2008 KATMAI BEAR TRIP REPORT: PART 5 (GEOGRAPHIC HARBOUR - INDIVIDUAL BEARS)

Al (a.k.a. Scarface) - the alpha boar in Geographic during our stay in 2008.

One of the big stars of Geographic was a big, heavily scarred male that we called “Al” (as in Al Pacino - Scarface). He appeared to be the dominant bear, as all other bruins in the area gave him wide berth. While we never saw any bears fighting at Geographic, the evidence of some serious combat was obvious.

A boar with a serious flesh wound. Injuries like this typically heal very quickly.

On one of our last days in Katmai, we observed a large boar with a flap of flesh peeled back from a large, open wound on its hind quarters. Every adult boar had war wounds. In most cases, these were gashed on the forelegs or wounds around the neck area. One bear had a gash on its head that almost reached the eye (at first we thought the eye had been damaged). While everything seemed fairly copasetic during our stay, the area was no doubt an arena from some terrific bruin battles.

A large boar bearing wounds on the forelegs and around the neck - war wounds from intense bruin battling!

Grizzly Aggression

Stonorov and Stokes (1972) found that there were four situations in which aggression most often occurs in brown bear aggregations. They were: 1. when one bear moves too close to another bear (invades personal space) 2. when one bear loses a challenge but then redirects its aggression toward a nearby bear (displacement aggression) 3. when two bears compete for a preferred fishing site 4. when two strange bears meet.

Stonorov and Stokes describes what happen during an intense, aggressive encounter between two bears that are similar in social ranking. The first thing that occurs is the bears confront one another – the two brown bears face each other with the front legs stiffened, the heads are lowered slightly and the movements occur in slow motion, the ears are laid back, both have their mouths wide open (this exposes the canines) and there is excess saliva production.

One of two things may happen at this point – one of the bears may back down or one or both bears may charge one another. When charging occurs one or both bears run at each other, the head is lowered and the ears are back and the mouth is open slightly. If neither bear breaks off the charge and retreats at this point, the big bears will come to blows. The bruins may swipe at each other with their fore paws, bite each other (usually on the neck) or lock jaws.

When one bear has had enough, it will drop its head even lower than its opponent and begin to slowly back away. At some point, the subordinate may walk or run away. During much of the encounter, there will be lots of vocalizations.

References:

Stonorov D. and A. W. Stokes. 1972. Social behavior of the Alaska brown bear. Int. Assoc Bear Res. & Mang. 23: 232-242.

© Scott W. Michael

2008 KATMAI BEAR TRIP REPORT: PART 4 (GEOGRAPHIC HARBOUR - INDIVIDUAL BEARS)

A sow with her older cubs attempts to teach them to fish, although they prefer to play and loot their mother's catch.

Geographic’s fishing grounds were also home to a vivacious family unit, consisting of a sow and a pair of ~ 2 1/2 year olds. The mother was an efficacious “fisherbear,” while her cubs did little fishing. Instead, they spent much of their time grappling with each other like hairy Sumo wrestlers! When they were not playing, they were shadowing their mom and stealing any fish that she hauled in. Most of the time she would let them take off with her catch, although she did occasionally attempt to wolf down some of her piscine prey before she was looted by her greedy brood. On one occasion she lost her patience and cuffed one of her overzealous offspring before giving in and letting go of her fish (see video below). Occasionally, the two hooligans attempted to include mom in their frolicsome behavior. She complied a couple of times, jawing at her young assailants.

A trio of grizzlies: a sow with her two offspring (these to youngsters are probably 32 months old). Note how she does all of the fishing, while they benefit from the fruits of her labor! Compare these two laggards with the adolescent fishing machine below.

In contrast to these impish, 2.5-year olds, we observed an amazing young bear that was a fishing machine! This bruin was a ~ 1.5 year old (usually referred to as a yearling) with a light colored (nearly blonde) mother. The pair initially made their presence known when the mother, with the cub trailing behind, were observed chasing another bear. They gave up their half-hearted chase and began to slowly meander toward the prime fishing area. Once they arrived at the river bank, it was not long before the yearling was chasing and even catching salmon! (There were few other bears in the area at the time.) The mother bear seemed to lag behind the young bear, keeping close enough to protect its progeny if the need arised, but yet far enough away to allow it to learn some life skills. The young bear was such an enthusiastic piscator that at one point it had a fish in its mouth, while it attempted to capture a second salmonid (see the video below)!

The fishing exploits of an ~ 1.5-year old (yearling) bear - this young bruin was a very effective fisherman, as you will see in the video above.

