Behavior of juvenile American lobsters, Homarus americanus, under predation risk |
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Authors: | E Spanier T P McKenzie J S Cobb M Clancy |
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Institution: | (1) The Recanati Center for Maritime Studies and Department of Maritime Civilizations, University of Haifa, Mount Carmel, Haifa, 31905, Israel, IL;(2) Parametrics, 5808 Lake Washington Rd. NE, Kirkland, Washington 98033, USA, US;(3) Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island 02881, USA, IS |
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Abstract: | The influence of predation risk and food deprivation on the behavior and activity of juvenile American lobsters, Homarus americanus Milne Edwards, was examined in single and paired individuals in laboratory experiments performed during 1988 and in the winter
of 1991/92. In the presence of a predator (the tautog Tautoga onitis Linnaeus) restrained behind a barrier, single lobsters significantly reduced the time spent feeding at night, consumed fewer
mussels, and quickly brought them back to shelter. Single lobsters did not forage during the day in any treatment. If deprived
of food for 60 h, they consumed more mussels and spent more time walking than recently fed (12-h food-deprived) lobsters.
Paired lobsters did forage during the day in the presence of a predator. The smaller lobsters (subdominant) in the pairs foraged
for a longer time in the presence than in the absence of a predator and significantly longer than single individuals. Shelter
occupancy was significantly shorter in single, recently fed lobsters in the presence of a predator compared to time spent
sheltering in its absence. Among food-deprived lobsters, paired individuals spent a significantly shorter time within the
shelter than single lobsters in the absence of a predator. Larger (dominant) lobsters, however, spent more time than subdominant
lobsters within the shelter during all periods of the day. Without a predator, paired lobsters spent significantly more time
than single ones in shelter-related activities. Under predation risk, subdominant lobsters concentrated shelter-building time
during the day and built a higher percent of alternative shelters than either single or dominant lobsters. In the absence
of a predator, paired lobsters walked in the open area for a significantly longer time than single ones in the absence of
a predator. This apparently was associated with fighting between dominant and subdominant lobsters and the attempts of the
larger lobster to drive the smaller one from its shelter. During the day, lobsters fought for a significantly longer time
in the presence than in the absence of a predator. When the tautog was not constrained, mortality rate was similar in both
single and paired lobsters. Mortality rate among subdominant lobsters, however, was seven times higher than among dominant
lobsters. We suggest that the risk of predation interferes with the ability of single juvenile lobsters to acquire and consume
food. They appear to trade off energetic consideration against risk of predation when foraging away from the shelter. The
introduction of a conspecific competitor to the system may further increase risk (of the subdominant) to the predator. Intraspecific
interactions tend to increase the risk of predation to smaller lobsters but increase the survival rate among larger lobsters.
Received: 6 February 1995 / Accepted: 2 September 1997 |
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