1 The herbivores
As you work through this course you will come across boxes, like this one, which give you advice about the study skills that you will be developing as you progress through the course. To avoid breaking up the flow of the text, they will usually appear at the start or end of the sections.
As well as the course text, you will be using The Life of Mammals book (LoM) and related The Life of Mammals DVDs, as described in the introduction to this course. Before you go any further, watch 'Plant Predators' on the DVD and read LoM Chapter 4. Unless stated otherwise, all the page references you encounter in this course will be to LoM.
In this section you are presented with information about the different groups of herbivorous mammals. Make a list of these groups, with the species in each group, in a notebook for reference. You can add more to the list as you continue to work through the course.
The plant predators, or herbivores, are a varied group, but they share certain characteristics. Many of them are large; among the smallest is the chevrotain (or mouse-deer) at about two kilograms weight, and the elephant is the largest, with a typical bull male weighing around six tonnes. Most herbivores can run fast and they usually have eyes at the sides of their heads, rather than at the front. These laterally pointing eyes provide wrap-around vision and enable them to feed while, at the same time, keeping watch for the animal predators that are likely to be a threat (the carnivores). For some, speedy locomotion enables them, more often than not, to make good their escape, as you will see towards the end of the TV programme 'Plant Predators'.
Most of these plant predators belong to a group generally referred to as the ungulates, whose identifying characteristic is that they have hooves, rather than claws. Within the ungulates, there are two orders, the odd-toed ungulates, or Perissodactyla, and the even-toed ungulates, the Artiodactyla. As you might guess, these groupings depend on the structure of their feet. The odd-toed ungulates are the horses and their relatives, like the zebras, with one toe, and the 'nail' modified as a hoof, and the tapirs and rhinoceroses which typically have three toes on each foot. You may already have spotted that there are some exceptions to these rules; the Brazilian tapir does have three toes on its hind feet, but its front feet have four - three functional ones plus a vestigial fourth toe. The even-toed ungulates have two or four toes, often with a gap between them, giving a cloven-hoofed appearance. They include the camels, deer, antelopes, cattle, sheep and goats. Additionally, included in this loose grouping of plant predators are the elephants, or subungulates, and the sloths, which belong to the order Xenartha.
In this course I'll be looking in more detail at some of the problems and consequences of adopting a plant-eating way of life, building on what you know already from reading LoM and watching the TV programme. As you know from LoM, the plants that make up the diet of many herbivores are grasses and broadleaved plants that are comparable in leaf structure to the familiar garden plants. Herbivores that eat grasses and other herbaceous (non-woody) plants are generally termed grazers and many of the animals I refer to in the early sections of this course are grazers.