Post-release monitoring of pilot whales from a mass stranding in the Florida Keys

Tagged adult male pilot whale
One of two adult male pilot whales tagged with a satellite-linked transmitter prior to his release.

Responding to a request by NOAA Fisheries on Friday night, 6 May, SDRP staff drove to Cudjoe Key in the lower Florida Keys early on the morning of 7 May to tag two male short-finned pilot whales from a mass stranding of about 21 whales.

The animals were initially scattered through the area when the stranding began on 5 May.

The Marine Mammal Conservancy and others were able to move all of the whales to a more centralized location and set up a temporary enclosure for initial treatment and evaluation.

The two adult males were determined by the attending veterinarians and NOAA Fisheries to be in adequate health and condition for immediate release.

The remaining live whales were subsequently transported to a rehabilitation center for continuing care.

The males were tagged with single-point attachment satellite-linked transmitters produced by Wildlife Computers.

These tags provided data on location, dive depths, and dive durations. One of the males was tracked for 17 days, and the other for 66 days, until the tag’s AA battery was drained.

Map of satellite tracking locations
Map of satellite tracking locations for stranded pilot whale Y-400 after release.

Both whales remained close together for the entire period both tags were transmitting, as they moved northward, and the dive patterns of the two whales were very similar to one another.

Given the whales’ previous behavior, researchers speculate that the abrupt loss of the signal from one whale resulted from failure of the transmitter or attachment on the whale’s dorsal fin rather than a gradual decline in the health of the whale.

As can be seen from the map, the remaining whale, Y-400, continued around the north and east side of the Bahamas and then southward to the northern shore of the Dominican Republic, often moving with prevailing currents. It continued to the northeast tip of Cuba, and then remained in the Windward Passage, separating Cuba from Haiti, for the last days signals were received.

The whale made occasional dives to 1,000-1,500 meters and occasionally stayed down for more than 40 min, among the deepest and longest documented dives for this species.

One of the concerns for mass strandings has been that retaining all of the members of the group in rehab until all are sufficiently healthy to be released at once may be detrimental to those individuals who were initially healthy.

The apparently successful release of these whales supports the idea of evaluating initial health and releasing individuals from the stranding site rather than retaining entire groups. The tagging and follow-up monitoring were supported by the NOAA John H. Prescott grants program.

 

Assessing post-release success of rehabilitated odontocete cetaceans

Important questions have been raised regarding the relative risks and benefits of rehabilitating and releasing stranded odontocete cetaceans, but until recently few data have been available to support an appropriate evaluation.

In the early years of cetacean rehabilitation, success in getting the animals to the point of release was infrequent, but success rates have improved markedly in recent years thanks to increased experience and knowledge and improved diagnostics and facilities.

Concurrently, safe and practical techniques for monitoring rehabilitated cetaceans post-release have become available, especially involving radio telemetry, providing the potential for assessing the success of the animals released back into the wild. Decreased tag size and increased experience with attachments lasting for periods of months have helped to allay concerns about safety risks from the tags themselves.

Recognizing that rehabilitation can be a very expensive undertaking, requiring extended allocations of limited medical, facility, and staff resources, increasing effort has been made in recent years to monitor rehabilitated cetaceans post-release in order to be able to evaluate the success of the treatments.

With support of the NOAA John H. Prescott grants program and collaborative efforts involving Dr. Forrest Townsend, Dr. Frances Gulland, and Rob DiGiovanni, we engaged in a systematic review of post-release success relative to initial cause of stranding, aspects of rehabilitation, treatments, or life history parameters.

We compiled and reviewed 69 cases from 1986-2010 involving 10 species of small odontocete cetaceans.

Of these, 41 cases involved single strandings or rescues, while 28 of the cases involved mass strandings. Thirteen of the bottlenose dolphin cases and all 38 of the cases involving other species were strandings with subsequent rehabilitation efforts. Eighteen bottlenose dolphin cases were rescue captures brought about by entanglement, out-of-habitat, or maternal death situations. Seven of these interventions led to rehabilitation, while the remaining 11 rescues involved on-site examination, treatment if necessary, and release without rehabilitation.

A final report for this review is currently being prepared. Among the preliminary findings is a definition for release success: following release, the cetacean exhibits ranging patterns, habitat use, locomotion, behavior, and social interactions typical for the species, stock or individual, and/or at least does not exhibit abnormal behavior, for a minimum of six weeks. Not all of these data will be available in all cases. To obtain these data, direct visual observations are best, but in the absence of observations, some of these data may need to be inferred from radio-telemetry.

Based on this criterion, 80% of cases were identified as successful or unknown but likely to have been successful. In general, interventions prior to stranding led to higher success rates than did stranding with rehabilitation. Mass stranded individuals demonstrated greater success than single stranders. Young calves without their mothers, old animals, and animals with hearing deficiencies exhibited poor success post-release. In all cases, the importance of post-release monitoring was noted.

 

 

Dolphin rescues and disentanglements: 2006-2011

Dolphin entanglements and strandings in the Sarasota Bay area and elsewhere in recent years have led to rescues involving the SDRP. We were involved in three bottlenose dolphin disentanglements in 2011. The ongoing field efforts of the SDRP provide opportunities to follow-up on local rescue cases, as summarized below.

