​The Interagency Grizzly Bear Study Team (IGBST) has been radio-marking and monitoring grizzly bears in the Greater Yellowstone Ecosystem (GYE) since 1975. Over the several decades of monitoring, there have been various aspects of grizzly bear ecology and biology which prove to be increasingly rare. Since 1975, the team has collared and monitored 900+ unique grizzly bears. One of the rarities that has been documented only twice since 1975 in radio-marked bears, is cubs accompanying a female for a span of longer than two-years.
 
Typically, grizzly bear females will separate from their cubs when they are two-years of age, generally in the spring. During this time, males bears actively seek out a female companion sometimes pressuring the separation of cubs from their mothers, inducing the female into estrus.
 
Another somewhat related phenomenon which actively plays a role in reproductive ecology, is sexually selected infanticide or referred to as SSI. In Yellowstone and the GYE, this has been documented on various occasions. This process is a reproductive strategy utilized among brown and black bears throughout North America, not only endemic to the GYE. It involves a dominant male being removed, or inaccessible during mating. This allows for a new subordinate male to enter the picture. The subordinate male will kill newly born cubs, or sometimes yearlings sired by the now absent dominant male. The female will then be induced into estrus, allowing her to breed earlier.
 
Grizzly bears have the lowest reproductive rates among terrestrial mammals. Generally speaking, a sexually mature female can have litters of cubs about every 2 ½ years. However, those females that retain their offspring for additional seasons throw a curveball into the picture. There are benefits for the offspring, but not so much for the female.
 
During 2008, the IGBST identified a radio-marked female, who had kept her cubs until they were 3-years-old. Grizzly #533 was one of the few radio-marked females that the study team had recorded in nearly three decades of research, to have her offspring accompany her an additional year. More recently, an unmarked sow grizzly frequenting the East Entrance of Yellowstone National Park, was also documented with a cub that accompanied her for the same duration of three-years. Based on the frequency of this phenomenon over the decades, it appears to be a rare occurrence. However, this behavior (anecdotal) seems to have become more common in the past several years (more sightings of unmarked grizzly females accompanied by subadult offspring).

On June 28, 2009, grizzly #533 had a run in with hunters.  Shots were fired, but she managed to escape unscathed. DNA evidence later confirmed that she and her COY were involved in the incident.

(http://www.thewildlifenews.com/2009/07/14/island-park-grizzly-that-attacked-hound-hunter-found-alive-and-well-with-her-3-cubs/)

In 2010, #533 was observed with two of three cubs remaining (yearlings). In 2011, she was not observed with any cubs, and she later cast her collar. In 2012, she was captured at Moonshine Mountain, CTNF and collared again. That year, she was unaccompanied by any cubs. During 2013, it would prove to be a similar repeat of 2009. Grizzly #533 was surprised from her day bed by a researcher during July 2009. She proceeded to attack the researcher, later running away from the scene.

https://idahonews.com/news/local/researcher-attacked-by-grizzly-bear-in-eastern-idaho

Later that summer, grizzly 533 was killed. She was documented as a mortality in the 2013 IGBST Annual Report as:

Unique ID: 201320
Bear: -
Sex: F
Age: Adult
Date: 2013
Location: ID
Certainty: Known
Cause: Human-caused. Under investigation.

Grizzly #533 was 21 years-old at the time of her death.

What is your favorite memory involving grizzly bears in Yellowstone National Park? Do have a favorite place to observe bears? Listed below are some of the favorite memories of  viewing grizzly bears in Yellowstone National Park:

Becky Benson: Watching Scarface come walking down Dunraven Pass!

Karen Gates Enderson: Too many to name BUT....2015, Hayden Valley watched a sow with twin COY on a bison carcass. 1st thing in the morning, rangers weren't even there yet.

Lwren Chandler: RASPBERRY AND SNOW

Paul Roberts: On a one week visit we seen 39 sightings of grizzly, spring or fall best time and less people!

Benny Hickerson: First trip to Yellowstone in the 90s, saw one, so excited! At least one or more every trip since. Most exciting was last year, daughter and family went with us, first trip there, son-in-law really wanting to see bears. All the disclaimers about no guarantee, etc. First day out, 7 bears in GTNP before we even got to Yellowstone! Total for trip: 6 moose, 11 bears, plus everything else. Very happy family! 

Ken Stone: Favorite viewing was watching the Hayden Sow and her two cubs swim the Yellowstone River two or three years ago. I don’t think she has been seen since that summer. ​

John Caloia: having Scarface cross the Yellowstone River and climb out and walk off towards Mary Mountain/Alum Creek area. He was pretty close to me but he paid no attention to me as there were hundreds of others around. I am sure I could run faster than 1 of the people there.

Patty Mason: We saw one Grizzly Bear from quite a distance in Hayden Valley 9/18

Linda Joy Slagowski: Seeing Scarface up on Dunraven. I'll never forget him.
 
Linda Stageberg Petry: I also saw Scarface on Dunraven in 2009. We saw him dig up a ground squirrel and make a snack out of it.
 
Carol Bittner: My first several sightings of Raspberry with her new Cubs Rocky and Snow. Pure magic. 
Every sighting since then of Raspberry and Snow including the one a couple weeks ago. While they have parted company they were still within a quarter mile of each other. I am grateful for every joy filled minute watching them. I look forward to their 2019 return.
 
