My visit to Ramsey Canyon today was to photograph Coues (pronounced Cows) Whitetail Deer bucks in rut chasing does. So up the canyon I went walking slowly hoping to find the "good" buck a visitor had claimed to see earlier. I was fortunate to find a couple fairly quickly and then spotted a smaller but respectable 4 x 4 buck following 2 does. With some luck I might get him out in the open with some decent late afternoon light. But, like most of my photo quests, the animals were not cooperative and within minutes the doe the buck was interested in lay down, so the buck did as well some 50 yards behind her. No photo opps for a bit. I found a high spot where I could see them both and sat down as well. Within minutes both were "chewing their cud", what biologists call ruminating, which helps the breakdown of hard to digest plants. So with nothing to do for a while my mind started to wander. Since I was just watching the chewing motion, I began to ruminate on what I consider one of the most fascinating symbiotic relationships in nature; the process that allows those deer (all deer, elk, sheep, cattle, pronghorn, and other antelopes worldwide) to actually get energy from the plants on the surrounding hill side. I was hungry, but I couldn't eat the acorns and oak twigs these 2 were browsing on. In reality, without a lot of help from other species, neither could they and that takes some explaining.
To lay some ecological ground rules I'll start by stating that every calorie of energy on this planet was originally converted from sunlight by plants (or algae). So even if you are eating meat, the calories you ingest came from the plants that animal ate that had converted energy from the sun using chlorophyll in a process known as photosynthesis. So all animals need plants and we benefit from their ability to convert sunlight to an energy form we can use. The problem is, plants don't normally want to be eaten (there are exceptions but that's in another chapter). Plants don't have a brain to think about it, but it's not hard to imagine that a plant that is indigestible (so avoided by animals) would probably produce more seeds that grow to adult forms versus one that is digestible. So in each generation of plants, a mutation that makes them more indigestible will probably become more common and more and more plants will become difficult to digest. Give plants a few 100 million years and they are pretty good at preserving their energy and nutrients. Case in point…as I sit surrounded by millions of calories that I can't digest. Herbivores have to keep up with these changes and mutations that make them more efficient at digesting plants will become more common over time as well. The chief defense in most of the plant kingdom is a tough cell wall known as cellulose. Many animals, certainly you and I, do not have a digestive system that can cut through most plant species cellulose walls to get at the glucose (energy) and nutrients. I could chew all the acorns I wanted and not get enough energy to survive because of the cellulose. The deer seemingly has no problem, but actually the cellulose is indigestible to them as well so they need help.
Deer and the animals I listed above are known as ruminants, which are even toed, hoofed animals with a specialized digestive system, specifically a 4 chambered stomach that allows them to obtain energy from indigestible plant matter. There are just over 150 species of ruminants and it includes wild and domestic species including deer, sheep, goats, cattle, camels, giraffes, yaks, llamas, pronghorn, and the antelopes. They actually don't do the digesting, the quadrillion (that's 15 zeros) of bacteria and protozoa that live in the 4 chambered stomach complete the breakdown of cellulose because they have the ability to break it down. So by providing the microbes a place to live with the proper conditions, the deer get the energy released from the cellulose and hemicellulose in the form of volatile fatty acids (vfas) and from the bacteria themselves. To take advantage of this “deal” they have evolved a complex 4 chambered stomach with conditions almost perfect for the bacteria and protozoa which results in a superior fermentation chamber. A little different than your favorite winery, but similar in nature (excuse the pun).
