Identifying Sex
As a general rule of thumb, females and subadult grizzly bears generally tend to be lighter in color than adult male bears (Jonkel 1993). Male grizzly bears have a “blocky” like appearance, with wider noses, bigger heads, and bodies than females. A parallel could be drawn to female and male Labrador retrievers; males have blocky heads, and typically have larger bodies.
As a general rule of thumb, females and subadult grizzly bears generally tend to be lighter in color than adult male bears (Jonkel 1993). Male grizzly bears have a “blocky” like appearance, with wider noses, bigger heads, and bodies than females. A parallel could be drawn to female and male Labrador retrievers; males have blocky heads, and typically have larger bodies.
Figure 1: Weights documented by age class between spring and fall for female grizzly bears. Data compiled and used to create this chart was obtained via Blanchard 1986, and later published again in Jonkel 1993.
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Figure 1: Weights documented by age class between spring and fall for male grizzly bears. Data compiled and used to create this chart was obtained via Blanchard 1986, and later published again in Jonkel 1993.
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Photo: Notice the differences in the physical appearance of a male grizzly bear (bottom) versus a female grizzly bear (top). Color variation, breadth of the head (zygomatic arches) and body size. However, sometimes size and color are poor and inconsistent indicators of sex.
Photo courtesy of Kerry Gunther/NPS (bottom) and Yellowstone National Park/NPS (top)
Estimating Age based on tooth wear
During capture and immobilization procedures, it use to be standard for researchers and scientists to extract a tooth to age a bear. The most reliable method to age a bear is by extracting a molar (PM1) and examining the cementum layers microscopically. However, extracting a tooth is not always practical, nor preferred by many wildlife professionals. Immobilization and capture already presents a certain level of invasive procedures, and during such activity, it is important to minimize unnecessary invasive and otherwise stressful procedures at the bears expense. In the field, researchers and wildlife professionals can approximate and estimate the age of a bear by examining the physical state of their dentition (Palmisciano 1988, LeCount 1986). There are, however, downfalls to this method because of the variability of tooth wear, generally related to diet. Grizzly bears show great plasticity in their diets. It is theorized that bears residing in habitats with dry and rocky regions, where roots and tubers are consumed, that teeth can receive greater wear because of the abrasive nature of soils. In addition, it has been noticed that bears that reside and are handled in heavily managed ecosystems (Yellowstone, Glacier, etc.) have a higher incidence of broken or damaged teeth (Jonkel 1993). Some of these can be attributed to damaged caused during trapping operations with culvert traps, while some may be credited to natural processes of “wear and tear” on dentition.
During capture and immobilization procedures, it use to be standard for researchers and scientists to extract a tooth to age a bear. The most reliable method to age a bear is by extracting a molar (PM1) and examining the cementum layers microscopically. However, extracting a tooth is not always practical, nor preferred by many wildlife professionals. Immobilization and capture already presents a certain level of invasive procedures, and during such activity, it is important to minimize unnecessary invasive and otherwise stressful procedures at the bears expense. In the field, researchers and wildlife professionals can approximate and estimate the age of a bear by examining the physical state of their dentition (Palmisciano 1988, LeCount 1986). There are, however, downfalls to this method because of the variability of tooth wear, generally related to diet. Grizzly bears show great plasticity in their diets. It is theorized that bears residing in habitats with dry and rocky regions, where roots and tubers are consumed, that teeth can receive greater wear because of the abrasive nature of soils. In addition, it has been noticed that bears that reside and are handled in heavily managed ecosystems (Yellowstone, Glacier, etc.) have a higher incidence of broken or damaged teeth (Jonkel 1993). Some of these can be attributed to damaged caused during trapping operations with culvert traps, while some may be credited to natural processes of “wear and tear” on dentition.
If there is ever any doubt to the species being handled, you can simply measure the length of the last upper molar (M2). Black bears have an M2 that is < 1 1/8 inches in length; grizzlies have M2 that are > than 1 1/8 inches in length.
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The size of a bear can be misleading, especially during the fall when hyperphagia is in full swing. While size may be misleading and allow an individual to confuse a cub or yearling to a subadult, distinct dentition provides a more definitive answer. Listed are dental criteria based upon bear age (Palmisciano 1988):
When examining dentition after a bears first year, it is particularly important to note and observe the condition and color of the canines and incisors. Over time, permanent teeth will change color and yellow, or turn brown; they will wear flat or begin to round, crack/split, sometimes even breaking completely off.
