Belka (Белка,"Squirrel") and Strelka (Стрелка, "Little Arrow") spent a day in space aboard Korabl-Sputnik 2 (Sputnik 5) on 19 August 1960 before safely returning to Earth. ... They were the first Earth born creatures to go into orbit and return alive.
Dogs were the practical choice
"The launch of living beings into orbit was a necessary stage in the preparation of a manned space flight. Research began in the 1940s, initiated by the Ukrainian designer Sergei Korolev. First, they chose between monkeys and dogs. After lengthy discussions, the latter were chosen for the role of test subjects. Dogs were much cheaper, they trained more easily, and they tolerated long periods of inactivity easier."
"The ship with the dogs on board made 17 complete revolutions around the Earth. "Arrow" felt normal, Belka after the fourth loop became extremely restless, fussed and tried to get rid of the fastening elements, which indicated a deterioration in her health. Post-flight analyzes did not reveal any deviations in behavior. It was the behavior of Squirrel that led to the decision to conduct only one-orbit flight with human participation.
Belka and Strelka lived to a ripe old age and died a natural death."