Polar bear and grizzly bear interactions and accounts

[arctozilla]

Yeah a subadult tiger killing a bear cub.

[brobear]

A grizzly kills a 2-year-old polar bear cub. A tiger kills a 2-year-old polar bear cub. Even if a wolf, a wolverine, a cougar, or even a lynx were to kill a 2-year-old polar bear cub, it would be a meaningless event, except for the loss of a polar bear cub. Babies are easy to kill.

[oldcyansilverback]

/\ Carnivores often try to kill each other’s cubs as a way to rid each other of competition.

[Gorilla king]

Sept 27, 2022 5:58:22 GMT -5 brobear said:

A grizzly kills a 2-year-old polar bear cub. A tiger kills a 2-year-old polar bear cub. Even if a wolf, a wolverine, a cougar, or even a lynx were to kill a 2-year-old polar bear cub, it would be a meaningless event, except for the loss of a polar bear cub. Babies are easy to kill.

Yes, that is absolutely right, however, In forums, absolutely all accounts have to be posted for info sake, and because its fun i guess. We need to see everything, even the cubs being killed. But of course, killing cubs or females is no accomplishment.

[oldcyansilverback]

One thing to say: despite the fact the grizzly is more aggressive, the polar bear is still known as king of the arctic (including the areas where grizzlies enter, black bears enter the arctic circle in Churchill). Notice that there is nowhere it is said: ‘grizzlies are king of the arctic in areas they share territory with polar bears.’ It seems purely carnivorous are generally considered king in their domain. Yet just because an animal is considered king doesn’t mean it is the strongest.

[oldcyansilverback]

Reply 43. I also like to point out that posting all accounts makes our arguments more credible and objective in general.

[Gorilla king]

Nov 15, 2022 19:30:31 GMT -5 oldcyansilverback said:

One thing to say: despite the fact the grizzly is more aggressive, the polar bear is still known as king of the arctic (including the areas where grizzlies enter, black bears enter the arctic circle in Churchill). Notice that there is nowhere it is said: ‘grizzlies are king of the arctic in areas they share territory with polar bears.’ It seems purely carnivorous are generally considered king in their domain. Yet just because an animal is considered king doesn’t mean it is the strongest.

I agree with everything you said. Just for clarity sake though, Churchill is just outside of the Artic Circle, look at the left side of the map:

[arctozilla]

Reply #15 I think an old newspaper because it cames from La Domenica del Corriere, an italian weekly.

Inviato dal mio 21061119DG utilizzando Tapatalk

[Gorilla king]

Here we have the first documented case of an adult male polar bear successfully defending his kill from a grizzly bear:



F) A polar bear successfully defending a marine mammal carcass from an approaching grizzly bear, Kiask Island, 2013 (photo: Robert Rockwell).


Two observations were of grizzly bears feeding on subadult polar bears but in those cases neither observer could conclusively determine whether the grizzly bears had killed them, though the details of one case strongly suggested so. Grizzly bears are known to have killed and consumed polar bears on the sea ice in the western Arctic (Taylor, 1995) and typically dominate polar bears when they interact on shore in Alaska (Miller et al., 2015). These two observations contrast though with Rockwell’s 2013 observation of an adult male polar bear successfully deterring an approaching grizzly that appeared attracted to an unidentiable marine mammal carcass the polar bear was standing on (Fig. 2f).


The State of Knowledge about Grizzly Bears (Kakenokuskwe osow Muskwa (Cree), Ursus arctos) in Northern Manitoba


www.researchgate.net/publication/359235217_The_State_of_Knowledge_about_Grizzly_Bears_Kakenokuskwe_osow_Muskwa_Cree_Ursus_arctos_in_Northern_Manitoba

[brobear]

My thoughts are, Robert Rockwell was not mistaken in his observations. But since that time, the polar bears have been becoming more familiar with their smaller cousins. The fear of the unknown is fading. Being second in line to another predator is not a status that the grizzly has known since the end of the last Ice Age (excluding freaking humans). I believe that the near future will bring about stories to be told.

[oldcyansilverback]

Reply 48. The account confirmed my thoughts . The much bigger polar bear especially the older males have lost their fear of the grizzlies. We have seen every interaction in real life except that in the Russian Tiaga (briefly mentioning).

[oldcyansilverback]

My old post in shaggygod forum:

According to a book which I recently read called 'Spirit of the Bear':Younger male bears are acctually preferred by the younger female bears.

That explains how male barren ground grizzlies are able to mate with female polar bears.

[oldcyansilverback]

From Ursus Artos:

I have read this as well, according to observations of scientists studying coastal brown bears at McNeil. They claimed that all other groups of bears appeared to have a lot of fear for the large adult males (8.5+ y.o.); total bear activity at the falls dropped when they began to show up (~11:00 pm) as other age/sex classes left. For this reason females also appeared to be less receptive to the large males.

