calculate the surface area and the area inside the skull.”

After all that work came the actual data collection. “We got the ‘patient IDs’ [for the animals] and matched them up with the skulls,” Harold says. “Then we did a statistical analysis to see if over time, with exposure to humans, their brain size increased. Their skull size would have increased as well.”

Meadow vole skull

As always, the question is why is this research being done? Mahan explains: “When a landscape goes through urbanization, how do wild animals adapt to it? Animals who can exist in this environment have larger brains. We’re looking to see if there are differences in skull sizes over time. Research suggests that small mammals with larger brains are better able to persist in “novel”—human/urbanizing—environments. Therefore, as a landscape becomes influenced by human development we see a concurrent increase in wild mammal brain capacity.”

Why do we care if rodent brains increase in size due to exposure to humans? “It could influence how we do pest control—smarter rodentia avoid traps,” Harold says. “We can superimpose this model on other animals to see why animal populations have changed over time. Are they avoiding humans because of what they have learned or is it declimatization?”

In another of Mahan’s projects Harold helped collect bees. “We are studying ways to manage habitat under power-line right-of-ways,” says Mahan. “You have to keep the vegetation down under a right-of-way but it is also a natural state.” The study, part of a partnership between First Energy, Dow, and Asplundh companies, “has been going on for 60 years. I just took over two years ago and I was interested to know we’ve been managing for vegetation. We’ve studied birds and mammals. I wanted to know what’s happening with the pollinators.”

Curated bees for the Frost Museum (photo by Hannah L Stout, Entomologist)

Harold explains how the bee collection was carried out: “Our goal was to collect bees in a few different areas that were under different areas of vegetation control, such as mowed, herbicide, and handcut areas, to see how the population of bees varied in these different areas. We would hike up and down and catch them with butterfly nets and put them in a jar with acetone. Then they were taken to the entomologist at University Park for identification. We caught bees for an hour and set sugar traps as well.”

For now, Mahan says, “we have all the bees curated at the Frost Museum at University Park. This winter we start on the curating, which means preparing the specimens for inclusion in a museum collection: pinning, identifying, labeling, and organizing in special museum drawers and cases.”

Harold has another year of school before she’s off to medical school. In the meantime she’ll continue to work on various research projects with faculty members. But you never forget your first one and she now has something to remember all those craniums by; she says, “I’m so interested in skulls, I collect them now.”

Therese Boyd, ’79

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