© Scott W. Michael

2008 KATMAI BEAR TRIP REPORT: PART 3 (GEOGRAPHIC HARBOUR - INDIVIDUAL BEARS)

A sow with a first (spring) cub. Bother were very flighty. At one point, the cub ran into the tall grass and it took the nervous mother 20 to 30 seconds to relocate her progeny.

During our stay at Geographic Harbour, we spotted one sow with a first year (spring) cub, both of which were quite flighty. The sow had large, white fringed ears and her cub looked very healthy (it was quite chubby!). The first time we saw them, they made a brief appearance at the river when four or five other big bears were around. Their stay was brief, being cut short when the nervous cub was startled and dashed into the tall grass. Mother gave chase and after 20 to 30 anxious seconds was able to relocate her frightened offspring. The pair disappeared after that, apparently in search of safer pastures in which to feed.

On our last day at Katmai, this sow and her cub reappeared. The mother’s desire to increase her nutrient intake apparently overcame her concern about exposing her cub to conspecifics. The mother succeeded in catching a few fish, with the cub trailing right behind her (this includes venturing into the rapid moving water in the center of the stream). The cub also ate some its mother’s catch. It is sad to think that this tubby little bear has about a 40 % chance of surviving to adulthood.

Ginger Bear - a young bear, possibly chased off early from its mother. This is one of many pink salmon this little bear was able to capture.

On our second day at Geographic, we observed a small bear that cautiously made its way to the river. It appeared to be a young bear – possibly a runty three-year old. We speculated that it may have been run off by its mother prematurely or possibly it had somehow lost its maternal parent? It came to the river to fish and was successful in its efforts. Rather than eating it near the stream bank, the little bear grabbed its salmon by the tail and sought solitude in the tall grass. When fishing, it was very aware of its larger ursid neighbors, no doubt cognizant of its greater vulnerability because of its small size. This bear had a very distinct appearance – it was rather skinny and had large ears (it almost had a fox-like look about it). We dubbed it Ginger Bear because of its lighter pelage. We were to encounter ginger bear on a couple of occasions (more on this bear later).

2008 KATMAI TRIP REPORT: PART 2 (GEOGRAPHIC HARBOUR)

Geographic Harbour (Amalik Bay) is picturesque, sheltered and infested with brown bears!

On previous trips to Katmai, most of our bear-viewing had taken place at Hallo and Kukak Bays. On our 2008 trip, we didn’t get to either of these sites as bear numbers were sparse at the time. Instead, we spent much of our adventure in Geographic Harbour, a picturesque site at the head of Amalik Bay. Like the rest of Katmai, the scenery is magnificent and bears are ubiquitous - there are usually at least two or three bears fishing in the main stream that flows into the bay. The harbour is surrounded by a high profile landscape that provides natural protection from the inclement weather that rushes across the Gulf of Alaska. It provides an ideal anchorage and a calm landing “strip” for float planes.

The downside of Geographic, is that on a clear day you are likely to share the prime bear-viewing spots with a number of “day-trippers” (these bear-viewers arrive by floatplane and remain in Geographic for two to four hours before being whisked back to Homer or Kodiak). During our stay, there were times where we were in close proximity to at least 30 other bear-viewers. While it certainly takes away some of the “wilderness feel” of the experience, this “bear paparazzi” did not seem to bother the bears that frequent Geographic Harbour (mind you, there may be other bears that would come and fish here but do not while the viewers are present). Also, in the early mornings and from mid-afternoon on, we were the only people among the bears.

A rotund sow (possibly a barren female - see notes in text below) exhibiting the typical Geographic Harbour dark pelage.

Interestingly enough, the bears that frequent Geographic Harbour tend to be darker in color than their Hallo Bay “cousins.” While you see some darker bears in Hallo, almost all the bears at Geographic are chocolate brown. While I am sure it varies from year to year, there were fewer bears at any one time on the Geographic stream than we had seen in early to mid-August at Hallo (we saw as many as 23 bears at once during one of our previous Hallo Bay visits, while the most Ursus arctos in view at any one time in Geographic was less than 10). This may be due to the fact that the prime fishing spots (at least those in view of the bear-viewing areas) in Geographic are not as abundant so there is less space for bears to fish comfortably around one another (fishing spots are more abundant when the tide is out).

