Hundreds of thousands of Mexican free-tailed
bats roost under a causeway in California. Our intrepid photographer
shares some amazing photos from their nightly feeding.
Fri, Sep 13 2013 at 4:59 PM
http://www.mnn.com
Photos by Jaymi Heimbuch unless otherwise noted
After a dusty drive over the dirt roads of a rice farm, the caravan
of cars stopped. We all exited our vehicles and moved to the front of
the line. Dragonflies flitted over the tall, waving stalks of rice and
mosquitoes began to appear in clouds. Tour leader Corky Quirk dropped a
large box filled with bottles of OFF next to the orange cones she had
set out. This was the 50-yard mark. We stood and waited while the sun
set, because 50 yards in front of us, we were about to see 250,000 Mexican free-tailed bats take flight.
Photo: USFWS Headquarters/Creative Commons
The Mexican free-tailed bat is one of the most widespread mammals
in the western hemisphere. These tiny, 3.5-inch long flying mammals have
a tail that is nearly half its body length, and while many species of
bats have skin that creates a webbing between the tip of the tail and
the body, called the uropatagium, the Mexican free-tailed bat's
uropatagium goes only about half way up the tail. Hence the name,
free-tailed.
Photo: USFWS Headquarters/Creative Commons
They can be found in the southern half of the United States,
throughout Mexico, Central America and into South America. In fact, it
is called both the Mexican free-tailed bat and the Brazilian free-tailed
bat because that is where they migrate to each year — the species
summers in the northern part of its range and migrates south for the
winter. However, exactly where it goes and how it spends its
winters is not clear — though how it spends its summers certainly is.
Here in the U.S., Mexican free-tailed bats are well known and loved — at least those who understand them.
The states of Oklahoma and Texas have named the Mexican free-tailed bat
the official state bat, and where this species roosts in large
colonies, humans are drawn to watch the nightly spectacle of their
emergence from roost to sky.
That is exactly why we were gathered next to a causeway in Davis,
Calif. A happy accident of engineering made the underside of this bridge
an ideal habitat for roosting Mexican free-tailed bats. The expansion
joints offer three ideal features that bats look for in a roost: they
retain heat, and this species loves heat; they are inaccessible to
predators; and they offer tiny cracks perfect for these bats to wiggle
into and feel safely hidden. It also helps that this causeway spans a
large wetland, including the Yolo Bypass Wildlife Area.
It is here that one of the largest wetlands restoration projects in the
west has taken place and, with the recovery of native habitat comes an
enormous food source for bats: insects. Mexican free-tailed bats eat as
much as four times their own body weight in insects every single night.
Their presence is a huge boon for local farmers, who benefit from the
free pest control. In fact, a recent study showed that bats save farmers billions of dollars every year in reduced pesticide use and reduced crop damage thanks to their help with eating harmful insects. As problems like white-nose syndrome increase, so too does the cost of farming. Protecting bats directly translates to protecting our food supplies.
Corky Quirk, the tour leader, is a local expert on bats and runs
Northern California Bats, a nonprofit focused on rescuing,
rehabilitating and releasing bats. She also is a teacher, and volunteers
with the Yolo Basin Foundation, providing tours to people curious about
local wildlife. While the Yolo Basin Foundation offers a whole range of
events and tours for wildlife, it is the bat tours that are perpetually
sold out. When Quirk asked for a show of hands among the 30 or so
attendees who had become a member of the foundation specifically to go
on a bat tour, more than half the hands were raised (the other half were
probably mostly guests of the members!) There is something both
mysterious and enchanting about bats, especially when you know you'll
get to see a quarter of a million of them take flight at once.
After the sun had set but well before the light had gone, the first
wave of bats began. For several minutes the bats streamed out of the
causeway, exiting away from the bridge and over the fields, to the
amusement and amazement of the onlookers. After awhile, the stream
petered out, but that was only the end of the first wave — yet another
wave of bats began a few minutes later. Cars and trucks continued to
make their way across the causeway, lucky in their timing to also get to
witness the event. One semi-truck gave a horn honk and a wave as it
passed the thousands of bats and small group of staring people. The bats
flew off into the darkening blue sky where they would hunt at an
elevation of about a mile up for the rest of the night.
Yolo Basin Foundation isn't the only place where people gather to
see the species emerge for the evening. Other areas where the colonies
draw crowds are Bracken Cave near San Antonio, Texas, where nearly 20
million bats roost; and in a more urban setting, under the Congress
Avenue Bridge in Austin, Texas. where 1.5 million bats emerge every
night during their summer stay.
Photo: USFWS Headquarters/Creative Commons
While abundant elsewhere, the population of Mexican free-tailed
bats on the West Coast is actually experiencing a decline, and it is
considered a species of special concern in California. Factors include
problems such as pesticides, which reduce its prey source; predators
including house cats and even fly strips; construction and renovation on
homes or trimming trees where bats roost; and the fact that the species
prefers to roost in large numbers in a few locations. This means that
vast numbers can be killed in one swoop if someone decides to cut down a
particular tree or, in the case of the Davis, Calif., colony, if there
is construction on the causeway that they call home. Thankfully this
particular colony has the Yolo Basin Foundation and many fans to look
out for their well-being.
