Dolphins appear twice in Island of the Blue Dolphins, once when Karana is returning Ghalas-at after her failed expedition across the sea, and again as at the end of the novel when Karana is watching her island fade into the distance as she rides away on the white men's ship. The first time dolphins appear, Karana explains that they are a good omen, and indeed, she says that, "more than anything, it was the blue dolphins that took [her] home" (chapter ten). They provide the first break in the loneliness Karana has been feeling ever since winter began ad she lost hope that the white men would ever come back for her. The second time Karana sees the dolphins, she does not say much about them, but they became a symbol of good fortune and friendship during her last journey, and so they imply that good thing are in the future for Karana. This second time they appear, the dolphins are following Karana away from the island, whereas before they were following her toward it, and this may represent good fortue in the new land to which Karana is traveling, for she did find good fortune and happy times on Ghalas-at after the dolphins escorted her home.
Karana explains in chapter one the power of secret names, and also that she cannot understand why her father gave his secret name to a stranger. When Chowig is killed, many of the villagers, Karana included, believe he died because he revealed his secret name to Captain Orlov. Revelation of a secret name, then, is an important symbol of trust. It is therefore a milestone for Karana when she tells Tutok her secret name.
Tumaiyowit is the god who, as Karana explains in chapter twelve, once lived on earth with Mukat, back in the time when there were straight trees on Ghalas-at. Later, when Mukat did not want people to die (as he did) he angrily went down into an underworld, and so "people die because he did." Tumaiyowit and references to the underworld make a number of subtle appearances, most notably when Karana visits some of the caves underneath Ghalas-at. Tumaiyowit is at once a symbol of death and of ancestry, for Karana's ancestors inhabit this underworld.
This is the mark that, when Karana's tribe is leaving Ghalas-at, Ulape makes on her face to signify that she is unmarried. When Karana leaves the island eighteen years later, she also makes this mark on her face. Not only is the mark a symbol of maturity, but it is also a symbol of hope for a new life. Ulape makes the mark when she is leaving for a new place, hoping to start a new life, and Karana does the same. The mark takes on a slightly different meaning for Karana, however. For her, it recalls the day her people left the island, and expresses a solidarity with her tribe.