Using cougar tooth data to understand the cougar age structure on the landscape
It may be interesting to guess the age of the cougar you harvest based on the size and sex. It might be a kitten, sub-adult — less than two-years-old — or an adult. But, you (and we) can’t be sure about an animal’s age without closer inspection and tooth data.
Washington hunters are required to bring harvested cougars to WDFW for inspection and sealing. Sealing is a process where we put a tag in the pelt to show that the cougar was harvested legally.
The first part of our inspection is to determine if the animal is male or female. One good indicator is if there is a black spot on their back-end. If so, it’s almost certainly a male. If the animal is a juvenile and has not sexually matured, this may not be as obvious as you’d think.
In addition to identifying sex, we also try to determine their age by looking at their teeth,
Teeth can tell you a lot about age. Kittens replace their canine teeth at a specific age. And, once adult teeth are in, they continue to grow. The size of their teeth, or, more accurately, the amount that protrudes from the gums, can help us differentiate adults from sub-adults.
This process is called “field aging” because it’s a process that uses averages, it’s generally — but not always — accurate. Factors that can cause a biologist to misidentify the age of a cougar can be due to experience, the condition of the animal being inspected, and how long it has been since the animal was killed.
The condition of the gums is probably the biggest factor, and can be altered by freezing and thawing, which can occur if a hunter has frozen the hide and skull before bringing it for inspection.
Although field aging provides enough accuracy for us to manage cougar harvest guidelines and hunting closures, we can measure our accuracy assumptions by confirming the actual ages of harvested animals. That’s why we require a tooth from your cougar harvest. We send that tooth to an independent lab which uses a highly accurate aging method called cementum analysis.
As an animal ages, its teeth grow layers of cementum, a thin layer of material that helps cement roots in the gums. When the tooth is shaved (like a piece of garlic), stained, and placed under a microscope, lab staff can actually count these layers like tree rings to estimate age.
We submit teeth to the lab throughout the season, then results are returned to us several months later. Because of the time it takes to analyze this data, we are not able to utilize tooth aging for in-season decisions — instead, we use field aging.
But, in addition to helping us gauge the accuracy of our field aging assessments, tooth data also provides insight into the age structure of harvested animals. In most cases, the data mirrors cougar age structure on the landscape. We then use this information to inform our understanding of the cougar age structure in an area.
Hunters are also curious about the age of the animals they’ve harvested. Not only do they get to observe the inspection process and conclusions of our biologists, but they can use their WILD ID to access those ages about six months later. Field aging data can also validate cementum analysis logs too.
Earlier this year, we inaccurately logged some tooth ages associated with cougars and bears harvested in some PMUs. The discrepancy was caused by an automated data download error that has since been corrected. Thank you to the hunters that noticed a discrepancy between the field aging and tooth aging data sets and helped us correct the numbers prior to our annual analysis.
Hunters can also find the ages of deer, cougar and bear that they’ve harvested on WDFW’s Tooth Age Lookup page. And, hunters, in addition to sample submission and sealing, don’t forget to fill out your harvest report.