Why Rat and Squirrel Bite Marks Can Look Almost Identical

The first reaction to rodents inside a house may be a simple assumption that a cable with bites or a rough wooden surface, or even a damaged piece of lumber, must indicate one specific kind of rodent. However, according to the researchers, distinguishing rat teeth marks from those of other rodents, such as squirrels, is extremely hard due to the similar tooth formation among different kinds of rodents.

As mentioned in an article in the Animals magazine, rats and squirrels are both rodents and have the same dental structure, which consists of a unique pair of ever-growing teeth and a gap between them called a diastema. As scientists have stated, this similarity in the formation of their teeth causes similar damage on various surfaces since rats and squirrels have narrow teeth with which they can easily create parallel grooves on wooden or plastic surfaces, as well as wires covered with some coating material.

It can be concluded that it is highly dangerous for people who suspect rats to start exterminating the rodents without proper identification, since a damaged baseboard or gnawed cables do not mean the presence of rats at all.

Why the shape of the bite matters

Findings from studies in the Journal of Experimental Biology have revealed that there is no exact similarity in the mechanism of chewing employed by both rats and squirrels despite similarities in dental structure. For example, it was discovered that while rats exhibit more adaptability when moving from incisor to molar bites, squirrels tend to depend more on powerful bites from incisors.

According to experts, the differences can translate into variations in bite angle, pressure, and mark penetration depth. In essence, this means that two bite marks appearing to be identical from afar would actually indicate different processes behind them.

Moreover, rodents' bite marks are considered functional traces that depend not only on the type of animal involved but also on the specific technique used for biting and the duration of the teeth's contact with surfaces.

The material changes the evidence

The study by forensic scientists on rodent bites revealed that the surface on which the bite was inflicted greatly affects the appearance of the injury sustained. Various studies in forensic science have noted that the material composition of surfaces such as hard cable jackets, soft PVC trim, wood, and bones has different effects on bite marks despite coming from the same species.

This is one of the reasons why visual estimation tends to fail at times, since an indentation on the surface of plastic will be entirely different from a similar bite mark on untreated wood owing to different material compositions.

In this regard, the scientists noted that visual estimation is based on comparisons with a picture of what a rat bite and squirrel bite would look like, while, in reality, a much more complicated picture emerges due to the influence of teeth and surfaces.

What rodents choose to chew also matters

In a controlled experiment carried out in the Journal of Forensic Sciences, a comparison between gnawing activities of brown rats and gray squirrels revealed considerable differences in their chewing material. The findings showed that brown rats would prefer chewing cancellous bones filled with fats. Conversely, gray squirrels had the tendency to attack harder areas of bones that were depleted of fats.

While the results of this study did not address home repair, scientists state that this study provides a very important lesson since the damage done by the rodents may not only depend on their teeth but also on their feeding behavior and environmental factors.

This implies that, besides the nature of the tooth marks, the surroundings in which the destruction occurred could also provide useful insights into the matter.

Why experts warn against quick assumptions

For instance, the most recent case that gained popularity was the scientific examination of the “Chicago Rat Hole” done in 2025. It was considered that the hole was made by a rat; however, based on the findings obtained after conducting measurements and multivariate shape analysis, the hole is believed to be made by a squirrel, either an eastern gray squirrel or fox squirrel.

It was noted by scientists that popular opinions about bite marks are usually much stronger than actual evidence, as well-known stories seem to be more convincing. In such a way, the research proves that a proper measurement is capable of giving a completely new result compared to initial estimations.

In turn, researchers highlight that the primary point homeowners should consider is that a bite mark will undoubtedly prove rodent activity, but at the same time, it is unable to provide reliable information regarding a particular animal. It is stated that the best option in such cases would be a thorough comparison.