Effective implementation of age restrictions increases selectivity of sport hunting of the African lion

Abstract

Sport hunting of wildlife can play a role in conservation but can also drive population declines if not managed sustainably. Previous simulation modelling found that large felid species could theoretically be hunted sustainably by restricting harvests to older individuals that have likely reproduced. Several African countries currently use age‐based hunting for lions although the outcomes have yet to be evaluated in a wild population. Here we provide the first empirical evidence that a system of incentives sufficiently encouraged age‐based hunting and reduced offtake of a wild felid, thereby reducing the potential risk of unsustainable hunting on a threatened species. We examined long‐term hunting data and the lion population trend in Niassa National Reserve, Mozambique. To incentivise hunter compliance, a “points” system was developed, which rewards operators that harvest lions older than the 6‐year minimum trophy age recommended for sustainable hunting and penalises operators that hunt “underage” lions (<4 years). A key component of this system is the ecological application of key physical traits that predictably change with age in order to estimate (by hunters) and validate (by authorities) trophy individuals’ ages pre‐ and post‐mortem, respectively. Analysis of 138 lion hunts and 87 lion trophies from 2003 to 2015 revealed that after enforcement of age restrictions in 2006, hunters shifted harvests to suitably aged lions (>6 years), from 25% of offtakes in 2004 to 100% by 2014. Simultaneously, the number of lions and percentage of quota harvested decreased, resulting in lower lion offtakes. Following an initial decrease after enforcement of the ageing system, the percentage of hunts harvesting lions stabilised, demonstrating that hunters successfully located and aged older lions. Synthesis and applications. Evidence suggests that age restrictions combined with an incentive‐based points system regulated sport hunting and reduced pressure on the lion population. We attribute the successful implementation of this management system to: (1) committed, consistent enforcement by management authorities, (2) genuine involvement of all stakeholders from the start, (3) annual auditing by an independent third party, (4) the reliable, transparent, straightforward ageing process and (5) the simple, pragmatic points system for incentivising hunter compliance. Our study demonstrates that the use of age restrictions can increase the selectivity of sport hunting and lower trophy offtakes to reduce the possibility of unsustainable sport hunting negatively impacting species populations in the absence of reliable estimates of population size. It must be noted, however, that there was no measurable change in the lion numbers over the past decade that could be attributed to the implementation of this policy alone.

Assessing the performance of index calibration survey methods to monitor populations of wide‐ranging low‐density carnivores

“…The complexity of using the call‐up method is further increased by the recommendation to calibrate a site‐specific response rate by testing with >20 groups of lions, something which is very rarely achieved. For example, in Niassa Reserve, where some of the most extensive call‐up surveys have been conducted—with up to 153 call‐up stations per survey conducted within a year—only 16 prides in total responded (Begg, Miller, & Begg, ). Belant et al () found that lions habituate to call‐up sounds very quickly and that temporal and spatial variation of broadcasted sound did not reduce this habituation (Belant et al, ), which would imply that areas used for calibration cannot subsequently be surveyed.…”

Quantifying lion (Panthera leo) demographic response following a three-year moratorium on trophy hunting

“…Incentive-based quotas have been implemented inside reserves wherein the harvest of a suitably-aged male results in a quota increase for the following year, sometimes quite significantly [ 46 ]. However, reactive quotas still carry the risk the population can decline at a faster rate than the harvest can be adjusted, particularly when hunters increase their effort to confront scarcity [ 46 ]. Secondly, rewarding concessions with higher quotas after harvesting older male could reinforce vacuum effects in lion populations straddling strong gradients of protection.…”

“…Around the world, many conservation and natural resource agencies advocate using adaptive management when deciding how to conserve wildlife and ecosystems in the face of uncertainty. A foundational principle of adaptive management is ongoing monitoring of systems as regulations change to generate valuable insight into system functioning that can feedback into future policy formation [ 46 ]. Strong evidence that trophy hunting was driving population declines and skew in lion demography resulted from intensive monitoring of the South Luangwa lion population before and after the hunting moratorium.…”

Horn growth variation and hunting selection of the Alpine ibex

“…Trophy hunting has been found to trigger phenotypic changes in ungulate populations, such as reductions in body weight and size, as well as the dimension and symmetry of horns (Coltman et al, 2003;Douhard et al, 2016;Garel et al, 2007;Pérez et al, 2011;Pigeon et al, 2016). To avoid evolutionary consequences in managed populations (Allendorf, England, Luikart, Ritchie, & Ryman, 2008), harvests should not impose a strong selection (Begg, Miller, & Begg, 2017;Festa-Bianchet, 2016). Yet, it is still debatable (Ripple, Newsome, & Kerley, 2016) whether a properly managed trophy harvest can be used as a conservation tool for maintaining biodiversity (Di Minin, Leader-Williams, & Bradshaw, 2016).…”