The 4 chambered stomach has a chamber for each of the following functions, a sorting and filtering chamber for the chewed up vegetation, a fermentation chamber, a water absorption chamber, and a gastric stomach that is not as acidic as you and I have but serves somewhat the same function. The honey combed sorting chamber (ever eaten menudo?) or reticulum is the largest, and the series of folds and villi make sure that only small particles pass through to the bacteria. Larger particles are passed back up to the mouth to be rechewed, hence rumination or cud chewing. The next section, the rumen houses the bacteria. The animal must ensure that conditions are correct for the bacteria which require a warm temperature, a lot of water (saliva), and the opposite pH of our stomach. To keep the area moist and buffered, every ruminant produces an enormous amount of saliva, a cow is estimated to produce 100 – 150 liters a day. Once the bacteria do their job and the particles are small enough, they move into the Omassum where the ruminant tries to get as much water back from both the saliva and any water the plant had in it as it can before the mostly digested food continues on to the gastric stomach, the small intestine, and finally the large intestine. From an energy standpoint, the 3 byproducts of fermentation are the volatile fatty acids, the water soluble vitamins produced by the bacteria, and the superior proteins contained in the bacteria themselves. The vfa's are absorbed into the blood through the rumen wall, most of the vitamins and proteins a little later in the small intestine. As the foods continue to move along the digestive tract some microbes move along with it and food value and nutrients continue to be extracted throughout the small intestine. The large intestine is the chamber where the all the water possible is extracted before the feces is released. So by creating a stomach that has ideal conditions for a microbial population, the whitetail I’m watching can ingest things and get food value from items neither of us can properly digest.
Ruminants aren’t the only animals that take advantage of this symbiotic relationship however, most herbivores do since plants have built up defenses for over 500 million years. Other mammals such as rodents, birds, and even a couple of our lizard species have digestive chambers that evolved to house bacteria so the cellulose and hemi cellulose that protects plant energy and nutrients can be extracted. Most don’t have near the efficient system as the ruminant however. A couple other herbivores I can see as I wait for the deer to move are cottontail rabbits and Arizona gray squirrels. The rabbit doesn't have a 4 chambered stomach, but it does have a cecum located at the end of the small intestine. It's located the same area as our appendix. It's a large chamber (up to 60% of the digestive tract) and it's a most important part of the tract. The cecum is a fermentation chamber that has the same function as the rumen in the whitetail. The rabbit absorbs vfa's produced by the bacteria as they process the grass the rabbit ate. But the big difference between the two species is that the cecum is located at the end of the small intestine, not before it. Because of that, all the proteins and vitamins absorbed by ruminants are not absorbed by rabbits or other herbivores known as “hind gut fermenters”. The rabbit has a special adaptation that other animals do not. It's not appetizing to think about, but it works well. Rabbits actually produce 2 types of feces, a hard fibrous feces and a soft moist one known as cecotropes. To absorb the vitamins and proteins that the whitetail absorbs in the small intestine, rabbits eat the moist soft feces and then the proteins and minerals can be absorbed in the small intestine. Other species will eat their own feces as well, which is known as copraphagy. (Sometimes I need to tell my students to get the copraphagic grin off of their face!) The gray squirrel has a digestive system more like ours. A highly acidic gastric stomach, a long small intestine, and a cecum that is not that large. Their bacteria population is not large enough to digest the cellulose found in many plant parts and species thus their diet is more selective. Without softer berries, nuts, fungi (mushrooms) etc., they would starve. They are better at processing cellulose than you and I, but not that much better. You and I, we need to stick to our soft green beans, corn, lettuce, etc., all plants that have a weak cellulose wall if we want to access that energy. If you want to add Brussels sprouts to that list and eat them, fine. I think I'd rather try acorns.
Two years ago I enrolled as a volunteer at Boyce Thompson Arboretum near Superior; it’s an Arizona State Park and a 300-acre collection of towering trees, cactus gardens and paths -- fall foliage each November, and colorful wildflowers in March-April. All that vegetation means lots of habitat for "camera-ready" small animals - and the park boasts an impressive bird list. I’ve found it a good place for bird photography, some small mammals, and I finally got some shots at a couple of the foxes I know lived in the area.
If you go, the following is a suggestion from my go to friend at the Arboretum Paul Wolterbeek. “Get to know the groundkeepers and park staff; they're a friendly crew, welcoming to photographers, and usually quick to share insiders' tips about places and times to see and photograph animals and birds. When you pay your admission in the gift shop ($10-a-day, or $50-a-year to be a member), ask if Becky or Gonzalo are on duty that day, and if they'd have a minute to speak with you. Ask for Ricky, or Ruben or Chris Spencer -- each a knowl edgeable outdoorsman who knows the gardens and the animals which live there, knows their habits and what fruit trees they're feeding under this week!”