Ginger

In December 2008, a 3-year-old female resident dolphin named Ginger stranded on Siesta Beach and was taken to Mote Marine Laboratory for treatment for gastrointestinal and respiratory problems.

She was released 2 months later, with a small VHF tag and she was closely monitored for two months.

After the radio tag stopped transmitting and was jettisoned, we kept track of Ginger during our monthly photographic identification surveys.

Over time, her range has increased, and she has been seen in larger groups, often socializing with other juveniles including her recently independent younger brother, Wasabi. She was seen 26 times in 2011, and appears to be in good health.

In the case of Ginger, the reason for her stranding was unclear. However, in many other cases, human interactions are the primary cause necessitating a dolphin rescue.

Scrappy

In July 2006, Scrappy, an 8-year-old male, was observed in a large men’s bathing suit. His head had gone through the waist and one of the leg holes, and the suit was cutting deeply into the leading edge of his flippers. Scrappy was briefly captured, examined, treated and released on 3 August 2006, and the bathing suit was removed. Since his rescue, he has been seen more than 100 times, including 13 times in 2011. Recently, he was observed cooperatively herding fish with several other young adults in mid-Sarasota Bay.

FB28

On 22 June 2007, FB28, a 42 year old male, was seen entangled with monofilament fishing line, which was tightly wrapped three times from the dorsal fin to the fluke.

FB28 showing off his line-free fluke
FB28 showing off his line-free fluke during his most recent sighting on 27 October 2011. FB28 suffers from a chronic fungal disease called lacaziosis.

On 6 July 2007, a SDRP rescue team was able to approach FB28 with a long handled cutting tool and remove the line from the dorsal fin. The line was still draped across his fluke, but cutting the tension allowed the line to eventually clear the fluke on its own.

Now 46 years old, FB28 is one of our oldest known males.

During most of the 40 years we have known him, FB28 has emphasized the northern portion of our Sarasota Bay study area, and southern Tampa Bay. FB28 was seen 3 times in 2011, including a sighting on 27 October in the mouth of Tampa Bay, where he was showing off his line-free fluke while catching fish.

Nellie

In February 2010, SDRP staff noticed the 9-month-old calf of resident dolphin FB25 had some plastic

Nellie in Big Pass
Nellie in Big Pass on 17 October 2011.

twine and a metal hook entangled around her head. She was briefly captured on 1 March 2010, and the entanglement was successfully removed. Nellie has since become independent of FB25 (who had her 8th calf this year) and has been seen 32 times since her rescue, including a recent occasion where she was socializing with a group of 9 dolphins.

C797

C797 with his mom
C797 with his mom on 23 March 2011. Other than the entanglement, he appears to be in good health.

Although the three prior cases were successful rescues/disentanglements, occasionally an individual is not as fortunate.

C797 on 24 May 24 2011
C797 on 24 May 24 2011. Just two months later he is extremely emaciated, the line has cut deeply into the dorsal fin, and he has become entangled in even more fishing line.

On 18 March 2011, SDRP staff observed C797, the 9-month-old calf of long-term Sarasota resident FB79, entangled in fishing line. There appeared to be a hook inside the mouth, and line extended from the mouth around the body, cutting into the leading edge of the dorsal fin, and trailing behind the dolphin’s fluke.

Over the next 3 months, a number of attempts were made to disentangle C797. Both approaching the free swimming dolphin to cut line with a long handled cutting tool and temporary capture-release were tried a number of times.

C797 was seen by SDRP staff 20 times during his entanglement. On 10 occasions, we were able to attempt disentanglement with a long handled cutting tool. Unfortunately, he was very evasive and our attempts were mostly unsuccessful.

Efforts to locate, temporarily capture, and remove the gear from C797, involving 5-10 boats and 30-80 people, were made on 8 different days, but we were unable to find him in a safe capture situation.

C797 was covered in more than 25 meters of gear
C797 was covered in more than 25 meters of various types of fishing gear. The increased use of braided fishing line in the Sarasota area is concerning as it may do more damage more quickly than monofilament.

On 17 June, an emaciated C797 was seen with FB79, swimming lethargically. We were able to use the long handled tool to cut a small amount of line from him and eventually hooked some line, allowing us to pull him close to the boat, where we worked rapidly to remove all the remaining gear. He was released quickly and was soon seen surfacing next to his mother, completely free of gear!

FB79 was next seen on 22 June, without her calf. Despite our efforts, C797’s condition had probably deteriorated too far for him to be able to recover, but at least he was able to spend his final days clear of the painful line.

Examination of the gear suggested at least five different entanglements, involving more than 25 meters of monofilament and braided fishing line as well as 3 different hooks/lures.

Although SDRP staff and our numerous collaborators and volunteers have been successful in rescuing entangled dolphins in the past, this case tragically highlights that we will not always be able to help despite our best efforts.

