New Zealand Journal of Zoology abstracts
Fostering behaviour in New Zealand sea lions Phocarctos hookeri
SIMON CHILDERHOUSE
NICK GALES 1
Science and Research Unit
Department of Conservation
PO Box 10-420
Wellington, New Zealand
Ph. 64-4-471-3233. Fax. 64-4-471-3279.
Email. schilderhouse@doc.govt.nz;
nick.gales@aad.gov.au
Abstract The fostering behaviour of female New Zealand sea
lions
Phocarctos hookeri was studied to investigate simultaneously
nursing of two or more pups.
Surveys (n=44) documenting the frequency of
this fostering behaviour found that it is uncommon with a mean of 6.0%
(S.E.=0.5) of nursing females at any one time seen nursing two or more pups
simultaneously. Most of the multiple suckling events (n=149) observed were
females simultaneously nursing two pups (78%), although three (20%) and four
(2%) pups per female were also recorded. We used time spent nursing and a
nursing index to investigate relative nursing times. Females seen to nurse more
than one pup simultaneously (multiple nursers) spent significantly more time
nursing and had a significantly higher nursing index than females seen to nurse
only a single pup at any one time (single nursers). The impact of this on the
female and her pup are unknown but could represent a significant increase in
the cost of lactation over this period. Single nursers rejected almost all
(95%) pups that attempted to suckle from them when there was already a pup
suckling, while multiple nursers rejected less than half (46%) of the extra
pups and appeared more tolerant of additional pups suckling. The mechanism
through which this behaviour may have evolved has not been determined.
Keywords Phocarctos hookeri; New Zealand sea lion;
fostering; maternal behaviour; nursing
New Zealand Journal of Zoology, 2001, Vol. 28: 189-195
0301-4223/01/2802-0189 $7.00/0 (c) The Royal Society of New
Zealand 2001
1 Present address: Conservation and Land Management, Locked
Bag 104, Bentley Delivery Centre, WA 6983, Australia. Ph 61-8-93340290 Fax
61-8-93340278
Z00032
Received 7 September 2000; accepted 27
November 2000
PDF file of entire paper: medium quality (500K); (scanned from paper original: notes about this process)
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