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Evaluating how lethal management affects poaching of Mexican wolves

Naomi X Louchouarn¹, Francisco J Santiago-Ávila^1,2, David R Parsons²

¹Nelson Institute for Environmental Studies, University of Wisconsin-Madison, Madison, WI, USA.

Royal Society Open Science

|May 7, 2021

Summary

Reduced protections for Mexican grey wolves increased their disappearances by 121%, supporting the facilitated illegal killing hypothesis. This suggests current wildlife policies may inadvertently encourage poaching.

Area of Science:

Conservation Biology
Wildlife Management
Ecology

Background:

Illegal killing (poaching) is a primary threat to large carnivore survival globally.
The impact of lethal management policies on poaching rates remains debated, with two opposing hypotheses: 'killing for tolerance' versus 'facilitated illegal killing'.

Purpose of the Study:

To investigate the effect of policy changes reducing protections on poaching incidence of Mexican grey wolves (Canis lupus baileyi) in the USA.
To test the 'killing for tolerance' and 'facilitated illegal killing' hypotheses regarding lethal management policies and poaching.

Main Methods:

Utilized advanced biostatistical survival and competing risk analyses on individual resighting and mortality data of collared Mexican wolves.
Employed Bayes factors to rigorously assess the strength of evidence for competing hypotheses.

Main Results:

Found inconclusive evidence for a decrease in reported poaching following policy changes.
Observed a 121% increased likelihood of Mexican wolf disappearances during periods of reduced protection compared to stricter protection periods.
Noted minimal changes in legal removals by management agencies.

Conclusions:

Strong evidence supports the 'facilitated illegal killing' hypothesis, indicating reduced protections may increase illegal killing of Mexican grey wolves.
No support was found for the 'killing for tolerance' hypothesis.
Results suggest a need to revise US policies on environmental crimes and endangered species protection to improve effectiveness against human-caused mortality in wildlife.

Keywords:

Canis lupus baileyi conservation endangered species large carnivore policy signal survival analysis

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