Marin County is home to 13 bat species and 11 of them call the Elliott Nature Preserve home.
Bats: An Important Indicator of Ecosystem Health
Despite their secretive nature, bats are believed to be excellent ecological indicators. Changes in bat populations or activity were related to changes land use practices, such as climate change, water quality, loss and fragmentation of forest habitats, and habitat pollution (Jones et al. 2009). They play an essential role in pest control, pollinating plants and dispersing seed. Most current bat surveys rely on acoustic methods.
Unfortunately, bats are declining across the globe. Human activity resulting in loss of habitat and disruptions during hibernation are detrimental. Making matters worse, a fungal disease called white-nose syndrome has spread across North America at alarming rates. The fungus can be transmitted from bat to bat, tree to bat and even tree to tree as people inadvertently carry the fungus on shoes, clothing or equipment. Since many bats hibernate in the same trees over the winter, the fungus can decimate an entire bat colony once established.
Unintentional disturbance of a maternity colony can cause individuals to abandon roost sites, particularly if it occurs early in the reproductive season when females are pregnant. As a result, females tend to break up into smaller groups, often moving to less ideal roosts, where a variety of factors can greatly reduce growth rates and survival of young. In addition, disturbances can cause the outright death of young that are dropped by panicked mothers. Bats have one pup a year and usually in their second year. Consequently, their populations are built up over a long span of time, reducing the rate and probability of recovery from severe losses.
BATS ARE MAMMALS THAT BELONG TO THE ORDER CHIROPTERA (FROM THE GREEK CHEIR – “HAND” AND PTERON -“WING”).
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Katie Smith (she/they)
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Golden Gate National Recreation Area
Identify: Body length about 3.6 to 5.3″, with a 15-16″ wingspan. Beige fur above, almost white below. Broad wings. Has very big pale ears and good vision. Musk gland. Habitat: Roosts in rock crevices, caves, under bridges and tree hollows. Some hibernate; many remain active all year in low to mid-elevations.
Diet: Crickets, scorpions, beetles, grasshoppers, various other insects. Feed primarily on the ground as well as gleaning from leaves. With its large ears, it can hear the footsteps of insects on the ground, and then swoops down to grab them. Immune to scorpion venom.
Behavior: Emerges about an hour after sunset. Eat, then go to night roosts to digest food, then will hunt again before dawn. Roosts in small colonies of about 12 to 100 bats. Forms nursery colonies, bears one or two pups each year, which nurse 6-8 weeks. Able to fly at about 6 weeks. Lifespan in wild unknown, have lived 9 years in captivity.
Risks: Maternal colonies and hibernating bats sensitive to disturbance. Loss or modification of foraging habitat, esp. urban development. Species of Special Concern in California
Identify: Body length about 3.5-4.6″, with a 12-13″ wingspan. Pale to black fur with paler belly. Huge ears (over an inch long). Two lumps on either side of nose.
Habitat: Forested and open (edge) habitat. Roosts from ceiling frequently hanging by one foot.
Diet: Emerge an hour after sunset. Eats mostly moths, but also eats lacewings, dung beetles, flies and sawflies.
Behavior: Flight can go from swift to hovering. One pup is born and able to fly at two and a half to three weeks. May lose half of the body mass during normal over-winter hibernation. Life span 16 years or more.
Risks: Habitat loss, vandalism, and increased disturbance by cavers in maternity and roost colonies have reduced the numbers of this gentle bat. When roost is disturbed, they may abandon it permanently. Disturbance during hibernation leads to burning energy in an attempt to escape and they may not have enough fat storage left to survive the winter. Species of Special Concern in California.
Identify: These bats, no larger than your two thumbs together. Body length about 3.4-4.3″, with a 12-14″ wingspan. The fur is uniformly dark brown or dark grey. The tail extends beyond the tail membrane between hind feet. Long narrow wings provide for fast flight.Habitat: Form large colonies in caves, buildings, under roof tiles and under bridges.
Diet: Forages mainly on moths at very high altitude, up to 10,000 feet. Also eats flying ants, weevils, stink-bugs and ground beetles. Behavior: Emerge at sunset in columns. Young left in large group. Each mother gives birth to one pup which she finds and nurses among the many young. Lifespan about 15 years. Predators include Red-tailed Hawk and other birds of prey, as well as cats and dogs which locate roosts and wait for emergence. Are the fastest mammals on earth clocking in at 99 mph (160 kph) in level flight. Risks: Colonies once numbering in the millions have been dramatically reduces in size due to human disturbance and habitat destruction.
Identify: Similar in appearance to the Little Brown Myotis, but is slightly larger, fur extends from the ventral surface to the elbow on the wing undersurface, and the calcar is keeled. Wingspan is 10-12 inches (25-30 centimeters) and weight ranges from 0.2-0.3 ounces (6-9 grams) Habitat: Occurs mostly in forested mountain regions and river bottoms. Summer day roosts include trees, rock crevices, fissures in stream banks, abandoned buildings. Hibernacula include caves and mines.
Diet: Primarily eat moths, but a variety of soft-bodied insects including flies, mosquitoes, mayflies, aphids, true bugs, and small beetles are taken as prey.
Behavior: Emerge early, during twilight, and active all night foraging around tree canopy and over water. Flight is direct with prey pursued over long distances. Sexes segregated in summer. May live 21 years. Females have one young, usually born in late June or July.