In Geographic, there is high grass meadow (Calamagrostis spp.) that grows right up to the edge of some portions of the river. It was not uncommon to see subordinate bears, standing on their back legs, peering above the grass to make sure it was safe to take up a position along the water way. At low tide we would take-up a station on the intertidal flats, where bears fished in the dendritic tributaries that branched out from the main river channel. There is also a viewing pad, consisting of a flat, slightly raised bank situated along the edge of the stream that can be used at both low and high tide. It was not uncommon for bears working the stream edge to come within 15 to 20 feet of this viewing area.

While the area was never overrun with bears, there was often good fishing action in Geographic, especially at and around low tide. We saw numerous salmon pulled from the water by subadults, and both adult boars and sows (although the latter were slightly more abundant in the area). There were some fat, beautiful sows around the river, several of which were very effective at catching fish. One of these females was huge! Brad Josephs, brown bear expert, speculated that this was possibly a barren female, as they have a propensity to become very rotund.

2008 KATMAI BEAR TRIP REPORT: PART 1

In late August of 2008, Janine and I were joined by five other photographers/naturalists on a trip to Katmai National Park. This included Larry Jackson, Debbie Titus, David Salmanowitz, and Larry and Nancy Peterson*. I had been to Katmai in 2006 and 2007 and was excited to get back, as well as share this very special place with great friends. Based on their reactions, I think they too have caught the bear bug - at least three of the five have expressed an interest to go back next year!

We were the guests of bear-viewing guru John Rogers (Katmai Coastal Bear Tours). He runs a number of boats along the Katmai coast and he, and his guides, know the area and the bears like no one else. I had been with John on my two previous trips and once again, John and company came through with a truly amazing wildlife experience!

Katmai Notes

In my past two visits to Katmai, I did my bear-viewing in early to mid-August. This year, we arrived in the land of the great bear a little later in the season (from August 22 until August 31st). We hoped to see more corpulent bears (as a result of a few more weeks at the “salmon buffet,” which is available from July into September) as well as some different behaviors. It was highly likely there would be more fishing activity as at least three and possibly four species of salmon (chum, pink, sockeye, and possibly silver) could be “running” at that time. I also wanted to document bears feeding on moribund and/or dying salmon, as this food source is an important part of the diet of hyperphagic bears.

It turned out the fish were present in large numbers. In fact, in certain parts of the Alaskan Peninsula (e.g., Bristol Bay), there were reports of huge fish runs. I certainly observed bears catching more fish during this trip than I had seen on previous visits (in the past two years I had seen relatively small runs when I visited). We observed pink (Oncorhynchus gorbuscha), chum (O. keta) and sock-eye salmon (O. nerka) being plucked from Katmai’s rivulets. While there were definitely more fish, we saw fewer bears than we had on our past trips. Some locals speculated that the reduction in fishing bear numbers was a function of an abundant berry crop – many of the bears were in the ”bush” gorging on salmon berries. Even though Ursus arctos numbers were down, there were still more than enough bears to keep us in a constant state of awe.

First Stop Kodiak

We began our trip in Kodiak – the jumping off site to Katmai (i.e., you take a float plane from Kodiak to the Katmai coast to meet the “bear boat”). We arrived at Kodiak about five days before our Katmai trip was to commence. Katmai Coastal Bear Tours recommends that you show-up in Kodiak at least a couple days before your scheduled departure, just in case it is necessary to make an early trip to Katmai. If inclement weather is forecast for the day you are scheduled to travel to Katmai, John may have you fly out to the boat one or even two days earlier in an attempt to ensure you get to spend the time you paid for with the bears.

Spending some time on Kodiak is a treat in and of itself! It is one of the most beautiful places I have ever seen, especially when viewed from the air. There are valleys, mountains, rocky coastlines replete with tide pools, clear streams and lakes and lush vegetation (the latter is a function of the high precipitation levels [average annual rainfall of 173 cm, average snowfall 198 cm]). And, of course, it also has a large population of brown bears (a.k.a. Kodiak bears). How many Comfort Inns in the world have a sign posted on the door suggesting that guests be very careful while moving about the parking lot after dark as a curious bear has been sighted lurking around the hotel! During our stay, there were a couple reports of Kodiak bear being sighted fishing in local streams. While we did not see any bears on Kodiak, we did visit a beached humpback whale carcass in hopes of seeing some scavenging brown bears. We also did lots of hiking, learned about spatterdock (Nuphar luteu) (thanks to Larry, our amateur botanist), enjoyed some amazing scenery and found some great intertidal, invertebrate life.

Fortunately, the weather was good while we were on the island (although we arrived on a blustery, rainy night) and we were able to get off to Katmai on schedule. In the next post, we will take a look at our first bear-viewing stop, Geographic Harbour.

