Human impact on animal evolution is well accepted. It manifests itself both through species introduction and habitat alteration impacting selection criteria. There are many examples of new, hybrid breeds developing after a new species is introduced, or by a single breed being forced to adapt to changes in their natural habitat. But what happens when these two evolutionary factors combine can really be quite scary.
Some animal hybrids are obvious, like the mule. There is also the beefalo (cattle and bison), or camas (camels and lamas). The new hybrid animals are often infertile. If they can reproduce, the first few generations are often exceptionally well-suited to their environments, benefiting from what is called ‘hybrid vigour’, but invariably they lose the will to mate – subjected to ‘outbreeding depression’.
When a single animal is forced to adapt to a new environment, it’s often more successful. Fish from the Hudson river in New York are now immune to toxic waste. Elephants, so often hunted for their ivory tusks, are simply ceasing to grow them. Perhaps most impressively, stray dogs in Moscow have become truly urbanised – they use the subway system to commute from sleeping grounds to begging grounds, navigating the stations by smell and recorded announcements.
In the Arctic, however, these factors are playing out simultaneously. In the December 16 edition of Nature, three American researchers argued that global warming is encouraging the formation of hybrid offspring among Arctic mammals. “The rapid disappearance of the Arctic ice cap is removing the barrier that’s kept a number of species isolated from each other for at least ten thousand years,” the report said. According to University of Alaska evolutionary biologist Brendan Kelly, by melting the seasonal ice cap we are “speeding up evolution”.
This has predominantly been noticed among marine animals, as they are genetically more prone to hybridisation. The World Conservation Unit has identified 34 potential hybrids of marine mammals in the Arctic and near-Arctic, though it is hard to tell how many have been realised. Photographic evidence has shown the existence of a right-bowhead whale in the Bering Sea, and a beluga-narwhal off the coast of Greenland.
These breeds seem unlikely to survive because the hybrid offspring lack important features for mating rituals (for example the narwhal’s tusk). Seals seem to be breeding out the differences between them altogether, mating themselves into one generic breed. Sadly, we may be seeing the start of a similar process among bear populations, with the emergence of the grolar, or ‘pizzly’, bear.
As temperatures have risen, male grizzly bears have been able to follow caribou herds further north, making their first appearance in areas like Wapusk National Park on the west coast of Hudson Bay.
This has brought them into close contact with polar bears for the first time since they were separated during a period of global cooling 150,000 years ago. Furthermore, female polar bears – only half or even a third the size of males – are spending less and less time out at sea, as the ice caps are increasingly unstable and they are not capable of the long swims required. Kept near shore during breeding season, female polar bears resort to their new grizzly neighbours as mates because their own males are unreachable.
The resulting grolar hybrid was first confirmed by DNA tests after the shooting of what was thought to be a polar bear by Jim Martell in 2006 on Banks Island in the Canadian Arctic. Bears have complex mating rituals that last for days, so this was thought unlikely to be a one-off encounter.
Then, in 2010 DNA tests were conducted on a bear killed by David Kuptana on the nearby Victoria Island. This bear was confirmed not only to be a grolar, but to be a second-generation grolar, showing that the hybrid species is now actively breeding in the wild. The implications of this for us, though, are downright scary.
Like most hybrids, they show clear features of both parent breeds. They are slightly smaller than a polar bear, but still considerably larger than a grizzly, bringing them in at around 2.8 meters tall and weighing up to 700kg. They have the long, lean body and neck of a polar bear but incorporate the more muscular grizzly shoulder and its wide face and jaw. They retain the white fur of the polar but with brown faces and paws, and they have received the weaponry of both bears, with the larger and sharper teeth of the polar complimenting the longer stronger claw of the grizzly. They have the less hollow hair of the grizzly, which allows them to remain comfortable in much warmer conditions, as well as the thicker leather on their paws, which enables them to traverse a greater variety of landscapes.
