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  Bats & Spiders & Dead Things
  BQR ~ spring 1998

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 zoos).
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 Park:

• 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 on-site.
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 brownies!)
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.

Elaine Leslie

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!



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