Influence of Manatees' Diving on Their Risk of Collision with Watercraft

Watercraft pose a threat to endangered Florida manatees (Trichechus manatus latirostris). Mortality from watercraft collisions has adversely impacted the manatee population's growth rate, therefore reducing this threat is an important management goal. To assess factors that contribute to the ri...

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Bibliographic Details
Published in:PloS one 2016-04, Vol.11 (4), p.e0151450-e0151450
Main Authors: Edwards, Holly H, Martin, Julien, Deutsch, Charles J, Muller, Robert G, Koslovsky, Stacie M, Smith, Alexander J, Barlas, Margaret E
Format: Article
Language:English
Subjects:
Accidents - statistics & numerical data
Analysis
Animal behavior
Animals
Aquatic mammals
Balaena
Bayes Theorem
Bayesian analysis
Behavior
Behavior, Animal
Biology and Life Sciences
Conservation
Depth recorders
Diving
Diving behavior
Earth Sciences
Ecology and Environmental Sciences
Energy conservation
Engineering and Technology
Fish kills
Florida
Foraging (Animal feeding behavior)
Foraging behavior
Global positioning systems
GPS
Growth rate
Manatees
Marine mammals
Mathematical models
Models, Theoretical
People and places
Physical Sciences
Protection and preservation
Recorders
Risk
Risk assessment
Risk management
Risk taking
Shallow water
Ships
Sirenia
Statistical models
Strikes
Substrates
Trichechus manatus
Trichechus manatus - physiology
Trichechus manatus - psychology
Trichechus manatus latirostris
Water depth
Water vehicles
Wildlife conservation
Wounds and Injuries - veterinary
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Summary:Watercraft pose a threat to endangered Florida manatees (Trichechus manatus latirostris). Mortality from watercraft collisions has adversely impacted the manatee population's growth rate, therefore reducing this threat is an important management goal. To assess factors that contribute to the risk of watercraft strikes to manatees, we studied the diving behavior of nine manatees carrying GPS tags and time-depth recorders in Tampa Bay, Florida, during winters 2002-2006. We applied a Bayesian formulation of generalized linear mixed models to depth data to model the probability (Pt) that manatees would be no deeper than 1.25 m from the water's surface as a function of behavioral and habitat covariates. Manatees above this threshold were considered to be within striking depth of a watercraft. Seventy-eight percent of depth records (individual range 62-86%) were within striking depth (mean = 1.09 m, max = 16.20 m), illustrating how vulnerable manatees are to strikes. In some circumstances manatees made consecutive dives to the bottom while traveling, even in areas >14 m, possibly to conserve energy. This is the first documentation of potential cost-efficient diving behavior in manatees. Manatees were at higher risk of being within striking depth in shallow water (
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0151450