Nuisance Wildlife in Pest Management

March 2025 Issue: 

By: Schuyler Smith

When you think of the common pests that customers of FSS typically experience in and around their facilities, bats, birds, opossums, raccoons, and skunks may not come to mind, but they should. Nuisance wildlife must always be considered as part of a comprehensive risk assessment, and the reasons why are not so dissimilar from other pests which may be more prevalent. The most common of nuisance wildlife species listed above are found throughout the entire midwestern United States and can always pose a real threat to our customers by vectoring zoonotic diseases, causing structural damage, disrupting operations, and contaminating products or equipment.

Basic Biology

For the purposes of this article, we are going to focus on the three species that the author has most recently encountered in the field, bats, raccoons, and skunks. We will start by going over some basic biology as it is important to know what times of the year these animals are most likely to cause issues which will be in close association with breeding seasons. Most of the issues our customers will experience with nuisance wildlife will occur either when animals are establishing a nesting site or staking a claim on locations with abundant resources.

Raccoons

Raccoons will typically mate between January and March with a litter of 2-5 “kits” being born after around 65 days of gestation. Kits are then usually weaned after 16 weeks with the juvenile group dispersing in the Fall, females of the litter may stay closer to the home range in which they were born while the males can travel over ten miles away from the range. In the wild, the life expectancy of raccoons is between 2-3 years but could be many more with abundant resources and sheltering opportunities. While these animals are typically nocturnal, it is not uncommon for them to forage during daylight hours, especially when there are limited resources or high competition for said resources. Raccoons are omnivorous with a balanced diet of vertebrates, plant material, and invertebrates but will often develop a preference for those food sources that are the most easily accessible or prevalent.

Skunks

Skunks are most commonly associated with their defense mechanism of spraying a foul-smelling liquid from their anal glands to ward off predators and more commonly, rejected mates. This means that our customers are at a higher risk of being exposed to the offensive odor when females are burrowing under or near their facilities to establish dens and raise young, we may have a situation where a skunk has sprayed with no human or predator interaction at all. Skunks will usually birth their litters of 4-7 kits in May following a 66 day gestation period, the young will then typically stay with their mother until they are of breeding age around one year later. It is important to note that the young skunks have much less control over their scent glands and are significantly more prone to spray when startled by any signs of danger. Although these are omnivorous animals, they mostly prefer to feed on insects and plant materials making resource reduction difficult in many instances.

Bats

The midwestern United States are home to several species of bats, some of which with a higher predilection for roosting inside our customer’s facilities. Due to bat’s incredibly important role in insect mitigation in our ecosystems (estimated to save the agricultural industry billions of dollars annually on damaged crops and pesticide usage), virtually all species have protected statuses in every state. Most species of bats will mate in the Fall, directly before entering hibernation. The female can then delay fertilization for several months until the Spring when their food sources once again become plentiful. Following six to nine weeks of gestation, the female will usually give birth to only one pup although bats do tend to have a significantly higher life expectancy compared to other mammals and can have many successful births during their lifetimes. Our bat populations have also been ravaged by White Nose Syndrome, a fungal infection which spreads throughout colonies during hibernation and can lead to fatalities for up to 90% of the group. Should WNS be suspected in a hibernating group, local wildlife officials should be notified immediately.

Zoonotic Diseases

Probably the most significant danger posed by nuisance wildlife is the potential to transfer zoonotic diseases. These diseases (also known as zoonoses) are infections that can pass to humans from wildlife by direct contact (bites, scratches, or ingestion) or indirect contact (mosquitoes, ticks, contact with infected urine or feces, contamination). While many of these infections result in little more than moderate cold or flu-like symptoms, there are several parasites, bacterial, and viral infections which can prove to be fatal in humans such as Rabies, Coronaviruses, and Hantavirus. Virtually all species of wildlife have the capacity to transfer multiple diseases with the highest rates of exposure typically coming from droppings or urine, these can also easily contaminate our foods or equipment that processes our foods. Some of the more common diseases associated with nuisance wildlife include but are not limited to: Rabies, Hantavirus, Coronavirus, variations of roundworm, Salmonellosis, Tularemia, Giardiasis, Typhus fever, Leptospirosis, and Toxoplasmosis.

Control Methods

As is the case with the majority of pests we may encounter on a daily basis, the most important first step is exclusion. By preventing opportunities for nuisance wildlife to access a facility or resources, we can achieve a longer-term solution without the need for additional control measures. Although most species of nuisance wildlife are considerably larger than our usual commensal rodents, the same conditions for exclusion remain wherein all entry points large enough to allow access must be closed with adequate materials and tolerances that cannot be compromised by tampering with animals. Remember that foam and plywood are better than nothing, but we can’t expect sub-par exclusion to withstand the test of a potentially desperate animal’s sharp teeth and claws. Keep in mind, exclusion does not only entail limiting access to a facility but must also include excluding animals from resources as well. The use of wildlife deterrents may also prove beneficial, especially when used in conjunction with adequate exclusion efforts. Some deterrents can be physical (bird spikes, anti-climb sheeting), chemical (eviction fluid, predator urines), or sensory (audio alarms/calls, strobe lights) with efficacy varying depending on multiple factors although greater results are usually achieved by combining several methods simultaneously. For instance, a female raccoon with a litter will likely respond very strongly to the use of eviction fluid which mimics the male raccoon musk; male raccoons will try to destroy the female’s litter in order to influence her to mate again with said male, causing the female to manually transfer each of her kits to an alternative denning site which allows a window to exclude her from the primary den. Should all the above exclusion and deterrent options be implemented and fail, trapping will often need to be performed in accordance with state laws. Trapping should only be attempted by trained professionals with a proper understanding of humane methods and how to limit contamination and exposure to pathogens. 

When it comes to protecting FSS customer’s brands, it is imperative that we take an all-encompassing approach when considering both active and potential risks associated with pests AND nuisance wildlife; contamination can happen anywhere at any time, and it is our duty to not only BE ahead but also STAY ahead of risks and offer true solutions for any instance!