Paul alerted me this week about the Gray Fox, a tough species for anyone to photograph. He pointed out that the foxes have been seen daily - gobbling up the fallen fruit beneath the palm trees. They're also being seen climbing up in to the large, shrubby myrtle that overhangs the main trail just past the "pumphouse" (that's on your trail map), between the suspension bridge and the "catwalk" (that's not on your map - but any BTA staffer can point out the location. Fox are excellent climbers and will venture into trees after fruit, to raid nests for bird eggs, or just to nap on a limb. It wasn’t easy to find them but persistence and walking back and forth paid off.
I started this post saying I had signed-up as a volunteer, and here's an invite to meet me and learn why. Dec. 22 (Sunday) I'll be at BTA giving a lecture about bears, and showing a slideshow of recent photos. That's in the morning at 10am, and included with daily admission. That afternoon I'm giving a talk to the BTA Photo Club; that's not a public event, but you can attend if you're a BTA annual member and you're into photography. This is the 3rd time I've been involved with the BTA photo club - last year Lisa Langell and I offered a "tag team" presentation on wildlife photography, and then guided a walk into the gardens to demonstrate a few of the camera techniques we'd been discussing. Meet me at BTA on Dec. 22! As an added bonus, after the event at the Arboretum my family and I are heading over to one of my favorite Christmastime events in AZ, the once-a-year "festival of lights" up at the Besh Ba Gowah archaeological park in Globe, another 45-minutes drive east of BTA. The event is free, and lures photographers from across the valley. Read more & check out photos:
I just finished a book on Blurb for Dave Coray at Silver Salmon Lodge entitled "Answers to Questions about Brown Bears". Dave and I came up with the idea when I worked there in 2012 for a couple weeks developing educational materials for his lodge.http://www.silversalmoncreek.com/about.php
It's a 30 page "coffee table" book that answers the questions David and his guides are most often asked. I greatly enjoyed researching for it and much of the text is found her on this blog. Please feel free to preview at http://www.blurb.com/b/4331110-answers-to-questions-about-brown-bears#promote-pane
Just click on the link then click on preview. I'm not sure how I'm going to like the images published and I won't know that until I return from South Africa in July. The published versions are going straight to Dave's lodge now.
Coastal brown bears are one of the largest land carnivores in the world with males weighing up to 1500 lbs. On average polar bears are larger but the largest bear ever weighed was an Alaskan brown bear over 1800 lbs. This guy is probably a mere 1000 lbs, and will probably be 200 to 300 more after the salmon season.
This sow is probably just over 500 lbs while her 2 cubs are near a 100 lbs at 14 - 16 mos old.
How large do Coastal brown bears get?
The size of course depends on the age and the sex of the bear. A brown bear male (also known as a boar) is usually fully grown at 8 years old, and gains about 100 lbs a year from 3 to 8. His final weight will be from 800 - 1000 pounds, but brown bear males over 1500 pounds have been measured. A female (aka sows) usually stops growing at 5 years old and weighs about 350 -500 pounds midsummer. Both the male and female can easily gain a couple hundred pounds from early summer to late fall when they go into hibernation. An interior brown or grizzly boar could range from 500 up to 700 (but that's very large) and a female will be from 3 to 500 lbs.
Why are the Coastal Brown Bears larger?
The larger predictable supply of the vegetation and berries growing along the coast helps, but it’s primarily the salmon diet that helps them attain and keep a large size. Not only are coastal brown bears up to twice as large as inland browns, their populations are up to 10 to 20 times denser than interior populations, another facet based on the abundance of food. Females tend to have larger litters and are more successful at raising them. The predictable supply of the high fat/protein salmon diet gives them a tremendous ability to succeed.
At an average of 4000 calories per fish stored, this is when the coastal brown bears really put on the weight, eating from 10 to 50 fish/day
When do the bears begin to eat the salmon?