Amy Halsey: Having been blessed by being able to work in the park for years and then live not far from it, I have so many wonderful memories involving grizzly bears. Here are just a few: 1) Watching a sow grizzly graze on a hillside while her two cubs played with a buffalo pie, chasing it down a hill and rolling the rest of the way - for about a half an hour. 2) As a naturalist, letting visitors watch (through a scope) a grizzly play with a fish like a cat plays with a mouse and getting to hear and see how excited they were. 3) Getting charged by a grizz at Clear Creek at the park biologists' fish traps as we came up in a canoe. 4) Summer of '82 - getting to see a grizzly hang out at Mary Bay off and on all summer (I still wonder if she was Blaze's mom) 5) The summer that wolves were reintroduced - watching a sow and cubs come upon a wolf pack, charging them and getting charged back - they all seemed quite surprised. 6) Watching grizzlies and wolves feeding on a carcass at Lamar 7) Getting to see 755, his daughter and a grizz taking turns chasing each other off a carcass. 8) Finally getting to see Raspberry and getting halfway decent photos of her. My wish is to now get to see COY next spring and maybe seeing Snow.

Des N Shirley Peadon: We share your thoughts Carol, having also seen both of these magnificent bears up close in 2017 and again in May this year. I shall find a couple of photos and post them on here.

Des N Shirley Peadon: Raspberry and Snow up on the Sylvan Pass during September 2017

Carol Bittner: They had stayed close to Nine Mile and Lake Butte Point everytime I saw them this Summer. I drove up the day snow was kicked out found her on a ridge headed towards Lake Butte point.
They were at Sedge Creek and Sedge Bay.
I am very thankful for the protection the Rangers have provided. For the professional photographers who follow them. 
And most of all the reversal of delisting. That they may return to educate and thrill Bear lovers for another season. 
I live in Cody.
Huge numbers of Bears have been killed in Park County this year.
 
Des N Shirley Peadon: ...also back in May this year, we came upon a female bear with her two yearling Cubs. Shirley and myself were the first to spot them, feeding along the Shoshoni river along the Northfork a few miles east of Pahaska. Several other people joined us. While we were there, the two yearlings started to play fight and we managed to get some cracking photos and video.
A few I am posting below.
Unfortunately, we have been told only recently by a good friend, that these three bears were among the bears you mentioned that have recently been killed by F an G !

Carol Bittner: Bless Baby Bears. Such a fun source of entertainment. Always a pleasure and privilege to watch them.
 
Tonya Wood Boyte: In 2010 we got to watch a grizzle chase some buffalo. It didn't catch them and ended up crossing the road right in front of us. I don't know which one it was but we were so excited to watch.
 
Michelle Pearson:
I have two. The first was watching the Wapiti sow and her two cubs right before she got in trouble the second time and was killed, not knowing these 2 beautiful cubs would only be wild and free for a very short time. The second was watching Scarface take a carcass from the Wapiti wolves, only to have another big griz take it from him, not knowing it would be the last time I saw him.

Dianne Hunter: End of September, 4 miles in-Pelican Valley, spotted a grizzly!
 
Susan Stevens: We'd tried for years to find bears in Yellowstone. Finally, in 2010 we hit the jackpot. We had one big grizzly cross the road right by us out at Slough Creek. Then we had this grizzly and her two cubs on Mount Washburn. Taken safely from the passenger window of my car as we drove by.

Susan Stevens: Then this May we were out in Lamar Valley (my favorite place to find grizzlies). I don't have the fancy equipment that many of the regular photographers do, but was lucky enough to have just pulled up to a parking place when this guy moved that direction. I was taking this one from over the hood of my car, standing right by the driver's side door in case he got any closer.

Des N Shirley Peadon: We also saw these same bears on three other occasions during May.

Kim Spurlock Bennett: While looking for wolves in Hayden Valley...we parked along the road and walked out into a meadow. It was foggy but we could see a grizzly bear in the valley, out in the distance (at that time...she was called Valley Girl). There was a large group of us...at least 10-12 people. We had plenty of bear spray. The fog dropped and we lost sight of her. When the fog lifted...there she was...coming up the hill toward us. We all picked up scopes & cameras and headed toward the road where our cars were parked. Cars started stopping along the road and one person yelled out to us "she is behind you and starting to run"! We picked up the pace...but didn't run...just walked as quickly as we could. We all got to the road...I jumped into the backseat of a pick-up truck that stopped in the road. My husband didn't have a chance to get in...he moved toward the front bumper of the pick up truck as the grizzly bear crossed the road at the rear bumper of the pick-up truck. Looking back on it...there was such a large group of us...we probably could have huddled together and gotten over to the side of the meadow...she just wanted to cross the road. That was in September 2015...we have never seen her again and have often wondered what happened to her.

Chris Hartzell: I don't know where this article is showing, but with today's disrespectful tourists and overwhelming numbers trying to find wildlife, I find it in the best interest of everyone not to publicize locations of key animal species.

Natalie T. Bergholz: OOPS Tyler Brasington. I just saw this post

For me every wildlife sighting is a gift!
We humans can learn a lot from wildlife!