Scented Trail
PBI-Funded Zoo Research Helps Wild Bears
Conrad and Tasul of the Oregon Zoo are taking part in a study that will help scientists understand how polar bears use olfactory cues to communicate with each other and find mates. Photo courtesy of Christine Slocomb, San Diego Zoo. Click the image to enlarge.
How do polar bears manage to find mates in the vast expanses of the Arctic? A new, PBI-funded study led by scientist Megan Owen of the San Diego Zoo will help unravel that question and give biologists a better understanding of the polar bear's breeding process.
“Our hypothesis is that polar bears, like many other solitary, wide-ranging animals, use scent to communicate with each other over long distances,” says Owen. “Our research group, led by Dr. Ron Swaisgood, has done a tremendous amount of research on this with pandas. Now we're taking the same approach with polar bears.”
Owen's preliminary research has revealed that polar bears, like pandas, leave scent trails as they walk. Pandas will mark trees and other substrate using a distinct scent gland on their rear-end. Polar bears do not possess such a gland but appear to deposit scent from their feet to the ground. The study's hypothesis is that polar bears glean information from these trails, including such cues as whether a female is ready to mate.
The polar bear's use of scent trails as part of the breeding process could have implications in a warming Arctic, Owen says. “As the Arctic continues to warm and the sea ice melts, we expect to see more habitat fragmentation,” the scientist explains. “Scent trails could be broken up by larger stretches of open water, making it harder for the bears to find a mate.”
Cooperative Effort
U.S. Geological Survey scientists who work with polar bears are helping with the study by taking scent samples from the paws of wild bears that have been tranquilized during capture-and-release population studies. The field biologists use Q-tips to collect the scent, which they put in a vial and freeze. They then label each vial with data on the bear's sex, age, and condition (for example, a female with cubs or a female being courted by a male).
“The field biologists have been extremely cooperative and have gone out of their way to help us,” Owen says. “This study is a good example of how zoo and wild bear researchers can work together to solve important questions about the polar bear's biology.”
Don't Scratch—But Sniff
Owen says that the first phase of the study will focus on whether polar bears can discriminate between sex and reproductive condition by scent. To test this, Research Technician Christine Slocomb mounts a flat wooden box on the bars of a polar bear's enclosure, with a scent sample sandwiched inside. The box is mounted on the outer side of the bars so as to to preclude any physical contact between the bear and the scent. Slocomb records how much time a male polar bear spends investigating a female scent and how much time he spends sniffing a male scent. She tests responses from female polar bears as well.
“Our most basic measure of interest is the amount of time the bears spend investigating each sample type,” says Owen. “Our hypotheses are that the male polar bears will be more interested in the female scent and the females will be more interested in the male samples. We also expect males to be more interested in an estrous female than a non-estrous one.”
In addition to recording data on the time spent sniffing, Slocomb videotapes the response of each bear to the samples so scientists can learn to identify cues—such as flehemen, vocalizations or drooling—that indicate heightened interest or arousal. Owen says that they don't yet know what all of the cues will be, which is why they are videotaping each encounter.
“By the time we're finished with the study, we'll know much more about the behavioral repertoire of a polar bear's response to olfactory cues,” she explains.
Portable Study
Because the scent boxes are so easy to transport, Owen envisions being able to conduct the study with polar bears in all of PBI's partner zoos. So far, Slocomb has tested both male and female polar bears at the San Diego Zoo, the Oregon Zoo, and the Reid Park Zoo in Tucson.
“No training is involved with the bears,” Owen says. “We simply set the scent box up on the cage bars and let the bears in to see what they do.”
The team's initial testing has already yielded some interesting results. Conrad, a male polar bear at the Oregon Zoo, displayed a strong response to the female scent and some aggression to the male scent. His female sibling, Tasul, was so intrigued with the male scent that Slocomb had to pause the trial before the bear managed to completely destroy the hanging support of the scent box..
