ANIMAL BEHAVIOR—ERNEST P. WALKER 283 
on almost any part of her body and frequently take a position around 
her body almost like a belt. 
The Brazilian mammalogist, Joio Moojen, of the Museu Nacional, 
Brazil, has informed me that the baby of the rare sloth (Scaeophus 
torquatus) clings tightly to the mother and is almost completely hidden 
in her long loose hair. If no danger threatens, it may cling to her 
back, which is frequently the underside; however, if danger threatens, 
it is brought onto her chest or abdomen which is usually her upper 
side or is between her and a tree trunk. In this position it is well pro- 
tected between the mother and the trunk or branch to which she is 
clinging and is so well hidden in the fur that it can scarcely be seen 
(pl. 8, fig. 2). 
We commonly think of the marsupials as always carrying the 
young in the mother’s pouch. This is true for many of the forms, 
including the common opossums (Didelphis) of North and South 
America, but there are some marsupials that lack the pouch on the 
abdomen of the mother. In some of these species the young are 
carried or dragged about by the mother as they cling to her nipples. 
Good examples of this type are the small South American mouse 
opossums (Marmosa and allied forms) which range in size from 
about that of a house mouse to that of a common rat. The young 
hang suspended from the mother’s nipples which are in a cluster 
between her hind legs, and in this location they are well protected. 
When the young become larger, they are dragged on their backs, 
as the mother walks along the ground. If one becomes detached from 
the nipple, it is lost, for apparently they cannot again attach them- 
selves to the nipples, and the mother appears to make no effort to 
rescue them. The Metachirus pictured with the little ones hanging 
from her nipples had eight babies (pl. 9, fig. 2). 
Rodent babies of a number of different forms in various parts of the 
world also cling to their mother’s nipples until they are of good size, 
and when she travels about on the ground or through the trees, they 
dangle or are dragged about on their backs. The North American 
wood rat or pack rat (Neotoma) has this habit, and as many as four 
young, which individually may weigh almost a fourth as much as 
their mother, will be dragged about by her. 
In the Tasmanian “‘wolf”’ (Thylacinus), a marsupial, the pouch is 
a fold or shelf of skin on the abdomen between the hind legs which 
opens backward—a sort of rumble seat—and the young are carried 
in this. The best pouch of all is possessed by the kangaroos; they 
carry the babies in a large, deep, baglike fold of the skin of the mother’s 
abdomen until they may weigh almost one-fourth as much as the 
mother. When there are no young in this pocket, or when they are 
very little, it is shrunken and drawn up until it is rather small, but 
as the young grows the pouch stretches and can accommodate one 
