Silver-haired bats () are found in most of the United States, with the exception of the southeast and southwestern coasts of the United States. The species is found as far south as the Victoria province of Mexico. They inhabit areas as far north as the entire lower third of Canada, with a northward peninsular extension following the coast into the lower south-central part of Alaska. Occasionally, these bats have been documented in Bermuda.
During the summer months, some populations are sexually segregated, and it appears that distance and direction of migration differs among western and eastern populations. It appears that females will consistently migrate greater distances from hibernacula and spend the summer further northward than males. Western populations appear to leave hibernacula and migrate eastward and northward, while eastern populations only move northward. Populations in British Columbia may not migrate, as equal sex ratios are noted throughout the year. Females have been noted to be absent in mountainous habitats in the western U.S. during summer months.
Silver-haired bats are most commonly found in boreal or coniferous and deciduous forest near bodies of water, such as rivers, lakes, streams, estuaries or ponds. Summer day roosts are typically under loose bark in trees, willows (Salix), maple (Acer), and ash (Fraxinus) trees. These species may be most suitable regarding the structure of the bark and cavities they provide (Kunz 1982a). They can also be found in dead trees, also called snags, that have loose bark to provide cover, and cavities in these trees. These cavities are the locations of maternity colonies, as well as summer locations for bachelor males. Uncommonly, they use human structures (garages, sheds, etc.) but roosting here tends to be solitary. During the winter, these bats have been found in caves and other rocky area that provide shelter, in tree cavities, and in buildings. Winter finds tend to be anecdotal, as they don't seem to hibernate in large groups. (Arroyo-Cabrales, et al., 2008; Kunz, 1982; Patriquin and Barclay, 2003; Perry, et al., 2010)
The common name for silver-haired bats is derived from the silver or white tips of the black fur that covers both ventral and dorsal sides of the animal. Their fur covers almost all of these bats except for the wings, snout, ears and posterior portion of the uropatagium membrane, which is a membrane that goes between the bats legs that attaches at the ankle. The wing and uropatagium membranes are dark brown to black. The ears are 5-9 millimeters and rounded at the tops. They have a slight upturn to their snout. Adult males and females look alike.
These bats as adults will weight between 8 and 11 grams with the average being 9.5 grams. Their overall length is 9.5 to 11.5 centimeters with the average being 10 centimeters. Their wingspan is 27 to 31 centimeters with average being 29.5 centimeters. Their right forearm, 3.7 to 4.4 centimeters with the average being 3.9 centimeters. Their basal metabolic rate is 3.73 to 4.66 centimeters cubed of oxygen used per hour with the average being 4.14 centimeters cubed of oxygen used per hour.
These bats' young, called pups, are born blind, with ears folded, initially deaf. They will be born with no fur, but they will have dark skin in locations where fur will be found later as they develop. They will weigh 30 to 36% of the mother's body mass, which will about 2.0 g (range 1.4 to 2.3 g), depending on how many young they produce. (Kunz, 1982)
The males and females are polygynandrous and will form a swarm during migration. The sexes typically do not commingle during most of the year. During this migration time, mating occurs, and females store the sperm until April or May. Then gestation will start. After a gestation period of 50 to 60 days, the females will give live birth to typically 2 pups. (Kunz, 1982; Van Schaik, et al., 2015)