URSIDOPHILES 2008

* Larry and David are great dive buddies and accomplished photographers - Janine and I have spent many hours with them in the Western Pacific, both above and below the water! This was the first time we had traveled with Debbie - she was a delight to have on the trip and an accomplished photographer in her own right. Larry and Nancy are good friends from Lincoln, Nebraska (where we reside) that are passionate about wildlife. We want to thank these five great travel companions for sharing this wonderful ursid-rich experience with us!

© Scott W. Michael

A BEAR SHANGRI-LA

Hallo Bay, Katmai National Park.

Scott W. Michael and Janine Cairns-Michael

The great bear quest was conceived on a warm September night in our Nebraska home. A week before, my wife, Janine, and I had been roaming through rain forest on the Olympic Peninsula, Washington. While hiking the mountain trails, I was intrigued with the possibility that we may see black bears (much to my dismay and Janine’s relief, we did not see one). But I had caught the “bear bug.” After our return from this lush national park, I went to the local library and checked out every book they had on the Ursidae (the scientific designation for the family that contains all eight known bear species). One of the books I found was particularly mesmerizing – it was on the brown (grizzly) bears of Katmai National Park, Alaska. I was unfamiliar with this national treasure and the idea of observing these mighty creatures on their turf was very intriguing. Before long, I made the following proclamation to my beloved – “We are going on a trip to Alaska to walk among the grizzly bears.” Janine responded in her now-Americanized Kiwi accent, “Yes Dear, that would be nice.” She was not concerned about my proposal, assuming that like some of my obsessions before it, that it too would pass after a few weeks.

Ten months later, Janine and I were on a small skiff that was ferrying us (and a handful of other bear fanatics) from a converted crab boat, dubbed the “MV Kittiwake,” to the sandy shore that fringes portions of Katmai National Park. While I was sure that this was going to be a unique and exciting adventure, I had no idea how profoundly the next six days would impact my life.

A female brown bear in repose watches us as we set-up our photo equipment.

We arrived in Hallo Bay that afternoon on a Cessna floatplane. It was a beautiful, sunny afternoon and a magnificent flight from Kodiak. Rugged mountains, islets and sheltered bays rolled out beneath us as we made our way to the Shelikof Strait. By the time we reached the Strait, we could see the magnificent Aleutian Range and Katmai National Park. Our gracious pilot, Dean Andrews, made a high pass over the sedge flats where we were able to see numerous brown bears sleeping and grazing in the green expanse! After our smooth landing in Hallo Bay, we were immediately whisked by skiff to the “Kittiwake” to meet the rest of the bear-viewing party and prepare for our first bruin encounter. As soon as we were able to get our camera gear ready and our field gear on, we were on our way to the intertidal flats. At this point, my skin was literally tingling!

Not only were we “buzzing” at the possibility of seeing the second largest land carnivore, the setting that surrounded us was truly awe-inspiring. Even Janine (a citizen of New Zealand, one of the most “scenically-gifted” places on earth), was overwhelmed by the vista that spread out before us as we motored to the estuarine sand flat. At this point, it was evident to both of us that this was going to be a very special trip. We reached the drift-wood littered beach and we were immediately aware that the beasts we had come to admire were nearby – there were bear paw prints, of varying size, impressed into the sand.

On our way to the beach, Brad Josephs (bear expert and guide) gave us a briefing on how we should behave in order to both ensure our safety and to have the least amount of impact on the bears. We bunched-up and moved along the shoreline until we reached a tributary that held great promise. Before us, there were two light colored sows (i.e., female) that were standing in the middle of the water way. They were very vigilant, scanning the water’s surface for any turbulence that may indicate the presence of a piscine prize.

An older female dubbed Nana - although she is small, few bears mess with Nana.

We set-up our camera equipment near the water’s edge, leaving enough room for any bear following the meandering stream contour to safely pass in front of us. Within minutes, camera motor drives were whirring as the two bears began running up and down the stream, being provoked into action by ripples generated by a salmonid back or tail.

This was the beginning of the salmon run, when these anadromous “super-fish” smell their way back to their place of “birth” and re-enact the process of procreation that has occurred for millions of years. Soon after releasing their sexual products, the adult fish die, leaving a virtual “scavengers buffet” that is utilized by bears, eagles, gulls, foxes and wolves. During our six day stay, chum salmon (Oncorhynchus keta) were in the process of re-acclimating to a riverine environment. While the salmon were present, they were by no means as easy to come by or catch as they would be later in the season. We were amazed at how much energy the bruins used loping to and fro as they attempted to find and capture the illusive fish.

