Swan keeper Kate Deregibus can tell the Morris Arboretum’s new mute swans apart by their personalities: one, she says, is “docile” and the other…not so much.

The swans—one-year-old sisters donated to the Arboretum this spring by Nicholas and Athena Karabots—don’t yet have names, and Arboretum officials are asking the public for help.

The online “Name our new Swans” contest runs through Sunday, April 8. To enter, visit the Arboretum website and enter your suggestions, name, and email address.

The winner will receive a signed copy of “Morris Arboretum of the University of Pennsylvania: Through the Lens of Paul W. Meyer” by Arboretum Director Paul Meyer, a one-year membership to the Arboretum, and of course, naming rights.

If more than one winning name combination is entered, one winner will be chosen at random. More than 400 names have been submitted so far—Greek names, flower names, names of Arboretum members’ children, and pop culture monikers such as Thelma and Louise, Wilma and Betty, and Lucy and Ethel.

“The last ones [swans] we had were Bonnie and Clyde,” Deregibus says. Clyde was felled by health complications stemming from arthritis and a heart murmur. Bonnie died in a tragic accident. (Deregibus prefers to spare the details.)

In 1923, the first swans to inhabit the Arboretum’s Swan Pond were named Elsa and Lohengrin. In the 1980s, Ariel and Titania glided majestically across the tranquil waters.

Deregibus says the new swans have adapted well to their surroundings. She feeds them duck chow (like dog chow, but for ducks) and in the winter adds scratch grains to their diet, as well as lettuce donated by Weaver’s Way Co-op in Philadelphia. Although they are known as mute swans, they can grunt, snort, and hiss.

In 2005, the Swan Pond underwent a facelift. A much-needed fence was erected, long-neglected masonry was repaired, and new plants were added. But Deregibus says it’s the sister swans that have literally brought the Swan Pond back to life.