Natural foods for wildlife
An animal's place in its environment is determined, more than anything else, by what it eats. By studying what the birds and bats of American Samoa eat, and when those different foods are available, we are better able to develop plans to manage and conserve our wildlife and to help these animals in a crisis, such as after a hurricane.
Most animals can be grouped by what and how many kinds of foods they eat. Animals that eat many different things are called generalists, while those that eat only one or a few foods are called specialists. True specialization is often a two-way dependency: an animal depends on a plant for food, and the plant depends on that animal to help it disperse its seeds. On remote islands like American Samoa, there is often not that much of any one kind of food, and hurricanes can cause serious shortages of the foods that are available, so it is usually not a good idea for either a plant or an animal to rely on only one other creature. We have few bird or bat species that are specialists in American Samoa.
The technical word for the generalist, “omnivore”, literally means “eats everything”. Humans probably have the broadest diet of any animal -- we happily eat meat, leaves, seeds, fruit, and fungus -- not to mention Bongos. Animals that are most likely to survive in new environments - like when they first arrived on Tutuila - are often omnivores. A good example is the rat (isumu), which can eat fruit, eggs, crabs, fungi and probably many other things.
“Carnivores” are those species that eat almost exclusively other animals. We usually think of carnivores as fierce hunters, like wolves or lions, but actually any animal that eats other animals is a carnivore. The Barn Owl, or lulu, is the only Samoan animal that hunts other birds and mammals, but we have lots of other carnivores, including all our fish-eating birds and even our many animals that eat insects.
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| All illustrations on this page used with permission from Dick Watling from “Birds of Fiji, Tonga and Samoa” and “Birds of Fiji and Western Polynesia” (Pacificbirds.com). |
“Herbivore” is a description of those animals that eat only plants. This is a very general term, so it is better to specify what part of a plant is eaten, whether leaves, fruits, or nectar. Each kind of animal usually is good at eating only one, or at most two, of these parts of a plant, because they are so different. For example, to rely on leaves, you need strong teeth to grind up the tough fibers, and a big stomach to process all that material. Cows and horses are well equipped for the job. At the other extreme, to rely on nectar (the sweet liquid inside of flowers), you need to be able to zip between lots of flowers and reach inside to suck up the small amount of juice in each one. Nectar-feeders tend to be small and energetic, with long beaks or tongues to reach inside flowers. Finally, to eat fruit, you need to be able to travel long distances, since trees with fruit are often hard to find.
There are no native Samoan animals that are specialized for eating leaves (except insects and snails). However, leaves are regular parts of the diet of fruit bats (pe'a) and Pacific Pigeon (lupe). Perhaps the leaves contain a nutrient that can't be found in fruit, or maybe they help to fill up a hungry animal when there is little other food available.
Nectar is a very important food for many of our local animals. The beautiful red and black Cardinal Honeyeater (segasegamau'u) is our most specialized nectar-eater. Its long bill and tongue enable it to reach deep into flowers, and its small size allows it to perch on even the tiniest twigs to reach the blossoms. Other birds that eat lots of nectar are the Wattled Honeyeater (iao), and the pretty little parrot (segavao) found in Manu'a. It may come as a surprise that fruit bats also eat a lot of nectar. Bats eat flowers from many different kinds of plants, from those with large flowers (such as gatae and futu), medium sized flowers (such as fa'i), to those with large numbers of smaller flowers (such as asi, maota, and a'amati'e). The bats lick flowers using their long tongues, or sometimes take a shortcut and eat the entire flower.
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Fruit is the most common item in the diet of the Samoa Starling (fuia), Pacific Pigeon (lupe), Purple-capped Fruit Dove (manutagi), and fruit bats (pe'a). Though all these animals share many of the same foods, each has its favorites. Differences in what each species eats are partly caused by the different ways they feed and by their different sizes. Since lupe and manutagi swallow fruits whole, this limits the size of fruit they can eat. Manutagi seem to eat no fruits larger than moso'oi, but lupe are not as limited because they have really big mouths and can eat all but the largest fruits. Although fuia are smaller than lupe, they have stronger bills. This allows them to pry open tough husks, and to poke into very large fruits like esi. Pe'a can eat the largest and hardest fruits because of their strong jaws and sharp teeth. They have a very unique way of feeding: they take a bite from a fruit, but don't really swallow it. Instead, each bite is squeezed in the mouth, the pe'a swallows the juice and pulp, then flicks its head and spits out a flattened mass of leftover fruit called an 'ejecta'.
