The presence of bats near trees is often a sign of a healthy ecosystem, as they consume large quantities of insects. When bats use trees as permanent roosts near homes, however, humane intervention is often required to encourage relocation. Because nearly all bat species are protected by state and federal laws, any action must be non-lethal and comply with strict regulations. Successfully encouraging bats to leave involves first determining their activity and timing the exclusion process legally.
Understanding Bat Activity and Legal Protections
Before attempting removal, determine if the bats are merely foraging or if the tree hosts an established colony. Foraging bats fly around the canopy at night, feeding on insects. A permanent roost shows specific evidence, such as guano—small, dark droppings that crumble into dust when touched—accumulating at the base of the tree or on branches below a cavity entrance.
Bats frequently roost in natural tree features like rot holes, splits in branches, or behind loose bark, often leaving dark smear marks from body oils around entry points. Observing the tree at dusk or dawn can confirm a roost, as bats stream out to forage around sunset or swarm near the entrance before sunrise. Disturbing or harming a bat or its roost is illegal, and this protection extends to the roost even when bats are not present.
Exclusion efforts are strictly prohibited during the bat maternity season, typically from mid-April through mid-August, though specific dates vary by region. During this time, flightless young (pups) are dependent on their mothers and would perish if the entrance were sealed. Any attempt to exclude bats must occur outside of this sensitive period to ensure compliance with wildlife laws and humane treatment.
Habitat Modification and Physical Exclusion Techniques
One lasting method for discouraging bats involves altering the tree’s physical structure to make it less appealing as a shelter. Pruning is a strategic way to remove dead limbs, dense foliage, or areas of loose bark where bats prefer to hide. Increasing light penetration and airflow within the canopy and around the trunk reduces the secluded, dark crevices bats seek for roosting.
Pest reduction efforts can also make the tree less attractive for nighttime foraging, which is often the initial reason bats visit. Bats are drawn to trees that attract large numbers of insects, especially those illuminated by outdoor lighting. Turning off exterior lights near the tree at night significantly reduces the local insect population, decreasing the bats’ food source and incentive to linger.
Physical Exclusion Devices
If a specific cavity or hole is confirmed as a roost outside of the maternity season, a physical exclusion device can be installed. This involves placing a one-way mechanism, such as a PVC tube or a fine-mesh netting skirt, over the opening. The device must be securely fastened around the perimeter, leaving the bottom edge loose. This creates a flap that allows bats to exit but prevents them from crawling back in.
The netting mesh size should be fine enough to prevent re-entry, typically a quarter-inch. The device should remain in place for at least a week to ensure all bats have vacated the roost.
Auditory and Visual Deterrents
Sensory deterrents make the tree’s immediate vicinity uncomfortable for bats, especially when their activity is primarily foraging. Bats are highly sensitive to intense light, making bright, upward-facing floodlights aimed at the canopy an effective, temporary visual deterrent. The sudden presence of intense illumination discourages them from landing or resting in the exposed area.
Sound-based deterrents, such as ultrasonic devices, emit high-frequency sound waves that interfere with a bat’s echolocation system. While commercially available, their effectiveness is limited in open, outdoor environments like a tree canopy, and bats can become accustomed to the noise. Sudden, sporadic loud noises can temporarily startle bats and disrupt foraging patterns, but consistency is difficult to maintain throughout the night.
Some commercial bat repellents use strong scents to deter bats, often containing naphthalene, peppermint, or eucalyptus oils. These substances can be applied near a suspected roost opening or to the trunk of a tree. In an open-air environment, however, the potency of these odors dissipates quickly. They require frequent reapplication and generally serve only as a short-term solution.
When to Seek Professional Wildlife Assistance
For large, established colonies or when the roost is located high in a difficult-to-access area, professional intervention is the safest and most reliable option. Licensed wildlife control operators are trained in humane exclusion devices and are knowledgeable about local and federal regulations. They possess the proper equipment to inspect and safely work high in the tree canopy without harming the animals.
The presence of a large number of droppings or a strong, musky odor signals a substantial colony that requires professional remediation and cleanup. Professionals are aware of the timing restrictions related to the maternity season. Attempting exclusion during this time is illegal and would result in the death of flightless young, so professional consultation is necessary to determine the appropriate legal period for action.