While it is important to know the overall number of animals in a population, there are other factors that can be monitored that help us understand how the herd is changing. This information helps to support management decisions. The composition or categories of caribou that make up the herd and how these numbers relate to one another is an important part of the puzzle.

Each year, biologists monitor the Porcupine Caribou herd by flying aerial surveys at key times of the year to see what is happening with the following categories of Porcupine Caribou:


The number of adult cows in a population can make the difference between a herd growing or declining. The number of cows is always the basis for comparing the number or the ratio of calves or bulls in a population.


These are caribou less than a year old. It is important to know how many calves are born each spring. On average, biologists see about 80 calves born to every 100 cows. Of those calves, about 85% of them reach one month of age.

Biologists then monitor to see how many live to be about nine months old. If they can reach that age, the chance of them surviving to be a breeding adult is high. Having an idea of the number of caribou that will likely reach adulthood is another way managers can estimate what will happen to a herd over the next few years.


It helps to know the number of bulls in relation to the number of cows in a herd in order to understand if there will be enough bulls to mate with cows each year and to determine the impact of a bull oriented harvest. A healthy population will have at least 35 bulls per 100 cows in a herd. Researchers estimate the Porcupine Caribou herd has around 60 bulls per 100 cows.