Bats
INTRODUCTION
    Rainforest bats can be put into two groups: megachiropterans and microchiropterans.  The megachiropterans consist of fruit bats, flying foxes, and blossom bats.  Microchiropterans consist of insect-eating and predatory bats.  Fruit bats are generally large, one of more kg, with a wing span of up to 1.6m.  They have large eyes and good vision, so they do not need to use echolation like the microchiropterans.  Microchiropterans are small with a wing span of less than 30cm.  All are capable of echolation and the majority feed on insects.  Sometimes fish, birds, lizards and other bats are eaten.  The vampire bat feeds on mammalian blood and is part of the microchiropterans.    
   Bats play an important role in seed dispersal.  Numerous species of trees and flowering plants use bats as the sole means of getting their seeds into the forest.  By carrying large fruits away from the mother trees, fruit bats increase the reproductive success of many species.  Flying foxes eat the fruit from iroko trees when beginning their northward migration.  Fig trees are fed on by Buettikofer's and dwarf epauleted fruit bats.
   When feeding, the fruit bats swallow the small seeds, and then disperse them in their feces miles away.  If the fruit is too big to be eaten quickly, it is carried off to distant trees, thus distributing the large seeds hundreds of feet away.  The bats give two services to the trees they feed on: first they allow tress and plants to colonize areas that were previously inaccessible to them; and second, the seeds escape being eaten by insects if they are not allowed to fall in great quantities in a small area.  
   Seeds that pass through a bat's gut and are found in the feces have been shown to germinate first.  It is thought that passage through the bat's gut removes any germination inhibitors and leaves the seeds viable and primed to germinate.  The fecal seeds also escape predators better than seeds in fruit or in seeds that were left in the small mass of fibers spit out by the bats.  

MATERIALS AND METHODS
   Mist nests were placed at the Napo Lodge in two areas for two nights: along a trail and in a gap.  At the Aceer, the nets were placed along a trail, and then where two trails met, so the area was more open than where the first net was placed, for one night.  The last night of study at the Lodge, the nets were placed behind a cabin in an open area at the edge of the forest, and in the gap.  The nets were put up at approximately 5:00pm each day, but bats were not observed until 8:00pm.  Only one night during the week were the nets not put up because of a rainstorm.  The other nights were clear, with only a moderate amount of clouds present.  
The type of bat was identified as specifically as possible using the measurements from the wing span, the snout to tail length, the weight, the forearm, the sex, the tail length, the foot length, and the ear length.  Other distinguishing features, such as stripes over the eyes or belly color, were noted.  



RESULTS
    On the first night, 3 bats were caught and identified; two in the gap area and one along the trail. The bat along the trail was a female common fruit bat, while the bats in the gap were the males, species Artibeus jamaicenisis.  Two bats were caught at the Aceer: a female Jamaican and a male Fringe lipped Bat (Trachops cirrhosus) in the more open area.  Five bats were caught the last night at the lodge: a female Jamaican in the gap area, two Chiroderma, a male and a female, behind the house, a male Jamaican behind the house, and a male White lined fruit bat (Vampyrops) behind the house (see Table 1 for identifying measurements).  
    Guano was collected from 2 Jamaicans, the 2 Chiroderma and from the common fruit bat.  The guano was examined under a dissecting microscope for content.  The stool from the jamaicans had small, dark seeds in it, almost like poppy seeds, but more like flecks.  The consistency was loose, watery and yellowish - "fruity" looking.  The samples from the Chiroderma were very similar to the jamaican samples.  The stool was dark in color though and it was hard to distinguish the seeds from the rest of the sample.  The common fruit bat did not give me much of a sample to look at.  Instead of examining it, I let the sample sit for a month.  Upon examining it then, there were white hair-like projections growing in abundance from the guano, which had a green tinge to it.  








