Population bottlenecks are when population size reduces for a short period of time. Overpopulation may indicate any case in which the population of any species of animal may exceed the carrying capacity of its ecological niche.
The name zirconium comes from the mineral zircon, which is the most important source of the metal. The largest deposits of this mineral are found in Australia, Brazil, Russia, India, South Africa and the United States. Australia and South Africa are the largest miners of the mineral.
There are also three stable isotopes of zirconium also found in nature, which account for 79.82% of the total amount.   Yes, zirconium is radioactive (two natural isotopes):   Zr 94: half life 1,1.1017 years, double beta decay to Mo 94   Zr 96: half life 2,0.1019 years, double beta decay to Mo 94.