Characterization of Resting Holes and Their Daily and Nightly Use by Antillean Manatees Trichechus m

1
Characterization of Resting Holes and Their Daily
and Nightly Use by Antillean Manatees (Trichechus
manatus manatus) in the Drowned Cayes, Belize

• Marie-Lys C. Bacchus
• Loma Linda University
• Proposal
• 4/19/2006

2
Introduction
www.fknms.nos.noaa.gov
www.simplonpc.co.uk/ SCJPEGS/sc2158_Arurora.jpg

• Vulnerable on IUCN Red List (2004)
• Causes
• Hunting
• Habitat degradation
• Belize increase in tourism
• Increase in boat traffic
• Increase in development
• Siltation

Lebfevre et al., 2001
3

• Belize remains one of the last strongholds for
  this species in this part of the world. (OShea
  Salisbury, 1991)

http//www.4windstravel.com/shows/belize/map.jpg
www.sirenian.org
4
The Drowned Cayes

• Mangrove islands
• Marine habitat
• Ideal for manatees

5
Habitat Preferences

• Water Temperature (Irvine, 1983 Lebfevre et al.,
  2001 Deutsch et al., 2003 Jimenez, 2005)
• Freshwater (Hartman, 1979 Rathbun et al., 1990
  Olivera-Gomez Mellink, 2005)
• Vegetation (Hartman, 1979 Kinnaird, 1985
  Deutsch et al., 2003 Jimenez, 2005)
• Depth (Hartman, 1979 Lebfevre et al., 2000
  Olivera-Gomez Mellink, 2005)
• Currents Wave Action (Hartman, 1979, Lebfevre
  et al., 2001 Jimenez, 2005)
• Tides (Hartman, 1979 Jimenez, 2002)

By Alan Stevens
www.nps.gov/bisc/resource/ images/seagrass.jpg
6
Behaviors of Florida Manatees

• Florida manatees appear to be arrhythmic
• Spend time feeding, resting, idling, cruising,
  and socializing
• Resting for six to ten hours a day in stretches
  of two to four hours at any time
• Bottom rest wherever, even in man-made canals

7
Resting Holes

• Depressions in benthic substrate
• Quiet areas with minimal disturbance
• Two to three feet deep
• Manatee highway
• Reverse thermoclines
• Freshwater seeps nearby?

By Alan Stevens
By Renee Bickar
By Alan Stevens
8
Main Goal

• To characterize resting holes and to correlate
  diurnal and nocturnal resting hole use by
  manatees with environmental parameters such as
  salinity, water temperature, and currents.
• Importance
• First step in understanding daily and nightly
  habitat use by manatees
• Understanding which environmental characteristics
  play a role in these choices

9
Goals, Objectives, Hypotheses

• Goal 1 To characterize manatee resting holes.
• Objective Characterize resting holes by
  collecting quantitative data such as depth,
  salinities, and currents, and by analyzing this
  data in a Geographical Information System (GIS).
• Hypothesis 1 Manatee resting holes will have
  lower currents than other areas of the mangrove
  cayes.
• Hypothesis 2 Manatee resting holes will be
  characterized by reverse thermoclines.

10
Goals, Objectives, Hypotheses

• Goal 2 To document diurnal and nocturnal
  presence and behaviors of manatees in the Drowned
  Cayes.
• Objective Conduct daily and nightly 30-minute
  site scans at four resting holes in the Drowned
  Cayes while recording sightings of manatees and
  associated environmental parameters.
• Hypothesis 1 - There is a difference between
  daily and nightly resting hole use by Antillean
  manatees in the Drowned Cayes.
• Hypothesis 2 - Environmental parameters have an
  effect on daily and nightly presence of Antillean
  manatees in four resting holes in the Drowned
  Cayes.

11
Goals, Objectives, Hypotheses

• Goal 3 To assist in conservation efforts of the
  species.
• Objective Participate in development plans for
  continued monitoring of manatee populations and
  provide data to protected-area managers.

12
Goals, Objectives, Hypotheses

• Goal 4 To increase public awareness of general
  manatee behavior and the importance of
  conservation efforts.
• Objectives
• Provide updates of the project to the public
  through outreach websites (see Aquanews website
  of the Vancouver Aquarium at http//www.vanaqua.or
  g/aquanews/field/earthwatchupdates.htm).
• Conduct educational outreach to schools in Belize
  and the United States.

13
Goals, Objectives, Hypotheses

• Contribute 3 manuscripts for publication in
  peer-reviewed journals
• Characterization of Antillean manatee
  (Trichechus manatus manatus) resting holes in the
  Drowned Cayes of Belize
• Daily and nightly use of resting holes by
  Antillean manatees (Trichechus manatus manatus)
  in the Drowned Cayes, Belize
• Use of sonar to characterize manatee resting
  holes
• Make presentations at national and international
  meetings.
• Provide opportunities for Earthwatch volunteers
  from around the world to participate in field
  research.

14
Methods

• Characterization of resting holes
• Data collected
• Depth
• Width
• Water temperature
• Salinity
• Current through the water column above resting
  hole
• Distance to shore
• Type of substrate
• Sampling of benthic vegetation in a one meter
  radius
• Three samples of salinity near mangroves

15
Methods

• Thirty-minute scans of four resting holes
• 50GiCr
• Bogue B
• 31CLa
• 30CCo
• Daily (10 a.m. to 230 p.m.)
• Nightly (7 p.m. to 1130 p.m.)
• Nocturnal scans will utilize red-light to
  minimize disturbance
• Test hydrophone to detect manatees

16
Methods

• Environmental Data
• Tidal state
• Water temperatures
• Salinity
• Water velocity
• Sea state
• Wind strength and direction
• Air temperature
• Precipitation
• Glare
• Swell height
• Cloud cover

• Other Data
• Time of sighting
• Distance to manatee
• Activities
• Breaths
• Paddle-dives
• Behaviors
• Feeding
• Resting
• Traveling
• Whether manatee was in the resting hole or not

17
Possible Sonar Use

• Characterization of resting holes could be
  facilitated with use of a fish finder sonar
• Could also test the sonar at night to see how
  well it could detect manatees
• Daniel Gonzalez has obtained good results in
  capturing pictures of the substrate and of
  manatees in turbid freshwater

18
Data Analysis

• GIS
• Draw resting holes
• Integrate environmental data
• ANOVAs
• Differences in air and water temperatures,
  salinity, depth, width, distance to shore and
  water velocity between resting holes
• Logistic Regression
• Test if presence/absence of manatees can be
  predicted by one or more habitat characteristic
  variable

19
Results to Date

• ANOVAs
• No significant difference was found between four
  locations with resting holes for
• Air temperature (F (3,75) 1.550, p 0.209)
• Sea surface temperature (F (3,75) 0.176, p
  0.912)
• Surface Salinity (F (3,75) 0.213, p 0.887)
• Logistic Regression
• None of the habitat variables significantly
  predicted presence of manatees