One thing that seemed obvious from the get-go was that these bears were oblivious to our presence. They continued to move up and down the river and on a couple of occasions plodded along the bank very near to our group. Janine, who prior to arrival in Alaska, had expressed some consternation about how she would respond when she encountered Ursus arctos at close quarters, was not overcome by panic, but overwhelmed by a wave of veneration.

A grizzly bear stampede!

Both bears tired of pursuing their illusive quarry and eventually left the area, so Brad decided we would move further down the stream to see what we could see. We crossed a portion of the sedge meadow, where we saw moose and wolf sign, as well as two medium-sized female “brownies’ (slang for brown bear) grazing on the plenteous sedge, but even more amazing was the sight that greeted us upon rounding the bend. There were eight more brown bears of varying shapes and sizes. Several of the bruins were bounding through the water, while others were sitting or in repose on the bank, seemingly content to observe the frenetic behavior of their kin. Suddenly, five of the beasts were up and running our direction - it was a bruin stampede! The sleuth of bears, apparently in response to a noise or movement observed in the water adjacent to our group, ran past us, coming with 30 feet of our astonished gang. Once again, it was obvious that they could care less about us - they were only interested in the possibility of securing a salmonid meal.

As the bears past, a couple stopped and adopted a bipedal stance in order to better spy any stirring at the water’s surface. A large female past by with a yearly youngster in tow. She was the only bear that may have been agitated by our presence because as she past she engaged in a threatening vocalization known as jaw-popping (a unique utterance that is made by knocking the teeth together). It was impossible to tell if our group elicited this behavior or if it was the activity of the other bears around her. (We came to find out she was a rather nervous mother that would often jaw-pop if other bruins moved past.) The female and her offspring eventually moved down the bank a short distance and plopped down with their backs towards us. We watched these bears for some time before they disbanded and moved off. It was time to make our way back to the boat.

Snaggle-tooth looks more like a big shaggy cow, as he grazes on sedge, than a predatory bruin.

We took a different course back to the “Kittiwake,” opting to transverse the luxuriant sedge meadow. While in route, Brad spotted one of his old buddies – a huge male that had been appropriately dubbed “Snaggle-tooth.” This battle-scarred old warrior was once one of the dominant males in this area. His jaw has been broken during "mouth-to-mouth" combat and as a result his right canine tooth protruded from his mandible. As we approached, Brad informed us that he was a very “human-habituated” bear and even though he was approaching 1,000 pounds and had been at the top of the pecking order during his prime, “Snaggle-tooth” had never caused problems with any of Brad’s bear-viewers. We sat and watched this gentle-giant as he jerked mouthfuls of sedge from the earth and masticated it like a big, shaggy cow. What an impressive beast he was! Although not universally known to the general public, brown bears feed heavily on plant matter. Along the southwestern Alaskan coast, sedge grass, as well as a miscellany of other botanical species, make up an important food item in the diet of U. arctos.

A little further along the edge of the sedge meadow we encountered another massive old boar named “Flop-ear.” Steve Stringham, a bear expert that had come to greet and briefly joined our group, suggested that he was probably over 25 years of age and that he once instilled trepidation into the other male bruins that fished this bay. His immense frame was not as well-muscled as the younger males that now ruled the Hallo region. He was scarred and even sported a relatively fresh wound on his left flank. Later during our stay, we were happy to see both “Flop-ear” and “Snaggle-tooth” catch a number of fish. Hopefully, they were able to put on enough fat to see them through another winter dormancy.

Flop-ear was once a dominant boar in the region, but now he no longer elicits trepidation in the younger males that are in their prime.

John Rogers, the skipper and owner of Katmai Coastal Bear Tours, met us with the skiff to ferry us back to the "Kittiwake." I had spoken with John a number of times during the 10 months prior to this day and he assured me that I would be blown away by the trip. I could tell he was waiting for a response when we returned to the skiff, but we were gob-smacked! Janine and I were overwhelmed with what we had experienced in our first several hours of being bear voyeurs and did not know how to express our amazement in words. (After several minutes looking at him and shaking my head in disbelief, I simply grabbed his hand and began uttering “Wow” over and over.)

These were our first hours exploring Hallo Bay. There were to be many more amazing days of bear-viewing in Hallo, as well as Kukak, Kuliak and Kaflia Bays. Throughout our stay, I was impressed with Brad Josephs and his wildlife-viewing philosophy. He went to extreme lengths to ensure that our presence did not deleteriously impact the bruins. As a couple interested in the welfare of the animals we are taking photos of, we try to consider the impact our behavior has on our photographic subjects. With Brad and Katmai Coastal Bear Tours, I never felt as though I was “crossing-the-line” when it came to the well-being of the bears.

