Uncertainty and precaution in hunting wolves twice in a year

Abstract

When humanity confronts the risk of extinction of species, many people invoke precautions, especially in the face of uncertainty. Although precautionary approaches are value judgments, the optimal design and effect of precautions or lack thereof are scientific questions. We investigated Wisconsin gray wolves Canis lupus facing a second wolf-hunt in November 2021 and use three legal thresholds as the societal value judgments about precautions: (1) the 1999 population goal, 350 wolves, (2) the threshold for statutory listing under the state threatened and endangered species act, 250 wolves; and (3) state extirpation <2 wolves. This allows us to explore the quantitative relationship between precaution and uncertainty. Working from estimates of the size wolf population in April 2021 and reproduction to November, we constructed a simple linear model with uninformative priors for the period April 2021-April 2022 including an uncertain wolf-hunt in November 2021. Our first result is that the state government under-counted wolf deaths in the year preceding both wolf-hunts. We recommend better scientific analysis be used when setting wolf-hunt quotas. We find official recommendations for a quota for the November 2021 wolf-hunt risk undesirable outcomes. Even a quota of zero has a 13% chance of crossing threshold 1. Therefore, a zero death toll would be precautionary. Proponents for high quotas bear the burden of proof that their estimates are accurate, precise, and reproducible. We discuss why our approach is transferable to non-wolves. We show how scientists have the tools and concepts for quantifying and explaining the probabilities of crossing thresholds set by laws or other social norms. We recommend that scientists grapple with data gaps by explaining what the uncertainty means for policy and the public including the consequences of being wrong.

Uncertainty and precaution in hunting wolves twice in a year: Reanalysis of Treves and Louchouarn

“… Simulation results predicting wolf population size in April 2022, assuming an uncertain fall harvest of 0–600. The three horizontal lines represent population thresholds of 350 (1999 population goal), 250 (relisting threshold), and 2 (extirpation) considered in Treves and Louchouarn [ 2 ]. …”

“…Using the parameter values from TL, and assuming the TL specification for the initial population size, as estimated by the occupancy model, the predicted spring 2022 population size was 500 (95% credible interval = 218–784), or approximately 51.5% of the estimated spring 2022 population. When TL recalculated projections based on their corrected pup mortality as described in the comment on TL [ 2 ], the predicted population under a zero-harvest scenario was 648 (range 291–1017), or about 67% of the estimated spring 2022 population, and about 2% of predicted values crossed below the threshold of 350 wolves (see 7 Aug 2022 online comment on [ 2 ]). Although TL stated in their comment that their conclusions did not change after the correction, we note that this probability was substantially lower than before the correction ( Table 2 ).…”

“…Although the mean is 0.2, the most likely value is 0.17, and the 97.5th percentile is 0.49. Moreover, the estimate is incorrect, and TL posted a comment on their paper (7 Aug 2022) acknowledging the error, stating therein that their conclusions nonetheless remain unchanged [ 2 ]. In their correction, TL cited S = 0.29 (range = [0.14–0.58]) as mean (min/max) from Table 6.3 in Wydeven et al [ 4 ], but they do not define this distribution analytically.…”

“…Treves and Louchouarn [ 2 ] (hereafter TL) urged precaution in harvesting wolves twice in a calendar year, and suggested that a zero death toll would be precautionary. TL used a simple one-step population model to predict wolf population size in Wisconsin, given a range of harvest scenarios, including a zero harvest scenario, for a hypothetical fall 2021 hunting season.…”

Simulated effects of roadkill and harvest on the viability of a recovering bobcat population

“…A quota‐based implementation for harvest, whereby there is pre‐defined number of animals that can be harvested in a set period, could reduce harvest bias; however, this is not a guarantee because of uncertainty in a number of factors (e.g., potential for compensatory reproduction due to harvest, additive harvest and roadkill, fluctuating distribution of age classes, environmental conditions, hunter and trapper effort). A quota‐based approach can also introduce other concerns such as quota overshoot if there is delay in reporting harvest as seen from recent cases of new hunting and trapping seasons (i.e., for wolves in WI), in which the quotas were rapidly reached and surpassed because of a lag in communication between the hunter and trapper communities and the management agency, and uncertainty in wolf population and underestimation of wolf deaths in the year prior to the 2021 harvest (Gilbert et al 2022, Treves and Louchouarn 2022). Thus, if a quota is implemented, including an expected overshoot in the initial quota as a precautionary measure would be advised.…”