Herbivore Classification K. Launchbaugh Herbivore Classification NPS.gov K. Launchbaugh REM 456 - Integrated Rangeland Management

Animal species differ in: Digestive anatomy Body size Diets Foraging strategies Habitat requirements K. Launchbaugh J. Peterson K. Launchbaugh J. Olness

Browser-Grazer Continuum Intermediate feeder 70% dicots (shrubs/forbs) Usually small 70% monocots (grass/sedge) Usually large Mix of dicots & monocots Usually medium-sized

Differences between browses and grasses Thin cell wall More lignin in cell wall Phenolics, terpenes, & other toxins Grasses Thick cell wall More cellulose in cell wall Silica

Differences between browses and grasses Low-high growth form New growth added to tips Diffuse architecture Patchy dispersion Grasses Low growth form New growth added at base Compact architecture More uniform dispersion

Differences between browsers and grazers (Concentrate Selectors) Grazers (Roughage Feeders) Small, simple foregut Larger true stomach Larger cecum (more food escapes rumen) Large, subdivided, complex foregut Smaller true stomach Smaller cecum

Browsers Grazers Large reticular-omasal orifice Faster passage More food escapes fermentation Less thorough cellulose digestion Small reticular-omasal orifice Slower passage Less food escapes fermentation More thorough cellulose digestion

Browsers Grazers Cell solubles ferment rapidly Long, dense even papillae for quick absorption More initial chewing, less rumination Cellulose ferments more slowly Sparse, uneven papillae for slow absorption Less initial chewing, more rumination

Browsers Grazers Larger liver for detoxifying plant toxins Small liver Large parotid salivary glands Copious serous saliva to buffer & aid passage Proline-rich proteins for binding tannins Small liver Small parotid salivary glands

Browsers Grazers Narrow muzzle & incisor row Wider mouth opening & more prehensile lips Longer, narrower, more pointed tongue Less cornified tissue Molars lower & more fragile More selective feeding Wider muzzle & incisor row Smaller mouth opening Shorter, fatter, more blunt tongue More cornified tissue Molars tougher with higher, sharper ridges Less selective feeding

Body size interacts with feeding strategies Small animals have relatively high metabolism, thus require energy faster relative to their size Small herbivores can speed up digestion by eating higher quality food (browses) and passing food through the digestive system faster Smaller mouth and lower absolute energy requirements allows small animals to select higher quality food Mouse to elephant curve Body mass (kg) 11

Browsers (Concentrate Selectors) Cannot tolerate large amounts of fiber in their diet Consume plants with high cell contents and low cell wall components Rapid Rate of fermentation Rumination is less important Feeds on smaller amounts frequently Are generally smaller These animals feed primarily on forbs and shrubs throughout the year. Examples of concentrate selectors are moose and roe deer. Non ruminant concentrate selectors include bears and birds (grainavores). These animals don’t do well with diets high in CWC.

Intermediate feeders (Mixed feeders) Adapted to either browsing or grazing Shifts feeding behavior according to plant availability Eats less frequently than browsers and more frequently than grazers Large variation in dietary fiber content between species Are often intermediate in size Examples of these animal species include goats, white-tailed deer, sheep. These are opportunistic feeders.

Grazers (Roughage feeders) Eat mostly grass Large rumens to process forages Longest retention time necessary to digest high percentage of cell wall components Often large-bodied Examples of GR include cattle, bison, sheep. They avoid shrubs that are high in volatile oils (junipers, rabbitbrush, various sagebrushes). We will discuss why later in the lecture—salivary glands. From an integrated range management standpoint know what you want and what animal types can use as management tool.

Summary Anatomy, physiology, and body size of herbivores influences What herbivores can eat Where they can live What other species they can live with How they affect plant communities

Herbivore Classification K. Launchbaugh Herbivore Classification NPS.gov K. Launchbaugh REM 456 - Integrated Rangeland Management