As I mentioned above, this trip really did change our lives. Upon returning home, I began gathering up as much literature on bear biology as I could find and I am currently trying to figure out a way that I can spend more time in the field photographing and studying these amazing mammals. Janine no longer suffers from “bear-phobia.” Her fear of bears has been replaced with a healthy respect and she is looking forward to upcoming bruin encounters in Alaska, Canada and the lower 48 states. But more than anything, we have both been overwhelmed by the magnificence that is Ursus arctos. We now feel that we must be advocates for the bear and teach others just how important and special these creatures are and how wanting the North American wilderness would be without them.

For more on bear-viewing in Katmai go to www.katmaibears.com!

©2008 Scott W. Michael

BROWN BEAR FISHING BEHAVIOR: PREY SELECTION

A big brown bear with a big salmon. There is more to the fishing behavior of Ursus arctos than meets the eye! Photo by Scott W. Michael.

“In small backwaters where the fish collect in shoals and where the fins of the fish are visible while they move against the current. The bears either enter the water attempting to drive the fish into the shallows, or stand in the water, lowering the head to the surface while waiting for the fish and catching it rapidly with the paws.... The catching of fish is easier in spawning places with calm water, where the fish are less cautious and strong. When the fish are numerous the bear eats mainly the head and part of the back, when fish are scarce, they are eaten completely. The stomach of a large bear may contain 20 kg of fish. However, plants and berries are always found together with fish.” Yu. V Averin (1948) describing the feeding behavior of the Russian brown bears in the Kronoki reserve (in Stroganov 1969)

As far back as 1889, bear-watchers reported that bears selectively ate parts but not all the salmon they caught. A. M. Nikol’skii (in Stroganov 1969) stated that when fish are abundant, Russian brown bears eat only the head and roe of the salmon, leaving the body. When the fish are scarce, they consume their entire catch. Yu Averin, in the 1948 quote above, also reported on this phenomenon.

Most salmonids are anadromous. That is, they hatch in freshwater, move into the sea, and return to the freshwater streams where they hatched to spawn themselves. While it varies from one species to the next, in many parts of Alaska, three different species of salmon spawn during the months of July through early October. The salmon enter their spawning grounds and typically live in freshwater for 5 to 25 days (depending on the species and location) until they die of senescence. Many die before this time as a result of bear predation. In one study, of 1,933 salmon tagged by researchers as they entered three different Alaskan streams, 64 % of the tagged fish were killed by bears, 33 % died of senescence, and 2.6 % died from other causes (like stranding on the beach or were killed by other predators).

When a salmon makes its way into freshwater, it stops feeding and expends incredible amounts of energy on reproduction and the act of swimming upstream – as a result, from this point forward the nutrient value of a fish will drop as they burn stored fat and protein. Researchers Hendry and Berg (1999) found that the total energy content of a salmon drops from 40 to 50 % and the lipid content plummets as much as 80 to 95 % from the time the fish enter a stream and the time when they die of senescence. It would make sense then that brown bears would attempt to capture and consume those fish that have spent less time in Alaska’s streams and that the fish that the bears find least attractive would be those that are reproductively spent and in the process of dying.

But how could a bear determine the nutrient value of a fish (e.g., how long it had been in freshwater)? In some salmon species there are very overt signs of senescence. For example, male red or sock-eye salmon (Oncorhynchus nerka) develop hooked jaws during the spawning period. Salmonid energy stores are depleted and the immune system begins to suffer, as a result of stress and malnutrition, the skin becomes discolored and patches of fungus appear. The longer a salmon is in freshwater engaging in the spawning process, it picks-up more wounds on the body from fighting and frayed fins as a result of nest digging. So, it maybe that these outward signs of a salmon’s physical condition (potential energy content) could be used by grizzlies to help select the most valuable prey.

Researchers have examined if brown bears target those fish that have been in freshwater for a shorter period of time (“younger” fish) and thus have greater nutrient content. They found that in streams where bears can easily capture salmon that they do select younger salmon. In one such stream, the bruins fed most heavily on fish that have been in the stream for three days or less, while they totally ignored fish that had been in freshwater for over 12 days. However, in streams that were wider, had deep pools and/or lots of structure (e.g., sunken limbs and overhanging banks) brown bears fed more on “older” fish (individuals that have been in the stream for over 12 days). In these streams, the salmon that have recently entered freshwater are more energetic and better able to elude the bears, while “older” fish that have expended lots of energy and are “on their last fin” are easier to catch. While the “younger” fish may have more nutrients, the bears will expend more time and energy to catch them. Therefore, in these streams, going after the less elusive, but less nutrient-rich fish, is a better strategy.

