Bg. Walker et Pl. Boveng, EFFECTS OF TIME-DEPTH RECORDERS ON MATERNAL FORAGING AND ATTENDANCE BEHAVIOR OF ANTARCTIC FUR SEALS (ARCTOCEPHALUS-GAZELLA), Canadian journal of zoology, 73(8), 1995, pp. 1538-1544
We evaluated the difference in average durations of foraging trips and
nursing visits to shore between one group of female Antarctic fur sea
ls (Arctocephalus gazella) carrying radio transmitters only and anothe
r group carrying time-depth recorders (TDRs) and radio transmitters du
ring their first five postpartum foraging trip - nursing visit cycles.
Data were collected from 105 different fur seals in five breeding sea
sons (1989-1990 to 1993-1994) on Seal Island, Antarctica. Average fora
ging-trip and nursing-visit durations were significantly greater for t
he seals carrying TDRs and radio transmitters than for seals carrying
radio transmitters only (two-way ANOVA, year x instrument type; trip,
P = 0.004; visit, P = 0.04). Historically, instrument-effect studies o
n marine animals have focused on smaller species and larger instrument
to body size ratios. Because of small sample sizes (the number of ins
truments successfully deployed and retrieved) and the typically variab
le nature of data from TDRs, the statistical power to detect significa
nt differences due to instrument effects has been low. The evidence of
instrument effects on Antarctic fur seals has possible implications f
or studies utilizing devices attached to similar-sized animals: result
s may not be representative of the natural (non-instrumented) populati
on.