There had been other animals that were put on rockets and fired skyward, but it was only during the era of the famed Russian dogs that attempts to put animals to orbit were carried out.
Before Belka and Strelka became the first creatures to make it to orbit and back unharmed, 3 dogs went up on rockets and died.
The first one we all know during history / science lessons in secondary school – Laika. This is her in her space capsule:
After the cover is closed, it looks like this:
This is a mock-up of her space capsule:
Laika aka Zhuchka aka Limonchik aka Muttnik is the first living Earth-born creature, other than microbes of course, that was successfully blasted into orbit, and possibly the first living passenger to go into space. She was aboard Sputnik II. The momentous date: 3rd November 1957.
Laika died 5 to 7 hours into her flight from stress and overheating. Her cause of death was not immediately known and decades of speculation followed, until October 2002, when the Russian scientist in charge of the project told all; he also expressed regret for allowing Laika to die.
Almost 3 years later, another 2 dogs, Bars and Lisichka were next. They died when their rocket exploded less than 30 seconds after launching on 28th July 1960.
However, less than a month later on 19th August 1960 another 2 brave dogs, Belka and Strelka finally managed to get to orbit and back home safely.