Thursday, December 11, 2008

Fall elk

Fall in Yellowstone Park means rutting bull elk. It's mating season and the time when large bulls gather groups of cows called harems. The bulls watch over their harems in order to mate with the cows as they come into estrus.

Mature bull elk use a tremendous amount of energy participating in the rut each fall. Bulls will chase and collect cows in order to establish harems and then chase the cows some more in order to keep the harems together. Bull elk must remain vigilant in order to keep other bulls from stealing or mating with their cows.

During the rut bull elk will often vocalize, or bugle to announce their size, strength, and status.

               This herd bull has spotted another mature bull and is bugling to make his presence known.

If two bulls are evenly matched in antler and body size a fight may occur. Here the herd bull leads a rival away from his harem and into an open meadow.

The two bulls posture to show each other their antler size and demonstrate their physical condition.

Here the bull on the left feigns an attack, acting as if he may jab the other bull with his antlers.

Testosterone levels are very high and the tension is palpable, yet neither bull wants to fight if it can be avoided. It's better to win through intimidation than risk serious injury in battle.

In this case neither bull backed down and a brief fight ensued. The fight lasted less than a minute before the former herd bull was vanquished and chased off.

After his victory the new herd bull bugled to let all of the cows and any potential rivals know that he was now in charge.

Every year in the Rocky Mountains during September and October countless dramas such as this play out. If you ever get the chance to go out and see and hear it for yourself you will never forget it.

Wednesday, December 10, 2008

Tough meal for a grizzly

Every spring in Yellowstone park grizzly bears awaken from hibernation and leave their dens feeling very hungry. While the bears were sleeping other animals like bison and elk were awake and doing their best to sustain themselves throughout the harsh winter.

Each winter many elk and bison don't make it and die for various reasons. Some of them fall through the ice while attempting to cross frozen rivers and lakes. The carcasses of these winter casualties then serve as an important food source for the bears each spring.

This grizzly bear has located a bison carcass in the middle of the Yellowstone River near LeHardy Rapids. I saw the bear from my car and stopped to photograph it. When I pulled up to the established parking area there was already a park ranger at the scene. I took my camera and found a good vantage point among the tourists watching the bear.

Here the bear is shaking off as it climbs onto the whitened carcass.

Although the bear is equipped with sharp claws and powerful jaws it still had great difficulty penetrating the dead bison's hide

Every so often the bear would stop and take stock of the growing crowd of people watching it.

The carcass seemed to be lodged on some rocks and the bear showed good balance as it was able to stay on while it bobbed in the current.

Again the bear surveys the crowd watching from the nearby shoreline.

Eventually the bear was able to use its teeth to make a hole in the thick hide and get a little to eat.

After awhile the grizzly stopped attempting to feed. I think it had had enough of people watching it.

With that the bear got off the carcass, swam to the opposite shore, and walked up into the forest.

A day or two later just after dawn I watched a grizzly bear again out on this carcass. it was too dark for photos so I watched from my car with the windows down. There were no other people around and I couldn't tell if it was the same bear or not.

Apparently the carcass still wasn't open enough for the bear to feed easily. The bear worked at the carcass while standing in the water and on top of it. After the bear pushed, bit and ripped at the carcass, it broke free from the rocks it had been lodged on. The carcass and the grizzly bear then started to float downstream.

With the windows open I could hear as the bear made what I thought were frustrated and unhappy sounds as it held onto its meal while being dragged along with the current. After going a short distance the carcass again got caught in some rocks and the bear left it and swam to the opposite shore. The grizzly then walked into the trees and I could no longer see it.

With that I left to go and photograph some locations that the sun had already reached. I returned later after the sun was high enough to light that stretch of river and found only the carcass, but no bear.

Tuesday, December 2, 2008

Grizzly bear school

One beautiful May morning in Yellowstone park I happened upon a sow grizzly and her two little cubs at a small creek.

At first the mother bear was on one side and her cubs were on the other. All three bears were vocalizing a lot. The sow was calling for the cubs to come to her, but they loudly protested and stayed where they were.

The sow grizzly then jumped the creek and joined her cubs.

After briefly encouraging them to follow her she jumped back across to demonstrate what she wanted from them.

The cubs stayed put and called to their mother while she continued to call to them from the opposite bank.

I watched the mother bear jump back and forth across the creek two more times before she changed the plan.

Her cubs were just a month or two out of the den and not willing to get into the water just yet. The swimming lessons would have to wait for another time. The mother grizzly stayed on the cubs' side of the creek and led them around the water and off into the distance.

Many of the strategies that bears use for getting food and surviving in the wild are learned behaviors that mother bears teach their cubs.