Swiftlets & sheath-tailed bats (o le
pe'ape'a):
A mosquito's nightmare
 |
| Mosquito after M. Service. 1993. Mosquito ecology field sampling methods. Chapman & Hall (UK). |
High above the villages, valleys, and mountains of Samoa flies a deadly predator, as terrifying as a tiger shark - if you're a mosquito (namu), that is. This is the pe'ape'a, the only bird in Samoa that lives entirely on a diet of insects.
But wait a minute - pe'a means bat: isn't the pe'ape'a a kind of small bat? Well, yes and no. Actually two completely different creatures share the name pe'ape'a in Samoa. One is a bird, the common White-rumped Swiftlet that is seen flying by day all over our islands. Like all birds, this pe'ape'a has feathers and lays eggs. The other pe'ape'a, more properly called pe'ape'avai, is a tiny bat, the Sheath-tailed Bat that is active only at night. This animal is now almost extinct in American Samoa. Like all bats, this pe'ape'a is a mammal and has fur and gives birth to live young that it feeds milk. The confusion arises because both creatures are tiny, active insect-eaters that are almost always in flight, and look similar as they dart and swoop after their prey.
 |
| Used with permission from Dick Watling from “Birds of Fiji, Tonga and Samoa” and “Birds of Fiji and Western Polynesia” (Pacificbirds.com). |
First let's talk about the common pe'ape'a: the bird. It belongs to a family of birds that are truly creatures of the air, the swifts. They have tiny legs and feet, and never land except at nests or in their roosting caves. Capturing and eating food, drinking, gathering nesting material, and yes, even mating, are all done in flight. In fact, it is likely that the pe'ape'a is like many other kinds of swifts and actually sleeps while flying. With their long, powerful wings and perfectly streamlined bodies, pe'ape'a are beautifully adapted for a life of flight.
As they fly, pe'ape'a are continually hunting for small insects, especially mosquitos, flies, and flying ants and termites. These are scooped up in the swift's huge mouth, which is made into an even larger trap by long bristle-like feathers around the mouth. The swiftlet is a very useful bird because of all the insects it eats.
When the pe'ape'a finally does decide that it's time to land, it heads for a cave or a protected overhang on a cliff. There it flutters in to grasp the rock, usually hanging vertically. These caves and sheltered overhangs are also the nest site for the swifts. The nest is a small platform made of moss and fine twigs cemented together with the bird's saliva, attached to the rock. Some close relatives of the pe'ape'a make their nests entirely from dried saliva, which (believe it or not) are collected and cooked up to make that famous delicacy, bird's nest soup. The nests of our pe'ape'a are not suitable for this, so anyone with a taste for bird saliva will have to look elsewhere.
Swiftlets lay one or two white eggs, and appear to nest at any time of year in Samoa. Although most nests are placed where at least a little light penetrates the cave, some are far back, where it is completely dark. How do the swifts find their way in and out? The answer is that these birds, like many small bats, have the amazing ability to echo-locate. They give loud clicking calls, and then listen to the echoes to orient themselves and avoid the walls of the cave. This ability is fairly undeveloped in birds, and the swiftlets don't use it to locate their insect prey, which is why they hunt during the daytime. In many small bats, however, echo-location is incredibly advanced, and is used to hunt tiny insects in complete darkness. One bat with this ability is the Sheath-tailed Bat, which brings us to our second pe'ape'a.
 |
| Sheath-tailed bat (pe’ape’a) |
| Photo by Jorge Palmeirim |
The Sheath-tailed Bat (Emballonura semicaudata) also feeds on mosquitos and other flying insects. But unlike the swift, this small bat does not seem to accept sheltered cliffs as roosting or breeding areas, inhabiting only deep and protected caves. There are few such caves in American Samoa, and therefore few good homes for the bat. Ever since Hurricane Ofa in 1990, the known bat caves on Tutuila have been almost deserted. Hurricanes Ofa and Val swept water and debris into several caves, and the days of strong hurricane winds may have made it impossible for the bats to find food. Unless more bats survive in caves that we don't know about, the long-term survival of this useful and fascinating animal in American Samoa is doubtful. There is little we can do to help the bat except to stay away from their caves to avoid disturbing the few surviving animals. Sadly, the Sheath-tailed Bat seems to be endangered throughout most of its range, including in western Samoa and the Marianas, as well as here.
 |
| Sheath-tailed bat (pe’ape’a) |
| Used withpermission from P. Ryan, Fiji's Natural Heritage, Exisle Publ. (Auckland) |
And what about the swift? Although the population of these birds was reduced by hurricanes in 1990-91, the species seems to be in no danger of extinction. It is still possible to see flocks of hundreds of swifts swirling together in areas where winds collect large numbers of insects, for example in Malaeimi Valley and in such highland areas as Aoloau and Afono Pass. There is every reason to believe that these birds will always enliven the Samoan sky - and strike terror into the hearts of mosquitos everywhere.
Pepper Trail, DMWR