Though Deleiris sketched in her early years, her career in art began around 1978. After graduating from the University of Maryland with a degree in zoology, she spent a summer as a research assistant at the Smithsonian National Zoo Conservation and Research Center in Virginia.
Afterwards Deleiris illustrated several books and articles, including two Dover coloring books and posters for National Geographic Special Publications. She illustrated articles for magazines such as Smithsonian, National Geographic Traveler, Cruising World and Ocean Realm.
Her continued interest in science often finds its way into her art. She took three trips to Antarctica under the auspices of the National Science Foundation Artist and Writer's program. There she lived in science stations and field camps painting, sketching and illustrating. She illustrated three books: Natural History of the Antarctic Peninsula, (Moss, Columbia University Press '88,) Antarctic Journal, text by Meredith Hooper, (Frances Lincoln and National Geographic 2000,) and The Island that Moved by Meredith Hooper, (Viking, and Frances Lincoln, 2004.) As well as exhibiting in group shows, she prepared several solo exhibitions of paintings at museums and galleries including Smithsonian Museum of Natural History in Washington, DC, Harvard Museum of Natural History, Newport Art Museum in Newport, RI and National Science Foundation, Arlington, VA.