A litter of mountain lion cubs born in the Santa Monica Mountains has been found to be the result of inbreeding. The announcement on Thursday by National Park Service scientists at the Santa Monica Mountains National Recreation Area represents the third time mating between either a father and daughter or between siblings has resulted in cubs.
Scientists said that the behavior has occurred, because the population’s habitat is isolated by development and the 101 Freeway.
“If animals can’t disperse out, you may be more likely to get close inbreeding, and we’ve seen a number of instances where fathers have mated with daughters,” said Seth Riley, a wildlife ecologist for the National Park Service at the Santa Monica Mountains National Recreation Area.
He estimates that only 10-15 adult mountain lions live in the Santa Monica Mountains. The animals tend to live at low densities and can range hundreds of miles.
“The Santa Monica Mountains are just not big enough by themselves for a viable population of mountain lions in the long run,” he said.
Severely inbred animals are susceptible to a number of ailments, including heart disease and sterility. The Florida panther, a subpopulation of mountain lions, became so inbred that their numbers dwindled to dangerously low levels. Conservationists resorted to a controversial tactic of bringing outside individuals into the area to breed.
Only one radio-collared male mountain lion is known to have successfully crossed the 101 Freeway. Called P-12, the male successfully mated with female mountain lions in the range, bringing fresh genetic material to the population. However, he has since mated with one of his daughters, resulting in the most recently discovered instance of inbred cubs.
“He doesn’t know; he’s just trying to mate with as many females as he can,” Riley said. “He’s happy about it because more kittens is better for his genes, but from a population point of view, it’s not as good.”
Riley said that the Santa Monica population’s genetic diversity could best be improved by installing wildlife corridors that would allow the animals to cross busy roads safely. The National Park Service estimates that installing a tunnel under the freeway would cost $10 million. Previous attempts to secure that funding have failed.
National Parks Service scientists began monitoring mountain lions in the mountain range in 2002. Since then, they’ve found six litters of cubs. The preliminary DNA results announced on Thursday means that half of observed litters in the range have been inbred. More undiscovered litters have been reared in that time, but the high percentage of inbred litters in the sample size may be indicative of population-wide trends. Genetic analysis is providing evidence of re-crossing branches on the population’s family tree.
On Tuesday, Riley was tracking a trio of mountain lions in the Santa Monica Mountains, using an antenna and headphones to hone in on signals broadcasting from chips embedded within them. The two cubs he was monitoring were not the result of first-order inbreeding, but their mother was, as was her daughter from a past litter. In fact, it was that daughter P-19 that birthed the three recent first-order inbred cubs.
Riley said that hallmark physical defects from severe inbreeding haven’t shown up yet in the mountain lions but that they likely will unless a solution is found.
“In the long run, if the lions are completely isolated here in the Santa Monicas, I think it’s just a matter of time before we start to see these genetic issues,” Riley said.