A lot of people ask me whether they should get a second turtle or tortoise as a companinion
for their animal. They wonder whether their pet is lonely. Or they would like
to get a second turtle/tortoise for breeding.
My first answer is: "Don't."
Usually, turtles/tortoises that people acquire as babies or juveniles, get
along well. However, as turtles/tortoises mature, and their hormones kick in, more often
than not they will start to bicker and pester each other, and then you are
stuck with one setup and a number of turtles that don't get along.
See here: Fighting and Biting and Pestering
Your turtle is NOT lonely.
Your turtle does NOT need a companion to be happy.
Turtles/tortoises do enjoy company of other turtles/tortoises of the
same species, and, of course, they enjoy the mating game.
However, unless you are willing to provide a large enough enclosure
for the animals to hide from each other, or separate them during breeding
season, or maybe even for most of the time, don't get another turtle/tortoise.
Trust me, I've been there and done that.
Turtles/tortoises can be successfully managed in (breeding) groups of
the same (or similar) species (mixing species is possible but not
recommended because of different requirements), usually housing a small
number of males with a larger number of females.
Here is what I answered to someone on email who moved their
turtles into a new environment and they started fighting:
Your case is unusual in that your turtles lived together peacefully for
16 years (into sexual maturity) without fighting/pestering.
It seems clear that for some reason the new environment let the male
realize that he was, indeed male. Unfortunately, sometimes we want to do
good by our turtles and provide them with a new and improved environment,
and it backfires.
Yes, I can understand that you are sad that this didn't work out. It
happened to me, too. I ended up just separating my pair of Reeves turtles.
Since they had been living toghether for a few years, the male did
seem to miss the female (where had his mate gone), while the female
seemed more than happy to be rid of the pesterer.
I know that tortoises that have lived together all their lives will
miss a buddy or mate that dies. They don't understand death, but
someone familiar has left.
While water turtles in the wild often hang out in groups, they are
groups of safety (more turtles in a basking spot reduces the individual's
chances of getting eaten), not social groups.
It is natural for male turtles to chase away other males and to chase
females. Outdoors, a female not ready to mate will simply swim away and
hide; or, on occasion the female with turn back on the male and scare
him away. Injuries do happen but they are rare.
You could try housing them together again later in the year, when breeding
season is over, and they might do fine. Or they might not.
But, your turtles will not suffer unduly from this separation. The male
might be disappointed, and the female, most certainly, will be relieved.