PSU Deer Study

I am always amazed at how well deer survive in Pennsylvania. Now that the 2017 hunting season has ended I pulled together all our capture and mortality data from 2013-2017 to estimate survival and harvest rates.

To date, we have followed 357 radio-collared deer for a total of 2,884 monthly intervals during February through September of 2013-2017. In all those 2,884 intervals only 27 deaths occurred!

That translates to a monthly survival rate of 0.9906.  That’s right, deer have a greater than 99% chance of surviving each month outside the hunting seasons. 

I even looked to see if survival might vary monthly since we’re talking about winter, spring, and summer.

For males, no bucks have died over the past 5 years during May-August. The remaining monthly survival rates ranged from 0.963 – 0.990.

We have had females die every month of the year, but their monthly survival rates were still all greater than 0.978.

Because of these high survival rates, cumulatively over the 8-month period of February-September, 91.9% of deer survive. In other words, fewer than 1 in 10 die outside the hunting season.

Statistically, there is no difference between males and females. In the graph below, the 95% confidence intervals (a measure of the precision of our estimates) are wider for males because we monitor half as many males as females (females are more important to study because they are the ones that make more deer!).

The reason we estimate survival from February to September is because some deer are only ear-tagged and we need to be able to estimate the probability that an ear-tagged deer is still alive at the start of the hunting seasons in October.

Although few deer die between capture and the hunting season, we still account for this mortality with our ear-tag data to estimate harvest rates. 

February through September is easy living for deer in Pennsylvania.  But what about those hunting seasons?  Is that where the dying part comes in?  You’ll soon see.

-Duane Diefenbach

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