Other factors that will impact brown bear foraging strategies are the density of fishes in a particular stream and the weather. When the streams are chock-a-block with amorous fish, the bears can be more selective, while if the fish are few and far between, they cannot afford to be as particular. Likewise, if the streams are breaking their banks and the water is turbid as a result of excessive rain, bears are not as selective. It is get what you can, when you can! There are also individual bears that apparently develop a taste for rotting salmon carcasses. Bledsoe (1987) tells of a bear named “Zubin” at McNeil Falls that would leave a good fishing spot to go scavenge for dead fish.

Food handling in brown bears sometimes changes as the fishing season goes on. At first, the bears will consume the entire salmon, but as the season goes on, on if it has been a good salmon run, the bruins become more selective, restricting their feeding efforts to the more nutritious bits. They peel off the skin, they nibble out the brains, and tear open the abdomen to gain access to the roe. It is not uncommon to see a grizzly step on a fish, causing a stream of orange, nutritious eggs to spew forth. The bears use their tongue to lap-up the eggs.

References:

Bledsoe, T. 1987. Brown Bear Summer: Life Among Alaska's Giants. New York, New York, E P Dutton. 249 Pp.

Hendry, A. P. and O.K. Berg. 1999. Secondary sexual characters, energy use, senescence, and the cost of reproduction in sockeye salmon. Can. J. Zool. 77:1663-1675.

Quinn, T.P., S.M. Gende, G.T. Ruggerone, and D.E. Rogers. 2003. Density-dependent predation by brown bears (Ursus arctos) on sockeye salmon (Oncorhynchus nerka). Can. J. Aquat. Sci. 60:553-562.

©2008 Scott W. Michael

CLAM-DIGGING BROWN BEARS

A female brown bear nimbly uses her large claws to separate the valves of a razor clam and get to the juicy morsels within. See slide show below for more on this bear. Photo by Scott W. Michael.

When it comes to food, brown bears are very opportunistic. As discussed in past posts, they are also very intelligent. Consequently, they’re always looking for new food sources that they can exploit. Along the coast of Alaska, brown bears congregate in salt marshes in spring and early summer. They feed on sedges, grasses and forbs as they wait for migrating salmon to arrive in nearby estuaries. Some bears move out of the marshes and sedge flats and feed on animals that inhabit shore habitats. Along the Katmai coast, there are large tides that expose an expansive intertidal flat that is exposed for three to five hours a day. Certain bears utilize this habitat, hunting for mussels, isopods, barnacles, marine worms (polychaetes and peanut worms) and small intertidal fishes (blennies and sand lances). While it may seem that burrowing clams would be impervious to brown bear attack, there are some bruins that have learned how to locate, capture and handle these infaunal mollusks.

The intertidal zone along the Katmai coast is home to a handful of clam species. The four species that are known to be eaten by brown bears are the soft-shelled clam (Mya arenaria), the razor clam (Siliqua patula), Nuttall’s cockle (Clinodcardium nuttallii) and the Alaska surf clam (Spisula polynyma). These mollusks spend most of their lives below the sand surface, taking in fresh seawater and planktonic food through tube like siphons. The siphons extends from the clam up to the sand surface. (Those species with a shorter siphon remain near the sand surface in order to respire and feed, while those with a longer siphon can burrow to greater depths.) Many of the burrowing clams are adapted to living in the intertidal zone. When the tide goes out, they remain buried in their wet, sandy sanctuary and await the rising tide to bring back life giving oxygen and food.

Clam-hunting Techniques

At low tide along the Katmai coast, you may see an individual brown bear, or a bruin family (sow a cubs), slowly meandering across the tidal flat with nose skimming the sand surface. Somehow the bears detect the buried clams (possibly by using their keen olfactory senses). When they do, the ursid will stop and begin digging at a leisurely pace. The mollusk-hunting bear will lean on one front paw and use the other as a shovel. It will methodically lift the substrate from the hole and push it back behind the excavation. If the clam is deeper in the sand, the bear might lean on its elbow, laying its head on the foreleg, in order to thrust the digging paw deeper into the substrate. When it reaches the bivalve, it will extract it by lifting it out with its claws/paw or by shoving its head into the hole and grasping the clam in its jaws. Troyer (2005) reports that like fishing, bears vary in their clam-digging prowess. Some bears are very effective “clamers,” while others are inept. If a bear’s digging activity never or rarely results in positive reinforcement, they give up this activity after a time. Troyer also notes that when it comes to clam-digging, some bears are exclusively “right-pawed,” while others only use their left paw.

