Among the world's 44,444 species of mammals, bats are
unique. All 986 species fly, and they fly well. They provide their
own power and generally control their own flight plan.
A simple, positive step in the evolutionary course.
The ties that bind these mammals which have taken to the sky to
all of the other species of mammals on earth are few, but strong.
Each produce body heat internally, have hair and nurse their young.
These are the characteristics which set them apart from slimy amphibians,
scaly fishes, soaring birds and earth-groveling reptiles.
Bats belong to the order Chiroptera (hand-wing) and each fall into
two suborders: big bats (Megachiropterans) and little bats (Michrochiropterans).
Internally, the digestive, circulatory and nervous systems are much
the same as in other mammals, however, they reflect the evolutionary
changes associated with flight and a particular mode of life. Variation
amongst species is obvious. Bodies range from drab, mouse colors
to red, yellowish, or white spots on a jet black coat. The variations
in feeding strategies are truly amazing. Some bats have teeth and
jaws adapted for eating hard-bodied insects, others for soft-bodied
insects. About 70% of all bats practice insectivory, taking prey
on the wing or gleaning them from foliage. Yet others have small,
sharp teeth suitably sized to eat lizards, frogs, rodents and even
birds (carnivory). There are your fish eating bats (piscivory) and
even bat-eating bats (cannibals!). And, there are three species
with razor sharp teeth which drink fresh blood (sanquivory). Two
of these feed on birds and the third on livestock. Contrary to popular
belief, none of these live in Transylvania nor in Arizona (except
In Arizona, 28 species of bats are found, 19 of which are found
in Grand Canyon National Park, and 7 of which are federally protected.
Over the past two years, extensive survey efforts were conducted
by a cooperative, multi-agency task force along the Colorado River,
the North and South Rims and the Kaibab National Forest. Studying
bats is tricky work. Because of their nocturnal habits, flying capabilities
and ability to use sonar, they can detect objects in the complete
darkness (even fine mist-nets). Consequently, little is known about
bats' life history traits, reproductive rates or roost sites.
The surveys were conducted with three main objectives that relate
to establishing baseline data on the bat fauna of Grand Canyon National
• Information on species composition
• Relative abundance of different species
• General information on distribution and habitat occurrence
of different species
Two methods for acquiring information were utilized: fine mist-nets
to physically capture the mammals and an ultrasonic recorder. Ultrasonic
surveys have some important advantages as compared to mist-net surveys;
many bat species are difficult to capture in nets, especially if
there is a full moon phase or even the slightest of breezes. The
ultrasonic recorder is designed to identify bats by the pulse rate
and time pattern of the dominant frequency of their calls. The entire
echolocation frequency is recorded and analyzed by a laptop computer
Many exciting discoveries were made during these surveys. The first
documented Western Mastiff bat maternity roost site in Arizona in
30 years was discovered. Evidence from an exit count suggests re-establishment
of a summer colony of Townsend's big-eared bats at Stanton's
Cave. And at river mile 30, a new range record was established for
the Mexican long-tongued bat, over 250 miles north of its previously
recorded maximum northerly range! (This little guy was actually
caught by hand as he hovered over the sweet aroma of dutch-oven
Although these surveys added greatly to our existing knowledge of
Grand Canyon bats, new questions have arisen and others go still
unanswered. Long term ecological monitoring is needed in order to
analyze trends in these environmentally sensitive species.
This year, through a cost share funding agreement between Grand
Canyon National Park and Bat Conservation International, Grand Canyon
wildlife biologists will once again be conducting bat surveys along
the river corridor and on the north and south rim forested areas.
All things considered, bats are a keystone species to the world,
invaluable links in the web of life, and worth saving.
So there you were, bobbing down through the Canyon with the oars
behind your knees just enjoying the day and all of a sudden you've
got a spider web strung across your face. Your boating buddies are
pulling webs out of their hair, sunglasses, eyebrows, etc. Next
somebody is asking how do those spiders string the web across the
river? Did they walk across the river with silk in tow, or cut a
deal with Raven for a ride? Occasionally you may have noticed spider
webs floating in the air and you probably thought it was from a
broken web, but it really was “ballooning spiders”.
Ballooning is an aerial method of dispersal used by spiders. In
order to balloon a spider climbs up a nearby rock or tree to gain
elevation, then faces into the wind, raises its abdomen and starts
spinning some silk. As the spider creates more surface area to its
balloon the breeze will lift the spider into the air. Spiders can
even exert some control over their flight by pulling in threads
or spinning more threads. Ballooning spiders have been seen soaring
up to 10,000 feet, but generally soar around 200 feet in altitude
and can travel for hundreds of miles.
It was once believed that only one species of spider could fly through
the air and just once a year. Now it is understood that all families
of spiders contain species which can disperse spiderlings through
ballooning, especially in the spring after hatching. Late this past
October several river trips encountered massive Black Aphid hatches
that “fogged” the sky with these tiny midge-like flies.
Mixed in with the aphids were hundreds of ballooning spiders no
doubt enjoying a mid-flight snack.
Stacy Nichols and Joe Shannon
nau Aquatic Ecology Lab
The Aquatic Food Base Project at Northern Arizona University is
attempting to understand and document food web for the aquatic/riparian
community in Grand Canyon and we are requesting help this summer
from the river community. There are several ways of determining
the pathways of energy through an ecosystem, such as gut-analysis
to see who eats who, and general observations. However both of these
techniques are flawed in that 100% assimilation is assumed, which
we know is not true.
A more quantitative approach is through stable isotope analysis,
using the ratio of an element, say carbon, which has an atomic number
of 12 compared its naturally occurring stable isotope (non-radioactive)
which has an atomic number of 13. Every plant and animal has a certain
12C:13C ratio so one can detect not what the animal has just eaten,
but what is taken up in its tissues. So if we took a fingernail
clipping from you and ran it through a mass spectrometer and got
a 12C:13C ratio, all we would have to do is match it up with the
food items that you have might have consumed. If your winter diet
was only Taco Bell and beer we might be able to determine that you
assimilated the cheese and beans from the taco and that you actually
do only “rent” beer because that signal was not present
in your nail tissue.
The river community can help us by salvaging the dead animals (lizards,
birds, etc.) that you come across in your travels. We can collect
the majority of the aquatic organisms including fish, but want to
try using a salvage tactic to learn about the riparian dwellers,
instead of the traditional biologist approach of killing things
to better understand them. If you are interested in helping, we
would need to add your name to our collecting permits so during
transport you are legal. We will also give you a small collecting
kit and instructions.
Please contact Joe Shannon at 520/523-1740 or Joseph.Shannon@nau.edu
if you would like to lend a hand and earn a custom food web t-shirt!