Time found Location Weight (g) Wing span (cm) Snout-Tail (cm) Forearm (cm) Tail (cm) Foot (cm) Ear (cm) Sex Species
8:40pm Trail -L
44
31
6.3
4.4
 none
1.1
1.5
 female Fruit bat
9:00pm Gap -L
82
45
7.8
6.9
 none
1.35
1.7
 male jamaican
9:10pm Gap -L
88
50
9.5
7.1
 none
1.2
1.8
 male jamaican
8:00pm Aceer-O
99
54
9.6
4.4
 none
1.1
1.4
 female jamaican
8:00pm Aceer-O
62
41
7.8
6.2
0.6
1.2
2.6
 male Fringe lipped
9:26pm Gap -L
41
29.5
5.1
4.3
 none
0.9
1.5
 female jamaican
10:00pm House-L
44
28
6.29
4.6
1.1
1.05
2.4
 male Chiroderma
10:00pm House-L
42
29
5.2
4.35
1
1.1
1.85
 female Chiroderma
10:00pm House-L
88
40
9
7.2
 none
1.7
1.2
 male jamaican
10:00pm House-L
33
24.5
3
3.6
 none
0.7
0.9
 male Whitelined Fruit Bat

    Table 1 Measurements of Bats for Identification  The measurements were taken in cm (lengths) or grams of the weight, wing span, body length from snout to tail, the forearm, the tail, the foot, and the ear, and also the sex was noted.  The species was determined using these measurements.  L stands for Lodge, O for open area, House was the net set up in the area behind the cabin.  The bats were placed in cloth sacks after removal from the nets for ease of carrying to the examining table, and to try to get a guano sample.  They were weighed in the bags, measured, then released.  The guano sample was taken from the bag if the bat had defecated in it.  



