Sizing-up trophy antlers

by Sarah Snetsinger | June 9, 2022
a late-season buck peeking

As an Ontario Federation of Anglers and Hunters (OFAH) Fish and Wildlife conservation intern, I set out to learn if harvesting large white-tailed deer with impressive antlers causes selection against the very characteristics that make them trophy worthy, reducing the number of large deer in future generations.

My research to answer this question involved wading through dozens of academic papers before writing a report of my own. I concluded the answer is no, and here’s why.

Potential remains

While removing large bucks from the population might mean there are more small-antlered bucks in that instant, over time, the potential for large antlers remains. This has to do with the environmental factors that impact antler size. It’s important to distinguish between genotype — the genetic potential for a characteristic, versus phenotype — the physical expression of that trait. While the genotype is written in stone, the phenotype can change based on environmental factors, such as condition of the mother during gestation, nutrition that specific year, and the health of the individual.

Livestock production has long been able to produce desired characteristics in captive species by careful selection of breeders over generations, but wild deer populations cannot be controlled that carefully. If the phenotype doesn’t accurately reflect the genetic potential, then selecting large bucks for their appearance won’t have a significant impact on the gene pool.

Diversity in dads

Concerns over the loss of large bucks to the reproductive pool are often based on the assumption that only these large males are breeding in a normal population and removing them allows inferior males to breed and dilute the gene pool. Recent studies using genetic analysis of paternity have shown that offspring are sired by a more diverse group of bucks.

Males who employ alternative tactics for reproduction can experience success because sometimes dominant males are geographically distant from estrous (sexually receptive) females, there are too many females for one dominant male, or dominant males might be in poorer condition closer to the end of the rut. In litters of more than one fawn, there can even be more than one father if two bucks breed the same doe.

Young bucks factors, too

Younger males that breed might not have grown to their potential size, and therefore won’t be targets of trophy hunters yet, but still have the chance to pass on their genetics to future generations.

It’s also important to remember that females contribute half of the genetic information to their offspring, so regardless of impacts on the male population, the female half persists. Even if large females are harvested more, it’s unclear if their size is indicative of genotype for large antlers in offspring.

Hunter preference matters

What it really boils down to is that here in Ontario, not every hunter is intent on harvesting the largest buck. Harvest is limited by hunter preference, the chance of encounter, and deer behaviour, so the percentage of bucks being selectively harvested is much lower than the total harvest percentage. Even if there are some hunters who filter through their options like their trail cam is a catalogue and choose the biggest one, their impact on the overall genetic potential for large antlers in the population will be minimal.

It would only be in very certain cases that evolutionary change is possible through selective harvest. For example, an island population with no immigration, abundant food (so the phenotype accurately represents the genotype), and a strong hunting pressure over a long period of time. This is something we just don’t see in Ontario with current hunting regulations and common practices.

Originally published in the June 2021 issue of Ontario OUT of DOORS magazine. 

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