The white-naped fruit bats (pe'a fanua) seem to especially like fruits from plantations such as mangos, and those from coastal trees such as fetau, although maybe they really like flowers best. Samoan fruit bats (pe'a vao) generally prefer fruits found in the forest, both from non-native trees like ifi and native species such as a'amati'e, asi and gasu. Both bats like figs, especially the green-fruited kind of aoa, and perhaps most of all, ulu (breadfruit). But if you see bats in your ulu, you needn't worry that they are taking food from your mouth -- they like the overripe fruit that has been left on the tree so long that people wouldn't eat it anyway.
Our most common Columbiformes (lupe and manutagi) all love the fruit of moso'oi. It's funny to watch a little manutagi struggling to choke down a big moso'oi fruit - but they get it down every time. Another large fruit favored by lupe (and sometimes eaten by manutagi) is the nutmeg (atone). This is an interesting 'fruit', since what the birds eat is almost entirely indigestible seed - the useful part is just a thin, brightly colored network (red or orange depending on the species of atone) that covers the seed. This colored part is very fatty and is a good food for birds even if there is not much on each fruit. Apparently this is a successful way to disperse seeds, since atone is the most common tree in the mature forests of Tutuila.
Fruits preferred by manutagi include aoa, mati, the white berries of soga, and the seeds inside maota and mamala fruits. Lupe eat many of the same fruits, but are able to eat a greater variety because they are a big bird. They also eat the large fruits of mamalava, mamalupe, a'amati'e and ala'a. Mamalupe literally means 'pigeon's mouthful': one lupe once took a full 30 seconds to swallow a single mamalupe fruit!
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Nectar feeders and fruit eaters don't just use their food plants -- they can help them as well by fertilizing their flowers. This happens when pollen from one flower sticks to a bird's feathers or the fur of a pe'a, and then rubs off when the animal visits another flower. Fruit eaters also help plants. Most of the time this happens when they eat the fruit but don't completely digest the seeds; when the animal defecates, the seeds may have been moved far from the parent tree where they have a better chance to grow. Many plants actually count on animals eating their fruits, and so they coat their seeds with a substance that makes them hard to digest. In this way, immobile trees accomplish their most difficult task -- dispersing (spreading) their fruit. When a tree species has no seed dispersers, its spread to new areas will be limited, it can become restricted to only a few places, and it is vulnerable to extinction from hurricanes, diseases, or cutting by people. A good example of such a tree is ifilele, which tends to occur in only a few areas on the north side of Tutuila.
Probably the most important disperser of fruits in American Samoa is the fuia, since it eats a very wide variety of fruits. It is particularly important in regenerating (converting back to forest) areas that have been cleared for plantations or by hurricanes. You can see this by noting how quickly a cleared area will become covered with lau pata, maota, and masame, or how nonu or pualulu begin sprouting in a clearing deep in the forest. Once an area has these initial forest tree species, the area becomes more suitable for tree species that prefer mature forests, like mamalava or asi.
You can play an important role in helping the wildlife on our islands by helping our native trees. First, avoid cutting down or burning native trees, especially slower growing species such as au'auli or important coastal species such as fetau. Other trees are so rare or important that they simply should never be cut, including aoa, tava, and togo. Some plantations illustrate a good compromise between the needs of people and the needs of the forest. As the plantation is cleared, smaller, fast growing trees like lau pata or atone are cut, but larger trees are avoided, or only their limbs are pruned (cut off). In this way crops like talo (taro) get the sunlight they need, but it does not kill large trees that are adapted to recovering from hurricane damage. Such trees may resprout leaves and branches, probably about the time a farmer is done harvesting the crops from the plantation.
Second, help native trees by planting them. You can request seedlings of native species from the Land Grant at the Community College. Always plant native trees instead of exotic (foreign) trees unless needed for their fruit. For example, aoa should be planted instead of pulu trees. Flame trees, vaepovi and African tulip trees may look attractive to people, but these trees benefit fewer wildlife species than our own native trees. For areas such as lawns where large trees are not wanted, tree ferns (olioli) are an attractive native option, while the various kinds of mati are good choices for wildlife. In places where too much shade is undesirable, filimoto is a good choice.
Joshua Seamon, Pepper Trail, DMWR