Regulating trophy hunting: antlers or reproduction?

I proudly present a guest post from
Rocío Pozo (VM, MSc)
PhD candidate, Department of Zoology
University of Oxford
https://zoo-e2d.zoo.ox.ac.uk/ro_website/
http://www.ecoexistproject.org/reporting-back/scientific/meet-rocio-pozo/

 

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ResearchBlogging.org
Pozo, R., Schindler, S., Cubaynes, S., Cusack, J., Coulson, T., & Malo, A. (2016). Modeling the impact of selective harvesting on red deer antlers The Journal of Wildlife Management DOI: 10.1002/jwmg.21089

Imagine you are a trophy hunter. The red deer hunting season has just opened and you are ready to go out and get those trophies you have been waiting for. What would be the first question you would ask yourself? Exactly! What is the hunting quota?

(c) Jeremy Cusack (www.jeremycusack.com)

(c) Jeremy Cusack (www.jeremycusack.com)

Well, you are definitely not alone in wondering this. Although hunters and policy makers have been asking the same question for decades, the answer remains unclear. Depending on the population under harvest and the characteristics you are interested in preserving/modifying in the population (also called ‘traits’ in evolutionary terms), different answers could be put forward. So, let’s think a little bit more about what do we want when harvesting wild (red deer, for the purposes of this blog) populations.

A good start would be to maintain the population in the wild, that is, not making it disappear after a single hunting season. Therefore, a sustainable hunting quota would be ideal. In addition, trophy hunters tend to want to selectively hunt the biggest trophies (i.e. males with the largest antlers) every year, but still have enough males to harvest in the future. Both sounds like a good plan, but they are difficult to achieve, don’t you think?

For centuries trophy hunting has imposed artificial pressures on wild deer populations by selectively removing males from the population, and consequently imposing an unnatural mortality rate on adults. Removal of males with large trophies is likely to lower their reproductive value and the mean trophy size within the population. However, antler size response to trophy hunting has not been consistent across species, and in many cases environmental factors play a much stronger role on mean antler size than selective harvesting.

Considering the above, we would ideally like to test different harvesting quotas to assess the consequences on antler size and male fitness. But how do you do this without having to harvest males in the wild? To answer this question we used a demographic model to assess the effects of hunting rates (of 10%, 20% and 50%) on the male population and determine demographic effects on deer antler size and male reproductive value. Our results show that trophy hunting does not modify antler size, as much as male reproductive value. Also, our findings lead us to the tentative conclusion that trophy hunting rates between 10% and 20% are unlikely to have a substantial impact on male red deer antler size.