The California leaf-nosed bat (Macrotus californicus) is a species of bat in the family Phyllostomidae. It is found in Mexico and the United States.
California leaf-nosed bat
From Wikipedia, the free encyclopedia
The
California leaf-nosed bat (
Macrotus californicus) is a species of
bat in the family
Phyllostomidae. It is found in
Mexico and the
United States. Its natural
habitat is hot
deserts. It is threatened by
habitat loss.
Habitat
California leaf-nosed bats can be found in
Sonoran and
Mojave Desert scrub habitats in the
Colorado River valley in southern
California,
Nevada and
Arizona, and throughout western
Mexico. It is non-migratory and does not hibernate.
Physical description
Close-up view of California Leaf-nosed Bat
The California leaf-nosed bat weighs between 12 and 20
grams,
has a wingspan of over 30 centimeters and a body length of over 6
centimeters, and is brown in color. As its name implies, it has a
triangular fleshy growth of skin, called a noseleaf, protruding above
the nose. This bat is the only bat of the family
Phyllostomidae in the
United States to have large ears, usually over 2.5 centimeters. It is also one of the most maneuverable in flight.
M. californicus seems to spread its
uropatagium
widely only when hovering or performing other maneuvers requiring a
departure from straight level flight, but the extreme maneuverability
observed in
M. californicus is probably due to the specializations of its sensory equipment.
[2]
With short, broad wings, it can fly at low speeds using minimal energy.
Because of this adaptation, it is not suited for long-distance travel,
and is non-migratory.
[3]
This bat has an unusual reproductive pattern. After breeding occurs
in the fall, the embryos develop very slowly until March, when growth
continues at a more normal rate before birth in May or June. Twins are
common.
[3]
In
Macrotus the position of the hind limbs during level flight
differs even more form that in most other mammals. The hind limbs are
held behind the bat in a spider-leg- like posture, with the femur
extending dorsad and caudad, and with the shank partially flexed and
extending caudad and more or less downward.
[2]
The number of post cervical vertebrae in
Macrotus are as follows: twelve thoracic, six lumbar, five sacral, seven caudal.
[2]
Human impact
They are susceptible to human disturbance, which can be especially
detrimental to the species during summer months, when these bats are
rearing young. Human disturbance of caves in which they roost is a major
threat. Furthermore, because they often roost in abandoned mines,
reclamation practices and re-working old mines can severely impact
populations. Because California leaf-nosed bats do not hibernate or
migrate, the relatively warm mine shafts are critical for its survival
in the northern portions of its range.
[3]
Roosting habits
In the study area
Macrotus roosts in the daytime exclusively in caves, deserted mine tunnels and deep grottos.
[2]
They are usually within 30 to 80 feet of the entrance of the tunnel and
seem not to require dark retreats. On many occasions, leaf-nosed bats
roost in tunnels less than 20 feet deep and fairly brightly lit. In
order to be suitable, the
Macrotus retreat must be mostly enclosed and have overhead protection from the weather.
[2]
Roosting chambers are usually large enough to provide considerable
ceiling surface and flying space, and thus adequate space allows the
animal to find a place to roost while flying. The coolness of the roost
also plays a factor in
Macrotus selection of roosts, which is why
Macrotus would choose to roost in a cool cave in the hot summers.
Macrotus prefer to hang from sloping parts of the ceiling and actively grab the rock with ease due to the irregularity of the surface.
[2]
The bat seems to rest much of the time while hanging onto the rock with
only one foot. The free foot is often used for scratching and for
grooming the fur, and when the bat is engaged in these activities the
body usually swings gently like an erratically disturbed pendulum.
[2]
Flight
The flight of the
Macrotus is remarkable chiefly for its extreme maneuverability. The bat flies fairly rapidly on occasion, but the usual
foraging flight is slow and buoyant, and more nearly silent that of most bats.
[2] In level flight
Macrotus
wings make a soft fluttering sound that is less sharp and carrying than
the sounds made by the wing beats of most other bats. The method of
landing is most interesting. The bat flies six to eight inches below the
ceiling and upon the wings making a deep down stoke that is directed
nearly straight forward the hind limbs and uropatagium.
[2]
These movements cause the bat to swoop upward toward the ceiling and as
the bat nears the ceiling the wings are pulled back in an upstroke
while the bat rolls over 180 degrees so that its back is facing downward
and the long legs reach for the ceiling.
[2]
Stated briefly, then the alighting maneuver consists of an upward swoop
and a half-roll, at the end of which the feet wing rapidly toward the
ceiling, seize it, and the wings give a final beat to steady the bat.
Often these landings must require remarkably precise judgement of speed
and distance, as many landings are made in the midst of a fairly closely
spaced group of bats.
[2] Macrotus
has two main methods of launching into flight, by dropping form the
ceiling and taking flight after a short downward swoop, and by taking
flight directly form the roosting place. The bat often hovers, both when
foraging and when flying in its daytime retreat.
Macrotus seems to hover easily, and it’s able to hover for several seconds at a time.
Foraging habits
This bat is a "gleaning"
insectivore which captures prey such as
crickets,
grasshoppers,
beetles, and
sphinx moths
straight from the ground or foliage rather than in flight. It prefers
to use its large eyes to detect prey, although in total darkness it will
switch to
echolocation.
It typically hunts within a few feet of the ground, using its superior
eyesight to search for insects. It does not alight to capture its prey,
but hovers above it and snags it off the substrate. It then carries its
prey to an open roost such as a porch or open building to dismember,
then consume it.
[3]
These bats usually forage within three feet of the ground and often
drop down closer to the ground nearer the surface where they can
occasionally hover for a few seconds.
[2] Even bats released in the daytime flew fairly close to the ground. Leaf-nosed bats seem to be totally
insectivorous, and their food clearly reflects the bats’ foraging habits. Some insects regularly eaten by
Macrotus are almost certainly taken from the ground or from vegetation. The bats’ stomachs often contain
orthopteran insects, noctuid
moths and caterpillars, and beetles of the families
Scarabaeidae and
Carabidae, along with unidentified material.
[2] The lists of food items of
Macrotus
contain a plethora of insects that seldom fly, are flightless, or that
fly in the daytime. This constitutes strong evidence that this bat
consumes insects that are on the ground or on vegetation. Most
leaf-nosed bats forage sometime between one hour after sundown and four
hours after sundown, and then retire to a night roosting place. Each bat
seems to have a pre-midnight foraging period of roughly one hour.
[2]
The greatest activity in the early morning seems to occur between two
and one half hours before sunrise and thirty minutes before sunrise.
Bats generally begin returning with full stomachs to their daytime
roosts about two hours before sunrise, and the last bats usually return
approximately twenty minutes before sunrise. A Colony of California Leaf
Nosed Bats can consume up to 250,000 pounds of insects in one night.
[2]
Notes
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