Technical Papers

New Jersey Homeowner's Guide to Bats

Wednesday, July 8th, 2015 by Bill Cowley

Bat baby

Bats are warm-blooded, fur-covered mammals, and the only mammal with the ability to fly. Bats can be found all over the world, except for extreme arctic and desert regions. We get plenty of calls for bats, such as this homeowner in Allentown, NJ.

Bat Behavior

Bats are nocturnal. At dusk, they leave their roosts, the dark shelter where bats congregate to rest during the day, to feed, and then return just before dawn. Most bat species are active during the warmer months and hibernate or migrate during cold winters. Bats do not usually fly in bad weather. Rain and unseasonably cold weather will keep them in their roosts.

Different bat species have different diets. Smaller bats eat small flying bugs like mosquitoes and moths while larger bats often eat ripe fruit. Some bats eat animals such as frogs, fish, and scorpions.

Perhaps the most identifiable behavior of bats is their ability to fly. A number of mammals including flying squirrels, gliding possums, and colugos can glide through the air for short distances. However, bats are unique. They are the only mammals that can actually fly. A bat’s forelimbs form webbed wings that allow them to sustain flight. Unlike birds, bats do not flap their entire forelimbs; instead, they flap their spread-out their long digits, which are covered with a thin membrane.

New Jersey Bats

Of the close to 1,000 species of bats found throughout the world, approximately 40 species are found in the United States. New Jersey is home to just a handful of species New Jersey homeowners are likely to encounter: the Little Brown Bat (Myotis lucifugus) and the Big Brown Bat (Eptesicus fuscus). These paticular species frequently enter into man-made structures, like homes, barns, churches, and commercial buildings, so people are more likely to come in contact with them.

Physical Characteristics

Little Brown Bats - Little brown bats are, as indicated by their name, very small, between two and four inches long, and weighing no more than a half-ounce. They have a wingspan between nine and ten and one-half inches. Females are often larger than males.

A Little Brown Bat’s fur is glossy, ranging from dark-brown to a golden-brown, to even a reddish or olive-brown. The fur on its underside is lighter than the fur on its back.The bat’s hind foot has hair that extends past its toes. The wings and membranes between the bat’s legs are dark brown or even black. There is little to no hair on a Little Brown Bat’s wings, ears, and face.

Big Brown Bats- Big brown bats are approximately four and one-quarter inch to a little over five inches long with about a 13 inch wingspan. Like with Little Brown Bats, females are often larger than males.

A Big Brown Bat’s fur ranges from light brown to dark brown, and may have reddish hue. The underside of a Big Brown Bat is a lighter color thanthe fur on its back. Big Brown Bats have a black face, ears, wings, and tail with little to no fur on them. They have a powerful bite with strong, sharp teeth that allows them to eat large, hard-bodied insects such as beetles. 

Bat’s Diet

Little Brown Bat - Little Brown Bats are insectivores, almost almost always eat insects less than a half-inch long. They are very skillful hunters, especially when the insects are in large groups. The bats are able to catch insects both in the air and off surfaces like the ground. The bats tend to fly significantly faster when they get close to their prey. Although bats return to the same hunting grounds, unlike many animals, they do not protect their hunting territory from other bats.

Female bats who are nursing young need more food than other bats. Nursing females usually select larger insects than their male counterparts or female bats without young. The average bat can eat half of its own body weight in insects each night; whereas, female bats with nursing young can eat 110 percent of their body weight in a single night.

The digestive system of the Little Brown Bats works quickly. It only takes between 35 to 55 minutes for the insects to be eaten and pass through the bat’s digestive system.

Big Brown Bat - Big brown bats are also insectivores. Their diet is primarily beetles. Many studies indicate that Big Brown Bats consume significant crop and forest pests, including ground beetles, scarab beetles, cucumber beetles, snout beetles, and stink bugs. Although they eat mainly beetles, Big Brown Bats will also eat other flying insects such as moths, flies, and wasps. Their strong teeth allows them to chew through the hard outer shell of a variety of different insects. Like Little Brown Bats, Big Brown Bats eat a significant percentage of their body weight in insects every night, and pregnant and nursing females are able to eat more than their own body weight in a given night.

Bat’s Lifespan

Big Brown Bats can survive up to 19 years in the wild with males tending to live longer than females. A normal life span for a Little Brown Bat is less, usually 6 to 7 years, though some live well beyond 10 years. Like the Big Brown Bats, male Little Brown Bats usually live longer than females. Although bats may live for years, most bats die in their first winter. Many young bats do not eat enough during their first summer to store the amount of fat necessary to make it through their entire hibernation period so they often die in their winter roost.

Human Interaction with Bats

Bats, an integral part of our ecosystem, play an important role in keeping down the number of pest insects in a wide variety of places from back yards to corn fields. Unfortunately, once they enter human habitats, they can also create two significant health hazards for homeowners because of their bites and their feces.

A small percentage of bats are infected with rabies. In New Jersey, bats are one of the four species of animals that are classified as a rabies vector species along with raccoons, foxes, and skunks.  Rabies can be transmitted when saliva or body tissue of an infected animal comes into contact with a person or another animal. Although bat bites are rare, it is imperative that persons seeks medical treatment immediately if they sustain a bat bite. Many rabies-infected bats infected do not show symptoms.

Another danger from bats is their feces. Bat droppings can pose a serious health threat to the people living in the home. Fungi in bat droppings can cause histoplasmosis, a serious lung disease. Toxic bat droppings in a home it should be professionally removed, and the home should be decontaminated.

Bats are protected by law in most states, including New Jersey. Always check with animal control or a knowledgeable pest control professional before removing bats or attempting to bat-proof your home. Inadvertently injuring bats can result in a large fine.