DISCUSSION
    It is not surprising that most of the bats were caught along trails, since bats use them as aerial highways during flight and foraging.  All bats in the suborder Microchiroptera echolocate.  Flying along trails makes this easier because foliage and trees are not in the way, and the insects have nothing to hide behind, or are flying freely and therefore easy to catch.  I did find seeds in the guano of these bats; fruit and nectar are main staples of many bats' diets.  The jamaican, the white-lined fruit bat and the Chiroderma are all feed on fruit and nectar as well as insects. This would explain the watery consistency of the stool, as well as the yellow color observed in a sample.  Fruit is easily found by sight and smell, which these bats have a great senses for.  Surprisingly the eyesight of bats is well developed.  Many do not use their echolocation most of time, relying on sight and smell to find fruit and nectar.    
    When the bats had flown into the nets, it was at a very low height that we freed them from - between our chest and waist.  Perhaps the bats had been chasing an insect and flew into the net following their prey.  Another possibility is that it was easier to fly lower because there was no foliage hanging into the trail.  Also, the insects the bats were catching could have been on the ground or flying low to the ground to avoid being detected.  A study done on an island in Panama found 35 species of bats, and 9 food guilds.  Within each guild, there was partitioning of food resources according to particulate size.  Two of the categories were frugivores close to the ground and frugivore scavengers (forest floor).  The bats caught could have been from either of these food guilds, explaining why they were caught so low in the nets.  
    None of the bats were caught before 8:00pm, and most were caught between 9:00pm and 10:00pm.  If the bats were searching for food, one would think that they would be out sooner, with the setting of the sun, to take advantage of the extra light to help them find fruit.  Since they were out so late, when it was very dark, the bats seem to be relying more on their sense of smell to find fruit than their sight.  Bats do have good vision, but the forest is especially dark because the moonlight can not filter down through the dense foliage.  This may be another reason that the bats fly along the trails - there is more light for them to find fruit by.  Some insects are also attracted to lit areas, so insect gathering may be more productive along the open trails.  
    The white-lined fruit bat, the big eyes bats (Chiroderma) and the large-fruit eating bats (Artibeus jamaicensis) all belong to the neotropical fruit bats, subfamily Sternodermatinae.  They all feed on fruit, supplementing their diets with nectar and insects during the dry season.    To feed they pick fruit from a tree and fly away, carrying it in their mouths to a feeding roost.  I did not see any fruit on the ground below the nets indicating that they were foraging for fruit and had dropped it upon collision with the nets.  During the time that we were down there, the waters were rising.  Perhaps this encourages insects to breed and become more abundant, so the bats switch from fruit as being their main dietary staple to insects.  
    Bats are extremely important seed and pollen dispersers.  When they carry fruit away to eat while roosting, they move seeds away from the tree.  Large seeds are therefore carried away and then dropped on the forest floor if they can not be consumed.  Fruits that are smaller may get eaten at the tree, but the small seeds must go through the bats system before they are dropped, so they too get carried away.  Some bats drink nectar.  In doing so, they are brushed with pollen.  When they go to the next flower to feed, they brush the pollen that is on them onto the new plant, hopefully pollinating it.  Flowers that are far away from one another can still be pollinated and genetic diversity remains high.
    Unfortunately I was not able to collect a guano sample from the Fringe-lipped bat (Trachops cirrhosus).  These bats feed on frogs and lizards with some insects.  They are carnivores, and appear to mainly feed on frogs.  They have developed the ability to home in on frog calls and learn to avoid poisonous species by recognizing the call.  Fringe-lipped bats fly low in the forest under story, again why we caught them easily in the nets at a easily extractable height.  The guano from these bats might have proved interesting to examine.  I am not sure if these bats actually grind up everything in their mouth, including the bones, and then eat that, or if they spit the bones out while feeding. Some bone fragments or small bones must survive through digestion, which would have been a good clue as to what the bat had recently eaten.  
    The female bats compared to the male bats of each species (if each sex was caught) are smaller, with the exception of the female jamaican found at the Aceer in the open trail.  Her body weight was 11g more than any of the males.  Even taking into account the bag being made with extra material or extra thread would not equal 11grams.  This female may have been pregnant, but that is doubtful because her  weight, wing span and snout to tail measurements are also greater than those of the other males.  Interestingly, her forearm measurement, which was only 4.4cm compared to 7.1cm of the largest male, does not correlate with her increased body size and weight, or her wing span.  The largest male had a wingspan of 50cm with a forearm length of 7.1cm.  Females of many species have smaller frames, and she is no exception.  The other female jamaican found behind the cabin is about half the size of the large female and the other males.  The large female would seem to have potential to be a good choice to breed with.  Her large size may be an adaptation or it could be a hindrance.  She needs to eat more to sustain her large size, and males may be intimidated to mate with her.  Her large size may be good for defending her pups, or she may be able to bear pups more easily.  Specific studies could be done to test if size is an important factor in pregnancy and food gathering abilities.  Obviously, the larger the bat, the larger the fruit it can carry away.
    The tropical rain forests depend on bats as pollinators and as predators.  The insect populations are kept in check due to predation by the bats.  The bats may help maintain the insect diversity as well, since they eat by echolocation.  They are going to eat what they can find the most of.  If a species starts to become more numerous than other insect species in the same general area, it is going to be eaten more by the bats.  This is known as frequency dependent selection, which bats must rely on since they do not have a search image per se.  With their echolocation abilities, they do know the size of objects, but not the colors, how big the wings are, etc.  There is little that insects can do to get away from bats, other than jam the signals being sent out by the bats, or dropping out of the air when the bat nears.
    Bats have evolved highly sophisticated feeding techniques.  We did not catch any bats that were piscine or sanguine, but there are no other species of animals that have evolved to eat such a  wide variety of food. In all, the data collected match previous findings.  Several defining characteristics of each species enabled the identification of the bats, as well as our guide.  The nets along the trails were the most successful and the guano samples gave a good idea of what each species was currently consuming in their diets.  Several suggestions to answer some interesting findings have been posed.  These could be tested to get more definitive answers and possibly note new behaviors or even new species.  Interactions between bats and plants are well understood, but some bat species' behaviors and feeding patterns have not been documented.  I am sure that there are bats in the tropics that have not been identified yet as well.  Bats are an interesting species, and the possibilities for research are vast.

REFERENCES
Chambers Wildlife Rainforest Lodge. "Rainforest Bats." Accessed Feb. 14, 2000 from the World Wide Web: http://rainforest-australia.com/bats.htm

Emmons, Louise. Neotropical Rainforest Mammals: A Field Guide, University of Chicago Press, Chicago, 1999.

French, Barbara. "False vampires and other carnivores." Accessed Feb. 14, 2000 from the World Wide Web: http://www.batcon.org

Kricher, John. A Neotropical Companion, Princeton University Press, New Jersey, 1997.

Marks, George. "Echolocation -Moth defense system." Accessed Feb. 14, 2000 on the World Wide Web: http://www.batconservation.org/content/infoarticles/infoarticles.htm

Thomas, Donald W. "On fruits, seeds and bats." Accessed Feb. 14, 2000 from the World Wide Web: http://www.batcon.org