The research team includes Megan Owen of the San Diego Zoo and CRES as project leader; Dr. Ron Swaisgood of the San Diego Zoo and CRES as consultant and coauthor; and Christine Slocomb of the San Diego Zoo as research technician. Field biologists helping with the study include Dr. Steven C. Amstrup and Dr. Geoff York of the U.S. Geological Survey.
“Our hypothesis is that polar bears, like many other solitary, wide-ranging animals, use scent to communicate with each other over long distances,” says Owen. “Our research group, led by Dr. Ron Swaisgood, has done a tremendous amount of research on this with pandas. Now we're taking the same approach with polar bears.”
Owen's preliminary research has revealed that polar bears, like pandas, leave scent trails as they walk. Pandas will mark trees and other substrate using a distinct scent gland on their rear-end. Polar bears do not possess such a gland but appear to deposit scent from their feet to the ground. The study's hypothesis is that polar bears glean information from these trails, including such cues as whether a female is ready to mate.
The polar bear's use of scent trails as part of the breeding process could have implications in a warming Arctic, Owen says. “As the Arctic continues to warm and the sea ice melts, we expect to see more habitat fragmentation,” the scientist explains. “Scent trails could be broken up by larger stretches of open water, making it harder for the bears to find a mate.”
Cooperative Effort
U.S. Geological Survey scientists who work with polar bears are helping with the study by taking scent samples from the paws of wild bears that have been tranquilized during capture-and-release population studies. The field biologists use Q-tips to collect the scent, which they put in a vial and freeze. They then label each vial with data on the bear's sex, age, and condition (for example, a female with cubs or a female being courted by a male).
“The field biologists have been extremely cooperative and have gone out of their way to help us,” Owen says. “This study is a good example of how zoo and wild bear researchers can work together to solve important questions about the polar bear's biology.”
Don't Scratch—But Sniff
Owen says that the first phase of the study will focus on whether polar bears can discriminate between sex and reproductive condition by scent. To test this, Research Technician Christine Slocomb mounts a flat wooden box on the bars of a polar bear's enclosure, with a scent sample sandwiched inside. The box is mounted on the outer side of the bars so as to to preclude any physical contact between the bear and the scent. Slocomb records how much time a male polar bear spends investigating a female scent and how much time he spends sniffing a male scent. She tests responses from female polar bears as well.
“Our most basic measure of interest is the amount of time the bears spend investigating each sample type,” says Owen. “Our hypotheses are that the male polar bears will be more interested in the female scent and the females will be more interested in the male samples. We also expect males to be more interested in an estrous female than a non-estrous one.”
In addition to recording data on the time spent sniffing, Slocomb videotapes the response of each bear to the samples so scientists can learn to identify cues—such as flehemen, vocalizations or drooling—that indicate heightened interest or arousal. Owen says that they don't yet know what all of the cues will be, which is why they are videotaping each encounter.
“By the time we're finished with the study, we'll know much more about the behavioral repertoire of a polar bear's response to olfactory cues,” she explains.
Portable Study
Because the scent boxes are so easy to transport, Owen envisions being able to conduct the study with polar bears in all of PBI's partner zoos. So far, Slocomb has tested both male and female polar bears at the San Diego Zoo, the Oregon Zoo, and the Reid Park Zoo in Tucson.
“No training is involved with the bears,” Owen says. “We simply set the scent box up on the cage bars and let the bears in to see what they do.”
The team's initial testing has already yielded some interesting results. Conrad, a male polar bear at the Oregon Zoo, displayed a strong response to the female scent and some aggression to the male scent. His female sibling, Tasul, was so intrigued with the male scent that Slocomb had to pause the trial before the bear managed to completely destroy the hanging support of the scent box..
The research team includes Megan Owen of the San Diego Zoo and CRES as project leader; Dr. Ron Swaisgood of the San Diego Zoo and CRES as consultant and coauthor; and Christine Slocomb of the San Diego Zoo as research technician. Field biologists helping with the study include Dr. Steven C. Amstrup and Dr. Geoff York of the U.S. Geological Survey.
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