Guest post by Caitlin Wells – Small mammal ecology
On your safari through the picturesque savannas and miombo woodlands of East Africa, here are some species you probably will not see: the Kihaule’s mouse shrew (Myosorex kihaulei), the Southern Giant Pouched Rat (Cricetomys ansorgei), the Chestnut African Climbing Mouse (Dendromus mystacalis), and Wahlberg’s Epauletted Fruit Bat (Epomophorus wahlbergi). Weighing between a few grams and 2 kilos (the threshold for what scientists call a “small mammal”), most shrews, rodents, and bats are too small to attract much attention. Plus, most are nocturnal, venturing out only after the sun has set, when most potential humans observers are at home safely ensconced in their bednets. Yet the diminutive stature of these species belies their outsized role in the ecosystem. Because Leonard’s vision for Mkuyu graduates includes a comprehensive understanding of all pieces of the African ecosystem – from underground fungi to migrating raptors, not just the “Big Five” – he invited me to Mkuyu to talk about some of the “charismatic microfauna” of the area: rodents and bats.
Small mammals, particularly rodents, are one of the foundations of the savanna ecosystem. As you might guess, this is because many other animals find them delicious: they provide food for charismatic species like Long-crested eagles, juvenile Rock pythons, Banded mongoose, Caracals, and Black-backed jackals. But small mammals also provide at least two important services for the plant community: pollination and seed dispersal. The baobab, that iconic tree of Sub-Saharan Africa, relies on epauletted fruit bats to pollinate their large flowers; the resulting fruits, which are rich in calcium, provide nutrients for many primates (hence the name “monkey bread”), including humans. Other plants, like the protea, secrete extra-sweet nectar to attract mice to their flowers; in drinking from multiple flowers, striped mice move pollen from plant to plant. In East Africa, some forest trees (like Allanblackia and Carapa species) make large, oil-rich seeds to ensure their offspring have all the nutrients necessary for germination in poor tropical soils, but these seeds then are too heavy to be dispersed by wind, water, or birds. Enter the pouched rat and other rodents to the rescue: they eat some of the seeds immediately, but take extras away from the parent tree and bury them a few centimeters below to soil, the perfect depth for seeds to sprout if the rat forgets to come back.
The students had lots of great questions, some of which completely stumped me! As a group, we discussed some of the physiological and behavioral adaptations that many rodents have for being active at night (e.g. relying on smell, instead of sight) and for life underground (e.g. some mole rats living in large groups to cooperate on digging through hard soils). And did you know that not all bats use echolocation? Generally only the insect-eating ones do, which is why so many of them have wrinkled facial features and large ears - to generate and trap sound. By contrast, most fruit-eating bats use color vision to locate food; their large eyes and long snouts make them look more like dogs than other bats - hence the common name “flying foxes.” Understandably, mice, bats, and rats often get a bad rap: if you find one in your house, you start thinking about dirt and disease, not their more positive qualities. But in the wild, without these small mammals, many trees, flowers, snakes, birds, and carnivores would face a much tougher existence. So next time you drive through the Ruaha savanna, marveling at the giant boababs or an elegant black-shouldered kite, you can thank a smammal.
Caitlin Wells is an Ecology graduate student with Dr. Dirk Van Vuren at the University of California, Davis, Department of Wildlife, Fish, and Conservation Biology. She studies the reproductive ecology of birds and mammals.