BIOLOGICAL ASSESSMENT AND HANDLING OF CAPTURED FREE-RANGING MANATEES IN BELIZE

Robert K. Bonde¹, Alonso Aguirre² and James A. Powell²

¹U.S. Department of the Interior,
Florida Integrated Science Center, Gainesville, FL;
² Wildlife Trust, New York, NY

Presented at the 14th Biennial Conference on the Biology of Marine Mammals,
28 November - 3 December 2001, Vancouver, BC, Canada.

ABSTRACT

Free-ranging West Indian manatees (Trichechus manatus) were captured for a radio tagging study in Southern Lagoon, Belize.  Manatees were approached by boat and a 152 m long, 6 m deep, 13 cm stretch mesh nylon net was set in open water 1-1.5 m deep.  Captured individuals were then transported a short distance to a beach for examination. Fifteen individuals were captured 35 times between November 1997 and March 2001. Nine manatees were captured more than once. Out-of-water holding time ranged from 24 to 140 minutes with an average duration of 90 minutes.  Most animals were tagged with VHF and UHF radio tags connected to belts fitted around the tailstock and passive integrated transponder (PIT) chips were inserted to facilitate re-identification. Fat thickness measurements were recorded using ultrasound. Morphometrics, blood, urine, fecal and tissue samples were collected and analyzed or archived. Results of urine analyses revealed a new species of diplogasterid nematode.  Fecal samples were not pathologic but did allow for identification of local vegetation types.  Blood values for CBC and serum chemistry profiles indicated normal levels comparable to manatees previously examined in Florida and Puerto Rico.  Duplicate samples were collected from 6 animals and analyzed to check for laboratory quality control.  Dugongs have been prone to capture myopathy and typically display elevated serum enzymes and biological indicators of tissue damage. Florida manatees have been documented to tolerate capture and handling activities without susceptibility to capture stress. Variables examined to address potential affects of capture stress included the serum enzymes SGOT (range, 9.4-60.6 U/L), SCPK (10.1-287 U/L), and LDH (0-260 U/L); as well as biochemical indicators such as BUN (2.0-11.6 mg/dL), creatinine (0.76-3.0 mg/dL) and potassium (3.6-6.42 mmol/L).  Higher-than-normal elevations of serum enzymes were not detected in 12 individuals sampled 20 times.  No adverse effects of capture stress were detected post-release.

METHODS

Twelve free-ranging manatees were captured in Belize using nets deployed from a boat in open water. The net was 152 m long and 6 m deep, with a stretch mesh of 13 cm. The target manatee was circled with the boat as the net was set. Once deployed, the net was collapsed back to the boat where the manatee was pulled onto the deck of the boat or restrained along side, until transported to shore for examination.

Blood extraction was accomplished using the following protocol:  The medial aspect of the manatee's flipper was surgically scrubbed and sterilized.  Venipuncture was accomplished through a sterile 18-20 gauge, 1.5 inch needle inserted into the palpable interosseous space between the radius and ulna.  This blind stick includes target vessels within a small plexus (brachial vascular bundle) deep within the tissue.  Vacutainers were used to draw approximately 100 mls of blood into sterile tubes.  Samples were placed on ice and transported to the laboratory as soon as possible for standard hematology and serum chemistry processing.  Transit time ranged from 5 to 36 hours.

Ultrasound measurements were recorded using a Scanoprobe II 731C from Scanco.  Urine samples were opportunistically collected by cleaning off the urogenital aperture and placing a sterile Frisbee beneath the restrained manatee. Samples were removed and submitted for urinalysis.   Fecal samples were collected when feces were present.

Individual Animal Blood Data

Blood Value Data for This Study

Ultrasound Readings

Radio Tag Attachment

Net Boat

Net Captures

RESULTS & DISCUSSION

This is a long-term research project begun in 1997 to study the population of manatees in Belize. Twice per year the research team assembles and catches manatees as part of a larger radio tagging project.  Local field biologists stay on site and follow the manatees using radio tags.  Individuals are also monitored using satellite telemetry.  This program has afforded us the opportunity to monitor multiple individuals over several years. Data on health assessment and biology have been routinely collected.

The tagged manatees in this study were exposed to capture by net and handling during typical data acquisition.  There was no evidence to suggest that any of the wild caught manatees suffered any adverse effects due to capture stress.  Out of water holding times ranged from 24 to 120 minutes. Typically high levels of potassium (e.g. >10 mmol/L) associated with capture myopathy were not present in any of the blood values collected from this study. Other serum enzymes were considered normal as well.  Results from this study corroborate findings from manatee researchers in Florida.

All manatees were fitted with passive integrated transponder (PIT) tags to help facilitate re-identification. Urine samples were examined and a new, un-described diplogasterid nematode has been identified. Additional studies are underway to taxonomically classify this parasite.  Fecal sample analyses were normal.  Variation between fat thickness, girth and weight were apparent between different individuals, suggestive of possible changes in nutritional condition due to seasonality.

Genetic samples were also collected and preliminary results suggest three unique mtDNA haplotypes from the 17 animals sampled from this area.  More detailed microsatellite analyses are planned for the near future.

On 6 occasions duplicate blood samples were collected from each individual and processed together to determine local laboratory quality control. All variations in samples from these individuals appeared to be within acceptable limits.

ACKNOWLEDGMENTS

Many persons have contributed to the success of this project.  Primarily we would like to thank all the staff at Belize Coastal Zone Management and Institute, especially Nicole Auil, Janet Gibson and Angeline Valentine.  Keven Andrewin, Mesha Gough and Andrea Gill afforded valuable field expertise. Many friends, colleagues and researchers have participated in this program as well.  Additionally, we would like to thank the governmental officials in the Belizean Departments of Fisheries and Forestry. Financial contributions were provided by Wildlife Trust.