The Post-Domestic Cougar

Three years after I wrote a blog entry about wild cougars in Virginia I still get new comments on it regularly and I still get emails from total strangers on the subject about once a week. In fact, Helenah Swedberg, the documentary filmmaker I am working with, found me initially through that entry.

Lately I have been thinking a lot about the effects of population bottlenecks and their potential application to cougars in Virginia. I have personally encountered some very strange behavior among invasive species while traveling to work on 'Eating Aliens'. Often the accepted traits of a species as observed in its native habitat do not apply in an introduced habitat and population bottlenecks can sometimes account for that.

For example, the black spiny-tailed iguanas of Gasparilla Island, Florida, are very much omnivorous throughout their lives. I have personally watched adult spiny-tails pouncing on anoles and flying insects. I have examined the droppings and stomach contents of these iguanas and seen fragments of insects. Yet scientists who have studied the iguanas in their native range in Mexico will swear that only the juveniles have any carnivorous habits.

I think that the explanation for this is in the fact that the entire population on Gasparilla Island appears to be descended from a very few pets released by one individual. If one lizard among a population of tens of thousands has an unusual habit caused by genetic mutation then it can go unobserved. Most mutations are probably dead ends. Even the successful ones will take a very long time to propagate among an entire population unless there is some type of upheaval that gives a rapid edge in survival to the animals with that behavior.

That all can change when a small number of animals are introduced to a new area and the genes of those few animals are the template for everything there that follows. Early on in an invasive paradigm an exceptional mutation -- even a disadvantageous one -- can rapidly become the new standard.

Stay with me here because I promise this is going to come back to the wild cougars of Virginia.

Consider also that the bottleneck of two or three lizards came from a captive population from the pet trade. Animals kept as pets for generations are often selected by humans for particular traits. Is it possible that people who owned pet black spiny-tailed iguanas preferred the ones that they could watch eating live food?

A similar example was pointed out to me in a conversation last month with biologist Duane Chapman. Over a meal of silver carp that had literally jumped into my boat that morning, Duane told me that silver carp in their native range in China are not known for violent mass jumping at the approach of a motor boat the way that the invasive silver carp in America are. His explanation for this is the effect of the population bottleneck. Only a small number were initially imported into the US to begin the breeding program. One or two carp who happened to have this strange habit that also happened to be good breeders were able to have their strange genes dispersed among the entire new population as it grew.

Now you are probably wondering how this applies to cougars. We have a very good body of science that has been done on native wild cougars in Florida and out west. These are populations that have been continuously wild for their entire history. While this research is very sound I do not believe that it will necessarily apply to the habits of modern cougars in the eastern United States.

For reasons I have explained in other articles I do not believe that the cougars people are seeing here are the native (and probably extinct) eastern cougar subspecies. I strongly believe that these are primarily the descendants of cougars from the exotic pet trade that have escaped and sometimes been deliberately released.

What we have here is a population bottleneck stemming from cougars that were captive-bred for generations by humans. More aggressive cats were not top choices to use for breeding. Picky eaters that required only their wild diet were probably sorted out of that gene pool very quickly.

A population of wild cougars in the eastern US, descended from former pets, would behave differently than their wild cousins elsewhere in the US. They can get away with what might otherwise be disadvantageous behavior. The native wolves that used to live here are long gone. Aside from a few coyotes, modern eastern cougars do not have much competition for prey.

When we are weighing the veracity of cougar sightings I don't think that anything should be discarded on the basis of unusual behavior. For example, I've heard all sorts of stories about cougars in Virginia seen feeding on roadkill. In the western US, scavenging is something that cougars only seem to do occasionally. One study that has been following 21 cougars for the last three years found that only 13 of 21 have scavenged at all. That behavior was very rare in all but one animal in the study.

Given the small population of cougars here (I'm just guessing about that, figuring that if it was a large population then we'd have more physical evidence), it is easy for a biologist or policymaker to dismiss the frequent claims of roadkill-scavenging behavior. But the cougars here are probably the result of a bottleneck population.

Everything from preferred prey to habitat to the total size of their individual ranges could be completely different from what we have known about cougars until now.

To even begin having this conversation I think that we need a name for this population other than 'eastern cougar,' which already refers to a probably-extinct subspecies. I nominate the 'post-domestic cougar.'

'Feral' isn't quite accurate after the first generation and I wouldn't call them 'invasive' either, since cougars have been here for many thousands of years. Cougars seem to belong here in an ecological sense, though we still don't know how the post-domestic cougar is going to fit in.

[Photo copyright 2011 by Jackson Landers. I wish I had a picture of a cougar to use but I've never had the opportunity to take one. This depicts a black spiny-tailed iguana in Florida moments after bagging it with George Cera.]