Bats take flight in seasonal spectacle
Hundreds of thousands of Mexican free-tailed
bats roost under a causeway in California. Our intrepid photographer
shares some amazing photos from their nightly feeding.
Fri, Sep 13 2013 at 4:59 PM
Related Topics:
Photos by Jaymi Heimbuch unless otherwise noted
After a dusty drive over the dirt roads of a rice farm, the caravan
of cars stopped. We all exited our vehicles and moved to the front of
the line. Dragonflies flitted over the tall, waving stalks of rice and
mosquitoes began to appear in clouds. Tour leader Corky Quirk dropped a
large box filled with bottles of OFF next to the orange cones she had
set out. This was the 50-yard mark. We stood and waited while the sun
set, because 50 yards in front of us, we were about to see 250,000 Mexican free-tailed bats take flight.
Photo: USFWS Headquarters/Creative Commons
The Mexican free-tailed bat is one of the most widespread mammals
in the western hemisphere. These tiny, 3.5-inch long flying mammals have
a tail that is nearly half its body length, and while many species of
bats have skin that creates a webbing between the tip of the tail and
the body, called the uropatagium, the Mexican free-tailed bat's
uropatagium goes only about half way up the tail. Hence the name,
free-tailed.
Photo: USFWS Headquarters/Creative Commons
They can be found in the southern half of the United States,
throughout Mexico, Central America and into South America. In fact, it
is called both the Mexican free-tailed bat and the Brazilian free-tailed
bat because that is where they migrate to each year — the species
summers in the northern part of its range and migrates south for the
winter. However, exactly where it goes and how it spends its
winters is not clear — though how it spends its summers certainly is.
Here in the U.S., Mexican free-tailed bats are well known and loved — at least those who understand them.
The states of Oklahoma and Texas have named the Mexican free-tailed bat
the official state bat, and where this species roosts in large
colonies, humans are drawn to watch the nightly spectacle of their
emergence from roost to sky.
That is exactly why we were gathered next to a causeway in Davis,
Calif. A happy accident of engineering made the underside of this bridge
an ideal habitat for roosting Mexican free-tailed bats. The expansion
joints offer three ideal features that bats look for in a roost: they
retain heat, and this species loves heat; they are inaccessible to
predators; and they offer tiny cracks perfect for these bats to wiggle
into and feel safely hidden. It also helps that this causeway spans a
large wetland, including the Yolo Bypass Wildlife Area.
It is here that one of the largest wetlands restoration projects in the
west has taken place and, with the recovery of native habitat comes an
enormous food source for bats: insects. Mexican free-tailed bats eat as
much as four times their own body weight in insects every single night.
Their presence is a huge boon for local farmers, who benefit from the
free pest control. In fact, a recent study showed that bats save farmers billions of dollars every year in reduced pesticide use and reduced crop damage thanks to their help with eating harmful insects. As problems like white-nose syndrome increase, so too does the cost of farming. Protecting bats directly translates to protecting our food supplies.
Corky Quirk, the tour leader, is a local expert on bats and runs
Northern California Bats, a nonprofit focused on rescuing,
rehabilitating and releasing bats. She also is a teacher, and volunteers
with the Yolo Basin Foundation, providing tours to people curious about
local wildlife. While the Yolo Basin Foundation offers a whole range of
events and tours for wildlife, it is the bat tours that are perpetually
sold out. When Quirk asked for a show of hands among the 30 or so
attendees who had become a member of the foundation specifically to go
on a bat tour, more than half the hands were raised (the other half were
probably mostly guests of the members!) There is something both
mysterious and enchanting about bats, especially when you know you'll
get to see a quarter of a million of them take flight at once.
After the sun had set but well before the light had gone, the first
wave of bats began. For several minutes the bats streamed out of the
causeway, exiting away from the bridge and over the fields, to the
amusement and amazement of the onlookers. After awhile, the stream
petered out, but that was only the end of the first wave — yet another
wave of bats began a few minutes later. Cars and trucks continued to
make their way across the causeway, lucky in their timing to also get to
witness the event. One semi-truck gave a horn honk and a wave as it
passed the thousands of bats and small group of staring people. The bats
flew off into the darkening blue sky where they would hunt at an
elevation of about a mile up for the rest of the night.
Yolo Basin Foundation isn't the only place where people gather to
see the species emerge for the evening. Other areas where the colonies
draw crowds are Bracken Cave near San Antonio, Texas, where nearly 20
million bats roost; and in a more urban setting, under the Congress
Avenue Bridge in Austin, Texas. where 1.5 million bats emerge every
night during their summer stay.
Photo: USFWS Headquarters/Creative Commons
While abundant elsewhere, the population of Mexican free-tailed
bats on the West Coast is actually experiencing a decline, and it is
considered a species of special concern in California. Factors include
problems such as pesticides, which reduce its prey source; predators
including house cats and even fly strips; construction and renovation on
homes or trimming trees where bats roost; and the fact that the species
prefers to roost in large numbers in a few locations. This means that
vast numbers can be killed in one swoop if someone decides to cut down a
particular tree or, in the case of the Davis, Calif., colony, if there
is construction on the causeway that they call home. Thankfully this
particular colony has the Yolo Basin Foundation and many fans to look
out for their well-being.
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