The answer to this is easy, but not exact. It's as soon as they can! Bears seem to have an uncanny knack for knowing when the salmon begin to run and will show up within a few days, often congregating at shallow spots along the creek where it is easier for them to catch the fish. Depending on the geographic location in either Katmai or Lake Clark National Parks, salmon may be available as early as late June or as late as August-September in other areas.
How many salmon does a bear eat a day? Do they eat the whole
The short answer to both questions is it depends. How many salmon they eat depends how many they can catch, and how large of a bear they are. If the salmon are numerous and each bear can catch the number of salmon they want, they will catch somewhere between 10 and 20 a day, but large males have been seen catching and eating as many as 50.
Each salmon is roughly worth 4,000 calories in entirety, and 20,000 calories ingested a day is common. In the height of a salmon run, bears are estimated to gain from 2 to 4.5 lbs in fat a day. That’s very important for that winter hibernation period. If the salmon numbers are high, and the bear is skilled at catching fish (something they get better at with age), bears are known to switch to just eating the fatty parts of the fish. Fat has twice the calories of protein, so it's possible to see a bear just eat the brains, the skin, and the eggs if it's a female salmon. They may lay that carcass down and then go get another. Although you may consider that wasteful, nature won't allow it and the red mass of protein will be utilized later by less skilled bears, cubs, or even other species such as bald eagles, gulls, magpies, or even other fish like the dolly varden that follow the salmon.
This large bear is skinning the just caught salmon. When the fish are really running in large numbers some good fishing bears may only eat the skin, roe (eggs), and brains. The rest does not go to waste however, and the waste is quickly devoured by less skilled fishing bears and/or eagles and trout waiting near by.
Before I start this particular blog (or chapter may be more appropriate) I think it's important to point out that the life of a bear could be defined as a race. Each year is a race to put fat on before there is no food and the bear must hibernate. When they enter hibernation they have to count on the fat reserves they were able to store over summer. If there is not enough fat they could die during hibernation, or during the following spring before the summer growing period starts.
A female will only produce cubs if she has enough fat reserves when she goes into hibernate. Years of poor vegetation growth or salmon runs are followed by years of little to no cub production. A study of Katmai brown bear females found that they averaged losing 150 lbs when hibernating (approximately 30 to 40 % of their fall weight), most of which was fat. They need to get all of that back each year.
The questions below are one's I commonly receive so I put this blog in a question and answer format. I hope you enjoy reading it!
What do bears eat?
Coastal brown bears have access to 4 different food groups: 1) vegetation, 2) clams and other intertidal invertebrates, 3) berries, and 4) the food item they are most associated with, salmon. Vegetation is the most available, and green areas along the tidal zone appear first (as early as May 15). These early green ups are critical for bears emerging from dens that have lost so much weight.
What type of vegetation do the bears eat?
They won't graze on all the plants but brown bears have been recorded eating over 200 plant species so they are probably much more herbivorous than you thought. Goose tongue and arrow grass are some of their favorites in the Lake Clark National Park area.
The vegetation itself benefits from it's coastal location. First, the warming effects (just above freezing is warm for coastal Alaska in April-May) allow these zones to be the first ice free areas and the plants begin to grow. Second, each time the area is flooded with high tides it's essentially fertilized from nutrients in the water from the ocean. The slow retreat of the tide allows the vegetation to capture additional large particulates that adds important nutrients. A high tide essentially fertilizes the vegetation, and the bears take advantage of the extra growth and essential nutrient the plants provide.
Do bears digest vegetation as well as a cow?
Even though they seem to graze like cattle, bears are not near as efficient as extracting calories and nutrients from vegetation as a cow. One research model predicted that a brown bear must eat for at least 12 hours and ingest 20 lbs to just maintain it's weight This large amount of forage is necessary partly because of their poor ability to digest vegetation and partly due to their large size. There have been numerous studies with conflicting results on how bears fare as herbivores, which is the most common part of their diet when salmon are not available. Interior bears may eat up to 90% vegetation in a season, but most coastal bears switch to more nutritious salmon when they begin to show up. Most studies found emerging coastal brown bears continue to lose weight after hibernation at least until the vegetation green up occurs in Mid May. Most scientists estimate they maintain the weight after the green up by grazing, with maybe some minor weight gain. It's obvious that coastal brown bears must have access to more nutritious sources to put on weight, and reach their large size. As a fellow photographer I know the frustration of following grazing brown bears that seemingly never lift their heads. And Murphy always rules as their head seems glued down when you get that rare sweet light. I do ask however that you remain patient and not disturb the grazing bears. All that effort they are putting in for up to 12 hours just to maintain weight is a lot, and we don't want to negatively affect them by scaring them and reducing that valuable grazing time. They will pick that head up, just be ready!
