The natural history of the Canada lynx and the bobcat

Bobcat (top) and Canada lynx (bottom) from James Ellsworth De Kay's Preliminary List of the Mammals of New York (1842).

North America has two lynx species– the Canada lynx (Lynx canadensis) and the bobcat (Lynx rufus). Historically they have been regarded as being members of a single species that includes the Eurasian lynx (Lynx lynx), the largest and most widespread member of the genus in the Old World.

Both bobcats and Canada lynx evolved from the Eurasian lynx.  The lineage that led to the modern bobcat is believed to have diverged from the ancestral Eurasian lynx population around 2 million years ago.

The Eurasian lynx is a generalist carnivoran. It hunts a wide variety of prey, including deer and small rodents. It once ranged from the British Isles to the the Russian Far East and is found as far south as the Himalayas.

It widely varies in size from as little as 22 pounds to (officially) as much as 84 pounds.

These traits also exist in the bobcat species, which varies from as little as 9 pounds to as much as 49 pounds.

Note that the scale is much smaller for the bobcat than the Eurasian lynx.

Bobcats are essentially miniature versions of their Old World ancestor. They also hunt a wide variety of prey species ranging from mice to mule deer. The southern subspecies of bobcat are quite a bit smaller than those in the north of their range, which allows them to fill the niche of a small mesopredator. The northern subspecies are quite different, and in some areas, including West Virginia, they eat a lot of deer.

Bobcats evolved their smaller size as a result of the conditions during the last glacial maximum. They have only existed in their current form for about 20,000 years.

The advancing glaciers kept the gene flow from other ancestral Eurasian lynx from entering North America, but eventually, another wave of Eurasian lynx migration happened in the northernmost part of North America. It is not clear exactly when this happened, but the lynx population that colonized this part of North America evolved very differently from the bobcat. These cats likely evolved in the northern part of the continent that was at times free from the ice sheets but were still separated from the bobcats by glaciers that were further to the south.

Whereas the bobcat had retained much of its ancestor’s generalist behavior, these northern North American lynx became specialists. Perhaps the only prey available for lynx living in the far north were snowshoe hares, for these lynx became very much adapted to hunting only that prey.

These lynx became the modern Canada lynx, which is sometimes incorrectly called the “Canadian lynx.”    If a bobcat and a Canada lynx are in Canada, they are both Canadian lynx, just as if you find a Canada goose and a snow goose in Canada, they are both Canadian geese. But the actual species for both the goose and the lynx are “Canada goose” and “Canada lynx.”

Throughout its range, Canada lynx are almost entirely dependent upon snowshoe hares for sustenance. Snowshoe hares are prone to boom and bust cycles of population growth, and the Canada lynx population largely tracks snowshoe hare populations.

Because it hunts almost nothing but snowshoe hares, the Canada lynx is also smaller than the Eurasian lynx, but unlike the Eurasian lynx and bobcat, its size variance is more conservative, generally weighing only between 18 and 24 pounds. It is a longer legged cat than the bobcat, and it generally weighs more than the majority of bobcats. However, the largest bobcats are larger than the typical Canada lynx.

The only place in North America where Canada lynx existed without snowshoe hares was Newfoundland, and here the Canada lynx either re-evolved its generalist habits and somewhat larger size or it is the one subspecies of Canada lynx that has retained the generalist habits and phenotype of its Eurasian ancestor. Whatever the case, the Newfoundland subspecies of Canada lynx is known to attack caribou, but its numbers were always quite low in Newfoundland, leading some to speculate that the Canada lynx was never native to the island.

This all changed when snowshoe hares were introduced to the island between 1864 and 1876.  The hares were introduced as a supplemental food species for colonists on the island, and when the hares arrived, they were without any competition. Arctic hares lived in the north and west of Newfoundland, but they have very different habits from snowshoes.

The snowshoe hares thrived and greatly multiplied, and the Canada lynx population skyrocketed along with the hares. By the early 1900′s, the snow shoe hares had thoroughly colonized the island.

Then, they reached their carrying capacity, and as normally happens on the mainland, the snowshoe hare population began to drop. Leaving behind lots of hungry Canada lynx.

As I noted before, the Newfoundland subspecies of Canada lynx is capable of hunting caribou.

And many of the cats started doing just that.

And then the caribou numbers began to drop.

However, initially no one knew that the Canada lynx was somehow implicated in reducing caribou numbers.

