Technology normally used to study missiles at Hill Air Force Base is helping university and government biologists better understand how ocean sounds are affecting whales.
Dr. Ted Cranford, adjunct professor of research at San Diego State University, watched in anticipation as a minke whale was scanned in mid-January by the 309th Maintenance Support Group in its computed tomography facility. Cranford had previously been to the facility in 2005 to scan a fin whale’s head, and found the latest full-body examination to be the next intriguing advancement.
“It’s nice when you have this concept of an idea — that you can scan an entire whale — and a bunch of people tell you it’s impossible,” he said. “So when you accomplish the ‘impossible,’ it’s nice to say, ‘Hey, it’s not impossible; it’s just that sometimes, there’s a lack of imagination on the other side of the fence.’ ”
The minke whale being scanned — which Cranford describes as a smaller one — is 15 feet long and weighs around 2,000 pounds. A minke whale is one of several kinds of baleen whales, known for having two blowholes and whalebone plates instead of teeth. It was stranded, alive, on a Maryland beach two years ago, but after veterinarians determined the whale would not survive, it was euthanized and taken to a lab at the Smithsonian Institution in Washington, D.C.
The lab staff wrapped the whale in plastic, then packed it in foam in a cardboard tube that is used to form concrete bridge columns for freeways. It was stored at the Smithsonian, then shipped to Hill by FedEx when the scanner was available.
“From our perspective, that was kind of a lucky stroke because we knew when the animal died and that it could be salvaged and frozen while it was still fresh,” Cranford said. “Knowing these precision scans take awhile, we cut off the last third or so of the whale and stuck it into the tube, next to the head part.
“Now we’re actually scanning the head part and the tail part together so it takes less time to scan. We will have the whole whale, but it will take us half the time to scan it and not use up more time than necessary from this wonderful facility here.”
Cranford said the scans are the first geometrically accurate pictures that have been taken of an entire baleen whale. The digital information will be reassembled to make a three-dimensional model of the animal that shows every part of its anatomy.
“It’s a unique and new way of preserving basically the whole carcass or cadaver. Now we can look at the scanner’s projection and guide us through the sections,” said Charley Potter, Marine Mammal Collection manager for the Smithsonian, who worked with Cranford to preserve and scan the whale. “Another critical thing is when Ted and his colleagues publish this information, it will be saved so future scientists — the next class, the next generation — will be able to come back and look at this same information.”
The research, which has gone on for nearly 10 years, is conducted at the request of the National Oceanic and Atmospheric Administration and sponsored by the U.S. Navy, both the Office of Naval Research and the Chief of Naval Operations Environmental Readiness Division.
“The Navy noticed that when submarine-hunting exercises were happening in different places around the world, sometimes some whales would strand and die,” Cranford said. “It was fairly clear that something was going on between the whales and the sonar systems used to find the submarines, but we didn’t know what. It usually happened in specific areas where there was deep water near shore, so we decided to try to figure out what was going on.
“More recently, the National Oceanic and Atmospheric Administration wanted to come up with some regulations for allowable levels of noise exposure.”
It was through the research on the whale head scanned earlier at Hill that Cranford and others were able to discover how baleen whales hear low-frequency sounds. It is relatively certain that they can hear these sounds because they are in the same frequency range that the animals produce themselves, Cranford said.
“The basic reason we are doing this is to find out how these animals hear and then how sensitive they are to various frequencies. Once we have this information, we may be able to make some educated guesses about what are the potential effects from ever-increasing levels of ocean noise,” he said. “Then we can begin to zero in on sonar and try to estimate; for example, how close would a whale have to be for sonar to be too loud for these ocean-going giants. We can make those kind of calculations with the model that we have developed.”
He said they can also use the scans to help determine if these animals have directional hearing, like humans.
“It’s all well and good that they can hear the sound, but if the animals can’t tell what direction the sounds come from, it doesn’t do them that much good,” Cranford said. “If we can determine the directional characteristics of the whale’s hearing apparatus, then we can figure out, for example, if the Navy doesn’t need to be quite so concerned unless they are directly in front of the animal or really close,” Cranford said. “We can give them this kind of information that they’ve never been able to get before.”
By studying the previous scans, Cranford said they discovered the whale’s ears were rigidly attached to the skull and that the most sensitive hearing is based on bone conduction.
“Some researchers in the past have thought the fact that the ears are attached to the skull probably means that the skull might be involved in hearing, but they didn’t really know how,” Cranford said. “But the modeling system we built shows us how.”
An important question that remains about directional hearing, he noted, is researchers don’t understand how they can determine direction from sounds that are longer than the whale’s body length.
“We’re now pursuing this directionality question, so the timing of gathering the first full body scan for a baleen whale is perfect because it is a critical piece of information we need to fill in the rest of the puzzle about how these animals hear by this very strange bone conduction mechanism. Things are going great.”
Cranford said the study uses the data from the scan to answer questions that often lead to additional questions and additional ideas that create even more questions in an almost never-ending process. It is very much an iterative process.
“We’re building an anatomic library of information that can be used by researchers for generations,” he said. “We’ve already made use of multiple kinds of different scan data sets we’ve collected. And we couldn’t have done it without the people at this missile X-ray facility — I really appreciate their help and expertise.”