The entanglement of C797 is unfortunate; however, this case study is an excellent example to be utilized by conservation educators on the importance of responsible fishing practices. The best way to help is to reduce the chances of a dolphin encountering fishing line in the first place. Remember not to discard your fishing line into the water as it can be deadly to marine life. Please refer to the “Dolphin Friendly Fishing and Viewing Tips” card  for other ways to reduce negative impacts on dolphins.

Y06

On 8 August 2011, during NOAA health assessments in Barataria Bay, Louisiana, we caught a young male with healed presumed boat propeller wounds on his dorsal fin. The remaining pieces of fin had collected monofilament line, which we removed prior to release of the animal.

Tt256:

On three occasions in July 2011, Dr. Ann Weaver observed an entangled 6-month-old calf with its mother in John’s Pass, near St. Petersburg. Monofilament line formed a bridle through the calf’s mouth, wrapped around its right flipper, cut into the base of the dorsal fin, and trailed behind.

Tt256 with entangling monofilament
Tt256 with entangling monofilament fishing line and remoras on 21 October 2011. Photo by Ann Weaver.

The dolphin was not seen again until late October, at which point NOAA asked SDRP to lead a rescue capture.

On 15 November, after many days of high winds precluding rescue attempts, a team of 35 people including Larry Fulford, and staff from the SDRP, NOAA Fisheries Service, University of Florida, Mote Marine Lab, Florida Fish and Wildlife Research Institute’s Marine Mammal Pathobiology Lab, Busch Gardens, SeaWorld, Clearwater Marine Aquarium, and the Florida Aquarium was able to capture the calf and its mother in shallow water and remove the gear.

Although the line had cut deeply into the calf in several places, he was in generally good body condition, he responded well during the treatment, he exchanged frequent whistles with his mother throughout the brief procedures, and he swam off strongly with his mother upon release – we have every expectation that he will do well in the absence of gear.

 

Freed Pilot Whale: Final Update

The satellite-linked transmitter on the adult pilot whale has failed after 66 days. Powered by a single AA battery, the transmitter was expected to have a 2-3 month life expectancy.

This was one of two pilot whales returned to the sea after about 21 whales stranded in the Florida Keys in early May.

This whale was tracked, moving a total of about 4100 miles (6022 KM). It moved from the Keys north to off of the South Carolina coast, and back down into the Caribbean. The last few weeks were spent off the northeastern coast of Cuba.

The whale made occasional dives to 1,000-1,500 meters, and occasionally stayed down for more than 40 minutes. These are among the deepest and longest documented dives for this species.

This tagging effort and follow-up monitoring was supported by the NOAA Prescott Grants program, and conducted by SDRP Director Dr. Randall Wells.

The satellite-linked transmitters were attached to the whales’ dorsal fins by Randy, at the request of NOAA Fisheries. The maps are provided by the Satellite Tracking and Analysis Tool .

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Update on Pilot Whales

The two stranded pilot whales released together on May 7th, stayed together and moved north in the Gulf Stream off the Atlantic Coast.

Four other whales appear to be recovering with the help of an army of volunteers working with the Marine Mammal Conservancy, in the Florida Keys.

These whales were the survivors of a group of about 21 whales that stranded together near Cudjoe Key, in the Florida Keys on May 5, 2011.

Tagged and released:

Two of the largest whales, both males, were judged by veterinarians to be healthy enough, to be returned to the sea.

Prior to release, they were tagged with small satellite linked transmitters attached to their dorsal fins. The transmitters provide data on location and dive patterns.

After moving north, the whales moved generally counter-clockwise off the South Carolina coast,  where they followed prevailing currents called a gyre (see map).

Pilot Whale May 23rd tracking map
The track of two pilot whales moving north to an area off Charleston, SC. Each carried a satellite linked transmitter. Signals were received from only one of the transmitters on May 23, 2011.

This gyre, which is off the edge of the Continental Shelf, may be a good feeding area for whales.

The dive patterns of the two whales appear to be very similar, and this similarity has remained consistent over time.

On May 23rd, signals were lost abruptly from one of the transmitters.

Given the whales’ previous behavior, researchers speculate that the loss of signal resulted from failure of the transmitter, or attachment on the whale’s dorsal fin, rather than a gradual decline in the health of the whale.

Researchers will continue to monitor signals from the remaining transmitter.

Meanwhile back on shore:

Four pilot whales were transported to a rehabilitation center where they continue to receive around-the-clock care.

An army of volunteers is helping with the recovery of the whales at an rehabilitation center operated by the Marine Mammal Conservancy..

According to a May 23rd article in the Miami Herald, the effort is showing promising results due to the efforts of hundreds of volunteers.

“Blair Mase, the Marine Mammal Stranding Coordinator for the National Oceanic and Atmospheric Administration’s (NOAA) Southeast Region, is cautiously optimistic that 3 of the whales will recover enough to be released. The fourth is thought to be too young to survive without its mother, and would be placed in a public display facility.

 

 

This tagging effort and follow-up monitoring is supported by the NOAA Prescott Grants program. The satellite-linked transmitters were attached to the whales’ dorsal fins by SDRP Director Dr. Randall Wells, at the request of NOAA Fisheries. The rehabilitation effort is being conducted at the Marine Mammal Conservancy, in collaboration with NOAA.