Many caribou were dying as young calves– from bizarre bacterial infections that were almost always accompanied by some weird puncture marks on the neck.

It took a while to figure out that these bacterial infections were coming from failed predation attempts by Canada lynx. The puncture marks on the necks were those of the lynx’s teeth, which, for whatever reason, didn’t often produce a killing bite.

When it was discovered that Canada lynx were reducing caribou numbers, lynx trapping and hunting limits were liberalized, and there was an increase in the endemic Newfoundland caribou herds.

(You can read more about the Canada lynx, hare, and caribou dynamic on this post. It took only the introduction of snowshoe hares to disrupt the whole predator-prey dynamic in Newfoundland.)

But with the exception of Newfoundland, Canada lynx are not implicated as being any kind of major predator to large ungulates.

The larger subspecies of bobcat, however, do take deer on a relatively regular basis.

These larger bobcats are actually much more aggressive than Canada lynx, and where their ranges overlap, the bobcats generally dominate the lynx.

The range overlaps over most of the Canada lynx’s range in the United States and in the southern tier of Canada.

And not only do bobcats dominate Canada lynx, there is also evidence of introgression of bobcat genes into the Canada lynx population. As of 2008, seven Canada lynx/bobcat hybrids were documented in the states of Maine and Minnesota and the province of New Brunswick. Non-overlapping allele frequency analysis revealed that these cats all had some bobcat ancestry, and mtDNA evidence revealed that they all had a Canada lynx as a mother. One queen had three kittens, which shows that hybrids are able to reproduce in the wild, and another queen had placental scars in her reproductive tract.

The male-female combination in the hybrids is pretty similar to what we know about the the behavior of the two cats.  Bobcats are  just much more aggressive than Canada lynx. Because the female bobcat is quite aggressive, it would be very hard for a male Canada lynx to mate with her, but the male bobcat is aggressive enough to drive male Canada lynx away from their mates.

Of course, there is some suggestion that bobcats are starting to thrive in lynx habitat because of climate change, and that very well may be. But Canada lynx once were found very deep into bobcat range. In the Eastern US, they ranged as far south as West Virginia, which does have a population of snowshoe  hares. Perhaps during the Little Ice Age, snowshoe hares were much more widely distributed in West Virginia than they are now, which allowed the Canada lynx to colonize this far south. There is also some possibility that there were very large Canada lynx type cats in the Alleghenies, as this historical record suggests. Perhaps these large gray lynx were an offshoot of a Canada lynx population that moved south and evolved to hunt deer– or maybe they were a primitive Canada lynx that still possessed their ancestral Eurasian lynx size.  (Or it could have been a damn tall tale. Never discount that possibility!)

If Canada lynx ranged this far south, then there likely would have been a gene flow between bobcats and lynx.   It is possible that there could have always been some hybridization between the species once the glaciers separating the two were gone.

We honestly don’t know how much hybridization has happened between bobcats and Canada lynx. Currently, the suggestion is that hybridization isn’t common, but the genetic studies on bobcats and Canada lynx are somewhat limited– especially when compare them to wolves and coyotes, which recently were recently examined in the most in depth genomic assay ever performed on wild animals.

Something similar to the genome-wide study on coyotes and wolves needs to be performed on Canada lynx and bobcats. If one were peformed, I bet we’d find that those two animals have exchanged genes quite a bit in the past and continue to do so now. Perhaps they even have a species complex.

Roughly two million years of evolution separates the bobcat from the Canada lynx, which is more closely related to the Eurasian lynx than the bobcat.

But two million years may not be enough separation for the two cats to regard each other as separate species.

The little generalist lynx of North America meets its gray, hare hunting cousin.

The exact taxonomy of the two species has remained contentious for decades.

Initially they were regarded as different subspecies of lynx– and were conspecific with the Eurasian lynx.  Later, they Canada lynx was made a subspecies of Eurasian lynx, and the bobcat was moved into the house cat genus– Lynx rufus became Felis rufus.

Currently, we recognize that bobcats and Canada lynx are close relatives. Both derive from the ancestral Eurasian lynx, but both of these North American derivatives has gone its own way.

At least in the aggregate.

They have gone their own way.

But they have also converged.

How much they have converged is anyone’s guess– more studies need to be peformed.

But the genus Lynx has had a remarkable evolutionary history in North America.

And it may have a remarkable evolutionary future.