Berries can be important very early or late in their active season. The high sugar content can be crucial to provide the extra fat, especially after the salmon run, that bears need as they near the end of their race to regain weight in late fall. Key berries in Katmai and Lake Clark that brown bears consume include blue berries, salmon berries, elder berries, and nagoon berries. Berry crops not eaten the fall before also may provide forage just after hibernation if not covered by snow and ice.
Are the bears really clamming out at low tides?
You bet! Along the coast, many bears will hunt for the clams uncovered during low tides. The majority of clams eaten on the Alaskan coast are Pacific razor clams. Studies of Alaska bears found they like razor clams, soft shell clams, and a few types of molluscs, and polychaete or tube worms they find in the sand. They probably use all of their senses to find them as they walk around with their nose close the ground. Smell, vision, and even feeling the clam move though it's paws make them so successful. A study where bears were observed clamming on 233 days over a 3 year period found that the average bear ate a clam almost each minute it foraged. Many ate from 50 to 100 in the short periods the tide was low enough. Researchers found some bears are right or left pawed, but I've seen the same bear use both. How they break and extract the clam from the shell can be different between bears as well. Clams are only available for a few hours and only about 15 days a month when the tide is low enough to expose them so not all bears use them. However, they provide another important pre salmon food source, which contains 3 times the amount of protein as a similar amount of vegetation. One study found that a brown bear that ate 50 - 100 clams in a couple hours was able to reduce it's necessary grazing time by 25%. As I mentioned above, this valuable time could allow her to add more fat, and be more successful in making sure she can make it through the winter.
Why don't more bears make use of the clams that are exposed during low tides?
That is an excellent question and not one easily answered. Observations of clamming bears throughout the coast discovered 2 key points, sows with cubs are seen clamming more than you would expect based on their numbers, and large boars are rarely seen on the beach. In fact, in the study above, 45% of the bears observed were females with cubs, and 55% were "unidentified gender and smaller (< 500 lbs) bears". Why large boars don't frequent beaches given the higher protein content is unknown. Some scientists hypothesized that because of their large size, the energy required to walk that far for a smaller amount of food may not be worth it for a large boar. Why females with cubs are found more seems fairly easy to explain. First, lactating females need more and richer foods, as do their rapidly growing cubs. Second, for a Mother bear to find an area to forage where the main cub predator, large boars, is absent makes life easier on them.
Good question, the easy answer is both. Both the large bears you will see in Alaska and the smaller bears you might have seen at Yellowstone are not only the same species, but the same subspecies, Ursus arctos horribilis. The brown bears found on Kodiak are considered a different subspecies, primarily because of some differences in the skull. In general, bear biologists and those interested in bears tend to call the bears in Alaska brown bears, and those found in the Northern Rockies of the United States and Canada Grizzlies. The term grizzly comes from the silver tipped hair of the bears in the Rockies.
However, based on sizes, diet, and home ranges some biologists have recommended designating 3 groups of brown bears whose ranges are mapped below. The 3 groups described from studies of 25 different populations were the Coastal, the inland, and the barren ground brown bears. In Alaska, both in Katmai and Silver Salmon Creek, you are seeing the Coastal Brown, the largest of any of the brown bears found in North America or the world. There are large coastal brown bears in the former Soviet Union in Kamchatka as well.
(From Effect of energy availability, seasonality, and geographic range on brown bear life history by Steven H. Ferguson and Philip D. McLoughlin; Ecography, Copenhagen, 2000.)