Chlamydia is a major threat to koala populations across Australia. This bacterial disease infects between 20% and 90% of individuals in koala populations.
We had some koalas living in our backyard at one of the houses I grew up in. Evenings were spent relaxing to screaming from the female and grunting from the male...
One video I saw some twenty years ago was so disturbing due to how clearly distraught the female was that I haven't been able to think of koalas the same ever since. Like, she might have developed koala PTSD, it was that brutal.