Silver-haired bats breed once a year in the fall during migration. Females will store sperm after mating until the spring. After a gestation period of 57 days, ranging from 50-60 days. The female will give birth to (one to) two pups. The pups will weigh 1.4 to 2.3 grams with 2.0 grams being average. The young will nurse for approximately 36 days (range 34 to 39) at which time they will be independent. Age of sexual maturity will range between 145 to 160 days, with the average being 152 for both males and females. (Kunz, 1982; Lacki, et al., 2007a)
Males have no investment beyond mating in the fall. Females are responsible for the pup or pups. Females will nurse the young for an average of 36 days. During this time the female will forage normally. Prior to any kind of independence, the pups remain attached to the mother. The pups are born with teeth, so once independent, they can fully forage on their own. (Kunz, 1982)
Dental records have shown that silver-haired bats can live as long as 12 years. Expected lifespans in the wild have been reported as 7 years (range 5 to 10). These bats are not kept in captivity. (Kunz, 1982)
Silver-haired bats are solitary animals that will seek shelter and sleep under loose bark, in dead trees or snags, inside hollow cavities of trees where heart rot may have taken place and holes that may have been used for birds and squirrels. Very rarely will they seek shelter inside homes. These bats are most commonly found in willow, maple and ash trees. This is believed to be due to the deep fissures in the bark. They will forage multiple times during the early evening through out the night. Typical foraging times are early evening shortly after dark or right before, and early evening times just before dawn. According to Cryan (2003), the separation of times is due to avoiding flying at the same times as red (Lasiurus borealis), hoary (Lasiurus cinereus), and big brown (Eptesicus fuscus) bats. The red, hoary and big brown bats are faster fliers than the silver-haired bats. Silver-haired bats have been known to reach speeds of just 4.8-5.0 m/s; in order to be able to feed, they may wait for the others to be less active in suitable habitats.
During the summer months silver-haired males and females are geographically separated from each other and will not be near one another until fall, when migration occurs. As they migrate for hibernation, they form swarms, at which time the two sexes meet. It is during this fall swarm that the females and the males will mate, but the females will not become pregnant until after hibernation.
Hibernation of these bats will tend to happen in more xeric, dry and warm, site during the winter. They will hibernate from October until March.
These bats will use echolocation as a form of finding food as well as a way to communicate among bats. With wind turbines becoming more prevalent, echolocation is not able to help them avoid the blades or the wind "vacuums" that can kill them instantly. ("A Guide to the Bats of Virginia", 2015; Cryan, 2003; Kunz, 1982; Lacki, et al., 2007b; Van Schaik, et al., 2015)
Home range will varies for these bats, but will typically include a nocturnal foraging area of about 30 square kilometers (range 14 to 37 km^2). They do not actively defend a territory. (Kunz, 1982; Lacki, et al., 2007b)
Like most bats, silver-haired bats use echolocation, not only to perceive their environment but also as a way to hunt prey during the night. According to Voigt-Heucke et al. (2010), these bats use echolocation as a way to identify familiar and unfamiliar individuals. Newborn pups identify their mothers by scent. Contrary to the phrase "blind as a bat," most bats can see as well as humans during daytime hours.
According to Silvis (2016), who examined 15 known acoustic files for silver-haired bats, the average frequency at which these bats called was 29.26 kHz. The maximum frequency of a call recorded for these bats was at 35.77 kHz, with the lowest at 26.39 kHz. The only species to be measured with a lower frequency of bats in the mid-Atlantic U.S. is the hoary bat (Lasiurius cinereus).
