Field Book of North American Mammals: Descriptions of Every Mammal Known North of the Rio Grande, Together with Brief Accounts of Habits, Geographical Ranges, etc.

1. What they did

In 1928 H. E. Anthony, Curator of Mammals at the American Museum of Natural History, set out to write a pocket-sized field book covering every recognized mammal species and subspecies of North America north of the Rio Grande, written first for laypeople. He found no single work that gave descriptions, ranges and notes on habits for all of them.

He followed Miller’s 1923 List of North American Recent Mammals for names, and compiled descriptions from published taxonomic revisions and monographs, quoting or paraphrasing them in many places, as well as from the museum’s own skins. He gave each group at least one full description and kept the others brief by comparison. He left out skull characters (on which most classification rests) except where external features alone could not separate a form. He added common names, creating or choosing them where none existed, and measurements in inches.

The book has 32 coloured plates, 175 photographs, pen-and-ink sketches and range maps, a colored life-zone map, a bibliography and an index of common names.

2. What they found

What the book contains

• Accounts of 1,445 species and subspecies, arranged by order and family, from opossums to dolphins and porpoises.
• For each form: names, key external features, measurements (total length, tail, hind foot, sometimes ear), and geographical range, often by life zone. Range maps support identification of closely related forms.
• For each group: notes on habits, such as preferred haunts, food, dens and burrows, breeding and young, and value to people.
• An exception for grizzly and big brown bears: the most recent review then listed 84 forms in the area, many known only from skulls, so these are treated in broader groups.

Guidance for readers

• Larger mammals can usually be identified at a distance by markings, size and form; geographical range then helps narrow down closely related forms.
• Many small mammals (meadow mice, white-footed mice, pocket mice, jumping mice) are seldom seen even where common, so the author recommends box-traps and gives baits, as well as how to prepare museum study skins.
• Descriptions are norms for an average individual; individuals may vary by 10% or more in size.
• Weights of large mammals are poorly known, and the author asks sportsmen to record them.

Examples of habits described

• The red fox prefers varied country with cover and hunting grounds, avoiding unbroken forest and open plains. One fox usually covers an area no more than 5 to 10 miles across during the year. Foxes are mostly active at night, dig burrows or use hollow logs and stumps, and both parents care for four to nine young born in March or April.
• The Texas armadillo account, quoted from Vernon Bailey, describes dens with worn doorways, trails that can be followed for half a mile, small hoof-like tracks, washboard-like prints of the armor in mud, and rope-like prints of the dragging tail.

3. What they concluded

• No single volume can serve both scientists and laypeople, so this one puts the layperson first and refers technical readers to the cited revisions.
• External features are not always diagnostic on their own, but they serve well when combined with the known geographical range.
• Much remains unknown about the behaviour of even common mammals, especially small and nocturnal ones. The author strongly recommends that people outdoors keep a journal of the mammal behaviour they see, which may supply new and valuable data.

4. How tracking was or was not used

The book is a field guide, not a tracking study, and does not give a systematic guide to tracks and signs. Tracks and trails come up only in passing in some species accounts, for example that a red fox track is very like that of a small dog, and the quoted description of armadillo trails and prints.

6. Other technologies, skills or innovations

• Standard measurements of mammals (total length, tail vertebrae, hind foot, ear from crown or notch), with instructions on how to take them.
• Range maps and the United States Biological Survey life-zone system as aids to identification.
• Live-trapping with box-traps and the preparation of museum study skins.