Their breeding cycle includes the construction of white "tents" where the caterpillars spend the winter.

BBC: Natural invasion causes health problems

Given a start with some other fissile material (U-233, U-235 or Pu-239) as a driver, a breeding cycle similar to but more efficient than that with U-238 and plutonium (in normal, slow neutron reactors) can be set up. (The driver fuels provide all the neutrons initially, but are progressively supplemented by U-233 as it forms from the thorium.) However, there are also features of the neutron economy which counter this advantage.

FORBES: Is Thorium the Biggest Energy Breakthrough Since Fire? Possibly.

The problem is so rampant in central Kenya, where breeders have made in-roads into breeding rhinos in captivity on private reserves, that during the monthly full moon cycle, when poachers are not reliant on torches or headlamps for light, the rhinos need to be protected 24 hours a day.

BBC: The rhino wars of central Kenya