- Cub (during spring)
- Deciduous teeth, various stages of eruption
- Molars not yet present
- Middle permanent incisors (I1) starting to erupt (maybe)
- Canines deciduous
- Cub (during mid-summer)
- Molar 1 and incisor 1 nearly erupted
- Incisor 2 tips visible in gums
- Cub (during fall)
- Canines are deciduous, just starting to erupt
- Molars 1 & 2 plus all incisors are mostly erupted
- Molar 3 on the lower jaw will be absent, or barely even visible
- Yearling (during spring)
- Will have all permanent teeth
- Canines and 3rd molar = partially erupted
- Best gauge = canine which will be 1/8 to ½ erupted
- Yearling (during mid-summer)
- Lower 3rd molar = mostly grown
- Canine = ½ to ¾ erupted
- Yearling (during fall)
- Teeth appear smooth, unworn
- Canine = 7/8 erupted
When examining dentition after a bears first year, it is particularly important to note and observe the condition and color of the canines and incisors. Over time, permanent teeth will change color and yellow, or turn brown; they will wear flat or begin to round, crack/split, sometimes even breaking completely off.
- 2-4 year-olds
- Smooth, white teeth
- Canine tips, incisors square off; cusps visible
- 5-6 years-old
- Canines flattened tips
- Incisors worn flat
- Middle incisors = cusps still present with dentine spots
- Most teeth stained yellow
- 7-10 years-old
- Canines flattened and yellow, some hairline cracks
- All incisors worn flat
- Two lower incisors show more wear
- 11-15 years-old
- Canines discolored, flattened (cracked or broken)
- Incisors visible barely above the gum line; worn straight across
- Two lower middle incisors, worn, slightly rounded (maybe broken)
- 15 year-old
- Extremely worn & discolored, broken front teeth
- Molars intact, slight wear, heavily stained dark yellow, brown hues
- Canines may be broken or rounded smooth at gum line
- All incisors usually worn straight across at gum line
- Lower incisors have rounded crowns
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Bears that are 15 years-old and older, especially males, are generally quite large and surprisingly healthy. The oldest bear captured was 32 years-old, in the Cabinet Mountains (Kasworm & Manley 1988). The bears teeth were broken and its incisors were worn down to right above the gum line, however, the bears general body assessment and condition was still good. While senior bears (15+) may have more difficulty biting, shearing and grinding up food opposed to younger bears, that is thought to be possibly compensated by a senior bears experience and efficiency when finding and locating a food source. Ultimately, the natural life of bears depends on their dental health (Jonkel 1993)
Photo: Black bear (22055) cranium recovered in Grand Teton National Park. This bear was 23 years old and killed by another bear at an elk carcass during 2008. The dentition of this bear (not visible) is deformed.
(Tyler Brasington 2017)
Sources Cited:
Blanchard , B. M. (1986). Yellowstone grizzly size/growth patterns. International Conference of Bear Research and Management. 7:21-25
Elbroch, M. (2006). Animal skulls: a guide to North American species. Stackpole Books.
Jonkel, J. L. (1993). A manual for handling bears for managers and researchers. US Fish and Wildlife Service, Office of Grizzly Bear Recovery.
Kasworm, W., & Manley, T. L. (1988). Grizzly bear and black bear ecology in the Cabinet Mountains of northwest Montana. The Department.
LeCount, A. L. (1986). Black bear field guide: a manager's manual (No. 16). Research Branch, Arizona Game and Fish Department.
Palmisciano, D. (1988). Dental characteristics relative to age in grizzly bears. Montana Dep. Fish, Wildlife and Parks working paper. Unpubl. Bozeman.
Blanchard , B. M. (1986). Yellowstone grizzly size/growth patterns. International Conference of Bear Research and Management. 7:21-25
Elbroch, M. (2006). Animal skulls: a guide to North American species. Stackpole Books.
Jonkel, J. L. (1993). A manual for handling bears for managers and researchers. US Fish and Wildlife Service, Office of Grizzly Bear Recovery.
Kasworm, W., & Manley, T. L. (1988). Grizzly bear and black bear ecology in the Cabinet Mountains of northwest Montana. The Department.
LeCount, A. L. (1986). Black bear field guide: a manager's manual (No. 16). Research Branch, Arizona Game and Fish Department.
Palmisciano, D. (1988). Dental characteristics relative to age in grizzly bears. Montana Dep. Fish, Wildlife and Parks working paper. Unpubl. Bozeman.