These bats are generally solitary, but do use visual tactile communication while mating in the fall months. ("Classification trees for acoustic identification of bat species in the mid-Atlantic", 2016; Voigt-Heucke, et al., 2010)
According to Lacki et al. (2007), silver-haired bats will prey upon different 11 different orders of insects. In this study, moths in Order Lepidoptera made up over 40% of their diet. In many parts of their range, they are considered moth specialists. Flies and beetles made up most of the rest of their diet in this study. Other studies suggested that they are opportunists and that diet is reliant on geographic location, time of the year and availability of prey. For example, the stomach contents of two bats were made up entirely (or nearly so) of caddisflies (Trichoptera). Spiders and termites also have been found. These bats have been caught by mouse traps, and some researchers suggest that they forage on the ground or glean. Further evidence of gleaning are reports of silver-haired bats taking larvae directly from trees. Data on food of these bats is derived from gut content, direct observation of feeding, culled parts and most commonly from feces or guano. Direct observation is rare. (Arroyo-Cabrales, et al., 2008; Kunz, 1982; Lacki, et al., 2007b)
The main predators of silver-haired bats are owls, such as the great horned owl Bubo virginianus. Mammalian predators include striped skunks Mephitis mephitis that find the bats during times where they are not active. One case reported a rabid hoary bat Lasiurus cinereus killing a silver-haired bat, but this was likely an isolated incident. Recently, sharp-shinned hawks (Accipiter striatus) have become a major predator because of habitat changes. Logging has disrupted some of these bats' formerly contiguous habitat, creating fragmented patches of suitable habitat. This has caused a change in both feeding habits and time which they feed. These bats now navigate in more echolocation clutter while foraging. The edge habitat included more open areas, which have made the bats more vulnerable to predators of owls and nocturnal hawks. (Kunz, 1982; Patriquin and Barclay, 2003; Perry, et al., 2010)
According to Kunz (1982a), parasites of silver-haired bats include mites in the families Sarcoptidae (Sarcoptidae lasionycteris) and Laelapidae (Laelapidae myotis). Most of the mites were found to be on the wing membrane or on top of the ears or inside the ears. They also suffer from parasites known as bat flies, which are wingless and blind, and feed much like a tick. Two species of of bat flies from the families Nycteribiidae (Basilia forcipata) and Streblidae (Trichobius diphyllae) have been documented as using the silver-haired bats as host. Bat bugs from the family Cimicidae (Cimex piosellus) are known parasites. They've also been reported to host one flea species.
Endoparasites that have been found are nematodes (Capillaria palmata), trematodes (Acanthatrium lunatum), and cestodes (Hymenolepis roudabushi).
While there are many parasites that use silver-haired bats as a host, the parasites found on or in a bat that lives in the eastern part of the U.S. can often vary from species than those found on a silver-haired bat who live in the western part of the U.S. (Blankespoor and Ulmer, 1970; Boyd and Bernstein, 1950; Kunz, 1982; Whitaker Jr. and Easterla, 1974)
Silver-haired bat economic importance alone hasn’t been studied, but the economic value of bats in the United States (as a whole) has been estimated by Boyles et al. (2011) to be $3.7 to 53 billion per year as a natural pest control for crops. The bats also carry a species-specific strain of rabies they are hence a focal animal for rabies research. (Boyles, et al., 2011; Messenger, et al., 2002)
Silver-haired bats have been known to carry a species-specific form of rabies virus that is known to infect humans. Most rabies recordd are based on state health department reports, and less than 5% of all bats submitted for testing are silver-haired bats. Those cases that can be attributed to silver-haired bats can be done so via molecular testing of the infected person. The highest concentration of rabies cases are in the northeastern United States, because that is where they are most common during summer months and most likely to interact with humans. (Messenger, et al., 2003; Messenger, et al., 2002)
Silver-haired bats are listed under as a species of "Least Concern" on list by the IUCN Red List, CITES and U.S. Federal Endangered List and in the state of Michigan. According to Adams and Pedersen (2013), an increase of wind turbines being constructed in migration corridors, near or at foraging sites, or generally within the summer home ranges of individuals, causes declines in populations of silver-haired bats. Logging also is a threat to their habitat continuity. They are proposed as a Tier IV species in Virginia, which means that they are currently secure, but multiple looming threats (logging and wind turbines) causes concern for the species. In Mexico, where they are considered a rare find, they are "subject to special protection" (Arroyo-Cabrales et al., 2008). ("A Guide to the Bats of Virginia", 2015; Adams and Pedersen, 2013; Arroyo-Cabrales, et al., 2008)
Justin Bentley (author), Radford University, Karen Powers (editor), Radford University, Alex Atwood (editor), Radford University, Marisa Dameron (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.
The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
An animal that eats mainly insects or spiders.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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