However, data from a microsatelite DNA analysis by Craighead on a non-hunted population of grizzlies found no evidence for reproductive success by any grizzly bears under 9 years old (interestingly, 8.5 was the cutoff for classifying males as adolescent vs adult males in the Alaskan population based on behavior as well; note that sexual maturity comes at a much younger age than this). Also of note: only 50% of bears older than this were found to have had reproductive success, indicating very high levels of competition (for comparison, male black bears had an even lower number, at 33%, but younger males did manage to reproduce).

The coastal population could be different, but in this one at least it appears that females strongly preferred the older males.


Info on the Swedish brown bears (heavily hunted) found much more equality in reproductive success, however young bears still didn't come off well-age was positively correlated with reproductive success in the North and South. While in the South body mass (which is correlated with age) was more strongly related to reproductive success than age (suggesting the correlation between yrs and age was a result of the relationship between yrs and body mass) it was the other way around in the North. The article attributed this to a biased sample however, as reproductive success in the North was dominated by a very old male.


Whatever observations may show, data on actual relationships consistently shows much higher reproductive success for older male bears.
Perhaps apparent preferences are merely a ruce to reduce the probability of infanticide.

To draw more confident conclusions (apparent preference was observed in a coastal population of brown bears; the two studies on paternity of brown bears involved non-coastal populations, and American black bears are a different species entirely) more studies would be needed.


References:
Microsatelite Analysis of Paternity and Reproduction in Arctic Grizzly Bears, by Lance Craighead, et al.

The Social Behavior of Brown Bears on an Alaskan Salmon Stream, by Allan Egbert and Allen Stokes.

Determinants of male reproductive success in American
black bears, by Costello, et al.

Genetic estimates of annual reproductive success in male brown bears: the effects of body size, age, internal relatedness and population density, by Zedrosser, et al.

[oldcyansilverback]

From Graaah:
IMO, it is very likely the Barren ground grizzly bears mating with the polar bear are older males.

Male polar bears (including these in Svalbard, Churchill, and Alaska) are much bigger and stronger than
male barren ground grizzlies. Therefore, the post from Graaah makes sense.

[oldcyansilverback]

Reply 46. Churchill is outside the arctic circle yet known as polar bear town. It shows that polar bears can venture out of the arctic circle.

[arctozilla]

Is there any evidence of male grolar bears being fertile?

[Gorilla king]

May 3, 2024 4:00:56 GMT -5 arctozilla said:

Is there any evidence of male grolar bears being fertile?

Yes, it looks that way:

Pizzly Bears

When polar bears and grizzlies breed, they can produce fertile offspring. Why can’t other species?

slate.com/news-and-politics/2010/05/when-polar-bears-and-grizzlies-breed-they-can-produce-fertile-offspring-why-can-t-other-species.html

[oldcyansilverback]

They will eventually become no different from ABC brown bears.

[Gorilla king]

FULL GROWN BLACK BEAR KILLS AND EATS A LITTLE POLAR BEAR IN A CIRCUS:




"...was a bear fight after dark and one of the older, full grown black bears managed to get to the polar bear and killed it. Before Wally knew it had happened, the black bear tore open the little polar bear and was eating on the body when Naughton found them. The grown bear had..."


books.google.com.ar/books?id=ojhWAAAAYAAJ&q=was+a+bear+fight+after+dark+and+one+of+the+older

[Gorilla king]

Novel range overlap of three ursids in the Canadian subarctic


Abstract and Figures

We describe for the first time in the peer-reviewed literature observations of American black bear (Ursus americanus Pallas, 1780), grizzly bear (Ursus arctos Linnaeus, 1758), and polar bear (Ursus maritimus Phipps, 1774) at the same locations. Using remote cameras we documented 401 bear-visits of all three species at three camps in Wapusk National Park, Canada, from 2011–2017. These observations add to a growing body of evidence that grizzlies are undergoing a substantial range increase in northern Canada and the timing of our observations suggests denning locally. Polar and grizzly bears are of conservation concern regionally and internationally, so from the literature we assessed the potential effects on conservation efforts from interactions between these three species. In aggregate, those effects are likely to be positive for grizzlies and weakly negative for black and polar bears; further research is needed. Range overlap of these three species in this dynamic ecotonal region should not be viewed as a threat to any of them, but rather as an ecological response to environmental change that needs to be better understood.


(A) polar bear, (B) black-phase American black bear, (C) grizzly bear, and (D) cinnamon-phase American black bear at Owl River camp, Wapusk National Park



Potential effects on species conservation efforts from interspecific interactions in our study area: positive (+), negative (−), or neutral (0). Also denoted are species not involved (n/i)



www.researchgate.net/publication/328977222_Novel_range_overlap_of_three_ursids_in_the_Canadian_subarctic