In a study conducted on Katmai bears, it was found that the average harvest rate for clamming bears was 0.69 ± 0.46 clams per minute (Smith et al. 2004). The percentage of excavations that yielded clams was 63%. When it comes to the number of clams ingested, Troyer (2005) reported seeing individual brown bears dig up as many as 50 to 100 clams in one cycle of the ebb-tide. In one four hour period, I watched a female with cubs dig between 180 to 200 holes (it was impossible to determine how many clams the bear ate during this period).

Once they extract the mollusk from its subterranean refuge, the bear has to get to the meat that is housed within the clam’s calcareous armor. In the case of the soft-shelled and razor clams, the valves (which are the two parts that make-up the shell) are not that hard. A bear’s clam-handling technique can vary from one individual to the next. After pulling a clam from the substrate, some bears nimbly use the claws to pull the valves apart (see slide show below). Some bears place the bivalve on the beach and then stomp on it or roll it under their massive paw. This results in the valves breaking apart, which enables the bruin to extract the meat with their lips and tongue. In the case of soft-shell clams, the bear may take the entire bivalve into its mouth and masticate it. This resulted in their swallowing a considerable amount of shell material as well as the clam flesh (along the Katmai coast it is not unusual to see scat that contains clam shell fragments).

Clams Eaten

Katmai Brown bears do not feed on the various clams species in equal numbers. Smith et al. (2004) found that 77% of the time bears dug-up soft-shelled clams (Mya arenaria), 18% of the time they pulled out razor clams (Siliqua patula) and 2% of the time they excavated other clam species (namely Nuttall’s cockle [Clinodcardium nuttallii] and the Alaska surf clam [Spisula polynyma]). Clam species selection is thought to be more a function of species availability rather than preferences related to a species nutritional value. For example, the bears apparently feed more on the soft-shelled clams because they are found closer to shore and thus are available to foraging bears for longer period of time. There is not a difference in the bear’s harvest rate or success rate between soft-shelled and razor clams, even though the razor clam have what appeared to be a more effective anti-predation strategy – that is, when disturbed they pull themselves deeper into the substrate.

Who Digs Clams?

When it comes to a proclivity to dig clams, there are differences between the sexes. Smith et al. (2004) reported that of 233 clamming bouts observed, less than 1% of the clam-diggers were adult males, 44% were females with cubs and 55% were single bears of undetermined sex. How does the overall population of bears in this area compare with those observed clamming? The researchers found that of 16,738 bear (or bear family groups) encounters (over two years), 13% were large adult males, 8% were females with cubs-of-the-year (spring cubs), 17% were females with dependent young and 62% were single bears. It is obvious that females with cubs are overrepresented on the intertidal flats (44% of total population vs. 25% of bears observed clamming), while adult males are greatly underrepresented (13% vs. 1%). During focal sampling of bears working the intertidal zone (that is, where they followed individual bears and recorded their behavior), large adult males spent 0.1% of their time clamming, while females with dependent young invested 4.7% of their time digging mollusks (the single unsexed bears spent 1.4% of their time). The conclusion: females with young cubs most often feed on clams on the intertidal flats.

Benefits to Clam-digging

So what are the benefits for the bruins that dig clams? First of all, clams are a good source of digestible protein. Those brown bears that supplement their diets with these nutritional mollusks, are able to spend much less time munching on vegetation in order to meet their springtime energy requirements. Smith et al. (2004) predicted that a 160-kg brown bear that consumed razor clams for two hours a day could cut down total foraging time by 27% (compared to bears that only consumed vegetation). There is another advantage for clam-digging females that have cubs in tow. Because adult males are rarely seen on the intertidal flats, females with dependent young can forage in this habitat without exposing their offspring to potentially dangerous males. Less time spent feeding and less dangerous for young ones – a definite twofold advantage to hunting clams.

References

Smith, T.S. and S.T. Partridge. 2004. Dynamics of intertidal foraging by coastal brown bears in southwestern Alaska. Jour. Wildlife Manag. 68(20):233-240.

Troyer, W. Into Brown Bear Country. Univ. Alaska Press, Fairbanks, 130 Pp.

Copyright (2008) Scott W. Michael

The slide show below documents the clamming behavior of a female brown bear, with three spring cubs (the latter are not seen in the slideshow).