398 ANNUAL EEPORT SMITHSONIAN" INSTITUTION, 192 8 



of the subject. When, generations in the future, the count shalj 

 have been completed, the total number will certainly be found to 

 exceed 20,000. Imagine behind these living mammals the long lines 

 of extinct ancestral and related species reaching into the past and 

 preserved as fossils, and we may form some imperfect idea of the 

 ground to be worked. 



The exploration of this ground by the mammalogist divides itself 

 into two major phases: The collection of material in the field and 

 the study of it in the museum. The difficulties of mammal collecting 

 are greatly increased by the fact that the majority of the mammalian 

 population is made up of small or nocturnal creatures which elude 

 direct observation. While the larger mammals can bo shot, the 

 smaller ones must be trapped. For that purpose the well-equipped 

 collector goes into the field w^ith an assortment of traps specially 

 selected for the capture of mammals of the most varied kind and 

 for use in tlie most varied situations. To use them effectively he 

 must exercise his ingenuity and apply his knowledge in deciphering 

 the records which mammals leave behind them; a path or runway 

 through the grass here; a tunnel under rotting leaves there; foot- 

 prints in snow, mud, or sand; holes and mounds which show where 

 some creature has been digging for roots or grubs, or to make a 

 shelter; piles of the emptied sheljs of seeds, nuts, snails, mussels, or 

 crayfish — in short, a complicated code of signs, the right interpreta- 

 tion of which will lead to success, and the misunderstanding of 

 which may bring amusing failure, as on one occasion when a collector 

 caught nothing but mole crickets after setting many traps in tunnels 

 which he supposed had been made by smal] shrews. 



After being trapped or shot, a mammal must be prepared by the 

 removal of the skin and the drying of the skull or skeleton, as these 

 parts serve the most useful purpose in the subsequent studies.^ 

 Many specimens, particularly of the smaller kinds, are kept entire 

 in alcohol. When field work has been pursued long enough in one 

 place to have furnished representatives of most of the mammals 

 which are found there, the collector moves on to a locality where 

 diiferences in soil, vegetation, or climate give promise that other 

 kinds may be found. In this way a systematic survey of an area 

 is made. After the specimens obtained in the field are received at 

 the museum it is necessary to arrange them so that they may be 

 available for study and safe from the danger of deterioration. To 

 begin with they must be catalogued, numbered, and labeled in ac- 



1 Directions for Preparing Specimens of Mammals, a 22 page illustrated pamphlet, is 

 issued by the Smithsonian Institution (Bull. U. S. National Museum, No. 39, pt. N, ed. 5, 

 revised,, 1925), 