Identify: Body length about 3.4-3.9″, with a 10-12″ wingspan. Long, glossy brown fur on back and lighter belly. Habitat: Found in coniferous forested areas and semi arid shrub lands. Roosts singly or in very small groups. Small maternal colonies. Roost in abandoned buildings, hollow trees, niches under bark, cliff crevices, caves and mines.
Diet: Emerges half hour after sunset. Forages in forests. Catches insects on the fly, gleans off vegetation or the ground. Prefers moths and beetles. Also consumes true bugs, flies, lace wings, other insects as well as spiders and wasps.
Behavior: Flies slowly, can hover. Mother gives birth to one pup. Life span 22 years.
Risks: destruction of rocky areas for development.
Identify: Body length about 4″, with an 11-13″ wingspan. Orange-brown to yellow-brown fur with a fully furred tail membrane. Long pointed wings. Short rounded ears. Habitat: Edge habitats of forest, rivers, fields and urban areas. Roost in trees, generally in the open, but with incredible camouflage. Roost in leaf litter in the winter. Diet: Peak activity one to two hours after sunset. Eats moths, beetles, flying ants and other insects.
Behavior: Fast, strong fliers at treetop to a few feet above the ground. Hangs by one foot with head tucked in furry tail membrane. Gives birth to up to 4 pups. If the mother has to move with her pups, she may become grounded due to weight of pups and unable to return with pups a roost. Predators: Scrub Jays, falcons, hawks, owls, opossums and domestic cats. Risks: Loss of riparian zones and controlled burns of leaf litter.
Identify: Body length about 3.6-4.6″, with an 11-13″ wingspan. Black with silver-tipped fur and black wings. Tail membrane is lightly furred close to the body. Habitat: Roosts singly or in small groups in wooded areas, especially in old growth forests. It typically roosts in hollows, loose bark and cracks and crevices of trees.
Diet: Mostly feeds on moths, but also true bugs, flies, mosquitoes, termites and beetles. Have been seen flying before the sun has set. Feeds over water and above treetops in woods. Behavior: One of the slowest flying bats. Generally give birth to twins which can fly at 4-5 weeks of age. Lifespan 12 years or more. Risks: Logging and loss of large snags, loss of riparian areas.
Identify: Body length about 2.4-4.0″, with a 9-11″ wingspan. Glossy pale tan to dark brown, evenly colored fur. Long hairs on toes. Small, black pointed ears with blunt tragus. Habitat: Roosts in large groups in caves, rock crevices. Also use dead and dying trees near water. Diet: Emerges at late dusk. Gnats, crane flies, mosquitoes and mayflies, beetles, moths, bugs, flies. Can eat more than their body weight each night. Behavior: Lifespan 34 years or more. Forage over water and around trees and lawns. Give birth to one pup which can fly at 14 days. Baby kept beneath wing during day. Risks: Removal of snags, alterations in riparian areas, timber harvest and forest recreation which causes disturbance.
Identify: Body length about 5.1-5.9″, with a 13-16″ wingspan. Blackish-brown or tan fur with frosted appearance. Tail membrane fully furred. Chattering and hissing sounds audible to humans. Ears rounded and glossy black. Golden color around face. Habitat: Roosts in foliage of trees near ends of branches. Blends with the bark of trees. Diet: Emerges late in evening, two to five hours after sunset. Hunts at treetop level, fields, over streams and around outdoor lights. Eats moths, true bugs, mosquitoes, dragonflies, and other insects. Behavior: Solitary bat. Furry tail used as a blanket. One to four pups (two is norm). Pups fly at 4-5 weeks. Predators: Jays, kestrels, hawks, owls and snakes.Risks: Loss of habitat. In suburban settings, quantity of jays poses a major threat.
Identify: Body length about 2.8-3.7″, with an 11-13″ wingspan. Light tan to black dull fur. One of the smallest of our bats. Habitat: Day roosts in crevices, under bark, rock outcroppings, hollow trees, behind signs or in caves and mines. Hunts mostly over the water and along the forest edge. Diet: moths, mosquitoes, flies and beetles. Behavior: Peak activity about 1 hour after sunset. Mothers give birth to one pup. Females roost alone or form small maternity colonies. Lifespan 15 years or more
Identify: Body length about 3.0-3.5″, with a 9-10″ wingspan. Light brown to dark brown back and paler under side. Large feet and short ears. Wings and ears are dark brown. Very similar to the Little Brown Bat Habitat: Emerges just after sunset. Found in buildings, cliff crevices, trees, caves, mines and under bridges. Diet: Usually feeds near water. Mayflies, caddis flies, midges, small beetles, flies, termites, and small moths.Behavior: Flies low. Forms colonies of up to 5,000 bats. Mother bat gives birth to one pup. Maternal colonies do not tolerate disturbance by people.
* Bats are the only mammal capable of true flight.
* The fastest bat in the world is the Mexican Free-tailed Bat, flying in short bursts at speeds up to 100 mph!
* Of the 1,400+ species of bats in the world, only three are vampire bats that drink blood.
* Many females do not begin reproducing until their second year, and most species give birth to only a single pup annually.
* Bats typically have long life spans (10 to over 30 years)
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