While there are only a total of four confirmed wild grolar bears, this is because DNA testing is only possible when a bear is killed, and is not common practice among hunters. There have been upward of 30 sightings in national parks across Canada, and Inuit hunters claim they are encountered regularly, including in family groups. Inuits from Ulukhaktok, who killed three grolars earlier this year, claimed they could tell straight away that these weren’t your normal polar bears – they were abnormally aggressive. Robert Kuptana told the Toronto Star the hybrid was “pretty nasty. They (hunters) usually stalk the polar bear using a dog, but this bear was so aggressive they couldn’t use a dog on them. It was too dangerous.”
This is in accord with studies of grolars in captivity, which claim that their behavioural patterns are as mixed as their physical characteristics. 80 per cent of a grizzly’s food is plant matter, which is supplemented by scavenging from dead moose and caribou. But they are extremely curious, assertive, and even aggressive, due to living in highly competitive ecosystems. Polar bears are true predators, surviving entirely from meat, but they live in isolation and non-competitive environments, meaning they are shy and rarely aggressive.
The grolar bear is a truly terrifying mixture of these characteristics. It is a predator like the polar (in captivity they stomp and hurl toys as polar bears hurl their prey), but it is extremely inquisitive and belligerent.
When one puts this all together, one comes to the unnerving realisation that has made them so popular on the Internet, so let me recap.
1. Grolar bears are fertile, and sightings are rapidly increasing.
2. Grolar bears are equipped to survive in grizzly habitats, which may draw them towards food-rich human settlements across Canada and the northern United States.
3. Grolar bears are predators, equipped with polar bear teeth and grizzly bear claws.
4. Grolar bears display the curiosity and aggressiveness towards humans of grizzlies.
What this means is that as their population and distribution continues to grow, human beings are going to be living in increasingly close proximity to extremely large carnivorous animals that are not shy. No longer will children need to be scared of disturbing a bear in the woods, they need to be scared of that bear actively tracking them down where they play, or sleep. Whether or not this will happen any time soon, grolar bears are part of a high-stakes game of survival of the fittest, and the most populated. “It’s partly a numbers game,” says Andrew Whiteley, a conservation geneticist at the University of Massachusetts at Amherst.
“If a lonely narwhal encounters nothing but beluga whales during mating season, cross-species sparks may fly. Repeat enough times, and pretty soon you’re left with few pure narwhals. At the very least the rarer species is wasting its reproductive efforts.”
In New Zealand, the introduction of Mallard ducks didn’t destroy local duck populations through competition for food. They simply bred them to the point of extinction. Similarly there are very few genetically pure red wolves left in the United States because, decimated by hunters, they resorted to mating with coyotes. As more polar bears are forced ashore and warmer weather continues to make the north more agreeable to grizzlies, there will be more opportunity to mate.
The traits we see inherited by the grolar would exist for some time, but will likely be bred closer and closer to the standard grizzly as time goes on. The polar bear, as we know it, could simply be bred out of extinction.
Neither national nor international organisations have any official policy in dealing with hybrid species. There are instances of rangers and park managers culling hybrids in order to preserve the racial purity of rare species, but no organised thought has been put in to the benefits or harms of such behaviour and so culling procedures have come under pressure from environmental groups.
Theoretically the hybrids could be fitter and better-adjusted animals, but their ‘outbreeding depression’ makes this unlikely. “People often talk about species adapting to climate change,” Brendan Kelly says. “But…individuals don’t adapt genetically. Populations do. That requires generations, which requires time. Bears, seals, whales – these are long-lived animals. They need decades and centuries to adapt.
“But we’re talking about losing the Arctic summer sea ice in a matter of a few decades. So the time for adaptive response may not be there.” Organised policy would serve as a catalyst for the necessary research to find out what is really going on with hybrid populations in remote areas such as the Arctic.
It remains to be seen if the grolars are genuinely adaptive, or if their success could be put down to short-lived ‘hybrid-vigour’. What seems increasingly clear is that polar bears are in trouble, though not of going extinct, but of fading back into the gene pool they emerged out of tens of thousands of years ago.