Like all the other members of Gutt's crew, Shira was once in danger for her life when Gutt rescued her from an unknown fate. This earned Gutt her loyalty.
Shira defected from Gutt when she met another saber named Diego, who convinced her to leave the crew and join the herd of animals that he was a part of. Realizing unlike Gutt, the herd would look out for her, Shira renounced her position as a pirate, and joined the herd.
Shira had once been part of a saber-tooth cat pack but decided to leave them behind, to make a life of her own and to don't let herself depend on anyone, a decision that was hard for her to accept. At one point, Shira was found by Gutt, an ape that had taken to the seas aboard a great ship fashioned from an iceberg: Gutt had saved her life and she joined him as first mate.
The Herd's capture
Gutt made his presence known to the castaways, stating that they were lucky to have been found by Gutt and his crew. Manny informed the ape that they only wanted to return to the continent, which Gutt mocked, and informed Manny that there was no way back. With that, Gutt ordered his crew to attack the ice floe, taking the castaways as captives. Shira leaped from the ship and stopped Diego, who was cutting the mooring lines that tethered the ice float to the ship. Shira stopped him before he could cut the last one, keeping it under her paw. Diego, keeping his pride, declared that he doesn't fight girls. Shira took advantage of this and let the line go, slapping Diego in the face, at which point she pounced on him and pinned him down while laughing slightly and then saying "I can see why." Then Diego, like the others aboard the ice floe, was brought aboard Gutt's ship.
The herd were brought on to Gutt's ship and tied up. Gutt, through the use of song, attempted to convince Manny and his friends to join the crew. When he was refused, Gutt decreed that they be made to walk the plank.
Manny and Diego managed to escape their bonds, but the ensuing battle between Manny and Gutt accidentally caused the collapse of Gutt's ship. Gutt and most of his crew escaped, but Shira was left behind. Though on the verge of drowning, she refused the herd's help. After Manny brought her on to their makeshift raft, Diego asked if she would like to join their "scurvy crew." Shira mocked the idea, calling the group a joke. Diego responded by calling her "kitty", which angered her into pouncing on him, which he quickly reversed. Granny’s comment of puking if they kissed, caused Diego to get off her.
The herd managed to find their way to Switch-back Cove. As soon as they hit shore, Shira attempted to escape, but was stopped by Diego, who discovered that Gutt was at the cove also. Shira was imprisoned within a tree to prevent another escape attempt. Diego came to her during the night with some water. Shira first growled at him. They discussed their pasts, and Diego compared Gutt to the herd, implying that Gutt didn't care about Shira, though she remained adamant in her beliefs.
Change of heartThe next morning, Shira somehow managed to escape, and returned to Gutt. However, the captain had a less than warm welcome for her. Gutt was furious that Shira failed to kill Manny, and further humiliated her by giving her position of first mate to Squint. When the Hyrax successfully diverted the pirates' attention, the herd stole Gutt's new ship. Shira managed to chase down Diego and pin him, but he convinced her to leave Gutt's side, telling her that the herd looked out for each other. Moments later, Shira agreed to, but instead stayed behind to preventing Gutt from reclaiming the ship. After Diego realizes what Shira did, they both looked at each other as they floated apart. After Gutt made a new ship, the incensed ape threatened Shira by telling her once all this came to an end, he would have a tiger-skin and he didn't care whose.
Shortly afterwards, when Gutt held Manny's family hostage, Shira was seen struggling to get up, suggesting she had tried to stop Gutt, but failed. During the battle, Shira attempted to free Ellie, but was waylaid by Squint, and knocked aside by Dobson. Following Gutt's defeat, Shira asked Diego if he still wanted her on their "scurvy crew", to which Diego replied in the positive, welcoming her to the herd. Shira and the rest of the herd traveled to a new home soon after. Shira made friends with a group of cougars, as mentioned in Ice Age: The Great Egg-Scapade, and hunts with them every night.
Personality and traits
At first seeming gruff and cold, Shira was loyal to those that helped her: Gutt had once made her his first mate, a position which, despite Gutt's indifference at her loss, she initially held close. Shira was not easily swayed in her resolve and could often be quick to anger when she dealt with those that caused her trouble. Despite her anger, Shira did fall in love with Diego, who introduced her to a better way of life than piracy: being part of a herd. Herd life was initially something that Shira was uninterested in, due to her snide, sardonic persona, which deemed individuals like Diego, who had turned down his former rough-and-tumble life in a saber pack, as soft and weak; this view changed quickly as she was accepted into Diego's collective herd. Shira is competitive and knows what she wants. Near the end of the film she is shown to be quite affectionate towards Diego, given they’ve become a couple. She is seen leaning on his shoulder when the herd sailed away to a new home, as well as nuzzling his side in the credits.
Shira, as a saber-tooth cat, sported the same features that other sabers had: short, compact build with powerful running legs, clawed paws, short tail and ears, and a pair of fangs that were shorter than Diego's and not as sharp. Shira was grayish in hue, almost sliver, unlike other sabers, which tended to be dark tan or orange: Shira's pelt was striped somewhat with dark grey stripes and her eyes were vivid teal. Shira wore two earrings on her right ear, fashioned from an unknown substance, one being small and blue, the other, larger and green.
Behind the scenes
Shira was voiced by actress and singer Jennifer Lopez.
Shira was initially supposed to have orange-red fur like most sabers of the franchise, but the directors decided to have her appearance stand out with a different fur color, to keep viewers from mistaking which saber was Diego and which one was Shira at wide screen shots. You can see a picture of Shira's early design in the Shira/Gallery.