Having left the safe nest, the survival rate of juveniles in many species is pitiful. Sometimes the greatest danger comes from males determined to exterminate a rival's offspring, as a tiger does after taking over a territory. Predators take a high toll, even from future ferocious hunters like crocodilians. Often harsh conditions simply mean excessive huger and cold, as for polar foxes. Some gang up in bands once expelled by the adults to collectively seize hunting rights, as keas do on the Falklands. Some perish during the exhausting annual migration, or have to be abandoned.