(full paper is archived in the Miller Library)
Title: Behavioral patterns of three intertidal whelks,
Nucella emarginata, Acanthanucella punctulata, and
Ocenebra circumtexta, in response to tidal variation.
Student Author(s): Eldon, Jon
Faculty Advisor(s): Watanabe, Jim
Pages: 25
Location: Final Papers Biology 175H
Date: June 2004
Abstract: This study examined behavioral patterns of three
intertidal whelks in response to tidal variation. Nucella
emarginata, Ocenebra circumtexta, Acanthanucella
punctulata have widely overlapping habitat but significantly
different resource utilization strategies. All three species were
found in the primary study site, a 6m by 9m region of rocky
intertidal shore with a vertical range of 0 to +2.5m above MLLW.
Individuals were marked and observed at low tide for a two week
period to discern basic patterns of movement and aggregation.
Following this, surveys of microhabitat and activity were taken of
the same area at daily high and low low tides for another two weeks.
Acanthanucella were highly responsive to tidal patterns with
76% feeding at high tide and only 27% feeding at low. They also fed
significantly more on sun exposed patches of barnacles, often
horizontal surfaces, during high tide (66% feeding in sun) than
during low tide (21% feeding in sun). Ocenebra show a slight
but significant tendency to feed less in the sun at low tide (27%)
than at high tide (46%). However, the frequency of feeding in shaded
areas does not significantly vary with the tide, possibly because
these whelks are unique in utilizing undercut habitat. Nucella
appear to have the most conservative behavior, feeding the least at
high tide (61%) and showing insignificant response to sun exposure
and the timing of the low tide.