Evening bats can be easily mistaken for Myotis species, even though the curved tragus can differentiate the two genera. They can also be confused with Eptesicus fuscus.
Although Eptesicus fuscus is more extensive, you can also distinguish them by the lack of keel on their calcar.
Evening bats are dark-brown. Their ears, on the other hand, are black. They are hairless in areas that include their wings, about, and tail membranes.
Evening bats, also known as Nycticeius humeralis, have a broad skull, short tragus that is round and curved, and a non-keeled calcar.
- Wingspan: Wingspan can range from 260 mm to 280 mm
- Tail: Can measure up to 33-42 mm long
- Weight: They can weigh up 6-14 g
- Ear: Their ears can measure up to 11-15 mm
- Forearm: Length of their forearms can measure up to 34-38mm
- Hindfoot: Can measure up to 8-10 mm long
- Body length: They can be as long as 86-105 mm long
- Dentition: The evening bats’ dental formula is 1/3, 1/1, 1/2, 3/3 = 30.
- Kingdom: Animalia
- Phylum: Chordata
- Class: Mammalia
- Order: Chiroptera
- Family: Vespertilionidae
- Genus: Nycticeius
- Species: N. humeralis
- Binomial name: Nycticeius humeralis
The northern limit of evening bats rests at the Great Lakes Basin. There have been three records of evening bats in Southern Michigan and one in Ontario.
The eastern boundary of their range is in North Carolina and Virginia. They can also be found as far west as Texas and far south of Florida.
Nycticeius humeralis prefer open habitats and forests such as wetlands and river corridors. They are categorized as forest bats and are never seen in caves. They instead roost in buildings, loose bark, and hollows of trees.
In their natural habitat, evening bats are expected to live for about two years, although studies have shown that some can live as long as five years.
Evening bats practice a polygynous mating system. Meaning, one male can mate up to 20 female bats. They have a harem-like association where twenty female bats have one male staying around them.
After mating, both the male and the female bats go separate ways. Female evening bats cluster up and give birth in colonies without the presence of any male adult.
Evening bats mate in the late summer into early fall. The reproductive tract of the female is used to store sperm until spring when ovulation and fertilization begins.
Young evening bats are born in colonies, mostly behind loose bark, hollow trees, and sometimes in attics and buildings.
Usually, female evening bats give birth to twins; however, some have been known to not only birth triplets but also raise them successfully. Pups can weigh 2 g at birth, and they are born pink, blind, and hairless.
Evening bats young may begin to open their eyes within a day or more after birth, and they won’t fly till they are about three weeks old. Pups are weaned after 6-9 weeks, and male pups separate themselves from the roost, while the females stay behind in the colony. Generally, bats breed the next year after they are born.
Bats develop rapidly, and this is why pups begin to fly when they are three weeks old. Pups are nursed for about six weeks. Parental care is given by female evening bats, although there have been reports of communal nursing.
Pups are recognized within the colony by auditory cues and scent by their mothers. This makes it easy for mothers to find their pups when they fall.
Evening bats are nocturnal. Their flight is gentle and steady. Members of this species can be seen flying high early in the evening and lower at night. They pinpoint their prey by using echolocation. Nycticebus humeralis are social migratory mammals and can be found roosting in colonies of around 30 bats.
Male even bats don’t follow the females to their northern colonies during the spring season. Throughout the year, they stay in the southern region of their range.
Communication and perception
Little is known about how these animals communicate. Mothers locate their pups by listening to their voices and perceiving their scent.
This means that they use both smells and sounds to communicate with each other. Evening bats use echolocation to track their prey, as do all members of the Vespertilionidae family.
Evening bats feed on flies, crickets, moths, beetles, and leafhoppers that they catch in midair while flying slowly. When a solitary bat hunts unsuccessfully, it would join a group of bats to look for food.
A large colony of bats (about 100) can eat over 1.25 million insects per season, and their use of echolocation makes finding food natural.
Evening bats may fall prey to raccoons, snakes, hawks, and owls. Specific anti-predator adaptations in this species are yet to be described.
Since the colonies of the evening, bats can consume millions of insects, it is highly likely that they play a vital role in controlling insect populations. As a result, they positively affect the vegetational community that insects feed on.
Economic importance for humans: Advantage
Evening bats consume an adult form of chrysomelid beetles, commonly known to farmers in their larval stage as the corn root-worms. These worms are regarded as agricultural pests. The number of root-worms are controlled when evening bats feed on them, hence, maximizing farm harvest.
Economic importance for humans: Disadvantage
Some bats roost in attics and buildings, and they can be a form of a nuisance to people. They are also carriers of rabies, which may be transmitted to humans when infected bats bite them.
The transformation of forested wetlands to agricultural and logging may have lead to prime foraging and roosting habitat. Temperate North American bats are faced with a fungal threat known as the “white-nose syndrome.”
The disease has left the population of eastern North American bats at hibernation sites devastated since 2007. The fungus (Geomyces destructans) has been noticed to spread rapidly in cold, humid conditions that are common with many bat hibernacula.
This fungus grows on bats, and in some cases, it invades the bodies of a hibernating colony of bats. This can lead to debilitating loss of vital metabolic resources and deaths. Surprisingly, the mortality rate noticed at some hibernation sites could be at 90 percent.
Even while there are yet to be reports of Nycticeius humeralis mortalities caused by the white-nose syndrome, the disease keeps expanding its range in North America.