How Does Illegal Hunting Affect Species Decline?

At the moment, there is little knowledge available on the impact of illegal recreational hunting. The scale of the problem could be so rare as to make little demographic or environmental difference, or it could have severe consequences for wildlife populations. This study sought to understand the scope and impact of illegal recreational hunting in Idaho, United States. 

As many animal advocates are aware, the use of wild animals for various purposes is a global phenomenon and is often legal. In some situations, the hunting of wildlife is considered by some to be beneficial to conserving natural biodiversity in a given area. On the other hand, illegal pursuits such as the killing of ungulates (hooved animals) for traditional medicine has resulted in a dramatic decrease in population for some species. The killing of wildlife in order to protect livestock from predators has also caused the collapse of some scavenger populations. 

The ecological consequences of hunting animals for recreation, as opposed to other purposes, are poorly understood. When a particular group of animals such as colonial rodents are recreationally hunted, their bodies are left in the field, providing a food source for scavengers. As the scavenger populations increase due to the change caused by human activity, other species may suffer a decline. The lead in bullets used to kill animals can also find its way into ecosystems through the soil. 

Commonly targeted species for recreational hunting in the United States include coyotes, marmots and jackrabbits. In the ~484 km2 area where the study was conducted, a conservative estimate of 152,720 ground squirrels are shot during each 18-week season (from March to June), which represents around 9% of all the ground squirrels living in that area. The amount of lead ammunition dropped on the land is estimated to be a whopping 190kg per year.

The laws which regulate recreational hunting vary by state. In Idaho, a hunting license is required which enables hunters to kill unlimited numbers of small mammals. However, it is forbidden to hunt some species of squirrel. Neighboring states have different regulations which may directly contradict those of Idaho, and sometimes no license is required to hunt unlimited numbers of some wildlife species. 

The researchers collected data on the illegal killing of wildlife in conservation areas in Idaho. These areas are hotspots for recreational hunters, with the landscape changing from shrub-steppe to grasslands as a result of their activities. During hunting season, hundreds of hunters may occupy a few kilometres of roadway. Species which are killed illegally include large birds and reptiles. The study focused on long-billed curlews, who make their nests in grassy areas. The researchers captured these birds and attached each one with a device which allowed their movements to be tracked. When the device appeared to stop moving, indicating that the bird had died, its body was retrieved and sent to the Idaho Department of Fish and Game Wildlife Health Laboratory to determine the cause of death.

Of the 21 birds who were tracked, 7 (33%) were shot illegally. A further 39 protected birds were found dead and, of these, 23 (59%) were shot. There was also evidence of illegally killed reptiles such as rattlesnakes and gopher snakes. The locations of the dead animals were ranked according to how frequented they were by hunters. The researchers wanted to understand whether the illegal hunts were being carried out by hunters who were killing protected and unprotected species indiscriminately, or whether the illegal activity was caused by different people. 

The illegal killing of birds was found to be strongly associated with areas where there is a prevalence of recreational shooting. Some of the protected species, while not targeted by hunters, were nevertheless killed by human infrastructure (e.g electrocuted by power lines or run over by traffic). The researchers concluded that the illegal killing of protected species during hunts is opportunistic rather than direct. Hunters may not set out to target protected species but do so anyway if they are there, or if there is an accidental targeting of a species who the hunter does not realize is protected. 

The ecological consequences of the illegal killing of protected wildlife turned out to be hard to assess in the study. However, the findings suggested that the overall rate of illegal shootings contribute to the long-term decline of long-billed curlews, who live long and reproduce slowly. Interviews with recreational hunters reveal a strong disdain for illegal shooting, which may suggest that some of the targeting is unintentional, or carried out by a few individuals. On the other hand, other studies have suggested that illegal hunting carried out by recreational hunters is a widespread problem and can result in strong persecution of offenders. 

The study provides a starting point for looking into the long term impact of this problem in more depth. Advocates might use the disdain of recreational hunters towards illegal shootings to open up a dialogue over whether recreational hunting is morally valid in general, regardless of the legal status of individual species which, in any case, seems to be at the discretion of individual states.