_P. dimidiatus_ was studied in the field and laboratory. _P. dimidiatus_
in captivity showed regular diurnal activity, coming out of the nest for
food at intervals. Individuals were fed a cereal mixture and nuts of
small size. The animals usually buried the nuts in the sand of the outer
cage. While holding the nut with the mouth and front feet, the animal
patted the sand rapidly, thus burying the nut, and it then pushed more
sand over the place with the front feet.
Sometimes the emergence from the nest is followed by a long yawning and
stretching ceremony. The animal spreads the fore and hind legs widely
apart, while the back is curved down and the head and tail turn upward.
Then one of the hind legs is stretched backward and, at the same time,
the mouth is opened widely and the tail is moved in an undulatory
fashion. The operation may be repeated using the other legs, or not.
_P. dimidiatus_ was regularly found in climax forest. The best shelter
and nesting ground was usually under boulders, commonly not farther than
10 meters from water. The entrance to the nest was kept clean. No more
than two adult animals (male and female) were captured in the same
shelter, and only a few times were young captured in the same place with
adults. Nesting places were located also at the bases of trees and near
fallen logs where litter accumulates.
Records of animals kept in captivity show that the species _dimidiatus_
survives more than two years. Specimen MN no. 5448 [M] was adult when
captured by the Serviços de Estudos e Pesquisas sobre a Febre Amarela on
December 5, 1938, and died on January 17, 1942. Therefore, it lived for
more than 1,139 days.
_Proechimys dimidiatus_, in Rio de Janeiro, as well as _P. i. bonafidei_
and _P. i. iheringi_ which live in the same region, were found breeding
from September to November and from March to May. _Proechimys
longicaudatus roberti_, in Anapolis, Goiaz, was found breeding from July
to November and from January to March. _P. g. hyleae_ and _P. g.
leioprimna_ in the lower Tapajoz and lower Tocantins rivers, Pará, were
found breeding in January.
It seems that in the Central Plateau and southeastern Brazil,
_Proechimys_ has two litters per year, one in the early spring and a
second in the late summer. The number of young per litter varies from 1
to 5, although 2 is the usual number.