The buccal cavity is modified in young red kangaroos by hemispherical indentations
into hard palate and tongue which receive the bulbous swelling at the end of the teat.
Attachment to the teat is aided by the formation of ridges on the hard palate and
the lateral fusing of the lips of the young. The epiglottis of the young red kangaroo
is intra-nasopharyngeal rather than intra-narial as is stated to be the case in other
marsupials.
Red kangaroos less than 1 day old were removed from the teat to which they
had attached and replaced on another teat in the same pouch. A grey kangaroo young
aged 13 days was replaced on the teat after removal and was removed and replaced at
7-day intervals thereafter. No difficulty was experienced in replacing 15 young aged
between 41 and 100 days on the teats from which they were removed.
The following transfers of young less than 1 day old were made: two red kangaroos
to foster-mothers of the same species, one red kangaroo to a grey kangaroo, two
grey kangaroos to foster-mothers of the same species, one tammar to a red kangaroo,
and two swamp wallabies to red kangaroos. All the transfers were initially successful;
however, one red kangaroo and one grey kangaroo were lost soon after the transfer,
apparently because the foster-parents were at the incorrect stage of their reproductive
cycles.
The followmg transfers of young 2-25 days old were made to foster-mothers
suckling young 2-20 days old: two swamp wallabies to red kangaroos, one red kangaroo
to a swamp wallaby, one red kangaroo to a red-necked wallaby, one grey kangaroo
to a red kangaroo, one tammar to a red kangaroo, and one red-necked wallaby to a
red kangaroo. All the transfers were initially successful except a 13-day-old tammar
which failed to attach to the teat of its foster-mother. A swamp wallaby young
transferred at the age of 25 days to a red kangaroo showed accelerated growth and early
sexual maturity compared to control swamp wallabies raised by their own mothers.
A total of 12 inter-species and intra-species transfers of young aged 41-255
days old were made. A 53-day-old young of the yellow-footed rock wallaby failed
to attach to the teat of a red kangaroo but all other transfers were initially successful
and, in most cases, growth of the foster-young was normal and they were reared to
at least the latter stages of pouch life.
Young placed in the pouches of foster-mothers were readily accepted and there
were indications that the behaviour patterns of the foster-mother were altered so that
they responded to calls made by the foster-young. Foster-young of species which
have a longer pouch life than the red kangaroo remained in the pouches of red kangaroo
foster-mothers for the time usual in their own species.
Foster-young transferred to the pouches of other species were usually reared
to the end of pouch life if adult sizes of transferred young and foster-mother were
nearly equal. Young of small species transferred to the pouches of larger species were
often lost before the end of pouch life.
Foster Mother-Infant Bonding: Associations Between Foster Mothers' Oxytocin Production, Electrophysiological Brain Activity, Feelings of Commitment, and Caregiving Quality
