Indirect observations

Many behaviors can be indirectly inferred from sign indexes and density estimates. Habitat selection is often measured through indexes that compare an animal's use between habitats or seasons. When indexes are used as a surrogate for direct observations, the closer the index is to the target behavior the less chance of error. For example, a browse index based on the number of buds clipped per tree is directly re lated to ungulate feeding, while pellet or track counts are more indirect indexes....

What is rumination

The act of rumination, or chewing the cud, is the regurgitation and remastication of undigested fibrous material before it is swallowed again. As the food reenters the rumen, it undergoes further fermentation. The products of fermentation in the form of broken-down food particles then slowly pass to the other parts of the stomach, where the usual digestive juices of the abomasum perform their work. Ruminants secrete copious amounts of saliva that serve to buffer fermentation products in the...

Nocturnal flight adaptations

The focus of this entry will be the adaptation for flight among bats, the only mammals to evolve structures for powered flight. Bats are not just fliers, they are mammalian, nocturnal fliers. Consequently, their adaptation to flight involves more than just the evolution of wings, but also requires solutions to nocturnal navigation, thermoregulatory problems, and energy considerations. Over a span of 65 million years of evolutionary history, natural selection acted to balance several physical...

Evolution and systematics

The mouse-like monito del monte is a small, inconspicuous species of marsupial from South America. Its unprepossessing appearance belies its huge zoological importance. This drab little mammal is a relic of a bygone era all that remains of a once-prominent group that may have given rise to the entire diverse marsupial fauna that now lives on the other side of the world in Australia. The Microbiotheridae are therefore considered part of the otherwise exclusively Australian group known as the...

Language

One of the major distinctions between human and nonhuman animals is language. At the beginning of the animal language projects, the object was to show that an individual from a nonhuman species could acquire and use language. Apes have been the primary participants in these projects. One of the first attempts to teach language to an ape was that of Keith and Cathy Hayes, who reared Viki the chimpanzee in their home from 1947 to 1954. With much effort, Viki learned to say four words, mama, papa,...

Gestation and neonate type

With only a few exceptions, each mammal species has a characteristic gestation period that shows remarkably little variation. In comparisons between species, gestation periods tend to increase as body size increases. However, effective comparisons of gestation periods among mammals must take into account a fundamental distinction in the state of the neonate at birth. As a general rule, it is possible to distinguish fairly clearly between mammals that give birth to several poorly developed...

Mammals IV

Abercrombie, PhD Wofford College Spartanburg, South Carolina Cleber J. R. Alho, PhD Departamento de Ecologia (retired) Universidade de Bras lia Bras lia, Brazil Universidad de la Rep blica Oriental Anders Angerbj rn, PhD Department of Zoology Stockholm University Stockholm, Sweden William Arthur Atkins Atkins Research and Consulting Normal, Illinois Paul J. J. Bates, PhD Harrison Institute Sevenoaks, Kent United Kingdom Amy-Jane Beer, PhD Origin Natural Science York, United Kingdom...

How to tell time

Light-dark rhythm (photoperiod) is known to regulate production of the hormone melatonin that, in turn, regulates circadian (meaning around a day, as in a 24-hour period) rhythms by a feedback mechanism. In surface-dwelling vertebrates (including human), melatonin is produced during dark hours. It can therefore be expected that subterranean mammals living in constant darkness would display high melatonin levels. This does seem to be the case, yet the role of melatonin in regulating activity...

Role of sensory data

Mammals sense or gather information about their environment and use it to make decisions that affect their survival and reproduction. Sometimes, species initially respond to one type of cue. For example, female hammer-headed bats (Hypsig-nathus monstrosus) in Africa locate groups of males by listening to their distinctive calls. Picking a male to mate with, however, is a decision females appear to make only after visiting several in the line of displaying suitors. A female's actual choice may...

Books

Mechanicsburg, PA Stackpole Books, 1998. Geist, V. Mountain Sheep. A Study in Behavior and Evolution. Chicago University of Chicago Press, 1971. Irwin, L. L. Migration. In North American Elk Ecology and Management, edited by Dale E. Toweill and Jack Ward Thomas. Washington, DC Smithsonian Institution Press, 2QQ2. Maddock, Linda. The 'Migration' and Grazing Succession. In Serengeti Dynamics of an Ecosystem, edited by A. R. E. Sinclair and M. Norton-Griffiths. Chicago...

The media

Most of the 5,000 or so living species of mammals have eyes and, in many, the keenness of their vision (visual acuity) is at least equivalent to that of humans. A few mammals have very limited vision, such as river dolphins (Platanistidae, Lipotidae, Pontoporiidae, and Iniidae) that live in extremely murky water or moles (Talpidae) that live in total darkness indeed, in some moles, the optic nerve has actually degenerated. In mammals' eyes, a lens focuses light on the retina, a layer of...

Echolocation

Before there could be nighttime fliers, there had to a way to navigate in the dark. Bats are active at night and they often inhabit darkened areas such as caves or the inside of hollow trees. Echolocation is an adaptation for navigating in visually limited environments. There are other mammals that employ echolocation, including various marine mammals and possibly members of the order Insectivora such as shrews. There is also some suggestive evidence that the colugo, a nocturnal glider, has...

Organizations

The American Society of Mammalogists American Zoo and Aquarium Association 8403 Colesville Road, Suite 710 Silver Spring, MD 20910 USA. Phone (301) 562-0777 Fax (301) 562-0888 < http www.aza.org > Australian Conservation Foundation Inc. 340 Gore Street Fitzroy, Victoria 3065 Australia Phone (3) 9416 1166 < http www.acfonline.org.au> Australian Regional Association of Zoological Parks and PO Box 20 Mosman, NSW 2088 Australia Phone 61 (2) 9978-4797 Fax 61 (2) 9978-4761 < http...