can account for up to 71% of hyena deaths in Etosha National Park. Hyenas have adapted by frequently mobbing lions that enter their home ranges. When the lion population in Kenya's Masai Mara National Reserve declined, the spotted hyena population increased rapidly. Lions tend to dominate cheetahs and leopards, steal their kills and kill their cubs and even adults when given the chance. Cheetahs often lose their kills to lions or other predators. A study in the Serengeti ecosystem revealed that lions killed at least 17 of 125 cheetah cubs born between 1987 and 1990. Cheetahs avoid their competitors by hunting at different times and habitats. Leopards take refuge in trees, but lionesses occasionally attempt to climb up and retrieve their kills. Lions similarly dominate African wild dogs, taking their kills and slaying pups or adult dogs. Population densities of wild dogs are low in areas where lions are more abundant. However, there are a few reported cases of old and wounded lion falling prey to wild dogs. Nile crocodiles may also kill and eat lions, evidenced by the occasional lion claw found in crocodile stomachs. Reproduction and life cycle Most lionesses reproduce by the time they are four years of age. Lions do not mate at a specific time of year and the females are polyestrous. Like those of other cats, the male lion's penis has spines that point backward. During withdrawal of the penis, the spines rake the walls of the female's vagina, which may cause ovulation. A lioness may mate with more than one male when she is in heat. Generation length of the lion is about seven years. The average gestation period is around 110days; the female gives birth to a litter of between one and four cubs in a secluded den, which may be a thicket, a reed-bed, a cave, or some other sheltered area, usually away from the pride. She will often hunt alone while the cubs are still helpless, staying relatively close to the den. Lion cubs are born blind, their eyes opening around seven days after birth. They weigh at birth and are almost helpless, beginning to crawl a day or two after birth and walking around three weeks of age. To avoid a buildup of scent attracting the attention of predators, the lioness moves her cubs to a new den site several times a month, carrying them one-by-one by the nape