Hannah measuring flow in a local stream after a storm
Our lab is interested in animal form and function, or how what an animal looks like affects what it can do. We combine approaches from physiology, biomechanics, ecology, and evolution to understand how animals interact with and survive in their environments. Our main research theme is understanding not only how each part of an animal functions, but how these parts work together for potentially new functions. Our main interest has been with interactions between the body (swimming) and head (feeding) during prey capture in fishes. As you might imagine, having to do two things at once is harder than doing either thing individually and this solving this problem can affect how animals interact with each other and their environment.
Think about it this way - have you ever tried to walk and eat at the same time? If so you've noticed that perhaps you don't do either of those things as well as you would if you did them separately. Animals have the same problem. Many of them have to eat other animals to survive but those organisms have strategies for escaping capture. This means predators can't just bite their prey, they have to chase it first using their body, legs, wings, fins, etc. But, to actually grab their prey once they are close enough, they use other body parts such as their mouth or tongue. The predator has to coordinate its body and head movements to make sure it's head is in the right place when it's mouth opens. If not, it risks missing the prey, like in the video traces of a bluegill below, and consequences could range from using more energy to continue hunting to starvation if food is hard to find.
Tracings from video frames of the side and bottom view of a bluegill chasing a small fish
The ability to coordinate between parts that typically perform different jobs (body and head) is hard to predict because behaviors can be flexible. For example, a predator that chases a prey might coordinate differently than one that waits for prey to come close enough on its own. We're interested in figuring out when an how predators rely on these interactions and how this integration of parts affects how they survive. Since parts have to work together, changes in one part can have consequences for how other parts can change, or how parts can work together. This means that understanding these interactions can tell us a lot about how animals work and how they may be able to adapt to new or changing environments.
HIGH-SPEED VIDEOGRAPHY: This is one of the primary techniques the lab uses to analyze feeding and swimming in fishes. The lab has 3 monochrome Edgertronic cameras that can capture up to 17,000 frames per second! A normal camera, like a GoPro or an iPhone camera, captures video at about 30-60 frames per second. The shutter on high speed cameras opens and closes much faster, allowing more images to be captured within the same amount of time. This is what causes it to look like the motion is slowed down - if you capture 1s of video at 500 frames per second, when you play it back at the standard 30 frames per second rate, it would take almost 17s to play the entire clip. We can then use these videos to track the motion of different body parts and calculate movements such as distances, velocities, accelerations, and timing of those movements.
Measurements of guppy biting kinematics from Hannah Cohen's work
SWIM TUNNEL: We have a swim tunnel equipped to measure oxygen consumption of fishes. Think of this as a treadmill for fishes that can tell us how efficient they are at swimming under different conditions. We can use this to ask questions about how animals are adapted to challenging environments, such as fast flowing rivers, or how exercise affects other behaviors.
3D PRINTER: With this printer we can do cool things like print different body shapes of fishes and put them in the swim tunnel. We have been working on building 3D models of guppies and their predators that can be modified and printed. I'm sure we'll think of lots more ways to use the printer!
MORPHOMETRICS: We have tools like dissection microscopes, dissection tools, a digital camera, and copy stand for taking photos of specimens and analyzing both internal and external morphological traits. For example, we can examine differences in body shape across species or perform dissections to ask questions about muscle physiology.
FIELD EQUIPMENT: Sometimes we use specialized equipment to collect fish in the field. This includes GoPros for taking photo and video, a backpack electrofisher for sampling fishes and returning them unharmed, nets, water quality and flow meters, etc. Since we are interested in ecological interactions between individuals and species, it's important to get in the field and learn directly about what fish are doing.