The Opossum: Benefits & Misconceptions - Furbearer Conservation

On April 18th 2014, the Cary Institute of Ecosystem Studies and NewsTimes published an article that focused on the role of opossums in the spread of Lyme disease with respect to their role in the ecosystem. The postings referred to the opossum as being a “sort of magnet” for black-legged ticks and related the once infamous marsupial to that of a tick-sucking vacuum. The study contends that opossums are fastidious groomers, most notably with regard to the presence of parasitic blood feeders such as ticks, which attach to host animals to feed on blood. The article, which pulls references from a 2009 study, found that 95% of ticks that latch on to an opossum have the potential to be consumed. In recent years, these findings have been grossly taken out of context by mainstream America with regard to the mitigation and remediation of Lyme Disease. Albeit a dead tick, in any capacity, is typically a good tick! In addition to the findings with a capacity of up to 95% individualized reduction in tick presence on the animal’s body, the study asserted that an opossum has the potential to kill roughly 5,000 ticks in a given season.

The Carry Institute report was, for many years, the most focused record on the relationship between the Opossum and the consumption of ticks. Taking the findings of “up to 5,000 ticks per season” consumed by a foraging opossum into discussion, one must also consider the biology of both species in order to comprehend the dynamics of opossums and Lyme impact.

The blacklegged tick, aka “deer tick” (Ixodes scapularis) is the only species in the northeastern, mid-Atlantic, and north-central United States known to spread Lyme disease. They are most commonly found along the eastern coast of the United States from Florida to Maine and as far west as Texas to the Great Lakes region of the upper Midwest United States. One adult female deer tick can lay as many as 3,000 eggs in the spring of each season. Ticks can only contract Lyme disease if they take a blood meal from an infected host. Since larva have not taken their first blood meal yet, they are unable to have or transmit Lyme disease. Despite the name “deer tick”, deer do not carry Lyme disease – and although deer species do contribute to increasing/spreading tick populations, they do not spread Lyme disease themselves. Of all the wildlife ticks feed upon, only mice, chipmunks, birds and shrews can carry and transmit Lyme disease to a feeding tick. Infected adult female blacklegged ticks cannot pass Lyme disease to their eggs. When a tick takes its first blood meal, it then may become at risk for contracting Lyme disease if the individual animal it feeds from is infected. With only 2-3 blood meals taken in its lifetime, only 2-3 opportunities are allowed for a tick to become infected. If the tick becomes infected during the 1st or 2nd feeding, it can transmit diseases to any animal it feeds on thereafter. (Read more on blacklegged ticks here.)

In contrast, the opossum’s home range varies individually; with factors that include habitat, available food resources, and gender. In general, the opossum’s home range size is thought to be about 12.5 to 38.8 hectares; females generally have a smaller home range. Males are believed to keep larger home ranges due to their reproductive success being contingent on their ability to find mates, whereas female success is based on the accessibility of food items. Virginia opossums were once considered nomadic but research has found that an individual maintains a fairly constant home range throughout their life. (Allen, et al., 1985; Gehrt, et al., 1997; Gipson and Kamler, 2001; Harmon, et al., 2005; McManus, 1974; O'Connell, 2006; Wright, et al., 2012). Additionally, wild opossums average a 2-year lifespan.

While it is noted that the opossum may consume ticks, the Cary Institute study clearly indicates that this is indicative of grooming habits - not a case of opossums actively seeking out ticks on the forest floor. Furthermore, not all tick species found on the opossum are a carrier of Lyme, such as the equally-common American Dog Tick (Dermacentor variabilis).

The notion that opossums actively consume ticks found on their body has been grossly overstated to suggest that the animal is an integral component in the “control” of Lyme disease - a statement that has yet to be proven in any capacity. The idea that opossums consume ticks is vastly different from the misconception that an opossum’s presence on a particular property “prevents” the spread of the disease. The above-mentioned findings would suggest that the opossum’s impact on blacklegged tick consumption is not substantial enough to effectively “control” a localized tick population, thus leaving little evidence that the opossum “controls” the spread and transmission of Lyme disease. Wildlife professionals across the nation tend to echo similar sentiments that nature is far too complex to conclude the opossum is responsible for curbing Lyme transmission.

Dr. Bret Collier, associate professor of wildlife ecology at Louisiana State University’s School of Renewable Natural Resources, takes the misconceptions a step further; contending that ticks are not, in any manner, selected during foraging by Virginia opossums.

He cites the 2021 peer-reviewed paper “Are Virginia opossums really ecological traps for ticks? Groundtruthing laboratory operations,” by Dr. Cecilia Hennessy and Kaitlyn Hild of Eureka College’s Division of Science and Mathematics. Collier notes the 2009 study (the one for which the 2014 Carry Institute report is based upon) looked at captive opossums, while Hennessy and Hild’s later work focused on wild ones - which dives deeper into opossum foraging - to include stomach contents, and scat sampling (as well as 23 scientific papers on the topic). For the 2021 study, Hennessy and Hild used a dissecting microscope to examine the stomachs of 32 Virginia opossums from central Illinois. They found absolutely no evidence of ticks or tick parts and thus concluded that ticks are not a preferred diet item for wild opossums.

“This body of (internet) memes turned out to be an extremely successful advocacy campaign for the opossum; allowing the oft-maligned scavenger to achieve cult status as a bio-control for ticks,” the report concludes. “Unfortunately, these purported benefits are not supported by our findings or by previous diet analyses,” adding that it’s still possible to appreciate opossums in light of the evidence.

This hasn’t quelled the flood of misconceptions to perpetuate, however. Some have taken the Opossum v. Lyme debate a step further, utilizing the animal’s varied diet as yet another indication of its ability to “control” Lyme. Opossums are noted as feeding on mice, which have been proven to be a primary vector for Lyme via the instar stages of blacklegged ticks that latch onto mice. However, similar to their tick consumption, opossums are opportunistic feeders - and no definitive research has determined their diets are comprised primarily of rodents, nor that their feeding on mice has any impact on localized mouse populations to the point of mitigating disease transmission. Similar to foxes and other wildlife, the fact that these animals may on occasion eat mice does not reflect a determination that they “control” the presence of this prey species in any capacity. (Read more regarding predator & prey relationships in our Predator Management section.)

The misconception that the opossum has the capacity to mitigate Lyme spread has taken on a life of its own in popular culture; to the point of raising criticism for the management of the opossum as an abundant species. Many states have bore witness to protests from animal protectionist groups seeking to disband the regulated hunting & trapping of opossums over their new-found tick-consuming fame. These types of knee-jerk, sensationalized demands have the potential to threaten other impacts of the opossum’s abundant presence; which includes their depredation on endangered nesting species such as birds and reptiles. Additionally, demands by homeowners to “hoard” opossums on their property in hopes of a “natural tick control measure” has the capacity to induce public safety issues for the homeowner, children, pets and neighboring properties - not to mention jeopardizing the health and well being of the opossum(s) in question.